Impact of radiotherapy for local control in T3 N0 rectal cancer managed with total mesorectal excision: A systematic review and meta-analysis.

3604 Background: Total mesorectal excision (TME) significantly improved rectal cancer outcomes. Radiotherapy (RT) is recommended for T3N0 rectal cancers, though benefit has not been demonstrated in combination with TME for this specific population. This meta-analysis could provide evidence to ameliorate toxicities from treatment. Methods: Randomized clinical trials and observational studies published until October 18, 2020 were identified via PubMed and Embase. Objective: To determine whether RT decreased the risk of local recurrence (LR) in T3N0 rectal cancer managed with TME. Study Selection and Extraction: Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were observed for literature search, extraction, and screening. Studies with LR data specific to T3N0M0 rectal cancer, treated with and without RT, were included. Reviews, non-English articles, and non-TME studies were excluded. Newcastle Ottawa Scale (NOS) evaluated quality. Meta-analysis was done with a random-effects model. Main outcome: Meta-analysis of the relative risk of LR was conducted. Results: 7,246 studies were screened, 134 full-text studies assessed for eligibility, 5 studies were included in the final analysis. No randomized data reported results specific to our study population. Five retrospective cohort studies involving 932 participants reported LR outcomes. The median follow-up ranged from 38.4 months up to 71 months. Four studies took place in Asia (797 participants) and one in North America (135 participants) (Table). Quality according to NOS ranged from 7–9. The estimated average relative risk for LR at 5 years was 0.63 (95% CI 0.31–1.29; I2=41.8%) when RT was used. Conclusions: This meta-analysis’ supports that there is no clear benefit to LR with the addition of RT in T3N0 patients with rectal adenocarcinoma undergoing TME. As meta-analysis was limited to retrospective cohort studies, there is concern for bias. Registration Prospero number CRD42020216058 .[Table: see text]