Background: Immune checkpoint inhibitors (ICIs) have changed the way many solid tumours are treated, but they also carry a recognised risk of thromboembolism. Most published work has looked at venous thromboembolism. Arterial thromboembolic events (ATE), which include myocardial infarction, ischaemic stroke and peripheral arterial occlusion, have received comparatively less attention despite their serious clinical consequences.

Objective: To systematically review and bring together the published evidence on the incidence, risk factors and clinical outcomes of arterial thromboembolic events occurring during ICI therapy.

Methods: Fifteen studies were assembled for this review. These included two systematic reviews with meta-analysis, six retrospective or observational cohorts, two pharmacovigilance or disproportionality analyses, and other primary reports describing arterial thromboembolic outcomes in patients receiving ICIs. The review followed Cochrane and PRISMA-informed methodology. Data on cumulative incidence, hazard, odds or relative risk estimates, and identified risk factors were extracted and brought together narratively, with quantitative pooled estimates drawn from the two included meta-analyses.

Results: Pooled arterial event rates across advanced solid tumours ranged from 1.0% to 1.1% (Solinas et al., 95% CI 0.5-2.1%), and stood at 1% in a lung cancer specific meta-analysis (Yang et al., 95% CI 1-2%, I²=80.9%). Cumulative incidence in an Austrian cohort rose from 1.0% at six months to 1.8% at twenty-four months. A Dutch cohort found a three-fold higher risk of myocardial infarction and stroke compared with the general population, along with a 2.2-fold higher mortality risk in patients who developed arterial events. Risk factors that appeared consistently across studies included prior thromboembolic or cardiovascular disease, smoking, obesity, poor performance status, combination ICI regimens, concurrent chemotherapy, and an elevated Khorana score, although the Khorana score performed less well in this population than it usually does in general oncology practice.

Conclusion: Arterial thromboembolic events affect roughly one in a hundred patients receiving ICIs, a rate two to three times above background risk, and they carry a noticeably higher mortality burden once they occur. Cardiovascular risk assessment before starting therapy, along with vigilance during treatment, particularly in patients on combination regimens or with prior vascular disease, appears sensible. Prospective trials designed specifically to test prophylactic strategies in this setting are still needed.

KEYWORDS: Immune Checkpoint Inhibitors, Arterial Thromboembolism, Myocardial Infarction, Ischaemic Stroke, Cancer-associated Thrombosis, Meta-analysis.