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 differ, 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 5040 cGy in the context of pathological response and follow-up events. SETTING: The database from a provincial tertiary cancer center in Canada was the source of information for this study. PATIENTS: Included in this study were 508 consecutive patients with rectal cancer with locally advanced disease (clinical T3/T4 or N1/N2) who received neoadjuvant chemoradiation followed by surgery. Of the 508 patients, 281 received the standard radiation dose of 4500 to 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 to 5040 cGy and >5040 cGy radiation groups with pathological complete response rates of 20.9% and 15.4% (p = 0.104); distant recurrence rates of 17.4% and 19.4% (p = 0.36); local recurrence rates of 3.2% and 3.5% (p = 0.36); and the median overall survival rates of 61 and 60.5 months (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 to 5040cGy failed to achieve meaningful clinical outcomes.