Showing posts with label surrogate endpoint. Show all posts
Showing posts with label surrogate endpoint. Show all posts

Thursday, August 15, 2019

The definition of SECOND biochemical recurrence (after prostatectomy AND salvage radiation)

There is no standard definition of SECOND biochemical (PSA-detected) recurrence (BCR); that is, after both prostatectomy and salvage radiation (SRT). There are two reasons to have a standard definition of second BCR:

  1. Time for next treatment: BCR (after any treatment) is the first indicator of treatment failure, and a signal that it may be time to consider additional treatment. It is not at all clear that immediate additional treatments are beneficial, although the TOAD RCT suggested that early systemic treatment may be beneficial. If a treatment becomes the standard of care after biochemical failure, then it will be necessary to define the PSA or PSA doubling time (PSADT) at which that treatment should begin.
  2. Comparison among radiation protocols: Lacking randomized clinical trials among all the variables of when and how salvage radiation are given (pathological characteristics, PSA, PSADT, radiation dose, adjuvant ADT, prostate bed radiation, radiation of pelvic lymph nodes), we can only look at effectiveness across studies to help us hypothesize that one strategy might be better than another. It helps if we have a consistent definition of success.
Miyake et al. looked at three definitions of second BCR:
  1. NARA definition: PSA never falls below 0.2 ng/ml; or, it falls below 0.2 ng/ml but later rises over it in two consecutive readings.
  2. RTOG 9601 definition: any post-SRT PSA over 0.5 ng/ml; or, nadir + 0.3 ng/ml; or the start of hormone therapy.
  3. GETUG definition: nadir + 0.5
They evaluated 118 patients using the 3 definitions. With 49 months of median follow-up after salvage radiation:
  • The Nara definition had the highest rate of second BCR; 53%, 45% and 40% for Nara,  RTOG and GETUG respectively.
  • Gleason score and Pre-SRT PSA independently predicted Nara BCR, while negative margins and PSADT also predicted RTOG and GETUG BCR.
  • There were no discrete cut-offs of the patient characteristics that reliably predicted BCR by any definition
It's worth noting that the definitions may differ for study entry and endpoint (it is usually called "biochemical progression" when used as an endpoint). Many clinical trials use the 0.2 ng/ml definition for the second BCR too.  This trial used PSA≥ 0.2 ng/ml or 3 consecutive rises after RP or SRT. We recently saw that another RTOG trial, the SPPORT trial, used a BCR endpoint definition of nadir + 2 because it correlated well with clinical recurrence.

It is sometimes necessary to define a THIRD BCR as an endpoint to determine whether a therapy that began after a second BCR was successful. For example, an ongoing trial of hormonal therapies for SRT-recurrent men uses a second BCR definition of PSA > 0.5 ng/ml and PSADT ≤ 9 months, and a third BCR definition of a confirmed 25% rise in PSA and nadir + 2 during therapy, and a fourth BCR definition of a confirmed PSA > 0.2 after hormonal therapy.

The definition for FIRST BCR of a confirmed PSA after prostatectomy of 0.2 ng/ml was an artifact of the current lowest discernible PSA before the 21st century, which was 0.1 ng/ml at the time. The American Urological Association decided that anything higher than that would be deemed a BCR. With the growing and widespread use of ultrasensitive PSAs in the 21st century, many question that definition. Radiation oncologists at the top institutions recommend that SRT should be undertaken at the lowest PSA that indicates that clinical recurrence is likely. That may be as low as 0.03 ng/ml when there was significant adverse pathology, or a much higher value if pathology was clean and Gleason score was minimal.

BCR is just one of a number of elements to be evaluated after SRT. A BCR with a high Decipher score may suggest that immediate salvage ADT is appropriate. With the new generation of PET scans, which can detect metastases at low PSAs, it may sometimes be beneficial to treat pelvic lymph node metastases and possibly distant metastases if SRT had only included the prostate bed.

This small, retrospective study will not establish a new definition, but it does raise the interesting question of whether we need a standard definition, or whether the definition ought to depend upon the purpose for which it is used. When we have definitive evidence that early treatment after failed SRT is beneficial, that will force researchers to investigate the optimum PSA (or PSADT) cutpoint.

Monday, March 19, 2018

Escalated radiation dose doesn't improve 8-year overall survival in intermediate risk men (but does it matter?)

Last week, we saw that escalated dose did not improve 10-year overall survival in high-risk men (see this link). The latest published findings of the randomized clinical trial (RTOG 0126) prove that 8-year overall survival was not improved in intermediate risk men who received a higher radiation dose. In both studies, we are left wondering whether that matters.

