Dose-volume analysis of planned versus accumulated dose as a predictor for late gastrointestinal toxicity in men receiving radiotherapy for high-risk prostate cancer

•Interfractional variations in organs at risk were observed in prostate radiotherapy.•Rectal accumulated dose was significantly higher at the intermediate-high dose region.•Rectal planned dose was significantly higher at the very high dose region.•Dose>78.2 Gy to 0.03 cc of rectum was predictive of late Grade 2 toxicity.•Patient age>72 years was predictive of late Grade 2 rectal toxicity.