Showing posts with label Lu-177. Show all posts
Showing posts with label Lu-177. Show all posts

Friday, April 30, 2021

First clinical trial of Lu-177-PSMA-617 in recurrent, hormone-sensitive men

While we expect only a few months of extra survival from the VISION trial of Lu-177-PSMA-617 in heavily pretreated, metastatic, castration-resistant men (see this link), we hope to get more out of the radiopharmaceutical if used earlier. Privé et al. reported the results of a pilot trial in 10 recurrent men treated with Lu-177-PSMA-617 at Radboud University in Nijmegen, The Netherlands. They were all:

  • Recurrent after prostatectomy ± salvage radiation (PSA>0.2 ng/ml) 
  • Rapid PSA doubling time (< 6 months)
  • Between 1-10 metastases detectable on a PSMA PET scan or USPIO MRI
  • At least 1 metastasis > 1 cm.
  • Unable to receive SBRT to metastases 
  • No visceral metastases 
  • Have not begun salvage ADT
  • Treated with a low dose (3 GBq) on day 1; second treatment (~6 GBq) after 8 weeks (compared to dose in VISION trial of 7.4 GBq in each of 4-6 cycles)

After 24 weeks of follow-up after Cycle 2:

  • 5 patients had PSA reduced by >50% (1 undetectable)
  • 2 patients had stable PSA
  • 3 patients had PSA progression
  • 6 patients had a radiographic response
  • 4 patients had radiographic progression
  • ADT-deferred survival was 9.5 months (median)
  • Those with lymph node only metastases had the best response
  • Those with any bone metastases had lesser response
After 2nd dose, comparing their 24-week PSA to their 12-week PSA:

  • PSA was continuing to decline in 3 patients
  • PSA was rising again in 6 patients

Side effects were mild (no grade 3) and transient:

  • fatigue in 7; nausea in 3
  • dry mouth (xerostomia) in 2

There are lots more questions than answers:
  • Would a higher dose and more treatments be more effective?
  • Would a higher dose and more treatments be more toxic?
  • Is it like Xofigo in that it's more effective with micrometatases? If so, would a combination with SBRT targeted at the larger metastases be more effective?
  • Since it was more effective on lymph nodes, would it make a good combination with Xofigo for patients who have both lymph node and bone metastases? (See also Th-227-PSMA)
  • Because there seems to be a continued abscopal effect for some patients, would combining it with Provenge be optimal?
  • Would pretreatment with ADT or a new anti-androgen (Xtandi, Erleada or Nubeqa) increase expression of PSMA, and increase radiosensitivity?
  • Can we predict who will benefit?
  • Use in other patient populations remains to be explored: high-risk, newly diagnosed metastatic, castration-resistant but chemo-naive. Optimal sequencing with other therapies remains to be explored.






Tuesday, August 11, 2020

PSMA-targeted radiopharmaceutical clinical trials in the US

Now that the VISION trial of Lu-177-PSMA-617 is no longer recruiting, some patients are wondering if they can still get PSMA-targeted radiopharmaceuticals in the US, without traveling to Germany, Australia, India, etc. Here is a list of trials that are active, still open to recruitment, or will soon be recruiting. 

Unless otherwise noted, they are all for men who are: 

  • metastatic
  • castration-resistant 
  • have had at least one taxane chemotherapy
  • at least one of the advanced androgen receptor therapies (e.g., Zytiga, Xtandi, Erleada, or Nubeqa)
  • no Xofigo
  • PSMA-avid on a PSMA PET/CT scan

Radiopharmaceutical

Adjuvant drugs

Extra criteria

Recruitment status/ contact

Locations

Lu-177-rhPSMA-10.1


±previous chemo

Not yet recruiting (begins June 30, 20220


Lu-177-PSMA-I&T


Chemo naïve, failed one hormonal

recruiting

• 21 locations

Ac-225-PSMA-I&T



Recruiting

• Houston

Lu-177-PSMA-617

 

