Clinical and dosimetric predictors of late rectal toxicity after conformal radiation for localized prostate cancer: Results of a large multicenter observational study

Abstract 

Purpose

Assessing the predictors of late rectal toxicity after high-dose conformal radiotherapy for prostate cancer.

Methods

One thousand one hundred thirty-two patients entered a prospective observational multicentric study; late rectal toxicity was evaluated by a self-reported questionnaire. Results concerning bleeding and faecal incontinence of 718/1132 patients with a complete follow-up at 36months were analysed. The correlation between a number of clinical–dosimetric parameters and moderate/severe toxicity was investigated by univariate and multivariate logistic analyses.

Results

Fifty-two (7.2%) and 57/718 (7.9%) patients were scored as moderate/severe bleeders and faecal incontinents, respectively; 19/57 incontinent patients showed persistent incontinence at 36months. Bleeding was mainly correlated with V75Gy while severe bleeding was mainly correlated with the previous abdominal/pelvic surgery; a different rectal dose–volume relationship in the two groups of patients (with/without surgery) was found. Moderate/severe acute toxicity was weakly correlated to late bleeding. The best predictor of faecal incontinence was acute toxicity (OR=4 and 7 for chronic and actuarial incontinence, respectively).

Conclusion

The application of rectal dose–volume constraints limited the incidence of rectal bleeding. The risk of bleeding may be further reduced by limiting V75Gy<5% and, in the case of patients previously submitted to abdominal/pelvic surgery, V70Gy<15–20%. Faecal incontinence seems to be mainly a consequential effect after acute toxicity.

Keywords: Prostate Radiotherapy, Rectal toxicity, Dose–volume effects