Fréquence et prédicteurs de cancer occulte en accident vasculaire cérébral ischémique

Introduction: Cancer promotes thromboembolism through inflammation and hypercoagulability, and an ischemic stroke may be the first sign of an undiagnosed (occult) malignancy. The frequency and predictors of occult cancer in people with acute ischemic stroke, however, remains unclear. We first sought to summarize the existing published data regarding the frequency and predictors of cancer after an ischemic stroke in a systematic review. We also conducted a retrospective matched cohort study to compare the incidence of cancer in people who experienced an ischemic stroke or transient ischemic attack (TIA) to that of people without stroke, using data from the Canadian Longitudinal Study on Aging. Methods: For our systematic 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). For our matched cohort study, we used data from the comprehensive sub-group (n=30,097) of the Canadian Longitudinal Study on Aging, a large population-based cohort of individuals aged 45-85 years when recruited (2011-2015). We built a retrospective cohort with individual exact matching for age (1:4 ratio). We used Cox proportional hazards models to estimate hazard ratios of new cancer diagnosis with and without a prior stroke/TIA. Results: For our systematic review, 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 to 24.8), higher in studies focusing on cryptogenic stroke (62.0 per thousand; 95% CI, 13.6 to 139.3 vs 9.6 per thousand; 95% CI, 4.0 to 17.3; p- value=0.02) and those reporting cancer screening (39.2 per thousand; 95% CI, 16.4 to 70.6 vs 7.2 per thousand; 95% CI, 2.5 to 14.1; p-value=0.003). The incidence of cancer after stroke was higher overall 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, involvement of multiple vascular territories, as well as elevated C-reactive protein and d-dimers. For our cohort study, we respectively included 920 and 3,680 individuals in the stroke and non- stroke groups. We observed a higher incidence of cancer in the first year after stroke/TIA that declined afterwards. The hazard of new cancer diagnosis in the first year after stroke/TIA was significantly increased (hazard ratio=2.36; 95% CI, 1.21 to 4.61; p-value=0.012) as compared to age-matched non-stroke participants after adjustments. The most frequent primary cancers in the first year after stroke/TIA were prostate (n=8, 57.1%) and melanoma (n=2, 14.3%). Conclusion: We observed in both studies of our research project that the frequency of incident cancer after an ischemic stroke is low overall, but higher as compared to people without stroke. The frequency of new cancer diagnosis after stroke is also 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 due to methodological issues in most studies of our review. Larger prospective studies with systematic ascertainment of cancer after stroke are needed to produce more valid and precise estimates of post-stroke cancer risk and guide randomized controlled studies of cancer screening in people with acute ischemic stroke.

Keyphrases: Cancer, CLSA, Cohort, Diagnosis, Epidemiology, Ischemia, Meta-analysis, Occult, Stroke, Systematic review