A retrospective analysis of CDK4/6 inhibitors among adult female patients with metastatic breast cancer.

Abstract

e13028 Background: The aim of this study is to examine the behavior pattern of cyclin-dependent kinase (CDK4/6) inhibitor combinations in adult females with de novo metastatic breast cancer as first therapy or following adjuvant hormonal therapy. Methods: Using United States open health claims and prescription data we analyzed metastatic breast cancer from 2015 Q1 to 2019 Q4, adult female patients (age ≥18). Patients were classified into 3 groups based on their first therapy: Group 1-Hormonal, Group 2-CDK4/6 Inhibitor Combinations, and Group 3-Everolimus Combination. Analysis was completed using the Chi-Squared goodness of fit test assessing the patients moving to next therapy by time period. We also compared the overall CDK4/6 group as a base for probability distribution to study the pattern of therapy change in individual groups. Results: Of 37,351 patients on CDK4/6 inhibitors as first therapy or following adjuvant hormonal therapy for advanced/metastatic diseases, the percentage of patients who moved to next therapy was 3.2% (1,200 patients). For most patients, change in therapy occurred within a 2-year period (87%) and those who remained on their first therapy continued for an extended duration. In both Groups 1 and 2 no statistically significant difference was found in the treatment pattern compared to the overall CDK4/6 inhibitor patient population. However, most patients in Group 3 (90%) compared to the overall patient population on CDK4/6 inhibitors moved to Chemotherapy within the first year of treatment (statistically significant at p-value = 0.02). Further analysis of granularity in individual patient pathways showed about 90% of patients with CDK4/6 inhibitors remained on therapy for about 1 year and, interestingly, about 2% extended beyond 2 years up to 4.5 years. Conclusions: The results show most patients on CDK4/6 inhibitors (95%) had progression free survival (PFS) for the period we analyzed. Overall, patients on CDK4/6 inhibitors behaved similarly when used as first therapy or following adjuvant hormonal therapy.