Michalski et al. reported the results of RTOG 0126, a randomized clinical trial (RCT) designed to prove that escalated dose improves survival in intermediate risk men. It was a very large trial:
  • 1499 men
  • 104 sites in the US and Canada
  • Patients treated from 2002 to 2008
  • Median age was 71
The patients were all intermediate risk, defined as:
  • Stage T1b-T2b, and
  • Gleason score ≤ 6 and PSA ≥10 and <20 (16%), or
  • Gleason score = 7 and PSA < 15 (84%)
  • 71% were Gleason score 3+4
The treatment consisted of:
  • either low dose 70.2 Gy/ 39 treatments 
  • or high dose 79.2 Gy/ 44 treatments
  • delivered using 3D-CRT (66%) or IMRT (34%)
  • none had adjuvant ADT, but they may have had salvage ADT or other salvage therapies if RT failed
After a median follow-up of 8.4 years:
  • 8-year overall survival was 75% for the low-dose group vs. 76% for the high-dose group (not significantly different)
  • 8-year prostate cancer mortality was 4% for the low-dose group vs. 2% for the high-dose group (not significantly different)
  • 8-year biochemical failure was 35% for the low-dose group vs. 20% for the high-dose group (significantly different)
  • 8-year local progression (felt with DRE) was 6% for the low-dose group vs. 3% for the high-dose group (significantly different)
  • 8-year distant metastases (bone scan/CT detected) was 6% for the low-dose group vs. 4% for the high-dose group (significantly different)
  • 8-year salvage therapy was 22% for the low-dose group vs. 14% for the high-dose group (significantly different)
Toxicity outcomes were as follows;
  • Acute grade 2+ urinary toxicity was 17% for the low-dose group vs. 17% for the high-dose group (not significantly different)
  • Late-term grade 2+ urinary toxicity was 7% for the low-dose group vs. 12% for the high-dose group (significantly different)
  • Acute grade 2+ rectal toxicity was 5% for the low-dose group vs. 7% for the high-dose group (not significantly different)
  • Late-term grade 2+ rectal toxicity was 15% for the low-dose group vs. 21% for the high-dose group (significantly different)
In a separate analysis of the high-dose group:
  • Acute grade 2+ urinary and rectal toxicity was 15% among those treated with 3D-CRT vs. 10% among those treated with IMRT (a significant difference)
  • Late-term grade 2+ urinary toxicity was not significantly different among those treated with 3D-CRT vs. IMRT
  • Late-term grade 2+ rectal toxicity was 22% among those treated with 3D-CRT vs. 15% among those treated with IMRT (a significant difference)
This RCT raises many important questions about the design of clinical trials and the validity of conclusions drawn from them. Dr. Michalski addressed some of these concerns in an audio interview presented with the published study. This was an enormous undertaking, running almost two decades from design to reporting, and coordinating the treatments and reporting of 1,500 men in over 100 sites spread throughout Canada and the US.

The results show that dose escalation was not needed to increase 8-year survival in these intermediate risk patients. But this probably won't change practice for a number of reasons.

The intervening endpoints are of considerable importance to patients: the anxiety associated with rising PSA, the toxicity of all the salvage therapies, and the pain and possible crippling due to metastases all impact quality of life.

The median age of the men at treatment was 71, and they were screened for good performance status. The actuarial life expectancy in the US for a 71 year-old men is 14 years. This implies that they ought not make a decision based on expected survival for only 8 years. Also, as radiation-treated men get treated at a younger age, the gap will become more pronounced. According to the Memorial Sloan Kettering Life Expectancy Nomogram, a 71 year-old intermediate-risk man in good health has only a 8% probability of succumbing to prostate cancer in 10 years (vs 3% in 8 years in this study), and 12% at 15 years if he had no treatment whatever. At the same time, his probability of dying from other causes is 30% in 10 years, and 51% in 15 years. The overall survival improvement may not become apparent until median survival is reached in 15 years. And differences in prostate cancer survival are difficult to discern when numbers are this low. But it is difficult and costly to track patients for 15-20 years. We have to look to surrogate endpoints.

While 8-year overall survival and prostate cancer-specific survival did not improve, all the intervening endpoints did. Biochemical failure, local progression, distant metastases, and use of salvage therapies were all worse in the low-dose group.  It is very costly and difficult to run an RCT long enough to see a survival difference in men with localized prostate cancer. As we've seen, the few RCTs that have run the longest for each type of therapy have been single institution studies with much smaller sample sizes. Distant metastasis-free survival is probably a better surrogate endpoint if the study can't run for 15-20 years. There were enough metastatic events to see a difference. A recent analysis by the ICECaP Working Group of 12,712 patients in 19 clinical trials of radiation in localized prostate cancer showed that 5-year metastasis-free survival was almost perfectly correlated with overall survival. By reducing the time needed to accumulate data, this might increase the relevance of such trials while reducing their costs.

As Dr. Michalski points out, survival in both groups was much better than expected when the study was designed in 2001. This is largely because life-extending salvage therapies (e.g., docetaxel, GnRH agonists, Zytiga, Xtandi, Xofigo, and Provenge) have become prevalent in the interim.

Toxicity was markedly reduced by the introduction of IGRT/IMRT technology that became increasingly available, especially in the US, in the last 20 years. With the improvement in beam accuracy and the knowledge of the dose/toxicity relation of organs at risk, tighter dose constraints for organs at risk have been utilized. Because of the technology changes, a high-dose regimen today is probably no more toxic than a low-dose regimen. So, if there is little toxicity cost to the more effective treatment, why not use it? Rapidly adopted changes in radiation technology in the last 20 years, especially the shift from 3D-CRT to IMRT, render many of the findings irrelevant to today's standard practice.

Another RCT reported by Nabid et al. at the 2015 Genitourinary Conference had similar findings. They found that 10 year overall survival was no different for higher dose (76 Gy vs 70 Gy) or the addition of short-term ADT. Biochemical failures were actually worse in the higher dose group, but only if short-term ADT was not used with it. Zaorsky et al. conducted a meta-analysis of dose escalation trials in intermediate risk men and arrived at a similar conclusion. A contrary finding was noted by Kalbasi et al. in their analysis of the National Cancer Database. They found that there was a significant survival increase associated with higher dose (hazard ratio = 0.84). In fact, for every 2 Gy increase in dose, there was an 8% reduction in the hazard of death in intermediate-risk patients. Being retrospective, their analysis suffers from selection bias - it may be that the frailest patients got lower doses. However, they did include more unfavorable intermediate risk patients, including those treated with adjuvant ADT.

We are now recognizing that unfavorable intermediate risk patients may benefit from adjuvant ADT and higher doses, whereas the favorable intermediate risk patients may not. EORTC 2291 and the Nabid et al. trial established that short term (6 month) ADT markedly improved progression-free survival. Several retrospective studies (like this one and this and this) suggest that the benefit is limited to those with less favorable disease characteristics. It may well be that higher doses are necessary to overcome the radioresistance of high volumes of Gleason pattern 4.

