Cancer-Associated Ischemic Stroke: The Bergen NORSTROKE Study

Abstract

Background: Stroke and cancer are both leading causes of death and disability in the Western world. Cancer can lead to a hypercoagulable state that can cause ischemic stroke. Mechanisms include disturbance of the coagulation cascade, tumor substance secretion, infections and non-bacterial endocarditis. Many types of cancer also share a similar risk factor profile to that of ischemic stroke. The cancer-stroke connection has not previously been studied in Norway. Further knowledge on which subgroups of patients are at highest risk for both stroke and cancer, as well as on how to recognize a cancer-associated stroke is needed. Methods and materials: The studies 1-3 are the foundation of the present thesis. All papers have used data from The Norwegian Stroke Research Registry (NORSTROKE). NORSTROKE is a comprehensive, prospective registry that since February 2006 has included all stroke patients admitted to the Stroke Unit at Haukeland University Hospital. For the present studies, the medical charts of all stroke patients were reviewed for collection of cancer diagnoses. Cancer data was quality assured through linking NORSTROKE to The Cancer Registry of Norway. Results: From August 2006 through August 2011, 1511 patients with ischemic stroke were registered in NORSTROKE. In study I, patients with cancer post stroke were excluded. In study I, a total of 1456 patients were included, of whom 229 (15.7 %) had cancer prior to index stroke. The prevalence of stroke was higher in stroke patients compared to the general population below the age of 70. In study II, patients with cancer pre stroke were excluded. In study II, a total of 1282 patients were included, of whom 55 (4.3 %) were diagnosed with cancer post index stroke. In study III, the inclusion period was extended and patients with inactive cancer were excluded. In study III, 1646 patients were included in the study, of whom 82 (5.0 %) had active cancer. The most common cancer types overall were cancer of the; colon, prostate, breast, lung, bladder, uterus and ovaries as well as of unknown primary site. Patients with active cancer had similar risk factors to patients without a history of cancer. Active cancer in stroke patients was associated with smoking, age, increased D-dimer and decreased hemoglobin. Active cancer was also associated with stroke of unknown etiology. Conclusions: The prevalence of cancer was higher in stroke patients compared to the general population below the age of 70. Findings in patients with cancer-associated ischemic stroke were elevated D-dimer, signalling hypercoagulation, lower hemoglobin and a history of smoking. These factors may also be used to predict active cancer in stroke patients and thus indicate which stroke patients could be screened for underlying cancer.