Chemo and immunotherapy naïve, failed one hormonal

Recruiting

(Phase 3 RCT)

• 19 US sites

Lu-177-PSMA-617


mHSPC

(M1 or N1)

Treatment naive

Recruiting

• 52 US sites

Lu-177-PSMA-617

Keytruda

No chemo since castration resistant

active, not recruiting

UCSF

Lu-177-CTT1403

 

No Jevtana

active, not recruiting

UCSF

Lu-177-PSMA-617

 

 

Active, not recruiting

•Weill Cornell

•Tulane

Th-227-Antibody

(see article)

 

 

active, not recruiting

• Royal Marsden (UK)

• Finland

• Tulane

• MSK

• Omaha, NE

Lu-177-J591

Ketoconazole

Prior RP or RT

CRPC

Non-metastatic

active, not recruiting

• Weill Cornell

• USC

• Georgetown

• IU

• U of Iowa

• UPMC

Lu-177-PSMA-R2

 

 

Active, not recruiting

• Stanford

• Yale

• Tulane

• Johns Hopkins

• Mt Sinai

• MD Anderson

• U of Wisconsin

• Phoenix

Ac-225-J591

 

 

recruiting

• Weill Cornell

• Brooklyn Methodist

Ac-225-J591 + Lu-177-PSMA- I&T

 

 

recruiting

• Weill Cornell

• Brooklyn Methodist

Ac-225-J591

Keytruda

No chemo since castration resistant

recruiting

• Weill Cornell

• Brooklyn Methodist

• Dana Farber

• Columbia

Cu-67-SAR-bisPSMA

 

Previous chemo OK, not required

recruiting

• Johns Hopkins

•Mayo Rochester

•Mayo, AZ

•Tulane, N.O.

•Barnes Jewish, St. Louis

•Omaha, NE

•Weill Cornell

Lu-177-PSMA-617

(VISION)

 

 

Active, not recruiting

• 84 locations

Results expected August 2020

I-131-1095-MIPS

(see article)

Xtandi

Chemo naïve

Failed Zytiga

Active, not recruiting

• 17 locations

Results expected December 2021


Sunday, May 31, 2020

Lu-177-PSMA-617 vs Jevtana (cabazitaxel): which should I do next?

We saw recently (see this link) that of chemo and hormonal medicines for metastatic castration-resistant prostate cancer (mCRPC), Jevtana (cabazitaxel) is the preferred third treatment after Taxotere (docetaxel) and Zytiga (abiraterone) or Xtandi (enzalutamide). But when should radiopharmaceuticals, either approved ones like Xofigo (Ra-223), or prospective ones like Lu-177-PSMA-617, be used in the optimal sequencing?

Michael Hofman reported the results of the TheraP randomized clinical trial (RCT). They randomized some well-selected patients to receive either Lu-177-PSMA-617 or Jevtana. Patients were selected according to the following criteria;
  • mCRPC (PSA≥20 ng/ml and rising)
  • must have had docetaxel
  • must have had either Zytiga or Xtandi or both
  • healthy, with good liver, kidney, and blood function
In addition, all patients received both an FDG PET scan and a PSMA PET scan. They were excluded from the trial if either:
  • Their metastases were insufficiently PSMA-avid - (10% excluded)
  • There were many metastases that showed up on FDG but not on PSMA PET scans (as described here) - (18% excluded)
  • 85 patients were treated with Jevtana
  • 98 patients were treated with Lu-177-PSMA-617

