Abstract S1-02: PrECOG 0102: A randomized, double-blind, phase II trial of fulvestrant plus everolimus or placebo in post-menopausal women with hormone receptor (HR)-positive, HER2-negative metastatic breast cancer (MBC) resistant to aromatase inhibitor (AI) therapy
Authors: Kornblum NS , Manola J , Klein P , Ramaswamy B , Brufsky A , Stella PJ , Burnette B , Telli M , Makower DF , Leach J , Truica CI , Wolff AC , Soori GS , Haley B , Nagarajan A , Wassenaar TR , Goldstein L , Miller KD , Sparano JA 
Published: March 2017

Background: Although AIs are an effective treatment for HR-positive MBC, whether used alone or in combination with CDK4/6 inhibitors, resistance to therapy and disease progression invariably develops. Therapeutic options for AI-resistant disease include the m-TOR inhibitor everolimus in combination with the steroidal AI exemestane, or the selective estrogen receptor downregulator (SERD) fulvestrant alone. We hypothesized that the combination of fulvestrant and everolimus would be more effective than fulvestrant alone in AI-resistant MBC.

Methods: Major eligibility criteria included post-menopausal women with HR-positive, HER2-negative MBC, recurrence or progression while receiving prior non-steroidal or steroidal AI therapy, ECOG PS 0-1, and ≤1 prior chemotherapy regimen for metastases. All patients received fulvestrant (500mg IM q2 weeks for 3 doses, then q4 weeks) plus oral everolimus (10mg) or placebo (1:1 randomization). Prophylactic corticosteroid mouthwash was not used. Tumor assessment was performed at baseline and every 12 weeks. Treatment continued until progressive disease (PD) by RECIST 1.1 criteria. Patients who discontinued everolimus/placebo due to toxicity continued fulvestrant until PD. The primary endpoint was progression-free survival (PFS), defined as time from start of treatment until progression or death. With accrual of 130 patients (120 eligible), the trial had 90% power to detect an improvement in median PFS from 5.4 months to 9.2 months (1-sided stratified log-rank test, type I error rate10%), with analysis planned after 98 PFS events.

Results: Of 130 patients treated (64 everolimus, 66 placebo), median age was 61 years (range 35-92), and treatment arms were balanced for stratification factors used in randomization, including ECOG PS 0 vs. 1 (59%/41%), measurable disease (66%), and prior chemotherapy for metastasis (17%). Grade 3/4 AEs were more common in the everolimus arm (53%/3% vs. 23%3%), including hyperglycemia (16%/0% vs. 0%), stomatitis (11%/0% vs. 0%), hypertriglyceridemia (9%/2% vs. 0%), lymphopenia (9%/0% vs. 0%), and pneumonitis (6%/2% vs. 0%). There were 3 grade 5 events (2 everolimus, 1 placebo arm), none of which were attributed to therapy. Selected grade 2 events of interest included fatigue (17% vs. 6%), hyperglycemia (6% vs. 0%), and stomatitis (6% vs. 0%). Everolimus/placebo was discontinued for adverse events, patient withdrawal, or physician discretion in 39% in the everolimus arm and 21% in the placebo arm. After 98 PFS events, median PFS was 10.4 months in the everolimus arm versus 5.1 months in the placebo arm (hazard ratio: 0.61, 95% C.I. 0.40 – 0.92; stratified logrank p= 0.02).

Conclusions: The addition of everolimus to fulvestrant significantly improved PFS in post-menopausal women with AI-resistant MBC. Everolimus used without prophylactic corticosteroid mouthwash exhibited a similar rate of oral mucositis and overall AE profile when combined with fulvestrant as when combined with exemestane.

Keywords: advanced breast cancer, PrECOG 0102, endocrine resistance, everolimus, exemestane, hormone receptor-positive, mTOR inhibitor, postmenopausal.

Citation Format: Kornblum NS, Manola J, Klein P, Ramaswamy B, Brufsky A, Stella PJ, Burnette B, Telli M, Makower DF, Leach J, Truica CI, Wolff AC, Soori GS, Haley B, Nagarajan A, Wassenaar TR, Goldstein L, Miller KD, Sparano JA. PrECOG 0102: A randomized, double-blind, phase II trial of fulvestrant plus everolimus or placebo in post-menopausal women with hormone receptor (HR)-positive, HER2-negative metastatic breast cancer (MBC) resistant to aromatase inhibitor (AI) therapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S1-02.