Should Short-Course Neoadjuvant Radiation Therapy Be Applied for Low-Lying Rectal Cancer? A Systematic Review and Meta-Analysis of the Randomized Trials.

Abstract

National Comprehensive Cancer Network guidelines recommend either long-course chemoradiation (LC) or short-course radiation (SC, 5 × 5 Gy) for rectal cancer before total mesorectal excision. However, they do not recommend SC for low-lying tumors. As early toxicity of SC is lower than that of LC, and postoperative complications as well as late toxicity are similar, the probable reason is a notion that for low-lying tumors LC may be more effective than SC in assuring local control. A systematic review and meta-analysis of the randomized trials comparing SC with LC was performed to test the hypothesis that for low-lying tumors, LC is superior to SC in reducing the risk of local failure. The systematic search identified 4 trials including, in total, 421 patients with tumors <5 cm from the anal verge; 221 were randomized to SC and 200 to LC. The meta-analysis showed that the difference in local failure rate between SC and LC was insignificant; the pooled odds ratio was 0.87, 95% confidence interval 0.53 to 1.44, P = .59. Heterogeneity between trials was insignificant; I² = 0.0%, P = .47. Our meta-analysis does not support the notion that LC given before total mesorectal excision is superior to SC in reducing the risk of local failure in low-lying tumors.