This was the subject of a retrospective analysis by Gandaglia et al. They examined the records of 525 post-prostatectomy patients treated with SRT at six international institutions between 1996 and 2009. Inclusion criteria were:
- Undetectable PSA (<0.1 ng/ml) after prostatectomy
- Biochemical recurrence - two consecutive PSA rises above 0.1 ng/ml
- PSA mostly ranged from 0.2 to 0.9 ng/ml (median 0.4) at the time of SRT
- No detected lymph node metastases
- Similar in age, initial (pre-op) PSA, and Gleason score
- More likely to be stage T3b/4
- Less likely to have positive margins
- Received higher SRT dose (70 Gy vs 66 Gy)
- Only those with a 10-year probability of distant metastases greater than 1 in 3 benefited from the addition of ADT
- The benefit grew exponentially with increasing risk
- Adjuvant ADT only benefited those with higher PSA (≥0.4 ng/ml), Gleason score 8-10, stage T3b/4.
- Higher SRT dose and whole pelvic SRT improved outcomes independently of whether adjuvant ADT was used.
The authors conclude that a higher radiation dose alone may be sufficient to treat many patients with a recurrence detected early enough, but for those with aggressive tumor characteristics, adjuvant ADT will improve outcomes measurably. While this was not proved with a randomized trial, it does suggest that adjuvant ADT will not be necessary in all cases of SRT. Patients who are undecided may wish to have a Decipher genomic classifier done on their prostate tissue to determine their 10-year risk of metastases.