Increased risk of venous and arterial thromboembolism in patients with colorectal cancer receiving cetuximab-based combination chemotherapy: A population-based study in Korea.

Introduction: Limited data exist on the risk of venous and arterial thromboembolisms (VTE and ATE) in patients receiving cetuximab plus chemotherapy. We aimed to determine the thromboembolic risk of patients with recurrent/metastatic colorectal cancer (CRC) treated with cetuximab plus chemotherapy compared to chemotherapy alone.

Methods: This population-based study used nationwide claims data from the Health Insurance Review and Assessment Service of South Korea from 2013 to 2020. Patients with recurrent/metastatic CRC treated with first-line oxaliplatin- or irinotecan-based doublets with or without cetuximab and no secondary prevention for VTE and ATE were included. Primary outcomes were the occurrence of any thromboembolic events, VTE, and ATE, which were determined using the cumulative incidence method incorporating death as a competing event.

Results: We identified 19,723 patients (cetuximab plus chemotherapy, N = 7630; chemotherapy alone, N = 12,093). The cumulative incidence of any thromboembolic events in patients with cetuximab plus chemotherapy was significantly higher than in those receiving chemotherapy alone (6-month, 5.62 % vs. 3.58 %, P < 0.0001). The rates of VTE (6-month, 5.11 % vs. 3.28 %, P < 0.0001) and ATE (6-month, 0.53 % vs. 0.32 %, P = 0.0218) were also higher in patients receiving cetuximab plus chemotherapy. In multivariable analysis, cetuximab plus chemotherapy was independently associated with developing any thromboembolic events (hazard ratio [HR], 1.63; 95 % confidence interval [CI], 1.42-1.87), VTE (HR, 1.62; 95 % CI, 1.40-1.87), and ATE (HR, 1.77; 95 % CI, 1.16-2.71).

Conclusions: Cetuximab with irinotecan- or oxaliplatin-based doublet chemotherapy was associated with an increased risk of any thromboembolic events, VTE, and ATE; further studies are warranted to examine the underlying mechanisms.