Abstract P2-05-03: Anastrozole and everolimus in hormone receptor-positive metastatic breast cancer: Safety profile, activity and associations of molecular alterations in the PI3K/AKT/mTOR pathway

Abstract

Abstract Background Combining aromatase inhibitors with PI3K/AKT/mTOR inhibitors in patients with hormone receptor (HR)-positive metastatic breast cancer has demonstrated clinical efficacy. There is limited data on associations between molecular signatures and activity. Patients and Methods We evaluated the combination of anastrozole and everolimus in 56 patients with HR-positive, metastatic breast cancer. The primary objective was to establish safety and maximum tolerated dose (MTD). Dose limiting toxicities (DLTs) were defined as serious grade 3 or 4 toxicities related to treatment that occurred during cycle 1. Dose level 1 was anastrozole 1mg PO QD and everolimus 5 mg PO QD and dose level 2 was anastrozole 1 mg PO QD and everolimus 10 mg PO QD (a dose level -1 included everolimus 2.5 mg PO QD). Secondary endpoints included evaluation of antitumor activity and molecular associations with response. When tissue was available, Next Generation Sequencing (NGS) was performed using genomic libraries selected for all exons of 236 (or 182) cancer-related genes sequenced to average depth of >500× in a CLIA laboratory (Foundation Medicine, Cambridge, MA, USA). An analysis was then performed for all classes of genomic alterations. Results The median age was 59 (range, 37-82) and the median number of prior therapies in the metastatic setting was 3 (range, 0-13). The initial oral daily dose of anastrozole 1 mg oral and everolimus 10 mg PO daily was well tolerated. Five dose-limiting toxicities (DLTs) were seen at full doses, including grade 3 thrombocytopenia (1 patient), grade 3 neutropenia (1 patient), grade 3 increased liver enzymes (1 patient), grade 3 hyperglycemia (1 patient) and, grade 3 mucositis (1 patient). The most common grade 3 or 4 treatment-related toxicities were neutropenia (5%), increased liver enzymes (5%), and hyperbilirubinemia (3%). Of the 56 patients on study, 36 were tested for at least one molecular alteration in the PI3K/AKT/mTOR pathway. Twelve of these 36 patients had NGS analysis of their tumor tissue. Eighteen of 36 patients (50%) tested had at least one alteration in the pathway, including mutations in PIK3CA (n=16), PIK3R1 (n=1), and AKT1 (n=2); PTEN protein loss (n=1); and, AKT3 amplification (n=1). Sixteen of 56 evaluable patients (29%) achieved stable disease (SD) /partial response (PR)/complete response (CR) ≥ 6 months (n = 3 (5%) with PR/CR). Thirteen of the 16 patients who achieved SD/PR/CR ≥ 6 months were tested for a genetic alteration in PI3K/AKT/mTOR pathway and 7 of these patients (54%) had at least one alteration in the pathway, including mutations in PIK3CA (n=6), PIK3R1 (n=1), and AKT1 (n=1); PTEN loss (n=1); and AKT3 amplification (n=1). Conclusions Combination anastrozole 1 mg and everolimus 10 mg is well tolerated and is active in heavily-pretreated patients with HR-positive breast cancer. The presence of a molecular alteration in the PI3K/AKT/mTOR pathway did not predict for clinical activity of this combination. Citation Format: Jennifer J Wheler, Filip Janku, Stacy L Moulder, Aung Naing, Sarina A Piha-Paul, Gerald S Falchook, Ralph G Zinner, Apostolia M Tsimberidou, Siqing Fu, David S Hong, Johnique T Atkins, Roman Yelensky, Vince Miller, Philip J Stephens, Vincente Valero, Funda Meric-Bernstam, Razelle Kurzrock. Anastrozole and everolimus in hormone receptor-positive metastatic breast cancer: Safety profile, activity and associations of molecular alterations in the PI3K/AKT/mTOR pathway [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-05-03.