Monday, April 30, 2018

First randomized clinical trial of SBRT

In the first trial ever to randomly assign patients to extreme hypofractionation, primary radiation therapy delivered in just 7 treatments had the same effectiveness and safety as 39 treatments.

The top-line results of the HYPO-RT-PC randomized clinical trial were presented at a meeting of the European Society for Radiotherapy and Oncology (ESTRO). There was an earlier report on toxicity. Details of the trial specs are available here. Between 2005 and 2015, they enrolled 1200 intermediate- and high-risk patients at 12 centers in Sweden and Denmark to receive either:
  1. Conventional fractionation: 78 Gy in 39 fractions
  2. SBRT (stereotactic body radiation therapy): 42.7 Gy in 7 fractions
The biologically effective dose is 19% higher for SBRT in terms of cancer control. The biologically effective doses are equivalent in terms of toxicity.

The patients were all intermediate to high risk, defined as:
  1. Stage T1c-T3a
  2. PSA> 10 ng/ml 
  3. Gleason score ≥7
80% of the men were treated with a technology called three-dimensional conformal radiation therapy (3D-CRT), which is seldom used for prostate cancer external beam therapy anymore at major tertiary care centers. It is never used for SBRT in the US because it is considered not precise enough, and too toxic. SBRT is usually delivered in 4 or 5 fractions in the US. CyberKnife and VMAT are the most common technologies in use, and use of sophisticated image guidance throughout each treatment is a common practice.

With follow-up of 1,180 patients for 5 years, they report biochemical recurrence-free survival of 84% in both arms of the study.

They also reported updated late-toxicity results. By 6 years after treatment:
  • Grade 2+ urinary toxicity was 3.5% for conventional fractionation, 2.5% for SBRT - no significant difference.
  • Grade 2+ rectal toxicity was 2.3% for conventional fractionation, 1.2% for SBRT - no significant difference.
Up until now, we've only had reports from clinical trials using SBRT (like this one) or conventional fractionation (like this one), and it could have been reasonably argued that SBRT results looked good because of selection bias. With this study, we now have Level 1 evidence of non-inferiority. This will not be surprising to those of us who have followed the randomized clinical trials of moderately hypofractionation vs. conventional fractionation (see this link). This will be hailed as a victory for patients who no longer have to endure and pay the high cost of 8 weeks of treatments. radiation oncologists, who are reimbursed by the number of treatments they deliver, probably will not be as thrilled.

Tuesday, March 27, 2018

Should perineural invasion influence active surveillance and radiation treatment options?

Perineural invasion (PNI) is a risk factor detected on a biopsy in 15%-38% of men with a prostate cancer diagnosis. It means that the pathologist saw nerves infiltrated with cancer cells. As they grow, tumors cause nerves to innervate them. The cancer infiltrates in and around small nerves that connect to nerve bundles (ganglia) outside the prostate, becoming a route of metastatic spread (see this link).  The data on whether it is independently prognostic for T3 stage after surgery are equivocal, although PNI is often the mechanism for extracapsular extension.  After considering Gleason score, PSA, stage, and tumor volume, PNI does not seem to add much to the risk of recurrence after surgery. PNI is not associated with higher surgical margin rates, and it is not considered sufficient to preclude nerve-sparing surgery. An open question is whether it raises risk enough to warrant more aggressive radiation options, like brachy-boost therapy, whole-pelvic radiation and long-term adjuvant ADT.

Peng et al. retrospectively examined the records of 888 men who were treated with external beam radiation at Johns Hopkins from 1993 to 2007. 21% of them had biopsy-detected PNI. Compared to men with no PNI, those with PNI had:

  • lower 10-year biochemical failure-free survival (40% vs 58%)
  • lower 10-year metastasis-free survival (80% vs 89%)
  • lower 10-year prostate cancer-specific survival (91% vs 96%)
  • similar 10-year overall survival (68% vs 78%)

It isn't surprising that PNI is associated with higher risk, but does it add any new information not already captured by Gleason score, stage, and PSA (i.e., the NCCN criteria for risk stratification)? After correcting for those other risk factors, PNI was still found to be associated with lower rates of biochemical failure-free survival, but not of metastasis-free survival, prostate cancer specific survival or overall survival.

