Clinical characteristics of second primary pancreatic cancer

Purpose Several studies reported the increased risk of second primary pancreatic ductal adenocarcinoma (2nd PDAC) in cancer survivors. However, data on the characteristics of 2nd PDAC are insufficient. Methods This retrospective cohort study included 1759 patients with PDAC. They were classified as having 2nd PDAC or first primary PDAC (1st PDAC) according to a prior diagnosed cancer of different origin, at least 6 months before PDAC diagnosis. Results There were 110 patients (6.4%) with 2nd PDAC and 1606 (93.6%) patients with 1st PDAC. Patients with 2nd PDAC presented with older age (66.5 vs. 62.2 years, p < 0.001) and higher rate of resectability (26.4% vs. 15.9%, p = 0.004) at diagnosis than those with 1st PDAC. Multivariate analysis without considering resectable status showed that 2nd PDAC (hazard ratio [HR] 0.73, 95% confidence interval [CI] 0.56-0.94, p = 0.016) was associated with better overall survival. After adjusting for resectable status, however, 2nd PDAC (HR 0.85, 95% CI 0.66-1.09, p = 0.198) was no longer associated with overall survival. When subgroups were separately analyzed according to initial treatment modality, the effectiveness of surgery and chemotherapy were similar between 2nd and 1st PDAC (33.1 vs. 28.5 months, p = 0.860 and 10.8 vs. 10.7 months, p = 0.952). Conclusions The proportion of resectable cases was significantly higher in 2nd PDAC. When surgery with curative aim was possible, the overall survival was increased even in patients with 2nd PDAC. These results suggest the importance of screening for second primary cancer in cancer survivors.