Early salvage radiation therapy does not compromise cancer control in patients with pT3N0 prostate cancer after radical prostatectomy: Results of a match-controlled multi-institutional analysis

Background: Previous randomised trials demonstrated that adjuvant radiation therapy (aRT) improves cancer control in patients with pT3 prostate cancer (PCa). However, there is currently no evidence supporting early salvage radiation therapy (eSRT) as equivalent to aRT in improving freedom from biochemical recurrence (BCR) after radical prostatectomy (RP). Objective: To evaluate BCR-free survival for aRT versus observation followed by eSRT in cases of relapse in patients undergoing RP for pT3pN0, R0-R1 PCa. Design, setting, and participants: Using a European multi-institutional cohort, 890 men with pT3pN0, R0-R1 PCa were identified. Intervention: All patients underwent RP. Subsequently, patients were stratified into two groups: aRT versus initial observation followed by eSRT in cases of relapse. Outcome measurements and statistical analyses: Propensity-matched analysis was employed, and patients were stratified into two groups: aRT versus observation and eventual eSRT, defined as RT given at a postoperative serum prostate-specific antigen (PSA) ≤0.5 ng/ml at least 6 mo after RP. BCR, defined as PSA >0.20 ng/ml and rising after administration of RT, was compared between aRT and initial observation followed by eSRT in cases of relapse using Kaplan-Meier and Cox regression methods. Results and limitations: Overall, 390 (43.8%) and 500 (56.2%) patients were treated with aRT and initial observation, respectively. Within the latter group, 225 (45.0%) patients experienced BCR and underwent eSRT. In the postpropensity-matched cohort, the 2- and 5-yr BCR-free survival rates were 91.4% and 78.4% in aRT versus 92.8% and 81.8% in patients who underwent initial observation and eSRT in cases of relapse, respectively (p = 0.9). No differences in the 2- and 5-yr BCR-free survival rates were found, even when patients were stratified according to pT3 substage and surgical margin status (all p ≥ 0.4). These findings were also confirmed in multivariable analyses (p = 0.6). Similar results were achieved when the cut-off to define eSRT was set at 0.3 ng/ml (all p ≥ 0.5). Conclusions: The current study suggests that timely administration of eSRT is comparable to aRT in improving BCR-free survival in the majority of pT3pN0 PCa patients. Therefore, eSRT may not compromise cancer control but significantly reduces overtreatment associated with aRT.