They randomly assigned 1,792 men with a recurrence after prostatectomy in 2008-2015 at 460 locations in the US, Canada, and Israel to one of 3 therapies:
- PBRT + STADT
- ADT consisted of 4-6 months of a combination of an anti-androgen and an LHRH agonist starting 2 months before salvage radiation.
- Radiation dose to the prostate was 64.8-70.2 Gy at 1.8 Gy per fraction.
- Radiation dose to the pelvic lymph nodes was 45 Gy at 1.8 Gy per fraction.
- The treated pelvic lymph node area was per RTOG guidelines and did not include the recently recommended expansion.
- 5-year freedom from progression (biochemical or clinical) was 89% for sWPRT+STADT, 83% for PBRT+STADT, and 72% for PBRT (all significantly different). They used a nadir+2 definition of biochemical progression because it correlated best with clinical progression.
- 8-year incidence of metastases was 25 for sWPRT+STADT (HR=0.52), 38 for PBRT+STADT (HR=0.64), and 45 for PBRT (sWPRT+STADT was significantly better than the other two)
The reported toxicity results were:
- GI grade 2 or higher: 7% for sWPRT+STADT vs. 2% for PBRT
- Bone marrow grade 2 or higher: 5% for sWPRT+STADT vs. 2% for PBRT
- Bone marrow grade 3: 2.6% for sWPRT+STADT vs. 0.5% for PBRT
- Late term bone marrow grade 2 or higher was 4% for sWPRT+STADT
There were some caveats. The researchers found that the benefit of salvage whole pelvic treatment and ADT was not maintained in men with very low PSA. There are further analyses expected based on patient risk characteristics and genomic biomarkers. We previously saw in a retrospective study that prostatectomy Gleason score had a significant influence. With better PET scans now, we can have more assurance that whole pelvic radiation is necessary. But at very low PSA (<0.2), even our best PET scans may not find the cancer. Also, it may be that long-term ADT may improve results even further, and that dose escalation may improve results. While this changes the standard of care for many men with persistent PSA and recurrences after prostatectomy, the patient and his radiation oncologist still must rely on judgment.