Is the Roach formula predictive for biochemical outcome in prostate cancer patients with minimal residual disease undergoing local radiotherapy after radical prostatectomy?

Purpose: To find out if the risk of biochemical failure can be predicted applying the risk assessment for lymph-node metastases as suggested by the Roach formula for patients with minimal residual disease after radical prostatectomy undergoing adjuvant radiotherapy. Materials and methods: Patients after radical prostatectomy presenting with pT3-tumours or positive surgical margins, negative nodes and with a post-operative and pre-radiotherapy PSA level <= 0.1 ng/ml and without hormonal therapy were selected. Patients had received local 3D-conformal radiotherapy in the prostatic region with 66-72 Gy. According to the risk stratification of the Roach formula patients were divided into two groups: Group 1 with probability of positive lymph-nodes <15% and Group 2 with >= 15% Biochemical recurrence was defined by reaching a PSA level >= 0.2 ng/ml. Results: A total of 55/288 patients could be identified, 26 patients in Group 1 and 29 patients in Group 2. Mean follow-up was 45 months. Biochemical recurrence free survival after 5 years was 78% for all patients and showed a significant difference between Group 1(100%) and Group 2 with (58%; p = 0.004). Conclusion: The risk for biochemical failure after adjuvant radiotherapy in post-operative patients presenting with minimal residual disease is significantly influenced by the Roach formula. These findings are considered to provide a rationale for the decision on the volume of post-operative radiotherapy. (C) 2010 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 94 (2010) 324-327