The endpoint used was the percent of patients whose PSA declined by at least 50% (PSA50) from baseline after the treatment. After a median follow-up of 13 months:
  • Lu-177-PSMA-617 had a PSA50 of 66% vs 37% for Jevtana
  • The percent who had PSA progression was 31% less in those getting Lu-177-PSMA-617 relative to those getting Jevtana
  • At 12 months, progression-free survival was 19% for Lu-177-PSMA-617 vs 3% for Jevtana
  • Pain improvement was better for Lu-177-PSMA-617 (60%) than Jevtana (43%)
  • It is too early for data on overall survival
  • Serious/life-threatening adverse events occurred in 33% of those taking Lu-177-PSMA-617 vs. 53% of those taking Jevtana
  • The most common adverse events reported by those taking Lu-177-PSMA-617 were fatigue, pain, nausea, dry mouth/eyes, low platelets, and anemia. Only 1 patient discontinued for toxicity.
  • The most common adverse events reported by those taking Jevtana were fatigue, pain, diarrhea, nausea, loss of taste, neuropathy, dry mouth, and neutropenia, 3 patients discontinued for toxicity
Given the comparatively low toxicity, it seems like Lu-177-PSMA-617 should usually be the preferred third treatment, over Jevtana, although longer follow-up will be needed to see if there will be a survival difference.

This study further highlights the importance of getting both an FDG and a PSMA  PET scan at about the same time.

PSMA expression is highly variable. It is not expressed in low-grade cancer in the prostate. Expression increases as metastases develop, reach a peak, and then decreases. PSMA expression also increases when second-line hormonals are first used, but then decreases with continued use. Given this variation over time and treatment, several questions about PSMA-targeted therapy remain unanswered:
  • Should it be used soon after second-line hormonals?
  • Should it be used before or soon after docetaxel?
  • Would the problem of heterogeneity be minimized if Jevtana and Lu-177-PSMA were given simultaneously?
  • Should it be used in minimally metastatic patients?
  • Should it be used in newly diagnosed metastatic patients?
  • Should it be used with immunotherapies (e.g., Provenge, Checkpoint inhibitors)?
  • Will PARP inhibitors enhance the cell-kill rate?
  • Is PSA the best biomarker of effectiveness?
  • What are the best radionuclides to use (e.g., Ac-225, Th-227)?
  • What are the best/most specific ligands to use? (e.g., PSMA-617, PSMA-I&T)
  • Are there better surface proteins to target, perhaps simultaneously (e.g., FAPI)
  • How do they compare to PSMA BiTE therapies?
  • How does it compare to Xofigo for bone metastases?

Sunday, December 15, 2019

Why Lutetium-177-PSMA treatment sometimes may not help, and may even harm

(updated)

Lu-177-PSMA usually improves survival

We've seen in a couple of small trials in Germany and Australia that Lu-177-PSMA seemed to provide better than expected survival. In Germany, median overall survival was 12.9 months across 104 patients. In Australia, median overall survival was 13.3 months across 50 treated patients. In both trials, all or almost all patients had already received taxane chemotherapy and either enzalutamide or abiraterone. There was no control group in either trial, so we can only guess at what overall survival would have been without the therapy.

In the "ALSYMPCA" trial of Xofigo, among the subgroup of patients who had received docetaxel for their painful mCRPC (see this link),  median overall survival was 14.4 months with Xofigo vs. 11.3 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.

In a recent trial of Jevtana as a third-line therapy, after docetaxel and either abiraterone or enzalutamide, median overall survival was 13.6 months for Jevtana vs. 11.6 months for the other second-line hormonal. 

So, in heavily pre-treated patients, Lu-177-PSMA seems to improve survival about as well as Xofigo or Jevtana when used as a third-line therapy. The VISION trial  found that LuPSMA treatment increases survival by 5 months in heavily treated patients (similar to Xofigo).

PSA is not always a good indicator of effectiveness, as has been found for Xofigo and Provenge. Lu-177-PSMA reduced PSA in about 2/3 of treated patients in most studies. That leaves about 1/3 of patients who derived no benefit (even though they had PSMA-avid tumors), and waterfall plots showed that a few patients had large increases in PSA following PSMA-targeted therapy.

It is worth noting that the PSMA protein contributes to the survival of the cancer, and just the PSMA ligand that attaches to it has some activity in delaying progression, even without a radioactive component (similar to the way an anti-androgen attaches to the androgen receptor, delaying progression). It is also worth noting that ADT initially increases PSMA expression, but decreases its expression with continued use.

