Adjuvant Chemoradiotherapy in Resected Pancreatic Ductal Adenocarcinoma: Where Does the Benefit Lie? A Nomogram for Risk Stratification and Patient Selection.

INTRODUCTION The impact of adjuvant sequential chemoradiotherapy (CRT) on survival in resected pancreatic ductal adenocarcinoma (PDAC) remains unclear and warrants further investigation. METHODS NCDB patients with R0/R1 resected PDAC who received adjuvant chemotherapy without CRT or followed by CRT per RTOG-0848 protocol were included. Cox regression for 5-year overall survival (OS) was performed and used to construct a pathologic nomogram in patients who did not receive CRT. A risk score was calculated and patients were divided into low-risk and high-risk groups. Patients from each risk stratum were matched for the receipt of CRT to assess the added benefit of CRT on survival. The Kaplan-Meier analysis was performed to compare OS. RESULTS A total of 7146 patients were selected, 1308 (18.3%) received CRT per RTOG-0848. Cox regression concluded grade, T stage, N stage, node yield < 12, R1, and LVI as significant predictors of 5-year OS which were used to construct the risk score. Matched analysis in low-risk patients (score 0-79) showed no difference in OS between CRT vs. no CRT (47.6 ± 5.7 vs. 45.1 ± 3.9 months; p = 0.847). OS benefit was 3% at 1 year, - 4% at 2 years, and 4% at 5 years. In high-risk patients (score 80-100), median OS was higher in CRT vs. no CRT (24.8 ± 0.7 vs. 21.7 ± 0.8 months; p = 0.043). Absolute OS benefit was 13% at 1 year, 5% at 2 years, and - 1% at 5 years. CONCLUSION CRT has a short-lived impact on OS in resected PDAC that is only evident in high-risk patients. In this subset, survival benefit peaks at 1 year and subsides at 3 to 5 years following PDAC resection.