Immune checkpoint inhibitors for cancer and venous thromboembolic events

BACKGROUND: Immune checkpoint inhibitors (ICI) are widely used cancer treatments. There are limited data the risk for developing venous thromboembolism (VTE) among patients on an ICI. METHODS: This was a retrospective study of 2854 patients who received ICIs at a single academic center. VTE events, defined as a composite of deep vein thrombosis (DVT) or pulmonary embolism (PE), were identified by individual chart review and were blindly adjudicated using standard imaging criteria. A self-controlled risk-interval design was applied with an “at-risk period” defined as the two-year period after, and the “control period”, defined as the two-year prior to treatment. The hazard ratio (HR) was calculated using a fixed-effect proportional hazards model. RESULTS: Of the 2854 patients, 1640 (57.5%) were men; mean age was 64±13 years. The risk for VTE was 7.4% at 6 months and 13.8% at 1 year after starting an ICI. The rate of VTE was >4-fold higher after starting an ICI (HR 4.98, 95% CI 3.65 – 8.59, p