More Is Not Better When It Comes to Treating Rectal Cancer With Multimodal Chemoradiation Beyond the Standard Radiation Dose of 5040 cGy.

Background Radiation dose schedules for neoadjuvant chemoradiation for rectal cancers differs, with the most common dose schedule using 5040 cGy in 28 fractions. Objectives The aim of this retrospective study was to assess the benefit of higher radiation doses beyond 5040cGy in the context of pathological response and follow up events. Setting Database from a provincial tertiary cancer center in Canada. Patients Five hundred eight consecutive rectal cancer patients with locally advanced disease (clinical T3/T4 or N1/N2) who received neoadjuvant chemoradiation followed by surgery were included in this study. Of the 508 patients, 281 received the standard radiation dose of 4500-5040 cGy and 227 received a dose >5040 cGy. Main outcome measure The postsurgical pathology, late toxicities and follow-up outcomes were analyzed. The outcomes were evaluated in relation to the dose of radiation received. Results Data regarding the clinical outcomes were comparable between the 4500-5040 cGy and >5040 cGy radiation groups with pathological complete response rates of 20.9% and 15.4% respectively (p=0.104); distant recurrence rates of 17.4% and 19.4%, respectively (p=0.36); local recurrence rates of 3.2% and 3.5%, respectively (p=0.36); and the median overall survival rates of 61 and 60.5 months respectively (p=0.8). No statistically significant correlation of improvement in outcomes was noted with radiation doses beyond 5040 cGy. Limitations This is a retrospective study. Conclusion Our study showed that dose escalation beyond the standard dose of 4500-5040cGy failed to achieve meaningful clinical outcomes. See Video Abstract at http://links.lww.com/DCR/B633.