PNI independently predicted for lower biochemical failure-free survival in low-risk and high-risk patients, but not for intermediate-risk patients.  Although it is a relatively rare finding among low-risk patients, when found, PNI also predicted for lower prostate cancer-specific survival. Biochemical failure in low-risk men with PNI differed according to whether they received adjuvant ADT or not:

  • 33% in men not treated with ADT
  • 8% in men treated with ADT

An earlier analysis of 651 men treated at the University of Michigan similarly found an association between PNI and biochemical failure-free survival, freedom from metastases, prostate cancer-specific survival, but not overall survival at 7 years after radiation treatment. They also found a more marked effect among high-risk patients. A meta-analysis of 5 studies among men who received EBRT found that PNI increased the risk of biochemical recurrence by 70%.

Although PNI may increase the risk associated with an unfavorable intermediate-risk or high-risk diagnosis markedly, brachy boost therapy is the best treatment for any such patient regardless of PNI, according to our best retrospective study and prospective studies like ASCENDE-RT. However, while adjuvant ADT may be optional for them ordinarily, this study suggests that adding ADT may be beneficial for these patients. Low and intermediate-risk patients with PNI who opt for conventional IMRT may also benefit from the addition of short-term ADT.

Biopsy-detected PNI may have implications for active surveillance. Cohn et al. detected PNI in only 8.5% of 165 men selected for active surveillance. Within 6 months, they were given a confirmatory biopsy. AS was excluded at the confirmatory biopsy due to higher Gleason grade in 57% of men with PNI vs. 13% of men without PNI. PNI should not automatically exclude active surveillance, but it should be recognized as a risk factor in the decision. It would be interesting to know if there is an association between PNI and genomic risk (based on Oncotype Dx, Prolaris, or Decipher tests). It has yet to be determined whether PNI is still a significant risk factor after NCCN risk category, % core involvement, and genomic risk have been accounted for.

It is worth noting that PNI is not always reported on biopsy cores by pathologists, and there is no uniform method for quantifying it. Whether nerve infiltration is small or large, or outside or inside the nerve sheath, it is just reported as PNI, if it is reported at all. It will be difficult to include PNI as part of any risk stratification system until its reporting has been standardized.

Note: Thanks to Daniel Song for allowing me to see the full text of the study.

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, March 15, 2018

Bounces after Primary Radiation Therapy

Perhaps the single most annoying "side effect" of radiation is not a side effect at all; it's the periodic fluctuations in PSA, called "bounces," that can occur for years after therapy. A new analysis from Memorial Sloan Kettering assures us that our anxiety is misplaced -- PSA bounces predict better cancer control.

Romesser et al. reported on a retrospective study among 776 patients treated from 1990 to 2010 with dose-escalated external beam radiation therapy. The median radiation dose was 81Gy. None received adjuvant ADT. They defined a bounce as a PSA rise ≥ 0.2 ng/ml but less than 2.0 ng/ml above the lowest level (nadir) it had reached thus far, followed by a decrease to as low or lower than the previous nadir. After a median follow-up of 9.2 years, they found:

  • 16% of patients had a bounce
  • The bounce occurred after a median of 24.6 months
  • It was a median of 0.37 ng/ml over the previous nadir

Bounces were more likely to occur in patients who:

  • were younger (see this link)
  • had a lower Gleason score
  • were lower  T stage
  • received a higher radiation dose

At 8-years follow-up, they reported that bounces were associated with:

  • Greater time to reach ultimate PSA nadir (43 months vs 26 months) 
  • Lower risk of PSA relapse (9% vs 29%)
  • Decreased risk of metastases (1% vs 10%)
  • Decreased prostate-specific mortality (0% vs 3%)
  • Decreased overall mortality (6% vs 11%)

Very similar findings have been reported for other forms of radiation: SBRT, Low Dose Rate Brachytherapy (seeds), High Dose Rate Brachytherapy, and Brachy Boost Therapy. A 2004 study of EBRT and bounces found an inverse correlation between bounces and PSA relapse-free survival. The difference is probably attributable to much lower radiation dose (only 1% received > 78 Gy) and because the higher risk men were treated between 1986 to 1995, mostly before PSA testing became prevalent.

