Thromboembolism during immune checkpoint inhibitor therapy: frequency and risk factors

Thromboembolism (TE) is a well-known complication during chemotherapy in cancer patients. However, the risk of TE associated with immune checkpoint inhibitors (ICIs) is unknown. This study was performed to investigate the incidence of TE and associated risk factors in patients treated with ICIs.

We conducted a retrospective chart survey of patients receiving at least one ICI at Shinshu University Hospital between September 2014 and October 2021. Age, sex, cancer type, body mass index, medical history, laboratory data at commencement of treatment, and medication data were obtained from electronic medical records. TE events (venous thromboembolism [VTE], arterial thromboembolism [ATE]) were identified after ICI initiation.

The study population consisted of 548 patients with a median age of 70.0 (19-89) years, 71.4% men, and a median follow-up of 15.1 months (range; 0.16-72.0 months). Nivolumab was the most commonly used ICI (45.8%), followed by pembrolizumab (23.9%), pembrolizumab plus anticancer drugs (7.8%), and nivolumab plus ipilimumab (5.1%). Thirty-eight cases of TE (6.9%) occurred (22 VTE, 16 ATE). Risk factors significantly associated with TE in multivariate logistic analysis were dyslipidemia (OR 2.44; 95% CI 1.17-5.09; p = 0.017), Khorana score ≥ 2 (HR 2.40; 95% CI 1.14-5.04; p = 0.021). Overall survival was not significantly different from patients without TE (p = 0.963).

These results suggested that the frequency of TE is higher than expected and should be considered and monitored in patients treated with ICIs.