Post-Prostatectomy Radiotherapy in a Single Tertiary Institution: Outcomes Relating to Pre-Radiotherapy Prostate Specific Antigen

Objective: Timing of post-radical prostatectomy (RP) radiotherapy (RT) in patients with high risk prostate cancer continues to be debated. This is a retrospective review aiming to evaluate the influence of pre-RT prostate specific antigen (PSA) values on postprostatectomy RT outcomes in one Australian center. Method: Eligible patients were treated at the Royal Adelaide Hospital between January 2004 and December 2013, excluding those with nodal or distant metastatic disease pre-RT, or those who received neoadjuvant androgen deprivation therapy pre-RT. The primary endpoint of biochemical failure-free survival (bFFS) was defined as time from RP to date of biochemical failure (bF). Covariates of Gleason score, post-RP PSA, and pre-RT PSA were further analysed in relation to bFFS. Results: 103 of 122 patients underwent final analysis (8 were excluded for the above reasons; 11 had missing data). Median follow-up from RP was 60 months. Kaplan-Meier (KM) estimates of 1, 2, 3, 4 and 5-year survival probabilities were 93.5%, 83.4%, 82.4%, 76.6% and 71% respectively. There was no statistically significant correlation between bFFS and pathological T-stage (p=0.1), surgical margin involvement (p=0.7), or RT total dose (p=0.8). Analysis based on KM survival distributions and log-rank tests suggest that pathological Gleason score may have some influence on bFFS (p=0.04). Doubling the pre-RT PSA whilst holding all other factors and covariates constant, increases the hazard of bF at a particular time-point by approximately 19% on average. Conclusion: This single-institution retrospective study provides reasonable evidence for influence of pre-RT PSA on post-RP RT outcomes, arguing for earlier referral for RT.