Temporal patterns of occult cancer incidence following acute ischemic stroke: A comparative study by stroke etiology

Backgrounds and Aims: This study investigates the temporal patterns of occult cancer incidence among survivors of acute ischemic stroke (AIS), with a focus on variations by underlying stroke etiology. Patients and Methods: We analyzed data from a prospective, multicenter stroke registry and a national claims database, identifying AIS patients hospitalized between 2011 and 2013. Patients were categorized by stroke etiology into two groups: unidentified stroke etiology (USE) and identified stroke etiology (ISE). We estimated the occult cancer incidence rates within both groups and the overall AIS cohort. Using Poisson regression, we evaluated variations in cancer incidence over time and by stroke etiology, adjusting for age, sex, and smoking status. We also compared the first-year cancer incidence rate in our cohort to the age-standardized incidence rate (ASIR) in the general Korean population. Results: Among 9759 AIS patients (median follow-up: 4.4 years), 976 occult cancers were diagnosed in 569 patients (5.8%). The first month post-stroke exhibited the highest cancer incidence rates across all groups: 8.3 (overall AIS), 14.3 (USE), and 7.6 (ISE) per 1000 person-months, with rates decreasing rapidly thereafter and stabilizing after 12 months. Compared to beyond 36 months, the adjusted incidence rate ratios within 1 month were 7.1 for overall AIS, 17.6 for USE, and 6.8 for ISE. The heightened risk in the USE group, compared to the ISE group, was significant within 1 month but diminished thereafter. Relative to the general population, the ASIR in this cohort was 1.6 times higher, particularly among men and those in the USE category. Conclusion: Occult cancer incidence is notably high in the early period following AIS, especially among patients with USE. These findings underscore the importance of vigilant cancer screening immediately after a stroke, especially for patients without a clear stroke etiology. Data access statement: Access to the linked data utilized in this research was restricted to authorized researchers and limited to a pre-defined period only. Therefore, it is not possible to guarantee access to the data after the completion of this study, even upon reasonable request.