Cancer incidence among patients using antiepileptic drugs:: a long-term follow-up of 28,000 patients

Objectives: The purpose of the study was to find out whether there is an association between use of enzyme-inducing antiepileptic medicines and cancer. Methods: A cohort of 14,487 male and 13,932 female patients who received reimbursement for antiepileptic drugs (AEDs) in 1979-1981 in Finland was followed for subsequent cancers up to 1997 through the Finnish Cancer Registry. Results: During the follow-up, 2242 cancer cases were observed, while the expected number based on national incidence rates was 1743. Over 40% of the excess was attributable to cancer of the brain and nervous system [standardised incidence ratio (SIR) 4.30, 95% confidence interval (CI) 3.81, 4.82]. The relative risk of meningiomas was very high (SIR 46.6, 95% CI 22.3, 85.6) only during the first year of reimbursement, while the risk of gliomas remained tenfold or higher for 7 years and was significantly increased for 19 years in patients taking AEDs. Also cancers of the larynx (SIR 1.77), liver (1.71), pancreas (1.35), colon (1.32), stomach (1.30) and lung (1.29) showed statistically increased risks. Conclusion: As epilepsy can be a symptom of cancers of the nervous system, the role of AEDs in their occurrence is speculative albeit possible. The excess of some cancers might be attributable to enzyme-inducing antiepileptic drugs, but the excess is not very high compared with the benefits obtained with these drugs.