Oncologic outcomes according to the location and status of resection margin in pancreas head cancer: role of radiation therapy in R1 resection.

Abstract

PurposeThe clinical significance of margin status in pancreatic head cancer is still controversial due to the nonstandardized definition of R status and pathologic reporting. This study aims to evaluate the impact of the margin status including location and the role of radiation therapy in pancreatic head cancer.MethodsA total of 314 patients who underwent curative-intent surgery for pancreatic head cancer between 2010 and 2017 were analyzed. Demographics, survival, and local recurrences were compared according to 2 definitions: 0-mm R1 as direct involvement and 1-mm R1 as close resection margin less than 1 mm. The specific margins were divided into 4 groups according to the location around the pancreas: pancreas transection, anterior surface, posterior surface, and vessel (superior mesenteric artery/superior mesenteric vein) margin.ResultsThe 0-mm R1-rate was 15.6%, and increased to 36.3% in 1-mm R1. The median overall survival rate of 0-mm R0 vs. R1 was 26 months vs. 16 months (P = 0.052) and that of 1-mm R0 vs. R1 was 27 months vs. 18 months, respectively (P = 0.016). In individual margins, posterior, anterior surface, and pancreas transection margin involvement were associated with poor outcome, and the 1 mm posterior surface involvement was an independent risk factor for disease-free survival (hazard ratio, 1.63). Adjuvant radiation therapy had oncologic benefits, especially in R1 patients (P = 0.011) compared to R0 patients (P = 0.088).ConclusionMargin status, especially 1-mm R1 status is an important predictive factor, and involved posterior surface has a clinical impact. Patients with positive margins should be considered adjuvant radiation therapy.