The percent of men who experience a bounce ranges from 15%-50%, and depends on how the researchers define a bounce. It ranges from a minimum of  0.1- 0.8 ng/ml above previous nadir in most studies. Bounces are often above +1 ng/ml, may last for more than a year, and are usually noted between 1 year and 4 years after therapy.

The reason that bounces occur is a bit of a mystery. There are various theories:

  • Prostatitis - either pre-existing, arising after invasive procedures (e.g., biopsy, fiducial placement, or brachytherapy), or induced by radiation.
  • Immune infiltration: after radiation releases cancer antigens, T cells are activated to eventually attack the remaining cancer in the prostate (see this link).
  • Cancer cells that have been dormant, eventually emerge and undergo "mitotic catastrophe."
  • Delayed apoptosis (cell death) among late-responding healthy cells
  • PSA drops most sharply and consistently in more aggressive cancers because radiation kills the most rapidly dividing cells first.
  • PSA measurement variation (e.g., different test kits, different labs, natural fluctuations)

Whatever the reason, bounces are a good thing. For patients that were diagnosed with low or intermediate risk prostate cancer, a slow, bouncy PSA decline should engender a feeling of relief rather than anxiety. But what of the unfavorable risk patient with bounces so high that they approach or exceed +2.0 ng/ml and stay elevated? While recurrences usually occur later than bounces, is there a method available for early detection of a local recurrence? Biopsies are invasive and non-informative while the cancer is still in the "slow death" phase. However, there is a kind of MRI called MR Spectroscopy (MRS) that may be able to non-invasively distinguish between bounces and PSA recurrence. In a pilot study (and this one), the researchers found that the MRS-detected choline/citrate ratio might be markedly elevated and focal if the cancer is metabolically active, but low and diffuse if there is only benign inflammatory activity.

Thursday, March 8, 2018

Brachy boost therapy and surgery extend survival about the same in high risk patients, but brachy boost does more

Two retrospective studies were published in the last week, and they had some similar findings, but some dissimilar things to say about which treatment is best for high risk prostate cancer. The three therapies they looked at were the combination of brachytherapy and external beam radiation (brachy boost therapy - BBT), external beam therapy alone (EBRT), and surgery (RP).

Kishan et al. reported on 1,809 men with Gleason score of 9 or 10 who were treated between 2000 and 2013 at 12 tertiary cancer care institutions (UCLA, Los Angeles VA, California Endocurie Therapy Center, Fox Chase, Mt. Sinai, Cleveland Clinic, Wheeling Jesuit University, University of Michigan, Johns Hopkins, Oslo University, William Beaumont Hospital, and Dana-Farber).

Patient characteristics:
  • 639 were treated with radical prostatectomy (RP).
  • 734 were treated with EBRT only.
  • 436 were treated with BBT (BT was either low dose rate in 62% or high dose rate in 38%).
  • All patients were Gleason 9 or 10 on biopsy.
  • Pelvic LN involvement was discovered in 17% of RP patients ; 40% had positive surgical margins.
  • RP patients were younger (61 years of age) compared to EBRT or BBT patients (68 years of age)
  • RP patients were lower stage ( 87% clinical stage T1/T2) compared to EBRT (70% clinical stage T1/T2 ) or BBT patients (79% clinical stage T1/T2)
  • RP patients had lower pre-therapy PSA (7 ng/ml) compared to EBRT or BBT patients (10 ng/ml)
  • RP patients had lower percentage of Gleason score 10 (4%) compared to EBRT (6%) or BBT patients (9%)
Treatment specs
  • Among the RP patients, 43% had adjuvant or salvage radiation therapy (68 Gy).
  • Among radiation patients, about 90% had adjuvant ADT
  • Median dose of EBRT was 74 Gy.
    • adjuvant ADT continued for 22 months, median.
  • Median equivalent dose of EBRT+BT was 92 Gy
    • adjuvant ADT continued for 12 months.
Oncological outcomes

After a median follow-up of 4.2, 5.1 and 6.3 years for RP, EBRT, and BBT, respectively, the oncological outcomes (adjusted for age and disease characteristics) were as follows:
  • The 10-year rates of distant metastases were
    • 46% for RP 
    • 44% for EBRT
    • 13% for BBT
    • Differences between BBT and the two others were statistically significant.

