Analysis of Gastrointestinal and Genitourinary Morbidity of Postoperative Radiotherapy for Pathologic T3 Disease or Positive Surgical Margins After Radical Prostatectomy Using National Cancer Institute Expanded Common Toxicity Criteria

Purpose: To evaluate the acute and late gastrointestinal (GI) and genitourinary (GU) toxicity of postoperative radiotherapy (RT) after radical prostatectomy (RP). Methods and Materials: A total of 78 patients with pT3 or positive surgical margins after RP were treated with RT plus 2 years of androgen suppression, according to a Phase II study. Acute and late GI and GU toxicity was prospectively assessed using the National Cancer Institute's Expanded Common Toxicity Criteria, version 2.0. The incidence of late GI and GU toxicity was estimated using a cumulative incidence method. A Cox proportional regression analysis was performed to evaluate the predictive factors for late toxicity. Results: The median patient age was 61 years at RP. The median interval between RP and postoperative RT was 4.2 months. The median follow-up was 42.4 months. Of the 78 patients, 76 and 74 were available for the acute and late toxicity analysis, respectively. Of these patients, 66%, 29%, and 1% experienced Grade 1, 2, and 3 acute GI or GU toxicity, respectively. The cumulative incidence of Grade 2 or greater and Grade 3 or greater late GI toxicity at 36 months was 8.1% and 0%, respectively. The cumulative incidence of Grade 2 or greater and Grade 3 or greater late GU toxicity at 36 months was 16.4% and 2.7%, respectively. None had Grade 4 or greater late toxicity. The severity of acute GU toxicity (less than Grade 2 vs. Grade 2 or greater) was a significant predictor factor for Grade 2 or greater late GU toxicity after adjusting for pre-existing GU dysfunction. Conclusions: Postoperative RT was generally well tolerated. Grade 3 or greater late GI or GU toxicity was uncommon