The degree to which RTOG 0126 is irrelevant to contemporary decision-making is heightened by the success of hypofractionated IMRT and SBRT in intermediate risk patients. Both provide much higher biologically effective doses, equal efficacy to conventional IMRT, and about the same toxicity. Also, their cost is lower and patient convenience is higher. Unless a patient has an anatomical abnormality such that dose constraints cannot be met, it is hard to come up with a reason why higher biologically effective doses should not be used.

Note: Thanks to Dr. Howard Sandler for allowing me to see the full text of the study.


Thursday, October 26, 2017

Why did biochemical control not translate into a survival increase after brachy boost therapy?

The first randomized clinical trial to prove that brachy boost (BB) therapy had better oncological outcomes among high risk patients was Sathya et al. (2005). After 5 years, 36% of those high-risk patients who received the brachy boost had a PSA recurrence vs. 66% of those who received external beam radiation (EBRT) only. In an update, the authors report that overall survival was not significantly different in the two groups. This seems to call into question whether PSA recurrence is a useful surrogate endpoint for survival, or if it is, under what circumstances?

Dayes et al. provided a 14-year median update on the original study and added further comments in this "Beyond the Abstract" essay. The 104 patients in the original study who were treated between 1992 and 1997 had the following characteristics and treatments:

  • Median age was 66
  • 60% were high risk, 40% intermediate risk
  • All had a negative pelvic lymph node dissection, negative bone scan and CT
  • Brachy boost (BB) comprised 35 Gy of Ir 192 over 48 hours plus 40 Gy of EBRT in 20 fractions for a total of 75 Gy [sic].
  • EBRT-only compromised 66 Gy delivered in 33 fractions using 2DRT (an outmoded external beam technology).
  • None received androgen deprivation as part of their radiation therapy, nor afterwards unless PSA reached 20 ng/ml.

As of the update on the 104 patients (with only 5 lost to follow-up):

  • Mortality from any cause was 67% among the BB patients, 77% among the EBRT-only patients -- not significantly different
  • Prostate cancer-specific mortality was 18% among the BB patients, 23% among the EBRT-only patients - not significantly different
  • Incidence of metastases was 20% among the BB patients, 28% among the EBRT-only patients - not significantly different
  • Improvement in PSA control was maintained: 47% higher rate of biochemical recurrence-free survival among the BB group

There was a biopsy given 2 years after treatment to 87 of the 104 men in the original study

  • In the BB group, 24% had a positive biopsy and 6% were metastatic
  • In the EBRT-only group, 51% had a positive biopsy and 6% were metastatic

The authors conclude:
Despite ongoing benefit with respect to biochemical disease control, long term follow up out to 2 decades failed to demonstrate improvements in other important outcomes such as development of metastatic disease, deaths from prostate cancer and deaths from any cause. 
Increased biochemical (PSA) control usually translates into increased survival later on. That correlation is well-characterized. So why did it not in this case?

This study, with a sample size of only 104 (51 BB, 53 EBRT-only), was not large enough to detect statistically significant survival differences. We note that directionally there was an improvement in survival even though the difference wasn't big enough for 95% confidence. Also, 40% were intermediate risk patients who are slower to have detectable metastases and are more likely to die of other causes. By contrast, the ASCENDE-RT trial of LDR brachy boost therapy recruited 398 men, 30% were intermediate risk, and may eventually be able to demonstrate overall survival differences with longer follow-up.

We have to acknowledge that the doses delivered in this study were below what is now considered curative, and the findings here are to a large extent irrelevant. I am at a loss to explain how a hot iridium implant could be left in a patient for 48 hrs without doing serious damage or cooking the prostate to a crisp.  Perhaps they used cooler implants back then.  I can only trust that Dr. Sathya is correct in not making a correction for the lack of fractionation, which would be typical. It seems the BB dose was sub-optimal as demonstrated by the fact that in a quarter of men, the cancer was left alive in the prostate. EBRT-only was worse - leaving cancer alive in the prostates of twice as many men. Although they dissected some pelvic lymph nodes that they could find, we now know that even with improved modern lymph node detection methods, we miss 44% of positive lymph nodes (see this link). The 6% who were metastatic might have been caught with some of our new PET scans. So, in both groups, there was a lot of cancer left behind. Many high-risk radiation patients today would have had whole-pelvic radiation and would have had hormone therapy for up to two years. This highlights the importance of expanding the treated area, using escalated doses, and adding systemic therapy when the probability is high that the cancer might have escaped the prostate.

Even though BB wasn't curative for many high risk patients, it is disappointing that death was not delayed by reducing the tumor burden. There are several clinical trials of treating the prostate (with surgery or radiation) even after metastases have been detected, thereby hoping to prolong survival by reducing the load of cancer cells. Metastasis-directed radiation is sometimes given in this hope as well. Both of those therapies decrease PSA, at least temporarily. But only treating PSA serves no purpose if that is the only outcome. If this study is any indication, the cancer will catch up and replace the killed cells with no net survival benefit. I hope that is not the case.

Monday, October 16, 2017

Does Lu-177-PSMA-617 increase survival?

We have enthusiastically reported the encouraging outcomes of the early clinical trials of the radiopharmaceutical Lu-177-PSMA, most recently at this link. Based on reduction in PSA, it performs well. But medicines have no real benefit if all they do is treat PSA. We want medicines that increase survival.

Rahbar et al. reported the outcomes of 104 patients treated with Lu-177-PSMA-617 at University Hospital Muenster, Germany. All patients had metastatic castration-resistant prostate cancer (mCRPC) and had already received docetaxel and at least one of abiraterone or enzalutamide. After the first of an average of 3.5 cycles, they had the following outcomes:
  • 67% of patients had some PSA decline
  • 33% of patients had a PSA decline of at least 50%
  • Median overall survival was 56 weeks (13 months)
The authors conclude:
177Lu-PSMA-617 RLT is a new effective therapeutic and seems to prolong survival in patients with advanced mCRPC pretreated with chemotherapy, abiraterone and/or enzalutamide. 
But is this conclusion justified? It's hard to know without a prospective clinical trial where patients are randomized to receive the radiopharmaceutical or standard-of-care. The best we can do is look at the overall survival from clinical trials involving patients with symptomatic mCRPC. In the "ALSYMPCA" trial of Xofigo, among the subgroup of patients who had received docetaxel for their painful mCRPC (see this link), overall survival was:
  • 14 months with Xofigo
  • 11 months with placebo
The ALSYMPCA trial was conducted before abiraterone and enzalutamide were approved, so it is impossible to know how prior treatment with one of those might have changed survival. There have been a couple of small trials of "third-line" medicines after docetaxel and abiraterone were used.

