Treatment patterns and outcomes associated with sequential and non-sequential use of CDK4 & 6 inhibitors in patients with HR+, HER2− MBC in the real world

Cyclin Dependent Kinase 4 & 6 inhibitors (CDK4 & 6i) have transformed the management of HR+, HER2− metastatic breast cancer (MBC); however, the optimal sequence of these treatments and other systemic therapies for MBC remains unclear.

This study analyzed electronic medical records from the ConcertAI Oncology Dataset. US patients who received abemaciclib and at least one other systemic line of therapy (LOT) for HR+, HER2− MBC were eligible. Treatment sequences were grouped, and data for two pairs of groups are presented herein (N = 397): Group 1 (1L CDK4 & 6i to 2L CDK4 & 6i) vs. Group 2 (1L CDK4 & 6i to 2L non-CDK4 & 6i), and Group 3 (2L CDK4 & 6i to 3L CDK4 & 6i) vs. Group 4 (2L CDK4 & 6i to 3L non-CDK4 & 6i). Time-to-event outcomes (PFS and PFS-2) were analyzed using Kaplan–Meier method and Cox proportional hazard regression.

In the total cohort of 690 patients, the most prevalent sequence was 1L CDK4 & 6i to 2L CDK4 & 6i (n = 165). For the 397 patients across Groups 1–4, sequential CDK4 & 6i demonstrated numerically longer PFS and PFS-2 versus non-sequential CDK4 & 6i. Adjusted results demonstrate that patients in Group 1 demonstrated significantly longer PFS (p = 0.05) versus Group 2.

Although retrospective and hypothesis-generating, these data demonstrate numerically longer outcomes in the subsequent LOT associated with sequential CDK4 & 6i treatment.