Abstract OT1-04-03: Alternative dosing of exemestane before surgery in postmenopausal patients with stage 0-II estrogen receptor positive breast cancer: Design and methodology

Background: The aromatase inhibitor exemestane (EXE) has shown to lower cancer incidence in high-risk postmenopausal women. However, undesirable symptoms and side effects (i.e., bone density loss, musculoskeletal ache, climacteric syndrome) may compromise patient motivation and adherence to a long-term preventive treatment. A less frequent drug schedule, compared to the standard regimen, may be more acceptable to healthy at-risk women. We hypothesized that comparison of two alternative less frequent dose regimens with the standard daily dose regimen will show that it is possible to decrease undesirable symptoms of EXE while still effectively reducing serum estradiol. Trial Design: We are conducting a multi-center, pre-surgical, double-blind, non-inferiority phase IIb study in which 180 postmenopausal women will be randomized to receive either EXE 25 mg/day or 25 mg/three times a week or 25 mg/week for 4 to 6 weeks prior to surgery. Surgery will occur on day 29, 36 or 43 after treatment initiation. Eligible subjects are postmenopausal women with histologically-confirmed ER-positive (ER >10%) primary breast cancer candidates for surgery. Participants with T0-2, N0-1, Mx or with larger tumors who refuse neo-adjuvant therapy before surgery are eligible. Subjects are stratified according to participating site and body mass index ( 25 kg/m2). The primary objective is to assess if the reduction in estradiol with EXE 25 mg/three times a week and EXE 25 mg/week is comparable with the standard dose of 25 mg/day of EXE. Methods: Blood will be collected at baseline and at the end of treatment. Tissue samples will be collected from the diagnostic biopsy and at the time of surgery. The primary endpoint is the percentage change of serum estradiol concentration between baseline and surgery in the three arms in a CLIA certified laboratory. Given the expected reduction of at least 80% change with EXE at 25 mg daily considered as reference group (control arm) against 25 mg/three times a week or 25 mg weekly, for the power calculation we assume a non-inferiority difference of 6% in percentage changes of circulating estradiol after treatment from baseline, using a one-sided, two-sample t-test. Secondary outcome measures are the incidence of toxicity and menopausal symptoms according to the CTCAE (v4) and by the self-administered MENQoL; the effect of the three regimens on sex hormones (estrone, estrone sulphate, SHBG, testosterone, DHEAS and FSH) and the effect on circulating estradiol levels using an ultrasensitive method given that the serum levels in postmenopausal women under EXE may be very low. Drug and metabolites levels will be measured in blood, cancer tissue and non-cancer tissue. Evaluation of serum insulin, glucose (homeostatic model assessment index), and lipid profile (total cholesterol, high-density lipoprotein cholesterol and triglycerides), leptin and adiponectin will be performed before and after treatment. Additionally, we will measure breast estradiol concentration in cancer and non-cancer tissue and compare changes in ER, PgR, and proliferation in cancer and non-cancer tissue samples obtained at time of biopsy and definitive surgery. Finally, we will also analyze the role of the polymorphic UGT2B17 gene (involved in EXE and 17-dihydroexemestane metabolism) as well as tissue proteomics. Preliminary results: Enrollment started in February 2017 and as of July 3, 2019, a total of 170/180 participants have been randomized (94% of the expected sample size). Preliminary data will be presented at the conference. IND Sponsor: NCI/DCP NCI contract: HHSN26120120034I Citation Format: Aliana Guerrieri-Gonzaga, Parjhitham Thomas, Andrea DeCensi, Katherine D Crew, Nagi Kumar, Sara Gandini, Lana Vornik, Brandy Heckman-Stoddard, Eva Szabo, Eileen Dimond, Jack Lee, Diane Liu, Matteo Lazzeroni, Sara Cagnacci, Davide Serrano, Mauro D9Amico, Flavio Guasone, Tania Buttiron Webber, Powel Brown, Bernardo Bonanni. Alternative dosing of exemestane before surgery in postmenopausal patients with stage 0-II estrogen receptor positive breast cancer: Design and methodology [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 OT1-04-03.