OBJECTIVES:

CDK4/6 inhibitors have changed the treatment landscape for women with HR-positive/HER2-negative mBC. This study assessed early real-world treatment and dosing patterns of ribociclib for mBC in a US community oncology setting.

METHODS:

This is a retrospective, observational, descriptive study of female mBC patients initiating treatment with ribociclib between March 1, 2017 and September 30, 2018 within the US Oncology Network (USON). Patients were followed through December 31, 2018 for a minimum of 3-months of follow up. USON’s iKnowMed^TM (iKM) EHR database was used to identify eligible patients and medical chart data review was conducted to abstract treatment information. Descriptive analyses were performed to assess patient and treatment characteristics, while the Kaplan Meier method was used to calculate duration of therapy (DOT).

RESULTS:

A total of 161 patients were selected for chart review, of which 116 patients who received ribociclib were confirmed as eligible. The mean age of patients was 66 (SD 14) years. Patients most commonly initiated ribociclib in the first-line setting (1L n= 52, 2L n= 30, 3L n =9, 4L+ n= 25) and in combination with letrozole (n = 33, 28.4%). Overall, 46.6% (n=54) of patients received prior neoadjuvant or adjuvant chemotherapy and 32.8% patients (n=38) received prior neoadjuvant or adjuvant endocrine therapy. One-fourth of patients (n=29) had a dose-hold and 27.6% (n=32) patients experienced a dose reduction with ribociclib therapy. Unadjusted for patient heterogeneity across line-of-therapy, the median duration on ribociclib was 8.5 months. Disease progression was the most common reason for ribociclib discontinuation (n=29, 25%), followed by toxicity (n=24, 21%).

CONCLUSIONS:

This study represents early ribociclib use in a real-world setting in the US. Although treatment sequences were diverse, ribociclib was most commonly initiated in the 1L setting. Future research should explore how the DOT may vary by treatment regimen and reasons for dose modification.