PSA reduction as predictor of biochemical relapse in low and favourable intermediate prostate cancer treated with radical radiotherapy.

[PURPOSE] Radiation therapy (RT) is standard treatment for localized prostate cancer (PCa). Prostate-specific antigen (PSA) kinetics, particularly PSA reduction (PSAr) after RT, are emerging as significant prognostic indicators for biochemical control. This retrospective multi-institutional study explores the correlation between PSAr and biochemical relapse-free survival (BRFS). This retrospective multi-institutional study explores the correlation between PSAr and biochemical relapse-free survival (BRFS).

[METHODS] 251 low-to-intermediate risk PCa patients treated with RT only were analyzed. Isoeffective RT schedules were: 39 fractions × 2 Gy, 28 × 2.55 Gy, 16 × 3.5 Gy, 5 × 7 Gy. Main objective was BRFS, defined as the time from PSA nadir (PSAn) to PSAn plus 2 ng/ml. PSAr was defined as the percentage of total PSA reduction from baseline. The optimal PSAr cut-off value was defined as 90%. Patients were stratified by PSAr, baseline PSA, Gleason Score (GS), and RT schedules.

[RESULTS] GS was 3 + 3 in 120 (48%) patients and 3 + 4 in 131 (52%) patients. After a median follow-up of 36 months (30-48), 2 and 5-year BRFS were 97.3% and 95.2%, respectively, in patients with PSAr ≥ 90% and 89.5%, 61.5% in patients with PSAr < 90% (p = 0.00). In the responder population, median time to PSAr 90% was 24 months and the median time to PSAn was 28.7 months (20-38). At univariate and multivariate analyses, PSAr was the only significant predictor of BRFS [HR 6.519 (95% IC 1.9-22.2), p = 0.003].

[CONCLUSIONS] PSAr could be a reliable prognostic factor for long-term biochemical control. This study underscores the potential of PSAr as a tool for risk stratification and personalized follow-up strategies in PCa management.