Real-World Analysis Finds Shift in Clinician Preferences for CDK4/6 Inhibitors for Patients with HR+/HER2− Metastatic Breast Cancer

There are 3 current CDK4/6 inhibitors (CDK4/6i) with Food and Drug Administration (FDA) approval for use for hormone-positive (HR+)/HER2− metastatic breast cancer. These CKD4/6i combined with endocrine therapy are the recommended first-line therapy for HR+/HER2− metastatic breast cancer and have demonstrated significantly improved progression-free survival (PFS) in patients. However, only 2 of these 3 medications have significantly improved overall survival (OS). To evaluate the optimal selection and sequencing of these medications, a real world clinical-genomic database was used to determine the use of the CDK4/6i agents and outcomes when used to treat patients with HR+/HER2− metastatic breast cancer. Cell-free circulating tumor DNA (ctDNA) testing done via Guardant360 formed the study database. Patients selected for inclusion had a metastatic diagnosis, ≥2 pharmacy or medical claims, and received CDK4/6i treatment for metastatic breast cancer between March 2018 and March 2023. Only those patients who had ≥12 months of follow up were included in the study. As proxy for PFS, real-world time to next treatment (rwTTNT) and real-world time to treatment discontinuation (rwTTD) were used.

In total, 4593 patients were included in the study. Palbociclib was received by 64 of the patients, abemaciclib was received by 24%, and ribociclib was received by 11%. After 2020, ribociclib use increased from 9% in 2020 to 18% in 2022; palbociclib use decreased from 63% to 54%; and abemaciclib use stayed steady at 28% both years. Patients who received ribociclib had a median age of 56 years; those who received palbociclib had a median age of 60 years, and the median age of those who received abemaciclib was 59 years. The patients who received ribociclib had fewer comorbidities than those receiving palbociclib or abemaciclib. When outcomes were analyzed, the mean follow up for patients receiving abemaciclib was 21.9 months, ribociclib was 21.9 months, and 27.6 months for palbociclib. The rwTTNT was 16.4 months for first-line palbociclib and 15.6 months for second-line treatment. For abemaciclib, rwTTNT was 14.0 months and 11.8 months for first-line and second-line treatment, respectively. The rwTTNT for ribociclib was 13.8 months and 14.2 months respectively. The rwTTD for first-line palbociclib was 10.3 months and for second line 9.6 months; for abemaciclib 6.5 months and 7.3 months respectively; and for ribociclib 7.8 months and 8.1 months respectively. The real-world overall survival for first-line palbociclib was 5.8 months. Real-world overall survival was not reported for first-line abemaciclib or ribociclib.

Source:

Weipert C, Wander S, Davis A, et al. Real-world (RW) utilization and patient outcomes across three CDK4/6 inhibitors in metastatic breast cancer (mBC). Poster presented at: San Antonio Breast Cancer Symposium. December 7, 2023; San Antonio, TX. Abstract # PO4-18-02.