In a non-randomized trial among 24 mCRPC patients after treatment with docetaxel and abiraterone, overall survival was:
  • 9 months with cabazitaxel
In a Danish study among 24 mCRPC patients after treatment with docetaxel and abiraterone, overall survival was:
  • 5 months with enzalutamide
So these data suggest that Lu-177-PSMA-617 may have prolonged life more than third-line treatment with another taxane or another hormonal agent. However, we expect much cross-resistance between abiraterone and enzalutamide, and resistance building up with prolonged use of taxanes. It is always hazardous to compare patient outcomes or declare success when they have not been randomized. Certainly there is enough suggestive data to warrant a Phase 3 randomized clinical trial.



Thursday, July 6, 2017

First US randomized clinical trial of oligometastasis-directed SBRT

In a recent commentary (see this link), we saw that some clinicians are making unsubstantiated claims of cancer control from treatment of oligometastases (less than 5 detected metastases). Only a randomized clinical trial (RCT) can prove that there is any benefit to such treatment. Johns Hopkins has announced the first such RCT in the US.

Stereotactic body radiation therapy (SBRT) is the treatment of choice because it is precise, as well as convenient for the patient (usually completed in 1-5 treatments). It is important to distinguish between two different situations that may involve oligometastases:
  1. Metastasis-directed SBRT after primary treatment (prostatectomy or prostate radiation) and any local salvage radiation has failed. This is sometimes called "metachronous" treatment of recurrent prostate cancer.
  2. Radiation to the prostate and oligometastases in newly-diagnosed men, or men who are radiation- or surgery-naive but have progressed to castration-resistance.
  3. Radiation to metastases for the purposes of pain palliation, or to prevent fractures or spinal compression.
In addition, the situation may be different depending on whether the oligometastases are in the visceral organs, bones, extra-pelvic lymph nodes, pelvic lymph nodes, or some combination of these.

Phuoc Tran is the lead investigator of the "ORIOLE" RCT (NCT0268058) at Johns Hopkins described at this link. It is a small, Phase 2 trial for men in situation A described above. It has some noteworthy characteristics:
  • 36 men will receive SBRT, 18 men will receive standard-of-care treatment
  • Oligometastases are diagnosed by bone scan and CT
  • Patients will be balanced based on whether initial treatment was surgery or radiation, whether they've had hormone therapy, and whether the PSA doubling time was less than 6 months.
  • The primary outcome will be radiographic or PSA progression (by >25% over nadir and by > 2 ng/ml) after 6 months.
  • To be deemed successful, the treatment will have to reduce this measure of progression by 50%
There are several interesting secondary objectives of this RCT:
  • identification of additional metastases using the DCFPyL PET/CT
  • toxicity of treatment reported by doctors
  • pain palliation reported by patients
  • local control of metastases (see below)
  • Number of circulating tumor cells (CTC)
  • Genomic analysis of CTCs
  • Immune (T cell) response to treatment
  • Time until patients have to start life-long hormone therapy
We will see if the radiation activates a systemic T-cell response that may destroy cancer cells beyond the treated tumors (the abscopal effect).

It may seem odd that detection of fewer than 5 metastases by the DCFPyL PET/CT (developed at Johns Hopkins and now in expanded trials) is not a qualifying criterion. Perhaps they will change that for the Phase 3 trial. Or perhaps they want to prove the concept with a bone scan/CT because it will be several years before that PET scan (so far, the most accurate) is widely available and covered by insurance or Medicare. If it works for bone scan/CT-detected oligometastases, it will certainly work for DCFPyL PET-detected metastases.

Update (August 2017): Dr. Tran has made the following change in protocol:
We did change the criteria recently to allow men who had detectable disease on DCFPyL to enroll on the trial, BUT only if the DCFPyL did not show anything more than what is visible on conventional CT-AP and bone scan.  Our thought was that this would allow some patients of the "future" if you will (as PSMA-targeted imaging will be the SOC in 3-5 years) to be included on the trial, but because we do not allow men on the trial with DCFPyL scans that show us more than what is on conventional , we feel that still holds to original concept. 

It is also important to note what is not an objective of this early clinical trial. The outcome we most want to know is whether SBRT treatment of metastases extends overall survival. This 6-month trial will not tell us that. There is no doubt that local control will be excellent, but stopping the progression of 1-3 metastases does not necessarily mean that the cancer has been slowed down systemically at all. Certainly, PSA will fall as an immediate result of treatment. For those who are used to monitoring PSA as a measure of their cancer's systemic progression, this can be confusing. It's worth taking a moment to recall what serum PSA comes from in detectably metastatic disease. PSA is a protein on the surface of prostate cancer cells (and healthy prostate cells too.) It doesn't leak out into the blood from prostate cancer unless a tumor forms with its own blood supply. Tumor blood supply tends to be leaky, and so PSA is detected in the blood serum. Larger tumors with more blood supply put out more PSA. So irradiating those tumors and shrinking them is likely to eliminate the PSA they put out. But what about the micrometastases that do not yet have appreciable blood vessels? If there are thousands of them, will it matter that serum PSA was reduced for 6 months? No one knows the answer to that question and this Phase 2 study will not provide the answer. I hope they will provide radiographic progression-free survival separate from PSA progression-free survival.

