Systematic review and meta-analysis of small bowel dose–volume and acute toxicity in conventionally-fractionated rectal cancer radiotherapy

The limited radiation tolerance of the small-bowel causes toxicity for patients receiving conventionally-fractionated radiotherapy for rectal cancer. Safe radiotherapy dose-escalation will require a better understanding of such toxicity. We conducted a systematic review and meta-analysis using published datasets of small bowel dose-volume and outcomes to analyse the relationship with acute toxicity. SCOPUS, EMBASE & MEDLINE were searched to identify twelve publications reporting small-bowel dose-volumes and toxicity data or analysis. Where suitable data were available (mean absolute volume with parametric error measures), fixed-effects inverse-variance meta-analysis was used to compare cohorts of patients according to Grade ≥3 toxicity. For other data, non-parametric examinations of irradiated small-bowel dose-volume and incidence of toxicity were conducted, and a univariate logistic regression model was fitted. On fixed-effects meta-analysis of three studies (203 patients), each of the dose-volume measures V5Gy-V40Gy were significantly greater (p