Early proctoscopy is a surrogate endpoint of late rectal toxicity in prostate cancer treated with radiotherapy

Purpose: To predict the grade and incidence of late clinical rectal toxicity through short-term (1 year) mucosal alterations. Methods and Materials: Patients with prostate adenocarcinoma treated with curative or adjuvant radiotherapy underwent proctoscopy a year after the course of radiotherapy. Mucosal changes were classified by the Vienna Rectoscopy Score (VRS). Late toxicity data were analyzed according to the Kaplan-Meier method. Comparison between prognosis groups was performed by log-rank analysis. Results: After a median follow-up time of 45 months (range, 18-99), the 3-year incidence of grade ≥2 rectal late toxicity according to the criteria of the European Organization for Research and Treatment of Cancer and the Radiation Therapy Oncology Group was 24%, with all patients (24/24; 100%) experiencing rectal bleeding. The occurrence of grade ≥2 clinical rectal late toxicity was higher in patients with grade ≥2 (32% vs. 15 %, p = 0.02) or grade ≥3 VRS telangiectasia (47% vs. 17%, p ≤ 0.01) and an overall VRS score of ≥2 (31% vs. 16 %, p = 0.04) or ≥3 (48% vs. 17%, p = 0.01) at the 1-year proctoscopy. Conclusions: Early proctoscopy (1 year) predicts late rectal bleeding and therefore can be used as a surrogate endpoint for late rectal toxicity in studies aimed at reducing this frequent complication.