Temporal Dynamics and Spectrum of Stroke Across Cancer Trajectories: A Multicenter Study of 190,000 Cancer Survivors

Background: Stroke risk is increased in cancer patients, but variations by stroke type, cancer characteristics, and treatment timing remain incompletely characterized. We investigated stroke incidence after cancer diagnosis and temporal patterns of ischemic stroke around treatments. Methods: We conducted a retrospective multicenter cohort study using linked cancer registry and administrative data from 68 cancer hospitals in Osaka, Japan. Patients diagnosed between 2019 and 2022 were followed for up to 1 year. In diagnosis-based analyses, standardized incidence ratios (SIRs) compared stroke incidence with the general population. In treatment-based analyses, ischemic stroke incidence rates and adjusted incidence rate ratios (IRRs) were estimated from 14 days before through 365 days after cancer treatments (surgery, chemotherapy, or radiotherapy). Results: Among 190,471 patients, 1660 strokes occurred: 1296 (78.0%) ischemic strokes, 315 (19.0%) intracerebral hemorrhages, and 49 (3.0%) subarachnoid hemorrhages. In diagnosis-based analyses, the overall stroke SIR was 2.13 (95% CI, 2.03?2.24), with a 1.01% 1-year cumulative incidence. SIRs were 2.37 (95% CI, 2.24?2.50), 1.72 (95% CI, 1.53?1.92), and 1.22 (95% CI, 0.91?1.62) for ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage, respectively. SIRs peaked immediately after diagnosis and declined thereafter. Excess risk persisted through 180 days for ischemic stroke, 30 days for intracerebral hemorrhage, and 7 days for subarachnoid hemorrhage. In treatment-based analyses, ischemic stroke incidence increased transiently around treatments. After surgery, the adjusted IRR peaked during days 0?7 (12.27 [95% CI, 8.50?17.71]) and remained elevated through days 31?90 versus days 181?365. A postoperative increase was observed even in early-stage disease. For chemotherapy, incidence was relatively high before treatment initiation. Conclusions: Stroke risk after cancer diagnosis varied by stroke type, cancer characteristics, and time since diagnosis. Ischemic stroke incidence increased transiently around cancer treatment, including an early postoperative increase in patients with early-stage disease. These findings identify periods and patient groups that may warrant heightened clinical vigilance.