The opportunities are:
  • to select patients who are likely to benefit
  • give alternative therapies (like Jevtana) to patients who are unlikely to benefit
  • provide adjuvant therapies that may increase survival

PSMA avidity - optimal point in time

It has long been known that PSMA is a moving target. The advent of PSMA PET scans has enabled us to track PSMA expression. Cancers that express a lot of PSMA (called PSMA-avid tumors) can be distinguished from cancers that express very little. Radiologists determine avidity by comparing the uptake of the tracer in cells that express PSMA to the uptake of the tracer in cells known to not express PSMA. Early low-grade prostate cancer does not express PSMA at all. Higher grade prostate cancer may express some PSMA. PSMA expression really starts to take off when the cancer metastasizes, although it is highly variable between patients. About 90-95% of metastatic men express at least some PSMA on their prostate cancer cells. At some point, however, as genomic breakdown continues, PSMA is no longer expressed by metastases. Thus, there is an optimal point for treating each patient with PSMA-targeted therapy. Treatment too early or too late, may exert selective pressure on the predominant non-PSMA-types, allowing them to take over.

Michael Hofman and others at the Peter MacCallum Cancer Center in Melbourne (see this presentation and this link) have initiated several clinical trials using Lu-177-PSMA at earlier stages of disease progression:

  • #lutectomy trial (Declan Murphy,  PI) is treating PSMA-avid high-risk patients with Lu-177-PSMA, followed by prostatectomy and pelvic lymph node dissection
  • #upfrontPSMA (Arun Asad, PI) is treating patients first diagnosed with high volume metastases with Lu-177-PSMA + ADT + docetaxel vs ADT + docetaxel.

Other opportunities for early use include Lu-177-PSMA treatment for those in the following settings:
  • active surveillance
  • persistent PSA after prostatectomy
  • salvage treatment after first recurrence
  • salvage treatment after second recurrence
  • metastatic CRPC before docetaxel or advanced hormonal therapies
  • non-metastastic (on bone scan/CT) CRPC before docetaxel or advanced hormonal therapies

Centers in Germany may be willing to treat patients per protocol (i.e., outside of a clinical trial) in some of those situations.

Repopulation

In radiobiology, one of the ways in which radiation can fail to destroy cancer is called repopulation. It means that when radiation kills some cancer cells but leaves many behind, the remaining ones now have access to space in which to expand and access to nutrients and oxygen that the other cancer cells had deprived them of. Paradoxically, the tumor can then grow faster than it ever would have before the treatment. This is sometimes seen with rapidly growing tumors, as some head and neck cancers. They sometimes irradiate those cancers multiple times a day to prevent repopulation.

Repopulation is never seen with X-ray (or proton) treatment of relatively slow-growing prostate cancers. X-rays penetrate throughout the prostate and kill all the cancer there. If there is any survival of an oxygen-deprived tumor core, it will be killed by the next fraction of X-rays in a day or two. However, Lu-177 emits beta rays that may only penetrate to about 125 cells around each target. Ac-225 (also sometimes used in PSMA therapy) only kills about 8 cells around each target. With such short-range killing, there is a real danger of repopulation if there are insufficient PSMA targets within the tumor. Multiple treatments are usually not given for several weeks, and the tumors may have changed by then.

PSMA heterogeneity

What we have learned recently is that not only does PSMA expression change over time, but in a given patient, some tumors may express PSMA and some may not. Moreover, even within a single tumor, some cells may express PSMA and some may not.

Paschalis et al. looked at the degree of PSMA expression of 60 patients with metastatic castration-resistant prostate cancer (mCRPC). They also looked at tissue samples of 38 of them taken when they were diagnosed with hormone-sensitive prostate cancer (HSPC). To detect the amount of PSMA expressed, they used an antibody stain that attaches to the part of the PSMA protein that lies above the cellular membrane. They rated the tumors "0" if there was no PSMA up to "300" if all cells expressed PSMA. They also performed a genomic analysis, looking for mutations in over 100 genes associated with DNA-repair defects.

