Postdiagnostic Calcium Channel Blocker Use and Breast Cancer Mortality: A Population-based Cohort Study.

BACKGROUND: There have long been concerns that calcium channel blockers (CCBs), widely used to treat hypertension, may contribute to malignant growth through the evasion of apoptosis and proliferation of cancer cells. Worryingly, a recent cohort study found breast cancer patients who used CCBs had higher death rates, but interpreting these results was difficult as they were based on all-cause mortality and medication use before cancer diagnosis. We used UK population-based data to more robustly investigate the association between CCB use and cancer-specific mortality.

METHODS: We selected a cohort of patients with breast cancer diagnosed between 1998 and 2012 from English cancer registries. We linked to prescription and clinical records from the Clinical Practice Research Datalink, and to death records from the Office for National Statistics. We used adjusted, time-dependent Cox regression models to calculate hazard ratios (HRs) comparing breast cancer-specific and all-cause mortality between postdiagnostic CCB users and nonusers.

RESULTS: Our cohort included 23,669 breast cancer patients, of whom 5,141 used CCBs and 3,053 died due to their breast cancer during follow-up. After adjustment, CCB users had similar breast cancer-specific mortality to nonusers (HR = 0.98, 95% confidence interval [CI] = 0.88, 1.08). There was no evidence of a dose-response relationship. We found similar associations for specific CCBs, and for all-cause mortality.

CONCLUSIONS: In this large population-based breast cancer cohort, we did not find any evidence that CCB use is associated with increased mortality.