Retrospectively Analyzing the Use of CDK4/6 Inhibitors to Treat Adult Female Patients with Metastatic Breast Cancer

The majority of patients with metastatic breast cancer receiving treatment with CDK4/6 inhibitors had progression-free survival, behaving similarly when used as first-line therapy or after adjuvant hormonal therapy.

Silvia Comis, MD, Senior Medical Director, Oncology-Therapeutic Science and Strategy Unit, IQVIA, Milan, Italy, and colleagues used US open health claims and prescription data to examine the pattern of behavior of CDK4/6 inhibitor combinations as first-line therapy or following adjuvant hormonal therapy in adult females with de novo metastatic breast cancer.

The researchers examined metastatic breast cancer between 2015 and 2019, in adult female patients aged >18 years. Based on their first treatment, women were classified into 3 groups (group 1, hormonal; group 2, CDK4/6 inhibitor combinations; and group 3, everolimus combination).

The percentage of patients who switched to next therapy was 3.2% (1200 patients) of the 37,351 patients receiving CDK4/6 inhibitors as first-line therapy or following adjuvant hormonal therapy for advanced or metastatic diseases. For the majority of patients, in 87% of cases, changing therapy occurred within a 2-year period, and those patients who continued with first-line therapy did so for an extended period of time.

Compared with the overall CDK4/6 inhibitor population in groups 1 and 2, no statistically significant difference was apparent in the treatment pattern. However, within the first year of treatment, 90% of patients in group 3 compared with the overall patient population receiving CDK4/6 inhibitors switched to chemotherapy (P = .02).

A detailed analysis found that the overwhelming majority (90%) of patients receiving CDK4/6 inhibitors remained on therapy for approximately 1 year, with a small percentage of patients (2%) extending treatment to between 2 and 4.5 years.

The researchers concluded that for the period analyzed, 95% of patients receiving CDK4/6 inhibitors had progression-free survival. Overall, when used as first-line therapy or following adjuvant hormonal therapy, patients receiving CDK4/6 inhibitors had comparable patterns of behavior.

Source: Comis S, Kandasamy T, Perrin AJ, et al. A retrospective analysis of CDK4/6 inhibitors among adult female patients with metastatic breast cancer. J Clin Oncol. 2020;38(15_suppl). Abstract e13028.