  • The 10-year rates of prostate cancer-specific mortality (PCSM) were
    • 23% for RP
    • 26% for EBRT
    • 13% for EBRT + BT
    • Differences between BBT and the two others were statistically significant.

  • The 10-year rates of all-cause mortality (ACM) were
    • 32% for RP
    • 39% for EBRT
    • 31% for BBT
    • None of the differences were statistically significant.
    • There was a difference at 7.5 years in favor of BBT that vanished by 10 years.
In additional analyses, the authors looked at outcomes by duration of androgen deprivation for those receiving any kind of radiation. They found that ADT duration made no significant difference in detected metastases or PCSM within EBRT or BBT, and did not account for the difference between them. They also looked at radiation doses. EBRT patients who received <70 Gy had PCSM significantly worse than those who received ≥ 78 Gy. The rates of metastases did not differ. Notably, very few (11%) of the EBRT patients had both ≥ 78 Gy and ≥2 years of ADT, a combination that is now considered standard of care. Those that did had superior outcomes compared to RP. The use of LDR-BT or HDR-BT as part of BBT made no difference.

The authors conclude:
Among patients with Gleason score 9-10 prostate cancer, treatment with EBRT+BT with androgen deprivation therapy was associated with significantly better prostate cancer–specific mortality and longer time to distant metastasis compared with EBRT with androgen deprivation therapy or with RP.

In an analysis of the National Cancer Database, Ennis et al. reported on the overall survival of patients who were treated with RP, EBRT, and BBT for high-risk PC from 2004 to 2013. The database covers about 70% of all new prostate cancer patients treated in the US. The patient profile was:

  • 24,688 patients treated with RP, at least at first
  • 15,435 patients treated with EBRT
  • 2,642 patients treated with BBT.
  • All EBRT patients also had adjuvant ADT
  • BBT patients may or may not have had ADT
  • All were high risk by the NCCN definition: Either Gleason score 8-10, stage T3/4, or PSA≥20 ng/ml
  • RP patients were younger (62 years of age) compared to EBRT (70 years of age) or BBT patients (67 years of age)
  • RP patients were lower stage ( 89% clinical stage T1/T2) compared to EBRT (84% clinical stage T1/T2 ) or BBT patients (85% clinical stage T1/T2)
  • RP patients had lower pre-therapy mean PSA (19 ng/ml) compared to EBRT (23 ng/ml) but the same as BBT patients (19 ng/ml)
  • RP patients had lower percentage of Gleason score 8-10 (70%) compared to EBRT (78%) or BBT patients (73%)
  • Comorbidities were similar among groups.
  • The above risk factors as well as socioeconomic factors and year of diagnosis were used to adjust the raw data.
  • It is unknown what percent of RP patients had adjuvant or salvage radiation.
  • There was no data available on post-reatment metastases or prostate cancer-specific survival
Because surgery is sometimes aborted when pelvic LN cancer is discovered, they estimated the probability that patients had positive nodes, and included it as a risk factor. This would seem to double count those risk factors, but the authors say it had little effect. Based on their model, they estimated that the percent who had positive nodes was 10% of RP patients, 34% of EBRT patients, and 23% of BBT patients.

