Abstract P5-13-03: An efficacy and safety trial of preoperative chemo-endocrine therapy in Luminal B-like (HER2-negative) breast cancer

Abstract

Abstract Background: The St.Gallen consensus guideline recommends the sequential administration chemotherapy followed by endocrine therapy as postoperative therapy for the higher risk of ER-positive breast cancer patients based on results of a single study. In metastatic settings, however, several trials conducted in the 1980s' demonstrated that tumor response rates were higher when chemotherapy and tamoxifen was concomitantly administered than when chemotherapy and tamoxifen administered were given sequentially. In the preoperative settings, pathological complete response (pCR) rate can be used as a surrogate marker to predict event-free survival or overall survival in Luminal B-like (HER2-negative) breast cancer. We, therefore, designed a prospective randomized safety and efficacy trial in order to test a hypothesis that the concomitant administration of an aromatase inhibitor and chemotherapy improves pathological complete response (pCR) rate than chemotherapy alone in the preoperative setting. Trial design: This two-arm randomized clinical trial enrolled operable breast cancer patients with Luminal B-like (HER2-negative) subtype. Patients were randomly assigned (1:1) to receive preoperative chemotherapy alone or preoperative chemotherapy concurrent with endocrine therapy for 24 weeks before surgery. Chemotherapy consisted of 12 cycles of weekly paclitaxel followed by 4 cycles of every 3-week AC. Endocrine therapy consisted of anastrozole for postmenopausal patients or anastrozole plus leuprorelin for premenopausal patients. Eligibility criteria: 1)Female patients with operable and histologically confirmed invasive breast cancer; 2)HER2-negative; 3)Either ER-positive or PgR-positive; 4)Either Ki67-LI>=14% and NG>=2 or NG=3 regardless of Ki67-LI. Endpoints: Primary endpoint is the pCR rate. Secondary endpoints are the clinical response rate (RECIST), the breast-conserving surgery rate, the adverse events, and HRQOL. Results: Between March 2012 and August 2017, 70 patients were randomly assigned to chemotherapy group (n=34) or chemo-endocrine therapy group (n=36). pCR rates were 8.8 % and 2.7 % in the chemotherapy and the chemo-endocrine group, respectively (P = 0.319). Similarly, clinical complete response rates were 5.9 % and 5.6 % in the chemotherapy and the chemo-endocrine group, respectively (P = 0.745). There were no clear differences in treatment-related side effects and HRQOL between interventions. Conclusion: The concomitant administration of endocrine therapy and chemotherapy in Luminal B-like breast cancer patients is similar to chemotherapy alone in pCR rate and clinical response in the preoperative setting. Citation Format: Roichi Matsunuma, Toru Watanabe, Yasuo Hozumi, Kei Koizumi, Yasushi Ito, Hirofumi Fujita, Hiroyuki Ogura, Keigo Goto, Hiroki Mori, Noriko Sawai, Norihiko Shiiya. An efficacy and safety trial of preoperative chemo-endocrine therapy in Luminal B-like (HER2-negative) breast cancer [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 P5-13-03.