Let’s begin with a shared understanding of the definitions of some commonly used terms and abbreviations:
- Adverse pathology means that the post-op pathology report indicates that cancer was found in one or more of the following places:
- Outside of the prostate capsule (pathological stage T3a), or
- In the seminal vesicles (pathological stage T3b), or
- Locally, but at a distance from the prostate (pathological stage T4), or
- At the surgical margin, where the surgeon has cut through the cancer — a “positive surgical margin” (PSM).
- Adjuvant radiation therapy (aRT) means radiation given after prostatectomy when there is adverse pathology, but before the PSA becomes detectable.
- Salvage radiation therapy (sRT) means radiation given after prostatectomy but also only after a biochemical recurrence (BCR).
- Early salvage radiation therapy (early sRT) means radiation given after the point that aRT would be given, but before sRT would be given.
- Wait-and-see is the strategy of waiting until after a BCR to decide what to do. The wait-and-see decision may be sRT at any time after BCR, or the patient may decide to forgo radiation, use hormone therapy, or do nothing until there is evidence of clinical progression.
- Biochemical recurrence (BCR) post-surgery is now defined as a confirmed PSA ≥ 0.2 ng/ml. This was chosen in 2007 because it was the most frequently used threshold in published studies. When those studies began, a PSA of 0.1 ng/ml was as low as could reliably be measured. Anything below that was undetectable at the time, and 0.2 ng/ml was arbitrarily deemed a biochemical recurrence.
- An ultrasensitive PSA (uPSA) test is any PSA test that can reliably detect PSAs below 0.1 ng/ml. While the definition of biochemical recurrence has not been changed, detectable levels of PSA are now as low as 0.001 ng/ml on some commercially available ultrasensitive tests.
Why start sooner than sRT/wait-and-see, but later than aRT?
Three major randomized clinical trials have shown that there is an oncological advantage to aRT over a wait-and-see strategy in patients with adverse pathology after prostatectomy. This is hardly surprising, especially because “wait-and-see” includes patients who never even received salvage radiation, or may have only received palliative hormone therapy. There has never yet been a randomized clinical trial comparing aRT to sRT.
Based on those studies, both the American Urological Association (AUA) and the American Society of Radiation Oncologists (ASTRO) endorse aRT in their guidelines. However, in spite of those guidelines, only 43 percent of men who get radiation after prostatectomy do so within the first 6 months of their surgery (see Sheets et al.). Why aren’t more patients choosing aRT?
Patients (and many doctors too) worry about over-treatment, and the adverse effects of radiation on recently cut tissues. Immediate aRT may represent over-treatment for many men for whom small, detectable amounts of PSA are leaked into the serum from benign tissue left behind by surgery, or men in whom any tiny amounts of malignant tissue left behind may be indolent or susceptible to scavenging by the immune system. Kang et al.found that, among men with capsular perforation, PSMs, or seminal vesicle invasion after surgery, only 17 percent actually went on to have a true biochemical recurrence. The other advantage to waiting is that it may allow for better recovery of continence and erectile function after surgery in at least some patients.
All three of those above-mentioned clinical trials accrued participants before uPSA tests became routinely available. Although the use of uPSA testing is controversial, its widespread use has led many patients and clinicians to wonder whether waiting for some low PSA value – “early salvage radiation” – might be equivalent in outcomes to aRT.
There are randomized clinical trials underway in Canada and the UK, in Australia and New Zealand, and in France to determine whether early sRT might be equivalent to aRT in terms of survival. The combined results of those trials may have sufficient power to answer the question. Those findings will be definitive, but in the meantime two groups of researchers have retrospectively analyzed their patient outcomes for clues.
Ultrasensitive PSA reliably predicts eventual biochemical recurrence (a UCLA study)
Researchers at the University of California, Los Angeles (UCLA) looked at available evidence that the uPSA test might afford radiation oncologists the opportunity to treat patients late enough that they are assured to be on a path to clinical recurrence, yet early enough that waiting for treatment does no oncological harm. Kang et al. conducted a retrospective analysis of data from 247 patients treated at UCLA between 1991 and 2013 who were found on post-op pathology to have adverse disease characteristics — stage pT3-4 disease and/or positive surgical margins — and who received uPSA tests. That cohort had the following characteristics:
- Positive margins in 79 percent of patients
- Patients were excluded if
- They had already received radiation and/or hormone therapy, or
- They were found to be node-positive at the time of surgery
- Pathological stage T3/T4 in 55 percent of patients
- Gleason score ≥ 7 in 81 percent of patients
- Initial, pre-surgical PSA ≥ 10 in 29 percent of patients
- Time to first post-op PSA, 3 months
- Median number of PSAs post-surgery and before subsequent treatment, 4
- Median follow-up, 44 months
Kang et al. found that a uPSA ≥ 0.03 ng/ml was the optimal threshold value for predicting biochemical recurrence (BCR). Other findings included:
- uPSA ≥ 0.03 ng/ml was the most important and reliable predictor of BCR. It predicted all relapses (no false negatives: no one was under-treated), and hardly ever predicted relapses incorrectly. Only 2 percent would be over-treated by waiting for this cut-off.
