Venous thromboembolism and cancer risk in patients with a history of migraine: a population-based cohort study.

Background: Migraine is associated with elevated risk of venous thromboembolism (VTE). Although unprovoked VTE is recognized as a potential marker of occult cancer, it remains unclear whether VTE in patients with migraine is a marker of cancer. Objective: To examine cancer risk following VTE in patients with migraine, compared with expected risks in the general population. Methods: A population-based cohort study using Danish health registry data. Patients with first-time VTE diagnosis and history of migraine (discharge diagnosis or migraine-specific medications) were identified between 1996-2022. Follow-up extended until cancer diagnosis, death, emigration, 15 years, or December 31, 2022. We computed cumulative cancer risk and standardized incidence ratios (SIRs) using national cancer incidence rates during the first year and from 1 to 15 years. Results: We identified 7131 patients with VTE diagnosis and migraine. Most (71.2%) were identified by prescriptions, and the median follow-up time was 5.4 years. Within the first year, the cumulative cancer risk was 4.4%, SIR 4.28 (95% CI, 3.81-4.78), and lung, pancreatic, and ovarian cancers were observed most frequently when comparing with expected observations from the general population. After first year of follow-up, cumulative risk was 15.6%, and the SIR was 1.15 (95% CI, 1.06-1.25). Conclusion: Patients with migraine and VTE had elevated short-term and long-term risks of cancer compared with the general population. These findings are in line with other VTE cohorts, suggesting that VTE may be a marker of occult cancer in patients with a history of migraine, particularly within the first year of follow-up.