The Addition of Chemoradiation to Adjuvant Chemotherapy is Associated With Improved Survival Following Upfront Surgical Resection for Pancreatic Cancer With Nodal Metastases

Background: It is unclear whether the addition of chemoradiation (CRT) to adjuvant chemotherapy (CT) following upfront resection of pancreatic ductal adenocarcinoma (PDAC) provides any benefit. While some studies have suggested a benefit to combined modality therapy (CMT) (adjuvant CT plus CRT), it is not clear if this benefit was related to increased CT usage in patients who received CMT. We sought to clarify the use of CMT in patients who underwent upfront resection of PDAC. Methods: Patients with non-metastatic PDAC were retrospectively identified from the linked SEER-Medicare database. Those who underwent upfront resection were identified and divided into two cohorts – patients who received adjuvant CT and patients who received adjuvant CMT. Cohorts were compared. Univariate analysis described patient characteristics. Kaplan-Meier and multivariable Cox proportional hazards modeling were used to estimate overall survival (OS). Results: 3555 patients were identified; 856 (24%) received CT and 573 (16%) received CMT. The median number of CT doses was 11 for both groups. Patients who received CMT were younger, diagnosed in the earlier time frame, and had fewer comorbidities. The median OS was 21 months and 18 months for those treated with CMT and CT (P <.0001), respectively, but when stratified by nodal status, the association with improved OS in the CMT cohort was only observed in node-positive patients. On multivariable analysis, receipt of CMT and removal of >15 lymph nodes decreased the risk of death (P <.05). Discussion: Receipt of CMT following upfront resection for PDAC was associated with improved survival, which was confined to node-positive patients. The role of adjuvant CMT in PDAC with nodal metastases warrants further study.