R1 pancreatic cancer patients benefit from chemoradiation when initiation of adjuvant therapy is delayed

BACKGROUND:Adjuvant chemotherapy (AC) following pancreaticoduodenectomy (PD) for pancreas cancer (PDAC) has been demonstrated to improve survival. However, the optimal adjuvant treatment (AT) regimen for R1-margin patients remains unclear. This retrospective study investigates the impact of AC vs. adjuvant chemoradiotherapy (ACRT) on survival (OS). MATERIAL AND METHODS:The NCDB was queried for patients with PDAC who underwent PD between 2010 and 2018. Patients were divided into, (A) AC<60 days, (B) ACRT<60 days, (C) AC≥60 days, and (D) ACRT≥60 days. Kaplan-Meier survival analyses and Cox multivariable regression analyses were performed. RESULTS:Among 13 740 patients, median OS was 23.7 months. For R1 patients, median OS for timely AC and ACRT, and delayed AC and ACRT was 19.91, 19.19, 15.24, 18.96 months, respectively. While time of AC initiation was an insignificant factor for R0 patients (p = 0.263, CI 0.957-1.173), a survival benefit was found for R1 patients who received AC<60 vs. ≥60 days (p = 0.041, CI 1.002-1.42). Among R1 patients, administration of delayed ACRT achieves the same survival benefit of timely AC initiation (p = 0.074, CI 0.703-1.077). CONCLUSION:The study suggests value in ACRT for patients with R1 margins when delay of AT≥60 days cannot be avoided. Hence, ACRT may mitigate the negative impact of delayed AT initiation for R1-patients.