Impact of prior cancer diagnosis on pancreatic cancer outcomes: A Danish Nationwide, population-based Cohort study.

ABSTRACT

BACKGROUND: The overall survival of pancreatic cancer (PC) remains low, underlining the need of further research to improve PC directed therapy. Some patients with PC may have experienced a prior cancer, refraining them from inclusion in clinical trials, despite not knowing the precise effect of a prior cancer on disease course of PC. OBJECTIVE: To examine the influence of prior cancer on the disease course in patients with PC. METHODS: We conducted a cohort study including Danish patients diagnosed with PC between 2004 and 2020 crosslinking data from the Danish Cancer Registry, the Danish National Patient Registry among several other databases. Using the Kaplan-Meier estimator, we calculated the overall and American Joint Committee on Cancer (AJCC) disease stage stratified survival, comparing patients with and without prior cancer. Furthermore, using inverse probability of treatment weighting (IPTW), we presented a covariate-adjusted model of the average treatment effect in the treated (ATT) of prior cancer on the overall PC survival and stratified for AJCC disease stage. RESULTS: We included 11,147 patients diagnosed with PC, of which 906 (8.1%) had a prior cancer. Comparing patients with and without prior cancer, the IPTW-adjusted survival, indicated a slightly better survival (ATT 1.5 months; 95% CI 0.7; 2.2 months). After stratifying by PC tumor stage, the difference was restricted to patients with stage IV PC disease (ATT 1.1 months; 95% CI 0.5; 1.7 months). Patients with prior cancer were slightly less prone to present with stage IV PC disease and were more likely to not receive active treatment compared with patients without prior cancer. CONCLUSION: Prior cancer was associated with a slightly better survival in patients with PC, but only in patients with stage IV PC disease. This is likely explained by lead time bias.