Among the tumor samples from men with HSPC they found:
  • 42% of the 38 men with HSPC  had no PSMA at diagnosis - it only emerged later
  • 5 of the 6 HSPC men diagnosed with Gleason score 6 or 7 had little or no PSMA expression at that time
  • About half of 30 HSPC men diagnosed with Gleason score 8-10 had little or no PSMA expression at that time
  • Those who expressed PSMA had a worse prognosis
  • Expression of PSMA varied greatly (heterogeneous) between patients
  • Expression of PSMA varied greatly between biopsy samples from the same patient
  • The higher the PSMA expression in a patient, the greater the amount of PSMA heterogeneity
Among the tumor samples from the 60 men with mCRPC they found:
  • PSMA expression had increased from when they were diagnosed with HSPC
  • Half of the tumors with no PSMA at HSPC diagnosis continued to have no PSMA
  • 73% expressed PSMA; 27% did not - only 1 of whom had neuroendocrine prostate cancer
  • 84% of those expressing PSMA exhibited marked PSMA heterogeneity
  • Heterogeneous patterns were identified:
    • PSMA positive and negative cells interspersed in a single area
    • PSMA-positive islands in a sea of PSMA-negative cells
    • PSMA-positive regions separated by >2 mm from PSMA-negative regions
    • Some metastases wholly PSMA-positive, some wholly PSMA-negative in the same patient
  • Bone and lymph node metastases had similar PSMA expression; liver metastases (none neuroendocrine) had lower PSMA expression
Analysis of DNA-repair defects revealed:

  • mCRPC patients with DNA-repair defects had higher PSMA expression
  • HSPC patients without DNA-repair defects were less likely to become PSMA-positive
  • Patients treated with PARP inhibitors were more likely to respond if they were PSMA-positive
  • For validation, in a separate sample of tumors, those with DNA-repair defects were found to have much higher PSMA expression than those without such defects. This was especially true for somatic mutations in BRCA2, ATM, and dMMR.
  • PSMA was downregulated in androgen-independent basal cancer cells (resistant to advanced anti-androgens) and neuroendocrine cells.

The significance of this study is that it may explain why about a third of PSMA-avid patients do not respond to Lu-177-PSMA therapy. The emitted beta particles may kill cells within about 125 cells from where they are attached at the PSMA site. Thus cells that do not express PSMA that are more than 2 mm from a PSMA-avid site will not be killed (see "Repopulation" above).

The authors hypothesize that DNA-damage repair defects cause PSMA to proliferate. If they are right, a PARP inhibitor (like olaparib), which has also been found to be effective when there are DNA-repair defects (see this link), may be able to increase the efficacy of PSMA treatment. This is the subject of an ongoing clinical trial.

Practical detection of heterogeneity/ clinical trials

Now that we know that heterogeneity can impact Lu-177-PSMA effectiveness, it behooves us to find a way of determining the degree of heterogeneity without doing a biopsy of every single metastatic site. One way is to give each patient two PET scans, so they could see the sites that exhibited PSMA expression as well as the sites that exhibited high uptake on an FDG PET scan.

It is futile to offer PSMA-targeted therapy if there are many sites that show up only on an FDG PET scan but few sites that display uptake of PSMA. It also may be futile to treat patients that show some sites where PSMA and FDG sites do not overlap - "discordant." On the other hand, where there is a high degree of overlap between FDG and PSMA - "concordant" - the PSMA radiotherapy will kill both cancers simultaneously. Of course, the ideal candidate would display only highly PSMA-avid sites.  Thang et al. reported on the survival of 30 patients who were treated with Lu-177-PSMA (who were either high PSMA/low FDG or concordant, compared to 16 patients who were excluded based on lack of PSMA (8 patients) or a high degree of discordant sites (8 patients). All patients were heavily pretreated.