For the answers to our most important questions we will have to look forward to the outcomes of some of the other RCTs that have longer follow-up than 6 months.

  • The CORE RCT (active, no longer recruiting) at Royal Marsden Hospital in London will have 5 years of follow-up (completion in 2024), and will include freedom from widespread metastatic disease and overall survival among the outcomes looked at. 
  • The STOMP RCT at University Hospital in Ghent had 2 years of follow-up looked at time to lifelong hormone therapy as its primary outcome (reviewed here). 
  • The PCX IX RCT (among castration-resistant patients) at Jewish General Hospital in Montreal will have 5 years of follow-up (primary outcome in 2025) and has radiographic progression-free survival as its primary outcome. 
  • The French RCT (recruiting, study completion in 2022) will look at radiographic progression-free survival with follow-up up to 3 years. 
  • The FORCE RCT at the University of Michigan (primary completion in 2022) will compare systemic treatment with ADT and any of Taxotere, Zytiga or Xtandi (at the discretion of the treating physician) to similar systemic treatment plus metastasis-directed SBRT for men with mCRPC who have not yet had any of those advanced systemic therapies. They will evaluate progression-free survival after 18 months. "Progression" is defined as alive and at least a 20% increase (and at least 5 mm net increase) in the size of tumors or any new metastases. They will detect metastases via bone scan/CT, However, they will also test whether PSMA-based PET indicators are as useful in among men with mCRPC as it is in men with newly  recurrent disease.





Monday, May 1, 2017

SBRT Dose Escalation

Is there an optimum treatment dose for SBRT? At the low end of the spectrum, Alan Katz found that 35Gy in 5 fractions gave equivalent oncological outcomes with less toxicity compared to 36.5 Gy. At the other end of the dose spectrum, a clinical trial pushed the dose as high as 50 Gy in 5 fractions with disastrous consequences (see this link).  A trial of high dose rate brachytherapy, which is radiologically similar to SBRT, failed to find an optimum dose.

But radiation safety is not only just about dose. We saw that two treatment schedules using the same prescribed dose (40 Gy in 5 fractions) had disparate toxicity outcomes (see this link). In fact, the 12 month toxicity outcomes of Dr. King's high-risk study were recently presented and look excellent (see this link). It's also worth noting once again the outcomes of the 5-year multi-institutional SBRT clinical trial that used 40 Gy in 5 fractions and had excellent oncological and toxicity outcomes (see this link).

Helou et al. reported the outcomes of their SBRT (they call it SABR, but it's the same thing) trials at the Sunnybrook Health Sciences Centre in Toronto, Canada. There were sequential trials conducted from 2006-2014:

  • 35 Gy/5 fractions/29 days - 82 low risk men only
  • 40 Gy/5 fractions/11 days or 29 days - 177 low and intermediate risk men

A few (12) men had up to 6 months of androgen deprivation to shrink their prostates prior to radiation.

As an early measure of oncological effectiveness, they used PSA at 3 years (PSA3Y) after radiation. After correcting for the other variables like age, baseline PSA, T stage, and ADT use, the dose received remained the biggest predictor of PSA3Y. Median PSA3Y was:

  • 0.64 ng/ml in those who received 35 Gy
  • 0.27 ng/ml in those who received 40 Gy
  • The difference was significant in both low risk men and intermediate risk men

The use of PSA3Y as a surrogate endpoint for biochemical recurrence is controversial. Because prostate cancer progresses very slowly and radiation, at the very least, reduces the cancer burden, it can take at least 5 years, and as long as 10 years, before we start to see concrete evidence that such therapy is curative. Also, a longer time until the nadir is achieved has been found to be correlated with failure-free survival (see this link). Nadir PSA has been proven to be a strong predictor of a lasting cure (see this link), but no one can tell when the nadir will be reached. In a recent study comparing the PSA at 1000 days after SBRT or HDR brachytherapy to the PSA at 1000 days after conventional IMRT, Kishan et al. reported that the PSA was lower for SBRT/HDR-BT. While the downward slope was about the same for the first 1000 days, the slope was steeper afterwards for SBRT/HDR-BT, indicating that a lower nadir would be achieved.

After correcting for confounders like age, baseline urinary function, and time between treatments, late term urinary toxicity of grade 2 or higher was 17 times greater among those who received 40 Gy compared to those who received 35 Gy.

The authors previously reported late term rectal toxicity. After 2 years, the cumulative probability of  grade 2 or higher rectal toxicity was suffered among:

  • 5% of the men who received 35 Gy with 4mm margins
  • 27% of the men who received 40 Gy with 5 mm margins
  • 42% of the men who received 40 Gy with 5 mm margins +  30 Gy to seminal vesicles received 

Grade 3 and 4 rectal toxicity was especially high (10%) in the group that had their seminal vesicles irradiated. There were 3 cases of fistulas that may be attributable to rectal biopsies. [Patients should be very careful about the use of any kind of instrumentation within at least 6 months of radiation. That includes cystoscopies and colonoscopies.] Since this study, the authors have changed their radiation planning to include faster (VMAT) linacs and improved rectal dose constraints. Other changes that might mitigate rectal toxicity may include use of intrafractional tracking, rectal immobilization, and a rectal spacer.

There was clearly a trade-off between SBRT dose and late-term side effects of treatments. Perhaps we will one day be able to identify those cancers that are curable with a lower dose, and treat only those with the more radio-resistant cancers with a higher dose. Some believe that such techniques as simultaneous integrated boosts or heterogeneous planning may cure the cancer in the prostate better with less damage to organs at risk. But they remain to be proved in randomized clinical trials.

Note: Thanks to Dr. Andrew Loblaw for allowing me to review the full text of the study.

