Does adherence to lipid-lowering medications improve cancer survival? A nationwide study of breast and colorectal cancer, and melanoma.

Abstract

Inconclusive findings of lipid-lowering medications (LLMs) on cancer survival benefit require more evidence. We tested the hypothesis that adherence to this drug is associated with reduced cancer-specific mortality in a homogeneous population who had used this drug before cancer diagnosis. The Australian Cancer Database was linked to the Pharmaceutical Benefits Scheme database, and to the National Death Index (up to 2015). Medication adherence was calculated by proportion of days covered. Cox regression models with time-varying covariates were used to derive multivariable-adjusted cause-specific hazard ratio (HR) and 95% confidence interval (CI) for the associations between adherence to LLMs, statins, lipophilic, and hydrophilic statins and cancer-specific mortality. From 2003 to 2013, 3 separate cohorts of 20 046, 11 719 and 6430 female patients with newly diagnosed breast, colorectal cancer, and melanoma respectively were identified. The 1-year adherence was similar at 1-year prediagnosis in the 3 cohorts, on average 82%. Each 10% increase in 1-year adherence to LLMs was inversely associated with cancer-specific mortality among women with breast cancer (fully adjusted HR = 0.92, 95% CI 0.91-0.93), colorectal cancer (fully adjusted HR = 0.92, 95% CI 0.91-0.93), or melanoma (fully adjusted HR = 0.97, 95% CI 0.94-1.00). The reductions in cancer-specific mortality were more pronounced for women who adhered to lipophilic than hydrophilic statins in all 3 cancers albeit not statistically significant for melanoma. Among LLM users, adherence to this drug is associated with a decrease in cancer-specific mortality. If confirmed, LLMs could be considered as an adjuvant cancer therapy to improve prognosis in cancer survivors.