The deleterious association between proton pump inhibitors and prostate cancer specific death.

309 Background: Proton pump inhibitors (PPIs) are a commonly prescribed class of medications. Although in-vitro and in-vivo data have shown PPIs to have anti-tumor effects, more recent studies suggest an increased cancer risk in several solid organs. Pantoprazole, a commonly prescribed PPI, has been shown to harbor a protective effect in human prostate cancer (PCa) cells. We aimed to investigate the effect of pantoprazole and other PPIs on PCa-specific death and additional PCa outcomes. Methods: In this retrospective, population-based cohort study, data were incorporated from the Institute for Clinical and Evaluative Sciences to identify all men aged 66 and above with a history of a single negative prostate biopsy between 1994 and 2016. We used multivariable Cox regression models with time-dependent covariates, to assess the effect of PPIs on PCa diagnosis, androgen deprivation therapy (ADT) use, and PCa-specific death. All models included other medications with a putative effect on PCa. All models were adjusted for age, rurality, comorbidity, and year of patient study inclusion. Results: Overall, 21,512 men were included, with a mean follow-up time of 8.06 years (SD 5.44 years). A total of 10,999 patients (51.1%) used a PPI. A total of 5,187 patients (24.1%) were diagnosed with PCa, 2,043 patients (9.5%) were treated with ADT, and 805 patients (3.7%) died from PCa. Pantoprazole was associated with a 3.0% (95% CI 0.3%-6,0%) increased rate of being treated with ADT for every six months of cumulative use, while any use of all other PPIs was associated with a 39.0% (95% CI 18.0%-64.0%) increased PCa-specific mortality. No significant association was found with PCa diagnosis. Conclusions: Upon validation of the potentially negative association of PPIs with PCa outcomes, the expansive use of PPIs may need to be reassessed, especially in PCa patients.