Statins and Reduced Risk of Liver Cancer: Evidence for Confounding

Abstract

A negative association of statin use with liver cancer risk has been reported frequently. We added laboratory measurements, to our knowledge not included in previous investigations, to a case-control analysis of 2877 case patients and 142 850 matched control subjects enrolled in Kaiser Permanente Northern California. Addressing confounding by indication by restricting subjects to those with elevated cholesterol greatly attenuated the negative association; eg, the multivariable-adjusted odds ratio (OR) rose from 0.41 (95% confidence interval [CI] = 0.35 to 0.49) to 0.87 (95% CI = 0.55 to 1.39) for receipt of 18 or more prescriptions. Confounding by contraindication was addressed by controlling for degree of abnormality of liver function tests, alanine or aspartate transaminase, measured within one year of the elevated cholesterol and strongly related to risk. The negative association of statins disappeared for all numbers of prescriptions received, with an odds ratio of 1.21 (95% CI = 0.53 to 2.75) for 18 or more prescriptions. Findings cast doubt on the causality of the frequently observed preventive association.