Effectiveness of image-guided radiotherapy for rectal cancer patients treated with neoadjuvant concurrent chemoradiotherapy: A population-based propensity score-matched analysis.

Abstract

The effects of image-guided radiotherapy (IGRT, an advanced RT technology) have been debated in the literature. We compared the outcomes of locally advanced rectal cancer (LARC) patients treated with neoadjuvant concurrent chemoradiotherapy (NCCRT; with vs without IGRT) in a large population-based propensity score (PS)-matched analysis. We identified LARC patients diagnosed between 2007 and 2015 via the Taiwan cancer registry (TCR) and constructed a PS-matched cohort to balance observable potential confounders. Outcomes (R0 resection, overall survival, incidence of local regional recurrence [ILRR], rectal cancer mortality [IRCM], other cancer mortality [IOCM] and cardiovascular mortality [ICVM]) were obtained from TCR and the national death registry. We compared the hazard ratio (HR) of death and other endpoints between IGRT and non-IGRT groups. We performed supplementary analysis (SA) to evaluate the robustness of these results in a subgroup, taking an additional potential confounder into account. Our study population comprised of 586 patients that were balanced with regard to observed covariables. There was no significant difference in HR for death (0.99; 95% confidence interval 0.70-1.39; P=0.94) between IGRT and non-IGRT groups. There were also no significant differences in R0 resection, ILRR, IRCM, IOCM or ICVM. The results of our SA were consistent with these findings. For LARC patients treated with NCCRT, the treatment outcome was not significantly different among patients treated with and without IGRT. Further study is needed to clarify these results with consideration to additional potential confounding factors and toxicity profiles at endpoints.