Maintenance Ribociclib and ET Following First-Line Chemotherapy in HR-Positive/HER2-Negative Metastatic Breast Cancer: Findings from the Phase 2 AMICA Trial

Approximately one-third of patients with HR-positive/HER2-negative metastatic breast cancer receive chemotherapy (CT) as initial treatment, with longer duration of CT associated with better long-term outcomes; however, CT duration is typically limited by toxicities and patient and physician preferences, usually resulting in treatment duration <6 months. Replacing CT with maintenance endocrine therapy (ET) is an accepted treatment strategy in real-world practice, but data on well-tolerated maintenance treatments with progression-free survival (PFS) and overall survival (OS) benefits are needed.

The phase 2 AMICA trial (NCT03555877) is a multicenter, prospective, open-label study to assess the addition of CDK4/6 inhibitor ribociclib to ET as maintenance therapy in patients with disease control after ≥4 treatment cycles of first-line CT as monotherapy or combination therapy at the discretion of the investigator. Initially, patients were randomized to receive ET with or without ribociclib; however, due to the slow accrual of subjects, the study was amended after 37 patients and all subsequent patients received ET plus ribociclib. Treatment was given until disease progression, unacceptable toxicity, or withdrawal of consent. Maintenance ET could have been initiated up to 6 weeks before enrollment in the AMICA trial. One previous line of ET including prior use of a CDK4/6 inhibitor was allowed. The primary objective was to assess the median PFS (mPFS) of patients receiving ET plus ribociclib; secondary objectives were median OS (mOS), safety, compliance, clinical benefit rate, and patient-reported outcomes. The trial was terminated prematurely due to slow patient accrual.

Between March 2018 and December 2021, 56 patients were enrolled and started treatment (n = 44, ribociclib + ET; n = 12, ET monotherapy). A total of 88.6% of patients were postmenopausal at the time of study entry, and 39.5% were M1 at primary diagnosis. Overall, 46.5% of patients received letrozole, 14% received anastrozole, 7.0% received exemestane, and 32.6% received fulvestrant. Ten patients (22.7%) in the ribociclib plus ET arm had at least 1 serious adverse event, with 2 having at least 1 adverse event of special interest (n = 1, hepatotoxicity; n = 1, overdose). In patients treated with ribociclib plus ET, mPFS was 18.9 months (95% confidence interval, 13.2-32.6), with 90.6% and 67.1% event-free at 6 and 12 months, respectively. mOS has not yet matured; however, 85.1% of patients were alive at 12 months, with approximately 60% of patients alive at 3 years.

Investigators concluded that the AMICA trial shows promising efficacy of ribociclib as part of endocrine-based maintenance therapy in delaying tumor progression after CT with an acceptable safety profile.

Source:

Decker T, Lüdtke-Heckenkamp K, Melnichuk L, et al. Anti-hormonal maintenance treatment with the CDK4/6 inhibitor ribociclib after 1st line chemotherapy in hormone receptor positive/HER2-negative metastatic breast cancer: a phase II trial (AMICA) GBG 97. San Antonio Breast Cancer Symposium 2022. Abstract P3-01-09.