Frequency and predictors of occult cancer in ischemic stroke: A systematic review and meta-analysis

Background The optimal approach for cancer screening after an ischemic stroke remains unclear. Aims We sought to summarize the existing evidence regarding the frequency and predictors of cancer after an ischemic stroke. Summary of review We searched seven databases from January 1980 to September 2019 for articles reporting malignant tumors and myeloproliferative neoplasms diagnosed after an ischemic stroke (PROSPERO protocol: CRD42019132455). We screened 15,400 records and included 51 articles. The pooled cumulative incidence of cancer within one year after an ischemic stroke was 13.6 per thousand (95% confidence interval [CI], 5.6–24.8), higher in studies focusing on cryptogenic stroke (62.0 per thousand; 95% CI, 13.6–139.3 vs 9.6 per thousand; 95% CI, 4.0–17.3; p = 0.02) and those reporting cancer screening (39.2 per thousand; 95% CI, 16.4–70.6 vs 7.2 per thousand; 95% CI, 2.5–14.1; p = 0.003). Incidence of cancer after stroke was generally higher compared to people without stroke. Most cases were diagnosed within the first few months after stroke. Several predictors of cancer were identified, namely older age, smoking, and involvement of multiple vascular territories as well as elevated C-reactive protein and d-dimers. Conclusions The frequency of incident cancer after an ischemic stroke is low, but higher in cryptogenic stroke and after cancer screening. Several predictors may increase the yield of cancer screening after an ischemic stroke. The pooled incidence of post-stroke cancer is likely underestimated, and larger studies with systematic assessment of cancer after stroke are needed to produce more precise and valid estimates.