Early radiation-induced mucosal changes evaluated by proctoscopy: predictive role of dosimetric parameters

Background and purpose: Late rectal complications are assessed according to different scoring systems. Endoscopy can provide a more sensitive estimation of early radiation damage. The aim of this paper is to investigate the correlation between dosimetric parameters and rectal mucosal changes after radiotherapy (RT).

Materials and methods: Patients with prostate adenocarcinoma treated with curative or adjuvant RT underwent endoscopy 1 year after RT. Receiver operating characteristics (ROC) analysis was performed to analyze the predictive capability of the dosimetric variables in determining mucosal changes classified by Vienna Rectoscopy Score (VRS).

Results: The best dosimetric predictors of grade ≥2 telangiectasia were rectal (r) V(60 Gy) (p=0.014), rV(70 Gy) (p=0.017) and rD(mean) (p=0.018). Similar results were obtained for grade ≥2 VRS. The set of rV(60 Gy)<34.4%, rV(70 Gy)<16.7% and rD(mean)<57.5 Gy was associated with a decreased risk of grade ≥2 telangiectasia and VRS.

Conclusions: rV(60 Gy), rV(70 Gy) and rD(mean) were the strongest predictors of rectal mucosal alterations. In-depth analysis is required to correlate each mucosal alteration with late rectal toxicity in order to suggest early proctoscopy as surrogate end-point for rectal late toxicity in studies aimed at reducing this important complication.