Friday, January 13, 2017

Nadir PSA predicts survival after radiation and androgen deprivation for unfavorable risk patients

If a treatment isn't working, we want to know as quickly as possible so we can try a salvage therapy while it can still make a difference. We want a measure of effectiveness, called a surrogate endpoint, that will predict survival, and we usually turn to PSA as our best early indicator. But there are different ways of defining mortality, and different measurements utilizing PSA. In an analysis of a randomized clinical trial (available here), the researchers sought to answer these questions for unfavorable risk patients who were treated with external beam radiation (EBRT) + androgen deprivation (ADT).

The purpose of the randomized clinical trial (NCT00116220) was to determine whether adding 6 months of androgen suppression improved freedom from biochemical failure over radiation therapy alone. This was a secondary analysis of the data. The details of the study were as follows:

  • All patients were "unfavorable risk," defined as PSA between 10 and 40 ng/ml or Gleason score ≥7 or extracapsular extension or seminal vesicle invasion.
  • Men were screened for minimal of no comorbidities.
  • Median age was 72.
  • They all received 70.2 Gy of 3D-CRT at 6 hospitals in the Boston area between 1995 and 2001
  • Half (78 men) got 6 months of ADT with the radiation; half (79 men) had radiation without ADT
  • PSA was evaluated every 3 months for 2 years, every 6 months for 3 years, and then annually.
  • When PSA climbed above 10 ng/ml they received salvage ADT.

In selecting the kind of "mortality" they wanted to use as the gold standard endpoint, the researchers selected "age-adjusted all-cause mortality (ACM)" rather than "prostate cancer-specific mortality." This was a reasonable choice for several reasons:

  • It is often difficult to discern whether  prostate cancer was the final cause of death. Men may die of kidney or liver failure or other final causes that are consequences of their prostate cancer. 
  • Prostate cancer has been found to be associated with other causes of death. 
  • The men in this study were only included if they had no or minimal comorbidities that might contribute to their death. 
  • Men were eventually diagnosed with metastatic castration-resistant prostate cancer, and most had received chemotherapy.
  • The mortality was age-adjusted for actuarial death rates. 
  • Follow-up was long enough (16.5 years, median) so that even slow-killing prostate cancer would be a significant cause of mortality.

They examined 4 PSA-related metrics as potential surrogate endpoints:

  1. PSA failure, defined as nadir + 2.0 ng/ml
  2. PSA nadir > 0.5 ng/ml
  3. PSA doubling time < 9 months
  4. Time to PSA failure < 30 months

They had several criteria for inclusion. Basically, they wanted to find metrics that predicted mortality, and that continued to make a difference in survival time after the effect of the adjuvant ADT no longer extended survival. All but "PSA failure" met their criteria. Of the remaining 3 metrics, PSA nadir > 0.5 ng/ml had the largest effect in explaining survival.

The following table shows the percent of 8-year all-cause mortality for each surrogate endpoint, when it was met and when it wasn't, and the percent of the treatment effect (adjuvant ADT) explained by each metric.



Percent mortality at 8 years
Percent of treatment effect explained by metric
Endpoint achieved:
YES
NO
PSA failure
32.5%
11.8%
NA
PSA nadir > 0.5 ng/ml
47.4%
13.6%
104%
PSA doubling time < 9 mos.
40.7%
14.1%
43%
Time to PSA failure < 30 mos.
39.4%
15.3%
41%

If the PSA nadir was over 0.5 ng/ml, it predicted the biggest difference in mortality. It also explained essentially all of the treatment effect of the added ADT.

Before anyone gets worried that their PSA is over 0.5 ng/ml, we must remember what "nadir" means. Because this analysis was done in hindsight, nadir is the lowest PSA ever achieved after treatment. It was not, in this case, the lowest value achieved so far. It often takes 5 or more years to achieve the nadir after radiation. For those who received adjuvant ADT with their radiation, the nadir will be achieved while they are still on ADT, and the PSA may rise above the nadir as the effect of the ADT wears off.

A nadir of only 0.5 ng/ml among those taking ADT in this clinical trial suggests that the ADT was not working completely. I assume that ADT was begun 2 months before the EBRT, continued during the 2 months of EBRT, and was continued for 2 months after that (6 months total). If the first PSA was taken 3 months after EBRT completion, the effect of the ADT had not worn off yet. Some of the cancer must already have been castration resistant. Patients received a bone scan, but some must have already had metastases that were too small to be detected by it. We see this reflected in how quickly the metric predicted mortality. In as quickly as one year from the start of treatment, mortality was 20% among those who had already reached a nadir, and it was over 0.5 ng/ml vs. 0% in those who hadn't reached it. At year one, the percent who had met the endpoint was negligible for the other endpoints. Clearly, patients with a PSA that never goes down below 0.5 ng/ml after radiation +ADT are at greater risk.

The authors recommend that patients whose PSA never achieves a nadir below 0.5 ng/ml after EBRT plus 6 months of ADT should be recommended for clinical trials of early use of second-line hormonal agents, chemotherapy, and other new therapies. This is a logical implication, but it is not likely to occur very often because standard of care has changed since this clinical trial began.

The DART 01/05 GICOR randomized clinical trial proved that among high risk patients, 28 months of adjuvant ADT was superior to the 6 months of adjuvant ADT that were used in the present study. It is less likely that the nadir will stay above 0.5 ng/ml with the longer course of ADT and with the escalated radiation dose (of about 80 Gy) that is now standard of care. So while a nadir > 0.5 ng/ml in this situation is still an endpoint indicating elevated risk, few patients will be observed to exhibit it.

Saturday, December 31, 2016

Ipilimumab (Yervoy) fails to increase survival, even when used earlier

Ipilimumab (Yervoy) is a type of immunotherapy that is known as a "checkpoint blocker." It blocks a protein in T-cells (called CTLA-4) that tells the immune system to stand down and not attack the cancer cells. It turns off the off-switch. The hope is that immune response against the cancer will continue longer than it ordinarily would.

