Immune checkpoint inhibitors (ICIs) may not increase the risk of venous thromboembolism (VTE) compared with chemotherapy among patients with cancer, according to research presented at the 2022 ASH Annual Meeting.

Previous research has shown inconsistent results as to whether ICIs increase the risk of VTE among patients with cancer. Although VTE rates have been high in this patient population compared with those who receive chemotherapy, many patients who receive ICIs often have a worse performance status (PS) and have undergone several lines of prior therapy.

For this retrospective study, researchers evaluated whether patients who receive first-line ICIs are at a heightened risk for VTE compared with those who receive chemotherapy, balancing for PS.

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All data were obtained from the US Veterans Affairs health care system. Data were from patients who received a cancer diagnosis with de novo disease between 2016 and 2020. All patients had stage III or IV cancers of the lung, skin, kidney, bladder, liver, or head and neck.

Overall, the dataset included 45,253 patients. Of these, 13.4% received an ICI (median follow-up, 334 days), though only 4.7% of patients received an ICI as a first-line regimen, and only 3.7% received an ICI for a US Food and Drug Administration (FDA)-approved cancer. The ICI and chemotherapy groups were not balanced for age, diagnosis year, cancer subtype, cancer stage, or time to therapy.

Analysis showed that 5.55% of patients in the chemotherapy group vs 6.1% of patients in the ICI group had had a VTE within 6 months of initiating treatment, corresponding to a weighted relative risk of 1.1 (95% CI, 0.83-1.46). A further analysis of patients with lung cancer only also revealed no significant difference between the 2 groups.

“In this PS-weighted analysis of 8,149 patients, we found that first-line ICI and chemo had a similar rates of VTE,” the authors wrote in their presentation. “Previous retrospective studies likely reported inflated rate of VTE in ICI due to indication bias.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, or device companies. Please see the original reference for a full list of authors’ disclosures.


May SB, La J, Milner E, et al. Venous thromboembolism risk in cancer patients receiving first-line immune checkpoint inhibitor vs. chemotherapy. Presented at ASH 2022. December 10-13, 2022. Abstract 3555.