Thrombosis in breast cancer patients on cyclin-dependent kinase inhibitors: Survival impact and predictive factors - A study by the cancer and thrombosis group of the spanish society of medical oncology (SEOM).

Thrombosis may be included in the profile of side effects associated with CDK4/6 inhibitors. Its significance might be greater than reported in randomized clinical trials. To investigate this, a retrospective, multicenter study was conducted. The primary objective was to calculate the incidence of thrombosis associated with CDK4/6 inhibitors. Secondary objectives included examining the impact of thrombosis on survival and identifying predictor variables for the development of venous thromboembolism (VTE) or arterial thrombosis (AT). A total of 986 patients were recruited. The incidence of VTE/AT associated with CDK4/6 inhibitor treatment during the follow-up period was 5.48 %. Survival analysis did not indicate that the development of VTE/AT during CDK4/6 inhibitor treatment significantly impacted patient survival (p = 0.133). In our analysis, two variables were found to be statistically significant (p < 0.05) as predictors of VTE/AT in breast cancer patients receiving CDK4/6 inhibitor therapy. These variables were the presence of central nervous system (CNS) metastasis with an odds ratio (OR) of 3.68 (95 % CI 1.18 - 11.49) and the use of abemaciclib with an OR of 2.3 (95 % CI 1.16 - 4.57).