Leuven, Belgium—While it is recognized that immune checkpoint inhibitors (ICIs) cause immune-mediated myocarditis, although rarely, little is known about the full extent of major adverse cardiovascular events (MACEs) after ICI treatment for cancer, according to a new report.

Belgian researchers from University Hospitals Leuven explain that the lack of information is because late occurring side effects are rarely reported in prospective clinical trials.

In response, they sought to identify incidence and risk factors of MACE in a real-life ICI-treated cancer cohort and also to compare incidence rates with patients with cancer who are not treated with ICIs and population controls. Results were published in the Journal of Clinical Oncology.

The study included 672 patients treated with ICIs; MACE, a composite of acute coronary syndrome, heart failure (HF), stroke, and transient ischemic attack, was defined as the primary endpoint. Secondary outcomes were acute coronary syndrome and HF separately.

Results indicate that the incidence of MACE was 10.3% during a median follow-up of 13 (interquartile range 6-22) months. Researchers advise that based on their multivariable analysis, a history of HF (hazard ratio 2.27; 95% CI, 1.03 to 5.04; P = .043) and valvular heart disease (hazard ratio 3.01; 95% CI, 1.05 to 8.66; P = .041) appeared to be significantly associated with MACE.

They add that cumulative incidence rates were markedly higher in the ICI group compared with the cancer cohort not exposed to ICI and the population controls. The authors suggest that a higher risk of HF events played a role in that.

"Cardiovascular events during and after ICI treatment are more common than currently appreciated," researchers conclude. "Patients at risk are those with a history of cardiovascular disease. Compared with matched cancer and population controls, MACE incidence rates are significantly higher, suggesting a potential harmful effect of ICI treatment besides the underlying risk."

Background information in the article explains that ICIs are now routinely used in cancer treatment and can induce immune-related adverse events, such as myocarditis.

"Our data stress the clinical relevance of a cardiovascular workup of patients with cancer before exposure to ICI treatment, particularly in those with pre-existing cardiovascular disease," the authors add.

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