Second primary pancreatic ductal carcinoma in the remnant pancreas after pancreatectomy for pancreatic ductal carcinoma: High cumulative incidence rates at 5 years after pancreatectomy

Objectives The aim of this study was to determine the incidence rate and clinical features of second primary pancreatic ductal carcinoma (SPPDC) in the remnant pancreas after pancreatectomy for pancreatic ductal carcinoma (PDC). Methods Data of patients undergoing R0 resection for PDC at a single high-volume center were reviewed. SPPDC was defined as a tumor in the remnant pancreas after R0 resection for PDC, and SPPDC met at least one of the following conditions: 1) the time interval between initial pancreatectomy and development of a new tumor was 3 years or more; 2) the new tumor was not located in contact with the pancreatic stump. We investigated the clinical features and treatment outcomes of patients with SPPDC. Results This study included 130 patients who underwent surgical resection for PDC between 2005 and 2014. Six (4.6%) patients developed SPPDC. The cumulative 3- and 5-year incidence rates were 3.1% and 17.7%, respectively. Four patients underwent remnant pancreatectomy for SPPDC. They were diagnosed with the disease in stage IIA or higher and developed recurrence within 6 months after remnant pancreatectomy. One patient received carbon ion radiotherapy and survived 45 months. One patient refused treatment and died 19 months after the diagnosis of SPPDC. Conclusions The incidence rate of SPPDC is not negligible, and the cumulative 5-year incidence rate of SPPDC is markedly high. Post-operative surveillance of the remnant pancreas is critical for the early detection of SPPDC, even in long-term survivors after PDC resection.