Biochemical control after adjuvant radiation therapy for prostate cancer: a unicentric, retrospective analysis

PURPOSE: To retrospectively evaluate the biochemical no evidence of disease (bNED) and late side effects after adjuvant radiotherapy in prostate cancer patients. METHODS: Patients (n = 85) treated with external beam radiotherapy between 1997 and 2013 following radical prostatectomy (RPE) with pathological tumour stage pT2c with positive surgical margins or pT3 and pT4 tumours with or without positive margins who presented with a postoperative and a preradiation prostate-specific antigen (PSA) level below 0.1 ng/ml. The mean dose applied was 66 Gy with conventional fractionation (4 field box-technique). No androgen deprivation therapy was administered, and patients with incomplete data (missing Gleason score, pT stage, or PSA values postoperatively and/or prior to radiation at the presentation at our department) have been excluded from the analysis. Biochemical recurrence was defined as reaching a PSA level > 0.2 ng/ml during follow-up and bNED rates were assessed. In addition, patients were divided into two groups according to the Roach formula for predicting the risk of pelvic node involvement at a cut-off value of 15%. Late urogenital and gastrointestinal side effects (EORTC/RTOG) were assessed. RESULTS: After a median follow-up of 60 months the bNED rate was 88% at 5 years and 72% at 10 years for all patients. Patients with low risk of lymph node involvement (group < 15%) had a 5 year and 10 year bNED of 97% and 85%, while patients with high risk of positive lymph node involvement (group > 15%) showed corresponding bNED rates of 77% and 52%, respectively. A significant difference according to the Roach stratification was detected (p ≤ 0.002). Late urogenital (UG) and gastrointestinal (GI) grade ≥ 2 side effects were detected in 10% and 15%, respectively. CONCLUSION: Postoperative radiotherapy with an average dose of 66 Gy to the prostatic fossa following RPE provides excellent tumour control rates with acceptable side effects. Patients with a higher risk of positive lymph nodes (> 15%) according to the Roach formula show significant worse tumour control rates.