After a median follow-up of 36 months, the relative oncological outcomes (adjusted for age and other patient and disease characteristics), expressed as hazard ratios were as follows:

  • RP: 1.0
  • EBRT: 1.53 (i.e., 53% worse survival vs. RP)
    • EBRT with < 79.2 Gy: 1.68
    • EBRT with ≥79.2 Gy: 1.33
  • BBT: 1.17 (not significantly different from RP)
    • not different if ADT included
    • no interaction between comorbidities and treatment effects
The authors conclude:
This analysis showed no statistical difference in survival between patients treated with RP versus EBRT plus brachytherapy with or without AD. EBRT plus AD was associated with lower survival. 
In an accompanying editorial, Ronald Chen discusses the problem of drawing conclusions about comparative effectiveness from this kind of registry data in the absence of clinical trial data. He points out that patient selection criteria are not completely reflected in comorbidity data. He believes that those who are selected for EBRT are just less healthy than those who can undergo anesthesia for surgery or brachytherapy. Other unmeasured confounders include burden of disease, and patient and physician preferences.

The two studies had similar conclusions, but tell us different things. They both found no effect of treatment on overall survival. Lest one walk away thinking it then doesn't matter, the experience of living with painful, crippling metastases and the experience of dying from prostate cancer are horrific in themselves. In the Kishan study among top institutions, there is greater confidence than in many studies that deaths due to prostate cancer could be distinguished from death from other causes. Still, overall survival is impaired in patients with cancer, even if the cancer itself isn't the ultimate cause of death.

Although several randomized clinical trials (RCTs) have demonstrated significant improvements in progression-free survival from BBT compared to EBRT, none have yet demonstrated improvements in overall survival. We saw this recently in the 2005 Sathya RCT. But the prostate cancer-specific mortality advantage of BBT has been confirmed in another study. In a recent analysis of the SEER database, PCSM was 40% higher among patients who had EBRT compared to those who had BBT.

Other than the lack of metastasis data and PCSM in the NCDB, there were other important differences between the two studies. In the Ennis study, only 25%-35% were gleason 9 or 10, whereas all were in the Kishan study. Other differences included the lack of comorbidity data in the Kishan study, and the lack of adjuvant/salvage radiation data in the Ennis study.

Prostate cancer-specific mortality rates were cut in half by BBT, and metastases were only a fraction compared to the other treatments. While this does not prove causality (only a randomized clinical trial can do that), it is highly suggestive that escalated dose can provide lasting cures. There may be good reasons why some high risk patients may have to forgo brachy boost therapy in favor of high dose EBRT or RP with adjuvant EBRT, but for most, brachy boost therapy will probably be the best choice. Patients who are treated with EBRT only, should receive a radiation dose of at least 79.2 Gy and two years of adjuvant ADT.

Sadly, a recent analysis of the National Cancer Database showed that utilization of brachy boost therapy for high risk patients has declined precipitously from 28% in 2004 to 11% in 2013. If a patient sees anyone other than the first urologist, he often only sees a single radiation oncologist who only informs him about IMRT. In most parts of the US, there is a dearth of experienced brachytherapists.

- with thanks to Amar Kishan for allowing me to see the full text.

Sunday, March 4, 2018

Erectile Function after SBRT

Erectile function after radiation is of great interest to many men trying to decide between surgery and radiation, and to decide among the several radiation treatment options. Dess et al. reported the outcomes of men who received stereotactic body radiation therapy (SBRT), often known by the brand name CyberKnife.

Between 2008 and 2013, 273 patients with localized prostate cancer were treated at Georgetown University. All patients filled out the EPIC questionnaire at baseline, which includes several questions on erectile function. The authors focused on the question asking whether erections were firm enough for intercourse, irrespective of whether they used ED meds. A similar questionnaire, SHIM, was also used, but results were similar. Answers were tracked over time with analyses at 2 years and at 5 years. Importantly, the median age at baseline was 69 years. At 2 years:
  • About half the men had functional erections at baseline
  • Among those with functional erections at baseline, 57% retained potency
  • The largest loss occurred by 3 months after treatment, with about 2/3 retaining potency at 3 months
  • 2/3 retained potency at 3 months regardless of age
  • Men under 65 suffered no further loss of potency, even after 5 years
  • Men 65 and over continued to lose potency
    • About half retained potency at 2 years
    • About 40% retained potency at 5 years
The authors also looked at other causes of erectile dysfunction, including partner status, BMI, diabetes, cardiovascular disease,  depression, baseline testosterone levels, and baseline use of ED meds. None of those, except BMI, had a statistically significant effect in this patient population at 2 years post treatment.  Some gained importance by 5 years, but because they are age dependent, and also affect baseline ED, none except BMI were independently important after baseline function and age were accounted for. A few known risk factors for ED were not included: medications (e.g., beta blockers, testosterone supplementation, etc.), smoking, and substance abuse. Some of that data was collected and may be included in a subsequent analysis.

