Neoadjuvant Endocrine Therapy for HR+/HER2- Breast Cancer

Young HOPE/JCOG2402 is a multicenter, randomized phase III study designed to evaluate response-guided therapy following neoadjuvant endocrine therapy to optimize adjuvant treatment in premenopausal HR+/HER2- Breast Cancer. Premenopausal women with intermediate-risk HR-positive/HER2-negative breast cancer derive benefit from the addition of chemotherapy to endocrine therapy. However, previous studies have demonstrated that patients who achieve an endocrine response (Ki-67 ≤10%) following neoadjuvant endocrine therapy have excellent outcomes without chemotherapy, irrespective of menopausal status. These findings suggest that endocrine therapy response may serve as a predictive biomarker to identify premenopausal patients who can safely omit chemotherapy. The primary objective of this study is to evaluate the non-inferiority of an ET response-guided treatment strategy compared with standard surgery followed by adjuvant therapy. The study aims to increase the proportion of patients who can be treated with endocrine therapy alone by omitting chemotherapy in those with highly endocrine-sensitive disease. Eligible patients are randomized 1:1 to upfront surgery or neoadjuvant endocrine therapy with an aromatase inhibitor and ovarian function suppression. The primary endpoint is EFS. Secondary endpoints include overall survival, relapse-free survival, distant recurrrence-free survival, HR-QOL, the rate of endocrine therapy alone in adjuvant therapy, ET response rate in an Arm B, the rate of non-menopause and safety. A total of 950 patients will be enrolled. Randomization is stratified by cN0 vs cN1, HG1 or 2 vs 3, and institution. The JCOG2402 trial addresses an unmet need in adjuvant therapy of premenopausal HR-positive, HER2-negative breast cancer with intermediate risk and may contribute to the establishment of a new treatment strategy.