295 Radiotherapy for Curative-intent Metastatic Rectal Cancer: A Systematic Review and Meta-Analysis

Abstract

Abstract Introduction The role and optimal regimen of radiotherapy in curative-intent treatment of metastatic rectal cancer is unclear and hence a single arm meta-analysis was performed. Method Medline, Embase and Cochrane Library databases were searched up to 16 May 2020. A Meta-analysis of binomial data was performed using a Freeman-Tukey double arcsine transformation, and pooled estimates were used to construct risk ratios and confidence intervals via the Katz-logarithmic method. Additionally, comparative meta-analysis was performed with the Mantel Haenszel model. Results 18 studies were included. Rectal pathological complete response (pCR) was observed in 14% of tumours treated with radiotherapy (n = 57/388, CI 0.07 to 0.23). Comparative meta-analysis of cohort studies showed that treatment regimens including radiotherapy were associated with higher pT1 tumour and better oncological outcomes compared to regimens without radiotherapy. Katz-logarithmic method showed that neoadjuvant radiotherapy had a higher proportion of pN0 staging (RR = 1.81, 95% CI 1.06 to 3.09, p = 0.029) and better oncological outcomes compared to adjuvant radiotherapy, and that short course radiotherapy (SCRT) had a lower proportion of pT3 tumours (RR = 0.778, 95% CI 0.609 to 0.994, p = 0.044) and similar oncological outcomes compared to long course radiotherapy (LCRT). Conclusions This study supports the evidence that radiotherapy should be used in curative intent metastatic rectal cancer.