There is a source of statistical error called colinearity, which arises when 2 variables, like baseline potency and age, are substantially interlinked. Although they were independently associated with erectile function, there is considerable overlap, especially when patient age was over the median (69). It may be useful to separate the effect of one from the other. This is accomplished by using age-adjusted baseline erectile function in the same way that economists look at inflation-adjusted GNP. I hope the authors will look at this. As we saw, an analysis of brachytherapy utilizing a different technique showed that half of the loss of potency among men who had brachytherapy was due to aging.

The effect of age on potency preservation cannot be overemphasized. Undoubtedly, radiation can cause fibrosis in the penile artery, and fibrosis is worse in older men. But, contrary to a prevalent myth, those radiation effects occur very early. Following that early decline, the declines in potency are primarily attributable to the normal effects of aging (which include occlusion of the vasculature supplying the penis.) As we've seen in other studies, most of the radiation-induced ED will show up within the first two years, and probably within 9 months of treatment. This was shown for 3D-CRT in the  ProtecT clinical trial,  for brachytherapy, for SBRT, and for EBRT.

Looking at other reports of potency preservation following SBRT, the Georgetown experience (57% potency preservation) seems to be on the low end. There has only been one report of lower potency preservation: 40% at 3 years among 32 patients. An earlier report from Georgetown reported 2-year potency preservation at 79% at 24 months. Dr. Dess explained that the earlier report included men with lower potency at baseline. However, because baseline potency is highly associated with post-treatment potency, the outcomes should be in the other direction. The discrepant data are puzzling. At 38 months post treatment, Bernetich et al. reported potency preservation in 94% among 48 treated patients. Friedland et al.  reported 2-year potency preservation at 82%. Katz reported potency preservation of 87% at 18 months. Although, different patient groups may respond differently, it is difficult to understand why potency preservation was so much lower in the current study. These discrepancies argue for a more standardized approach to analyzing erectile function after treatment, and the present study makes a good start towards that goal.

Compared to other radiation therapies, SBRT fares well. Evans et al. looked at SBRT at Georgetown and two 21st Century Oncology locations and compared it to low dose rate brachytherapy (LDR-BT) and IMRT as reported in the PROSTQA study. At 2 years, among patients who had good sexual function at baseline, EPIC scores declined by 14 points for SBRT, 21 points for IMRT, and 24 points for LDR-BT( the minimum clinically detectable change on that measure is 10-12 points). There has been only one randomized trial comparing extreme hypofractionation to moderate hypofractionation. In that Scandinavian trial, they used an older technique called 3D-CRT, which would never be used today to deliver extreme hypofractionation (at least I hope not!). In spite of the outmoded technology, sexual side effects of of the two treatments were not different. In an analysis from Johnson et al. comparing SBRT and hypofractionated IMRT, the percent of patients reporting minimally detectable differences in sexual function scores was statistically indistinguishable in spite of the SBRT patients being 5 years older.

Dess et al. also looked at sexual aid utilization in a separate study on the effect of SBRT. They found:

  • 37% were already using sexual aids at baseline
  • 51% were using sexual aids at 2 years
  • 55% were using sexual aids at 5 years
  • 89% of users say they were helped by them at baseline, 2 years and 5 years
  • 86% used PDE5 inhibitors only (i.e., Viagra, Cialis, Levitra or Stendra)
  • 14% combined a PDE5 inhibitor with other sexual aids (e.g., Trimix, MUSE, or a vacuum pump)

Erectile function is well-preserved following SBRT, and seems to be as good or better than after IMRT, moderately hypofractionated IMRT, or LDR brachytherapy. Based on reports of a protective effect of a PDE5 inhibitor, patients should discuss their use with their radiation oncologist starting 3 days before radiation and continuing for 6 months after. High levels of exercise and frequent masturbation may have protective effects as well.

