Increasing risks of ischemic stroke in oral cancer patients treated with radiotherapy or chemotherapy: a nationwide cohort study.

BACKGROUND: Several studies have identified correlations between cancer and increased risks of ischemic stroke (IS), particularly following radiotherapy (RT) or chemotherapy (CT). However, data regarding relative risks of IS in oral cancer are limited. The aim of this study was to compare hazard ratios (HR) of IS among oral cancer patients treated with and without RT, CT, or both (CCRT). METHODS: We analyzed data collected by the Taiwan National Health Insurance Research Database (NHIRD) from 1996 to 2009, which covered approximately 99.5% of the medical claims submitted nationally. A total of 21,853 patients diagnosed with oral cancer from 2000 to 2008 were included. The Cox proportional hazard model was used to estimate the HRs of IS among different treatment modalities and a matched cohort. RESULTS: The overall risk of IS was 1.24-fold greater in patients treated with RT/CT/CCRT than those treated with surgery alone and 1.08-fold greater for surgery with adjuvant therapy (radiotherapy or chemotherapy after surgery) after adjusting for confounding factors. The incidence of IS was 0.23-fold lower in matched control group than in the oral cancer cohort. In subgroup analysis, patients who received RT/CT/CCRT and aged <40 years old were at a 2.77-fold greater risk for IS than age-matched patients who underwent surgery alone, although this difference decreased with patient age. CONCLUSIONS: Oral cancer patients, particularly those aged <40 years, who underwent RT or CT are at increased risks for IS. Other significant risk factors for IS included Charlson comorbidity index (CCI)>1, hypertension, coronary artery disease, and atrial fibrillation.