Abstract P5-11-14: Palbociclib in combination with anastrozole or exemestane as first-line therapy for patients with locally advanced, inoperable or metastatic HR+/HER2- breast cancer in Germany: Interim results of the INGE-B phase 2 study

Background: The pivotal PALOMA trials investigated the combination of the cyclin-dependent kinase 4/6 inhibitor palbociclib with letrozole as first-line treatment or with fulvestrant after prior endocrine therapy in patients with advanced HR+/HER2- breast cancer. Based on these trials, extended European approval was granted for this patient population to receive palbociclib in combination with any aromatase inhibitor or with fulvestrant after prior endocrine therapy. Methods: The prospective, multicenter phase 2 INGE-B trial was designed for patients with locally advanced or metastatic HR+/HER2- breast cancer to generate efficacy, safety and quality of life data on the combination of palbociclib with letrozole (first line) or fulvestrant (first and later line after prior endocrine therapy) in accordance with the PALOMA trials and to generate so far lacking trial data on the combination of palbociclib with letrozole (later line) and the combination of palbociclib with anastrozole or exemestane (first line) in Germany. This pre-planned interim analysis was conducted to evaluate data on patients receiving palbociclib plus anastrozole or exemestane as first-line therapy. The primary endpoint was the clinical benefit rate (CBR) in patients with measurable disease according to RECIST v1.1. Key secondary endpoints included the overall response rate (ORR), the CBR for all patients, the disease control rate (DCR), quality of life (QoL) and safety. Data will be analyzed for each group separately with descriptive statistics. Results: At the cut-off date of the interim analysis (June 30, 2019), 66 patients (pts) have been enrolled to receive palbociclib plus anastrozole (palbo+ana) and 64 pts have been enrolled to receive palbociclib plus exemestane (palbo+exe). Thereof, 60 and 58 pts were evaluable, respectively. Median age was 63.5 years (palbo+ana) and 65.0 years (palbo+exe), 100% (n=60) and 94.8% (n=55) of pts had an ECOG performance score of 0 or 1, respectively. 35% (n=21, palbo+ana) and 22.4% (n=13, palbo+exe) of pts presented with non-measurable bone-only disease. The primary endpoint CBR in pts with measurable disease was 73% with palbo+ana (27 of 37 pts) and 70% with palbo+exe (31 of 44 pts).Selected outcome data are depicted in Table 1. Grade 3/4 adverse events experienced by at least 10% of pts were neutropenia (n=20, 33.3%) and leukopenia (n=9, 15.0%) in pts treated with palbo+ana and neutropenia (n=23, 39.7%), leukopenia and infections (both n=6, 10.3%) in pts treated with palbo+exe. Conclusions: This interim analysis of the INGE-B study will provide so far lacking trial data on the treatment of palbociclib in combination with anastrozole or exemestane. The data will be discussed with respect to results of the PALOMA trials and already published interim analysis results of the INGE-B trial. Citation Format: Manfred Welslau, Norbert Marschner, Ulrike Soling, Cosima Brucker, Oliver J. Stoetzer, Johannes Meiler, Pauline Wimberger, Steffen Dorfel, Jorg Sahlmann, Leonora Houet, Corinne Vannier, Karin Potthoff. Palbociclib in combination with anastrozole or exemestane as first-line therapy for patients with locally advanced, inoperable or metastatic HR+/HER2- breast cancer in Germany: Interim results of the INGE-B phase 2 study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-11-14.