Postoperative radiotherapy for localized prostate cancer: Clinical significance of nadir prostate-specific antigen value within 12 months

Aim: To analyze retrospectively the results of postoperative radiotherapy for localized prostate cancer and to investigate the clinical significance of nadir prostate-specific antigen (PSA) value within 12 months (nPSA12) as an early estimate of clinical outcome after radiotherapy. Patients and Methods: Seventy-six patients with localized prostate cancer treated with postoperative radiotherapy were retrospectively reviewed. Total radiation doses ranged from 50 to 70 Gy (median: 60 Gy), and the median follow-up period for all 76 patients was 47.9 months (range, 12.4-101.3 months). Results: The 5-year actuarial overall survival, progression-free survival, biochemical relapse-free survival (BRFS) and local control rates in all 76 patients after radiotherapy were 86.1%, 77.8%, 80.0% and 92.2%, respectively. Distant metastases and/or regional lymph node metastases developed in 11 patients (14%) after radiotherapy, while local progression was observed in only 5 patients (7%). Of all 76 patients, the median nPSA12 in patients with biochemical failure and that in patients without biochemical failure were 1.16 ng/ml and 0.05 ng/ml, respectively. The 5-year BRFS rates in patients with low nPSA12 (<0.5 ng/ml) and those with high nPSA12 (≥0.5 ng/ml) were 92.7% and 42.2%, respectively (p<0.0001). In univariate analysis, nPSA12, pre-radiotherapy PSA, Karnofsky performance status and the use of chemotherapy had a significant impact on BRFS, and in multivariate analysis, nPSA12 alone was an independent prognostic factor for BRFS. Conclusion: Postoperative radiotherapy results in an excellent local control rate for localized prostate cancer and nPSA12 is predictive of biochemical failure after postoperative radiotherapy.