Epilepsy as a risk factor for cancer

Epilepsy and long term use of antiepileptic drugs have been suggested to be associated with an increased risk of cancer. The authors therefore set out to analyse previous diagnosis of epilepsy as a risk factor for certain cancer forms in a case control study.

Incident cases of leukaemia, lymphoma, myeloma, and pancreatic cancer were identified from the Swedish Cancer Registry 1987-99, a total of 52 861 cases. Controls (n = 137 485) were randomly selected from the Swedish Population Registry stratified on age, sex, and year of cancer diagnosis. Cases and controls were linked to the Swedish Hospital Discharge Registry for 1969-99 to identify individuals with first time hospital discharge for epilepsy.

While an epilepsy diagnosis the same year as a cancer diagnosis carried an increased risk of non-Hodgkin's lymphoma (OR = 2.89, 95% CI 1.89 to 4.41), Hodgkin's disease (OR = 4.77, 95% CI 1.77 to 13.30), leukaemia (OR = 2.55, 95% CI 1.50 to 4.32), acute myeloid leukaemia (OR = 3.65, 95% CI 1.68 to 7.93), and pancreatic cancer (OR = 2.05, 95% CI 1.22 to 3.45), the authors found no support for an association between discharge with a diagnosis of epilepsy two years or more before the diagnosis of cancer and an increased risk of any of the types of cancer included in this analysis. The lack of association was also evident for individuals with an epilepsy diagnosis preceding malignancy/reference year by >10 years.

Clinical examinations prompted by seizure onset probably mainly explain the observed association between epilepsy diagnoses the year before a cancer diagnosis. However, these results lend no support to the suggestion that epilepsy, and presumably long term exposure to antiepileptic drugs, is associated with an increased risk of the types of cancer included in the present study.