Impact of Prior Malignancy on Survival Outcomes of Stage IV Pancreatic Adenocarcinoma: SEER-Based Cohort.

Pancreatic cancer is one of the most fatal malignancies and the fourth leading cause of cancer-related mortality in the USA. Most clinical trials involving pancreatic adenocarcinoma (PAC) patients exclude subjects with a prior malignancy because of the possible effect of prior malignancies on survival. However, no data in the medical literature support this assumption. In this paper, we aim to study the impact of having a prior malignancy on the survival outcomes of stage IV PAC. We used the surveillance, epidemiology, and end results database to review patients with stage IV PAC diagnosed between 1973 and 2014. We calculated overall and pancreatic cancer-specific survival of these patients using unadjusted Kaplan-Meier test and multivariable covariate-adjusted Cox models. We reviewed 66,874 stage IV PAC patients, of which 4942 had a prior malignancy. Kaplan-Meier and Cox models showed that a history of prior malignancy did not cause significant difference in overall survival (HR = 0.938, 95%CI = 0.880-1.000, p = .052). However, a prior malignancy was associated with a better pancreatic cancer-specific survival (HR = 0.855, 95% CI = 0.796-0.918, p < .001). A prior malignancy before stage IV PAC was not associated with worse survival outcomes. Researchers should take these results into consideration when including/excluding patients to improve the generalizability and accuracy of their results.