Prior stroke may influence ischaemic stroke risk in cancer patients

Prior history of ischaemic stroke appears to affect the risk of ischaemic stroke in patients newly diagnosed with cancer, according to a study from Canada presented at ASH 2021.

“[This is a novel finding as] previous cohorts have excluded patients with a prior history of stroke,” said study author Associate Professor Deborah Siegal from the University of Ottawa, Ontario, Canada.

“In individuals without a prior history of stroke, those with cancer had a 1.5-fold higher risk of ischaemic stroke at 1.5 years [post-diagnosis] compared to controls. In individuals with a prior history of stroke, those with cancer had a similar risk of stroke compared to controls,” the authors pointed out.

The study population was derived using linked health databases in Ontario, Canada, between 2010 and 2019 and comprised adults with a new diagnosis of cancer who were age- and sex-matched 1:1 to individuals without cancer (control group). Individuals with basal and squamous cell skin carcinoma and primary central nervous system tumours were excluded. There were two cohorts in this study. Cohort 1 comprised individuals without a prior history of ischaemic stroke (620,647 with cancer and 620,647 controls; mean age 65.7 years, 51 percent female), while cohort 2 comprised individuals with a prior history of ischaemic stroke (13,924 with cancer and 13,924 controls; mean age 75.5 years, 42 percent female).

Among patients without ischaemic stroke history, the risk of hospitalization or emergency department presentation for ischaemic stroke at 1.5 years following index date* was higher among those with cancer compared with controls (adjusted hazard ratio [adjHR], 1.40, 95 percent confidence interval [CI], 1.34–1.47). However, ischaemic stroke risk was reduced in those with cancer vs controls at 1.5–5 years after index date (adjHR, 0.72, 95 percent CI, 0.69–0.74). [ASH 2021, abstract 175]

Among patients with a prior history of ischaemic stroke, there was no difference in risk of ischaemic stroke between patients with cancer and controls at 1.5 years after index date (adjHR, 1.00, 95 percent CI, 0.88–1.14). At 1.5–5 years post-index date, the risk of ischaemic stroke was lower in individuals with cancer compared with controls (adjHR, 0.53, 95 percent CI, 0.46–0.62).

The authors noted that in both cohorts, all-cause mortality risk in cancer patients compared with controls was highest during the first 1.5 years after the index date, though the risk was greater among patients without vs with a history of stroke (adjHRs, 10.41 and 5.28 for cohorts 1 and 2, respectively). All-cause mortality risk in cancer patients vs controls was still elevated at 1.5–5 years after index date but to a lesser degree (adjHRs, 3.10 and 1.74, respectively).

“At 5 years post-index, the risk of ischaemic stroke was lower in cancer patients in both cohorts which may reflect high early mortality rates and lower stroke risk among long-term survivors of cancer,” noted the authors.

The lack of data on antithrombotic use in individuals aged <65 years, smoking status, and causes of death were limitations, Siegal said.

“Compared to cancer-free controls, the risk of ischaemic stroke among individuals with a new cancer diagnosis depended on presence or absence of prior history of ischaemic stroke,” concluded Siegal.

“We also saw that the risk of death among cancer patients was highest within the first 1.5 years after diagnosis in both cohorts, but the magnitude of risk differed [between those with and without prior history of stroke],” she continued. Studies are ongoing to analyse these findings according to cancer subtype and stage, she added.