Thrombosis rates in patients with cancer receiving immune checkpoint inhibitors: results from a prospective cohort study

Introduction Cancer is associated with an increased risk of venous thromboembolism (VTE), which is in part attributable to systemic cancer therapies. Immune checkpoint inhibitors (ICIs) have changed the treatment landscape in oncology but their impact on VTE risk is still debated.

Method We assessed VTE risk in a single-center prospective cohort study including patients with cancer initiating systemic anti-cancer therapies and comparing the risk of VTE between patients receiving different types of therapy. Patients recruited between July 2019 and April 2023 were included in this analysis. All-cause mortality was considered a competing event of interest and thus, competing risk analyses were performed.

Results In total, 880 patients (median age: 62 years [interquartile range, IQR: 53-70], 47% women) were included, compromising 459 (52.2%) patients with newly diagnosed cancer and 421 (47.8%) patients with recurrent or progressive disease. Of 831 patients with solid tumors, 551 (62.6%) had metastatic disease at study inclusion. After study inclusion, systemic treatment with chemotherapy alone was initiated in 427 (48.5%), with combined chemotherapy and ICI therapy in 147 (16.7%), with ICI therapy alone in 138 (15.7%), with targeted therapy and chemotherapy in 109 (12.4%), with targeted therapy alone in 44 (5%), and with targeted therapy and ICI therapy in 15 patients (1.7%). During a median follow-up time of 15.8 months (IQR: 9.3-27.7), 68 (7.7%) were diagnosed with VTE, including 11 catheter-related thrombosis, 20 deep vein thrombosis (DVT), 24 pulmonary embolism (PE), 4 superficial vein thrombosis (SVT), 4 portal vein thrombosis, and 4 patients with PE and DVT as index event. VTE was diagnosed in 43 (10.1%) patients receiving chemotherapy, 11 (7.5%) patients receiving chemotherapy and ICI therapy, 6 (4.3%) patients receiving ICI therapy alone, 7 (6.4%) patients receiving targeted therapy and chemotherapy, 1 (2.3%) receiving targeted therapy and in none (0%) receiving targeted therapy and ICI therapy. This translated into 6-month cumulative VTE incidences of 7.2% (95% confidence interval [CI]: 4.6-9.8) in patients with chemotherapy, of 5.8% (95% CI: 1.8-9.6) with ICI and chemotherapy, of 2.3% (95% CI: 0-4.8) with ICI therapy, of 5.2% (95% CI: 0.8-9.6) with targeted therapy and chemotherapy, and of 2.6% (95% CI: 0.0-7.7) with targeted therapy ([Fig. 1], [Fig. 2]).

Fig. 1  Cumulative VTE incidence after 6-, 12-, 24-month follow-up stratified according to systemic ICI – immune checkpoint inhibitors

Fig. 2  Cumulative VTE incidence stratified according to systemic therapy that patients started at

Conclusion In our single-center prospective cohort study, patients with cancer receiving systemic anti-cancer therapies had a substantial VTE risk. Patients with cancer receiving chemotherapy had the highest cumulative incidence, while the VTE incidence was lower in those treated with ICI therapy. In the future, further analyses considering other VTE risk factors are needed.

Publication History

Article published online:
26 February 2024