A previous trial showed that Yervoy did not extend survival when used in men who were metastatic and castration-resistant  (mCRPC) and who had failed chemotherapy. This is often the first group given a new drug because other options have been exhausted and because it takes less time to prove efficacy. Researchers hoped that it might have some effect if used earlier in disease progression. Unfortunately, it did not.

Beer et al. tested Yervoy this time in men who were metastatic and castration-resistant but who had not yet tried chemotherapy and who were asymptomatic or minimally symptomatic (i.e., no bone pain or organ dysfunction). In this multi-institutional study, there were 399 patients who got Yervoy, and 199 who got a placebo. Neither patients nor doctors knew who got which.
  • Patients were given 10 mg/kg of Yervoy or placebo every 3 weeks for up to 4 doses.
  • Therapy was repeated every 3 months thereafter to non-progressing patients
The outcomes were as follows:
  • Median overall survival was 28.7 months for those who got Yervoy vs. 29.7 months for those who got the placebo (no statistically significant difference).
  • Median progression-free survival was 5.6 months or those who got Yervoy vs. 3.8 months for those who got the placebo (a statistically significant difference).
  • 23% had a PSA response with Yervoy vs. 8% with the placebo.
The treatment-related adverse responses were:
  • Death that was treatment-related in 9 patients (2%).
  • Serious or life-threatening immune-related adverse events in 31%
  • Serious or life-threatening diarrhea in 15%
While there was a PSA  response, and an increased time during which more patients taking Yervoy were progression free, this did not translate to a lengthening of overall survival. This may be because there was a subset of patients who had a good initial response, but the response was not sustained. This also shows the difficulty of measuring the response to immunotherapy using PSA or other surrogate endpoint. We know that Provenge, the only approved immunotherapy for prostate cancer, lengthens survival without reducing PSA. Here, the converse is true.

Research continues on other checkpoint blockers. Keytruda has been approved for melanoma, lung cancer and head-and-neck cancer. In addition to Keytruda, there are several investigational immunotherapies targeting the PD-1/PD-L1 antigen. It may turn out that checkpoint blockers work better in combination with other immunotherapies (like Provenge or ProstVac), or perhaps they need to be primed with concurrent SBRT radiotherapy or chemotherapy. We need a better understanding about why an immunotherapy may work very well for one cancer, but very poorly for another cancer, We also can't lose sight of the fact that all  immunotherapies may be lethal. There is clearly much to be learned.

Thursday, September 15, 2016

The first randomized clinical trial comparing active surveillance, surgery and external beam radiation tells us little :-(

This was supposed to be HUGE! The first clinical trial ever where patients were randomly assigned to active surveillance (AS), radical prostatectomy (RP) or external beam radiotherapy (EBRT). The results were published in The New England Journal of Medicine (see this link). They started signing up men in the UK in 1999 and continued recruitment for 10 years. By 2009, they screened over 82,000 men for prostate cancer and found 1,643 men with newly diagnosed localized prostate cancer who were willing to be randomized to initial treatment with AS, RP or EBRT, about a third in each. They then followed them for a median of ten years to see how well they did with each therapy. Imagine the effort involved! Sounds good so far -- what could go wrong?

The bottom line was that all 3 therapies did about the same in preventing death. AS was found to cause higher rates of disease progression and metastases. We will explore why below.

There were several problems that arose.

1. They planned to detect mortality differences, but couldn't.

They thought there would be more deaths in the ten years of follow-up, but almost all the men defied those expectations. That's partly because of all the great new life-prolonging drugs that became available in the 21st century; drugs like docetaxel, Xtandi, Zytiga, and Xofigo. Also, in a clinical trial, patients are very closely diagnosed, treated, and monitored. They get far better care than the average patient in community practice. There were only 17 prostate-cancer related deaths

Men also survived longer because of progress in treating other diseases. But most of all, men lived longer because they frequently visited doctors as part of the study, during which they were  closely monitored for other illnesses. There were only 152 deaths from all other causes, only 9% of the total sample size. Men were 50 to 69 years of age  (62 years median) at the start of the study and were tracked for 10 years. On average, based on US actuarial tables, about 18% should have died from all causes. So the mortality rate was half of what was expected. On the average, men in the UK live two years longer than men in the US - not enough to account for the difference.

No worries. Instead of looking for mortality differences, the researchers had a secondary objective to look for differences in disease progression and rates of metastases. Those are excellent surrogate endpoints. But...

2. The intended treatment wasn't always what patients wound up doing

Although men were randomized to one of the 3 therapies, a lot of the men apparently changed their minds, as was their right. The authors of the study analyzed everything based on the intended treatment at the time they were randomized. This is how they said they would analyze the data, and they stuck with the plan. The switching that occurred was as follows:
  • Of the 545 men randomly assigned to AS,  482 (88%) stayed with it at least for 9 months. The rest decided to have surgery, radiation, no therapy, or dropped out.
  • Of the 553 men randomly assigned to RP, 391 (71%) did have surgery within the first 9 months following randomization. Most of the remainder switched to AS, the rest to radiation or other treatment, and a few chose no treatment or dropped out.
  • Of the 545 men randomly assigned to EBRT, 405 (74%) did have EBRT within the first 9 months following randomization. Most of the remainder switched to AS, the rest to surgery, other treatment, no treatment or dropped out.
  • In all, 22% of the men did not have the therapy they were originally randomized to, yet they are including in the analysis as if they did. It is unknown how this may have skewed the findings.
3. Their AS protocol was nothing like contemporary protocols.

     a. Inclusion criteria were much less restrictive

In contemporary AS protocols, almost all men are in the "low risk" category. "Low Risk" means they are stage T1c or T2a, their Gleason score is 6, and their PSA is less than 10. Some of the more restrictive AS programs, like Johns Hopkins, also include the "Epstein criteria." That means there were no more than 2 positive cores, no more than 50% cancer in any positive cores, and the PSA density must be less than 0.15 ng/ml/g. For the first time this year, NCCN included AS as an option for men with Gleason score 3+4 if no more than half the cores were positive, but only if they were otherwise low risk.