  • Treated patients survived 13.3 months (median)
  • Untreated patients survived 2.5 months (median)
(update 12/2020) Michalski et al. looked at 54 patients. Some had at least one tumor that was positive on FDG, but negative on PSMA (FDG+/ PSMA-). They compared outcomes to patients that had only PSMA+ tumors. They found:
  • A third of patients had at least one FDG+/PSMA- tumor
  • Overall survival was FDG+/PSMA- patients was 6 months
  • Overall survival for PSMA+only patients was 16 months
(update 2/16/22) A secondary analysis of the TheraP trial of Jevtana vs LuPSMA looked at patient response depending on whether their cancer showed up also on FDG PET scans. They looked at the percent of men whose PSA reduced by 50% or more (PSA50) in the cohort that received cabazitaxel vs the cohort that received Lu177PSMA. Each cohort was analyzed according to whether they were highly avid on a PSMA PET scan (SUVmean≥10) "high PSMA" and whether their metabolic tumor volume on an FDG scan was greater than 200ml (MTV≥200) "high FDG". They required high PSMA (SUVmax≥20), and excluded men who were FDG+ and PSMA-.

  • In men with high PSMA, the PSA50 was 91% for Lu177PSMA vs 47% for cabazitaxel
    • Among men with high PSMA, the odds ratio of responding to Lu177PSMA was 12.2 vs 2.2 for cabazitaxel 
  • In men with low PSMA, the PSA50 was 52% for Lu177PSMA vs 32% for cabazitaxel
  • In men with high FDG, the PSA50 was 57% for Lu177PSMA vs 20% for cabazitaxel
    • Among men with a high FDG, the odds ratio of any response to either treatment was 0.44
  • In men with low FDG, the PSA50 was 70% for Lu177PSMA vs 44% for cabazitaxel

It is unknown whether the survival of untreated patients might be longer or shorter had they received treatment. It is possible that discordant patients may benefit from sequenced (before or after) or concomitant treatment with:
It is possible that such adjuvant treatment may decrease the population of discordant sites, and minimize repopulation effects.

Based on this new knowledge, it is recommended that patients who are good candidates for Lu-177-PSMA therapy have both a PSMA PET/CT scan and an FDG PET/CT at around the same time. FDG PET scans are generally covered by insurance; PSMA PET scans are not covered by insurance yet.

Thursday, October 11, 2018

I-131-MIP-1095 has entered a phase 2 randomized clinical trial

As I reported last year, a new radiopharmaceutical has entered the pack. I-131-MIP-1095, a powerful beta-particle emitter attached to a PSMA-targeted ligand, will enter a multicenter phase 2 randomized clinical trial. Progenics®, the manufacturer, put out a press release, which can be read here. (Update 4/2020) The clinical trial has begun recruiting in 17 locations in the US and Canada.

They will be testing a combination of I-131-MIP-1095 with enzalutamide (Xtandi) in patients who are metastatic, castration resistant, have not yet had chemotherapy, and who have become resistant to Zytiga. It is hoped that Xtandi will radiosensitize the cancer to the radiopharmaceutical with a resultant PSA decrease.

175 evaluable patients will be recruited; half will get the radiopharmaceutical + Xtandi, half will get Xtandi alone. All patients will be screened using DCFPyL PET/CT to assure that their metastases are PSMA-avid. The primary endpoint - the percent who have greater than 50% PSA reduction - will be collected for a year. Secondary endpoints - radiographic response, progression-free survival, and overall survival - will be reported at the end of two years.

Another radiopharmaceutical in clinical trials is Lu-177-PSMA-617 .  There are various phase 1 and 2 clinical trials in the US and internationally (see list at the end of this link).

I recently reported about the very promising outcomes of Ac-225-PSMA-617 in Germany. Patients report that they are combining Ac-225-PSMA-617 and Lu-177-PSMA-617 to get the advantages of each. Weill Cornell in NYC is investigating Ac-225-J591 in a phase 1 trial.

For information on the trial of Th-227-PSMA, see this link.

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.