The Cancer of the Prostate Risk Assessment (CAPRA) in patients treated with external beam radiation therapy: evaluation and optimization in patients at higher risk of relapse

Background: The Cancer of the Prostate Risk Assessment (CAPRA) was developed to predict freedom from biochemical failure (FFBF) following radical prostatectomy (RP). Its utility following external beam radiation therapy (EBRT) has not been externally evaluated.

Methods: A retrospective study of 612 patients treated with dose-escalated EBRT at the University of Michigan Medical Center.

Results: Compared to the derivation cohort, EBRT treated patients had higher-risk disease (28% with CAPRA of 6-10 vs. 5%, respectively). A total of 114 patients (19%) had BF with 5-year BF ranging from 7% with CAPRA 0-3 to 35% with CAPRA 7-10. For RT patients the risk of BF at 5-year was similar to 4 surgical cohorts for CAPRA scores 0-2 but lower for all CAPRA scores ≥ 3. The difference favoring RT increased with increasing CAPRA score reaching a 27-50% absolute improved at 5-years for CAPRA scores of 6-10. On multivariate analysis each CAPRA point increased the risk of BF (p<0.0001) while Gleason pattern 5 in the biopsy also increased BF (p=0.01) and long-term androgen deprivation therapy (ADT) significantly reduced the risk of BF (p=0.015).

Conclusions: Compared to surgical series the risk of BF was lower with dose-escalated EBRT with the greatest difference at the highest CAPRA scores.