Abstract OT1-01-05: Endocrine treatment alone as primary treatment for elderly patients with estrogen receptor positive good prognosis operable breast cancer: A single arm phase II, single institution study

Background : It is estimated that approximately 46,000 women age >75 are diagnosed annually with breast cancer. Due to competing co-morbidities, there is wide variation in treatment recommendations which can lead to over- or under-treatment. Though surgery for breast cancer is considered low-morbidity, many elderly women given a choice, choose not to have surgery. Previous randomized trials comparing surgery with tamoxifen versus endocrine therapy alone in women age >70 unselected for ER status demonstrated similar overall survival with poorer local control in the latter group. A new standard of care needs to be defined for elderly women with good prognosis ER+ tumors, since these women may benefit from endocrine therapy alone to treat their cancer without compromising local and distant control. Hypothesis : We hypothesize that endocrine therapy alone provides adequate local and systemic control of breast cancer in a subpopulation of women age 70 or older with ER+ breast cancer and good prognostic characteristics. Primary Objective To correlate response to neoadjuvant endocrine treatment at 6 months with Oncotype DX Recurrence Score ( RS ) in women with early-stage ER+ breast cancer who are age >70. Secondary Objective 1. To determine the breast cancer-specific survival of women with early-stage ER+ breast cancer, age >70, treated with endocrine therapy alone. 2. To determine the rate of overall survival of women with early-stage ER+ breast cancer, age >70 treated with endocrine therapy alone. Study Design : This is a prospective single arm phase II study. Patients with clinical stage I/II ER+ breast cancer, grade 1-2, Ki67 Results : Between February 2017 and April 2018, 11 patients were enrolled into the study. Two patients could not tolerate endocrine therapy and received standard of care treatment. For the 9 patients on study, average tumor size was 1.7cm, average Ki67 was 15%, average RS was 14. All of the patients received an aromatase inhibitor. At 6 months, 71% of the patients had a partial response, 28% had stable disease. None of the patients developed progressive disease. Conclusion : A new standard of care needs to be defined for women age >70 with good prognosis ER+ tumors, since these women may benefit from endocrine therapy alone to treat their cancer without compromising local and distant control. We continue to enroll patients to determine the optimal tumor markers for identifying women who can be treated with PET only to control their cancer. Citation Format: Aft R, Cherian M, Frith A, Suresh R, Glover-Collins K, Naughton M, Moon C, Conant L, Ma C. Endocrine treatment alone as primary treatment for elderly patients with estrogen receptor positive good prognosis operable breast cancer: A single arm phase II, single institution study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT1-01-05.