- It was especially prognostic if found on the first uPSA test after surgery.
- Even if the first uPSA test was undetectable, any subsequent test where uPSA ≥ 0.03 ng/ml predicted BCR.
- Other lesser predictors of recurrence were pathologic Gleason grade, pathologic T stage, initial PSA before surgery, and surgical margin status.
- At 5 years of follow-up, 46 percent of patients had a BCR using the “standard” PSA ≥ 0.2 definition, 76 percent using the PSA ≥ 0.03 definition.
- Treating when an ultrasensitive PSA level reached 0.03 ng/ml gave a median lead time advantage of 18 months over waiting until PSA reached 0.2 ng/ml.
- It was necessary to monitor PSA for at least 5 years post-op, and to test at least every 6 months.
What is not known at this time is whether there is a survival disadvantage from waiting until uPSA reaches 0.03 ng/ml if it is not at that level immediately after surgery. (update 10/2018) Kang et al. report that there is indeed a survival advantage from treating if the first uPSA level (at 3 months after surgery) reaches 0.03 ng/ml. So the lead-time advantage actually translates to a survival advantage for men with adverse pathology who have a persistent uPSA of at least 0.03 ng/ml.
If the findings of this study by Kang et al. are confirmed by randomized clinical trials, there is certainly a strong argument that all patients with adverse post-op characteristics should be monitored routinely using ultrasensitive PSA tests, and offered treatment with salvage radiation when their PSA level reaches 0.03 ng/ml. It is also arguable that the definition of biochemical recurrence after prostatectomy should then be changed to 0.03 ng/ml, which would be more practical.
Ultrasensitive PSA can reliably predict eventual biochemical recurrence at 2 months after surgery (a Czech study)
A Czech study (Vesely et al. and updated here) looked at a group of 116 patients (205 updated) who had PSMs after surgery. Unlike the UCLA study, staging was not a selection criterion. The two studies’ goals were somewhat different. While the UCLA study didn’t start uPSA testing until 3 months after prostatectomy, in this study uPSA testing was begun at 2 weeks post-surgery. Most urologists wait for 3 months because surgery sheds a lot of PSA into the serum, and it takes a while for that excess to clear out. The goal in this study was to find out just how early in time after prostatectomy they could detect a uPSA prognostic for BCR, whereas the UCLA study sought to find out how late in uPSA progression they could detect a PSA prognostic for progression. The Czech cohort had the following characteristics:
- Only patients with PSMs were included
- Patients who received aRT or hormone therapy were excluded
- Pathological stage T3/T4 in 54 percent of patients
- Gleason score ≥ 7 in 51 percent of patients
- Initial, pre-surgical PSA ≥ 9.2 in 50 percent of patients
- Time to first post-op PSA, 14 days
All patients’ PSA levels were measured on days 14, 30, 60, 90, and 180 post-surgery, and at 3-month intervals thereafter; the median follow-up was 31 months.
Vesely et al. found that the uPSA on day 30 had predictive accuracy of 74 percent for recurrence, and reached a maximum of 84 percent by day 60, when the uPSA was 0.04 ng/ml (increases in accuracy afterwards were not statistically significant). The following table summarizes their findings:
- Applying the uPSA cut-off at day 60 as the indicator for sRT would result in the decrease of over-treatment from 53 to 4 percent. Of the 33 percent who would be under-treated, 86 percent would eventually be discovered at subsequent follow-up at 3 months, and 98 percent by 4 years.
- uPSA at day 14 was not prognostic for recurrence.
- The following were not predictors of recurrence in men with PSMs: pathologic Gleason grade, pathologic T stage, initial PSA before surgery.
- Neither the location nor the extent of PSMs had any significant impact on the frequency of BCR.
- At 5 years of follow-up, 47 percent of patients had a BCR using the “standard” PSA ≥ 0.2 definition.
The main conclusion of this study is that uPSA tracking can begin earlier. Even as early as 30 days post-op, uPSA has good accuracy for predicting BCR in men with PSMs, and at 60 days, the accuracy is even better. If duplicated in larger studies, this implies that uPSA testing ought to begin 1 or 2 months earlier than it usually does at present.
The predictive accuracy of this study is somewhat lower than the UCLA study, perhaps in part because the sample size was half as big. The results in terms of uPSA prognostic threshold values, however, are surprisingly similar. Here, the threshold was 0.04, 0.01, and 0.02 ng/ml at 2, 3, and 6 months, respectively. In the UCLA study, the threshold was 0.03 ng/ml at any time from 3 months onward. Because the uPSA ≥ 0.03 at 90 days and onwards was 100 percent predictive of BCR in the UCLA study, and led to almost no under-treatment, it may well obviate the need for earlier uPSA testing advocated in the Vesely et al. study.
As in the UCLA study, however, it is not yet known whether early sRT translates to a survival advantage over waiting for BCR.
For the first time, these studies give the patient and doctor new insight into the timing and use of uPSA to predict BCR. If confirmed, setting a uPSA threshold at about 0.03 ng/ml would reduce over-treatment compared to aRT, and would reduce under-treatment compared to sRT. We await the completion of three randomized clinical trials before we have more reliable data.