ESTRO 2024 - Abstract Book

S180

Brachytherapy - GI, paediatric, miscellaneous

ESTRO 2024

We analysed patients who had undergone both EBRT and CXB with curative intent, regardless of the treatment sequence, from the prospectively collected database at Clatterbridge Cancer Centre (2008-2019). Only patients who had well to moderately differentiated rectal adenocarcinoma (cT1-3, cN0-1, cM0) and small tumour size (≤ 3cm) were included. The variables of age, sex, fitness for surgery, performance status, tumour stage, nodal stage, EBRT regimen and CXB total dose, were considered possible confounders of the association between treatment regimen and outcomes. The balance of covariates before and after propensity matching and IPTW was assessed by examining the standardised mean difference (SMD) between the groups (Figure 1). The oncological outcomes based on the treatment sequence were first assessed in an unadjusted analysis followed by an adjusted model analysis considering all variables as confounders. Then, we performed propensity score matching (nearest neighbour method, calliper= 0.25) and calculated IPTW to weigh the full cohort in each regression model. Statistical analysis was performed in R 4.3.1. The primary outcome measures were overall survival (OS) and disease-free survival (DFS). Secondary outcome measures consisted of the local regrowth rate, organ preservation rate, and presence of post-treatment rectal bleeding.

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