In the ProtecT trial, the only inclusion criterion was that the men had to have localized prostate cancer. See this link for their protocol. This means that they allowed men who were higher stage (T2b and T2c), higher grade (Gleason score ≥ 7), and higher PSA (PSA could be as high as 10-20 ng/ml). In fact, they previously reported that, among the AS cohort:
  • 10% had an initial PSA between 10 and 20 ng/ml
  • 22% had an initial Gleason score≥ 7 (2% were GS 8-10)
  • 25% had a clinical stage of T2 - they do not break that into subcategories, presumably most were T2a
So, many of those higher risk men would have been screened out of a contemporary AS program. The authors did not analyze this higher risk subgroup to tell us how many of the 33 cases of metastases or 112 cases of clinical progression were among them, but they do report (Table 2) that of the 8 prostate-cancer deaths in the AS group, 5 were among men with Gleason score ≥ 7 at diagnosis (vs. 2 each for RP and EBRT). The remaining 3 deaths among those diagnosed as Gleason 6 was similar to the number for RP (3) and EBRT (2). It seems that all extra deaths were attributable to higher Gleason scores in their AS program.

     b. Monitoring of men on AS was below contemporary standards.

In contemporary AS protocols, there is always a confirmatory follow-up biopsy within a year of the first screening biopsy. The repeat biopsy schedule varies from that point on, and may be every year, as it was originally at Johns Hopkins. Some AS protocols utilize mpMRI to search for suspicious areas and only biopsy as suspicion arises, others implement a biopsy schedule that may vary depending on the findings of the last biopsy. Some do TRUS biopsies, some do mpMRI-targeted biopsies, some combine the two, and some do follow-up transperineal template-mapping biopsies. But all good AS programs include follow-up biopsies.

In the ProtecT trial, patients were screened for a high PSA (> 20 ng/ml), emergent symptoms, or a 12-month PSA increase ≥ 50%. So those who had a form of prostate cancer with a low PSA output (such as some of those with predominant Gleason pattern 5) would never be discovered until symptomatic metastases occurred. I don’t know what percent ever got a second biopsy.

We recently saw what happened in Göteborg when there was no pre-determined biopsy schedule: 54 out of 474 men (11%) failed on AS. They used a similar monitoring system as the ProtecT trial: quarterly, and then semi-annual PSA tests, and re-biopsy at the discretion of the doctor.

I sometimes talk to patients who get periodic PSA tests and claim they are on active surveillance. They are putting themselves in danger. Time and again, PSA kinetics have been rejected as a sole indicator of progression for very good reasons, mainly (1) PSA is affected by many non-cancer causes, and (2) some of the most virulent prostate cancer cells put out very little PSA. There is no substitute for confirmatory and follow-up biopsies.

Let's put perspective just how egregious a difference it is when active surveillance does not include follow-up biopsies. Current estimates are that one in three TRUS-guided biopsies (12 through the rectum) will miss a higher grade of cancer. So, if one biopsy failed to detect a higher grade cancer with odds of 33%, then the odds of missing it on two biopsies is (.33) squared, etc. As the following table shows, the odds of missing the higher grade cancer with annual biopsies for ten years is about 1 in a hundred-thousand.







Biopsy
Odds of missing higher grade in ALL the biopsies
1st
33%
2nd
11%
3rd
4%
4th
1%
5th
0.4%
6th
0.1%
7th
0.04%
8th
0.01%
9th
0.005%
10th
0.001%

Now, at Johns Hopkins, for example, it was their active surveillance policy to have annual biopsies, and they used the Epstein criteria discussed above. After 15 years of follow-up, the metastasis-free survival rate was 99.4%. Laurence Klotz at Sunnybrook in Toronto has the longest running trial of active surveillance in North America. They allowed some patients as high as favorable intermediate risk, and while there was always a confirmatory biopsy in the first year, their biopsy schedule was not as rigorous as Johns Hopkins. After 20 years, of follow-up, they report metastasis-free survival of 97.2%. In the ProtecT trial, there were 33 men out of the 545 men in the AS cohort - 6.1% had already been diagnosed with metastases after only 10 years of follow-up. The outcomes of the AS cohort are very out-of-line compared to active surveillance programs that have more rigorous selection criteria and monitoring protocols.


Selection criteria
Biopsy schedule
Active Surveillance Program
Follow-up
Metastasis-free survival
Strictest:
Epstein protocol
Annual
Johns Hopkins
15 years
99.4%
Less strict:
favorable risk only
Confirmatory and periodic thereafter
Sunnybrook
20 years
97.2%
Any localized regardless of PSA or grade

none

ProtecT

10 years

93.9%

4. Their EBRT protocol was below today's standards.

In the years prior to 1999 when they were planning this study, there were very different radiation therapies in place than have now become standard of care. This is a problem with all long-term clinical trials involving radiation technology. By the time we get the results, they are irrelevant because the technology and understanding has progressed so much. For an expanded discussion of this issue, see this link.

They used an older technology (3D-CRT) to deliver only 74 Gy in 37 treatments while adding 3-6 months of hormone therapy before and during treatment. Now, with IGRT/IMRT technology, the patients would safely receive about 80 Gy. Low and favorable risk patients probably do not benefit from adjuvant ADT -- it adds sexual side effects without adding to cancer control in most of them. Some have questioned whether the increase is justified for low or intermediate risk patients (see this link), but, as we saw, 10 years is not long enough to judge that, and there is no consequence to the higher dose in terms of side effects. It is entirely possible that the low dose they gave patients only delayed progression but did not cure the cancer.  If that is true, we may see the EBRT outcomes deteriorate when they present their planned 15-year follow-up.

ProtecT was a vast and expensive undertaking. It will probably never be repeated, and there isn't likely to ever be a US equivalent. Sadly, we can't learn very much from their current analysis of this major study, although it may yield more fruit with some subsequent analyses.