Outcomes in patients with pancreatic cancer as a secondary malignancy: a retrospective single-institution study. 
This study aimed to evaluate the clinicopathological features and oncological outcomes of pancreatic cancer (PC) patients with prior malignancies (2nd primary PC) compared with those of patients without any prior malignancies in their history (1st primary PC).  We retrospectively reviewed clinical data from 185 PC patients undergoing surgical resection.  Patients were divided into the 1st and 2nd primary PC groups.  Forty-three patients (23.2%) had a history of prior malignancy.  The 2nd primary PC group was significantly older than the 1st primary PC group (mean, 72.1 vs. 65.9 years, respectively, P < 0.001) and was more frequently asymptomatic compared to the 1st primary PC group (67.4 vs. 31.0%, respectively, P < 0.001).  The tumor size was larger, and extrapancreatic nerve plexus invasion, venous invasion, and lymph node metastasis were more frequently observed in the 1st primary PC group.  The rate of adjuvant therapy administration was lower in 2nd primary PC patients (72.5 vs. 51.2%, P = 0.009).  In the survival analysis, no significant difference in overall or disease-free survival was found between the two groups (16.8 vs. 16.4 months, P = 0.725, and 8.7 vs. 9.3 months, P = 0.284, respectively).  Despite significant surveillance bias, such as earlier detection in 2nd primary PC, the outcomes of patients with 2nd primary PC were comparable to those of patients with 1st primary PC.  Further investigation with a larger sample size and matching for patient age and tumor stage in both groups is needed to elucidate the biological features of 2nd primary PC.