Adjuvant Chemotherapy Improves Overall Survival of Rectal Cancer Patients Treated with Neoadjuvant Chemoradiotherapy Regardless of Pathologic Nodal Status.

ABSTRACT

BACKGROUND: After neoadjuvant chemoradiotherapy for rectal cancer, the interpretation of surgical pathology poses difficulties in deciding the need for adjuvant chemotherapy (AC). The aim of this study was to determine whether there is a survival benefit to providing AC in patients with node-negative disease on surgical pathology. METHODS: Patients with clinical stage II and III rectal adenocarcinoma who received neoadjuvant chemoradiation and definitive surgical resection from 2006 to 2012 were identified in the National Cancer Data Base. Patients were stratified by both receipt of AC and nodal status on surgical pathology. Propensity score matching was used to form two cohorts (AC vs. no AC) with otherwise balanced characteristics. Overall survival was compared by Kaplan-Meier analysis, and multivariable survival analysis was performed by a Weibull model. RESULTS: After propensity score matching, 4172 patients who received adjuvant therapy (2645 node negative and 1527 node positive) and 4172 patients who did not receive adjuvant therapy (3063 node negative and 1109 node positive) were identified. Among patients with either node-negative or node-positive disease, the use of AC was associated with a significant improvement in overall survival. These results were also observed after using a multivariable survival model to control for clinical stage as well as patient- and facility-related characteristics. CONCLUSIONS: In both patients with node-negative and node-positive disease on surgical pathology, the use of AC is associated with a survival benefit. In the absence of contraindications, AC should continue to be routinely recommended to patients after neoadjuvant chemoradiotherapy for locally advanced rectal cancers.