With thanks to Daniel Spratt and Robert Dess for allowing me to see the full texts of their studies

Saturday, February 24, 2018

A PSMA-based PET scan can change salvage radiation treatment decisions

The new PSMA-based PET scans provide a way to locate exactly where the cancer has spread to after an unsuccessful prostatectomy. Formerly, the only tools we had were scans that could only detect very large or rapidly growing tumors at PSAs well above the levels most radiation oncologists would be comfortable treating with salvage radiation; that is, there is widespread agreement that success rates improve the lower the PSA is when SRT is used. Even the newly approved Axumin PET scan only detects cancer in 38% of patients if their PSA is in the range of 0.5-1.0 ng/ml. By contrast, as we saw recently, the Ga-68-PSMA-11 PET scan has detected cancer in half of men when their PSA was still below 0.2, and in about two-thirds of men whose PSA was 0.2 - 0.4. The PSMA-based PET scan has the power to change SRT treatment decisions.

Calais et al. reported the results of a multi-institutional study of the Ga-68-PSMA-11 PET/CT in 270 men with biochemically recurrent prostate cancer after prostatectomy while their PSAs were still below 1.0 ng/ml (median 0.44). The institutions comprised UCLA, Technical University of Munich, Ludwig-Maximillian University of Munich, and University of Essen. Patients received PET scans from 2013-2017. Researchers painstakingly mapped all sites of cancer to find the locations of cancer that would have been missed if they had just blindly treated the prostate bed and/or the pelvic lymph node field recommended by RTOG guidelines.

The following table shows how treatment decisions might change based on their findings.

So, all in all, about half of treatment decisions might change - 30% in a minor way, 19% in a major way. The major changes would be: 
  • forgoing SRT entirely in up to 12%
    • consider metastasis-directed radiation in 8% - a treatment of unknown significance
  • changing from prostate bed-only to whole pelvic SRT in 11%, so as to potentially render curative what would have been a non-curative treatment
  • expanding the pelvic treatment field in 7%, so as to potentially render curative what would have been a non-curative treatment
At the above institutions, extended pelvic lymph node dissection (ePLND) is common practice - 81% of patients had a PLND. Consequently, 20% of patients already had detected pelvic LNs (N1) before the scan. At many institutions in the US where ePLND is less common in intermediate and high risk patients, this can cause a much larger and potentially curative change in the treatment plan from prostate bed-only to whole pelvic radiation. The researchers are to be congratulated for the painstaking work in contouring and comparing so many pelvic scans.

As one might expect, PSMA-based cancer detection was higher for those with Gleason score more than 7, and those with pathological stage N1 and T3. The patient's PSA at the time of the scan played a major role. While almost two-thirds had a PSA ≤ 0.5 ng/ml, the detection rate was 41% for those patients vs. 60% for those with higher PSAs. While detection improves with higher PSA, it is important for patients to understand that it is unwarranted (and potentially unsafe) to wait for PSA to rise just so that more cancer can be detected. That would be a self-fulfilling prophecy: by waiting for the cancer to put out more PSA, one is virtually ensuring that the cancer will grow, spread, and possible metastasize. Although we await definitive clinical trial data, most radiation oncologists recommend early treatment (before PSA reaches 0.2 ng/ml) for men with adverse pathology or for those evincing a distinct pattern of PSA progression after prostatectomy.

While a previous analysis showed that the Ga-68-PSMA PET had little effect on SRT decisions, and no patients were upgraded from incurable to potentially curable, this larger, more detailed study indicates that about 1 in 5 patients can be upgraded, and 1 in 6 can be spared SRT. This would seem to justify the cost. UCLA charges $2650 for recurrent (and high risk) patients. NIH is recruiting recurrent and high risk patients for an improved PSMA-based PET scan (called DCFPyL) that  is free (and transportation to Washington D.C. is covered as well).