Defining biochemical recurrence after radical prostatectomy and timing of early salvage radiotherapy

Background The optimal prostate-specific antigen (PSA) level after radical prostatectomy (RP) for defining biochemical recurrence and initiating salvage radiation therapy (SRT) is still debatable. Whereas adjuvant or extremely early SRT irrespective of PSA progression might be overtreatment for some patients, SRT at PSA >0.2 ng/ml might be undertreatment for others. The current study addresses the optimal timing of radiation therapy after RP. Patients and methods Cohort 1 comprised 293 men with PSA 0.1-0.19 ng/ml after RP. Cohort 2 comprised 198 men with SRT. PSA progression and metastases were assessed in cohort 1. In cohort 2, we compared freedom from progression according to pre-SRT PSA (0.03-0.19 vs. 0.2-0.499 ng/ml). Multivariable Cox regression analyses predicted progression after SRT. Results In cohort 1, 281 (95.9%) men had further PSA progression >= 0.2 ng/ml and 27 (9.2%) men developed metastases within a median follow-up of 74.3 months. In cohort 2, we recorded improved freedom from progression according to lower pre-SRT PSA ( 0.03-0.19 vs. 0.2-0.499 ng/ml: 69 vs. 53%; log-rank p = 0.051). Patients with higher pre-SRT PSA >= 0.2 ng/ml were at a higher risk of progression after SRT (hazard ratio: 1.8; p < 0.05). Conclusion The vast majority of patients with PSA >= 0.1 ng/ml after RP will progress to PSA >= 0.2 ng/ml. Additionally, early administration of SRT at post-RP PSA level < 0.2 ng/ml might improve freedom from progression. Consequently, we suggest a PSA threshold of 0.1 ng/ml to define biochemical recurrence after RP.