Abstract P3-01-09: Maintenance Therapy with ET and Ribociclib after 1st line Chemotherapy (CT) in Hormone Receptor (HR)-positive/HER2-negative Metastatic Breast Cancer (BC): a Phase II Trial (AMICA)

Abstract

Abstract Background: Approximately one third of HR-positive, metastatic BC patients receive CT as initial treatment. Longer duration of CT is associated with a better long-term outcome. However, the duration of CT is usually limited by toxicities and patients and physicians´ preferences, resulting in treatment duration < 6 months. Replacing CT by maintenance endocrine treatment is an accepted treatment strategy in everyday clinical practice, but prospective data are lacking. Well tolerated maintenance treatments with the potential to prolong progression-free survival (PFS) and even overall survival (OS) are urgently needed. Methods: The AMICA trial (NCT03555877) is a multicenter, prospective, open-label phase II study to test the addition of the CDK4/6 inhibitor ribociclib to ET as maintenance therapy in patients with disease control after at least 4 cycles of 1st line mono- or poly-CT at investigator´s discretion. Initially patients were randomized to receive ET +/- ribociclib. Due to slow accrual the study was amended after inclusion of 37 patients and all subsequent patients received ET+ribociclib. Treatment was given until disease progression, unacceptable toxicity, or withdrawal of consent. Maintenance ET could have already been started up to 6 weeks before enrolment. One previous line of ET including prior use of CDK4/6 inhibitor was allowed. The primary objective was to estimate the median PFS of patients treated with ET+ribociclib. Secondary objectives were median OS, safety, compliance, clinical benefit rate (CBR) and patient reported outcomes. The trial was closed prematurely due to slow recruitment. Results: Between March 2018 and December 2021, 56 patients were enrolled and started treatment (n=44 received ET+ribociclib, 12 ET alone). Median age of patients treated with ET+ribociclib was 60 years, 52.3% were overweight/obese, 88.6% were postmenopausal at study entry, 39.5% were M1 at primary diagnosis. Overall, 46.5% of the patients received letrozole, 14% anastrozole, 7.0% exemestane, 32.6% fulvestrant. A total of 10 (22.7%) patients in the ET+ribociclib arm had at least one serious adverse event, 2 at least one adverse event of special interest (N=1 hepatotoxicity, N=1 overdose). Conclusions: Results on the primary and secondary objectives will be presented at the meeting. Citation Format: Thomas Decker, Kerstin Lüdtke-Heckenkamp, Luidmila Melnichuk, Jenny Furlanetto, Kristina Lübbe, Mark-Oliver Zahn, Marcus Schmidt, Carsten Denkert, Ralf Lorenz, Volkmar Müller, Dirk-Michael Zahm, Christoph Mundhenke, Stefan Bauer, Marc Thill, Peter Seropian, Natalie Filmann, Sibylle Loibl. Maintenance Therapy with ET and Ribociclib after 1st line Chemotherapy (CT) in Hormone Receptor (HR)-positive/HER2-negative Metastatic Breast Cancer (BC): a Phase II Trial (AMICA) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-01-09.