EARLY real-world treatment and dosing patterns of ribociclib for metastatic breast cancer (mBC): A retrospective observational study.

Abstract

e13059 Background: Ribociclib and abemaciclib in combination with endocrine therapy have demonstrated survival benefit in 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 was 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) and followed through December 31, 2018. USON’s iKnowMed (iKM) EHR database was used to identify patients and medical chart data review was conducted to abstract treatment information. Descriptive analyses were performed to assess patient and treatment characteristics. 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 at initiation of treatment was 66 (SD 14) years. Among patients with documented menopausal status, 90% were post-menopausal, and 10% were pre-menopausal. Among patients with documented receptor status, 99% were ER+/HER2-. 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%). Eastern Cooperative Oncology Group (ECOG) performance score at time of ribociclib initiation was 0-1 in 60.4% of patients. Documented metastatic sites were present in bone (35.3%), lung (8.6%), and liver (6%). The most common comorbidities documented within 6 months of treatment initiation were cardiovascular disease (53.4%), diabetes (19%), and depression (18.1%). 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. 95% of patients started at the full dose of 600mg. One-fourth of patients (n = 29) had a dose-hold and 27.6% (n = 32) patients experienced a dose reduction with ribociclib therapy. Conclusions: This study represents early ribociclib uptake in a real-world setting in the US. Early utilization demonstrates patients receiving ribociclib are older and sicker than those in pivotal clinical trials. Substantial heterogeneity in ribociclib initiation by LOT was observed.