Neoadjuvant dalpiciclib, exemestane, and goserelin in premenopausal women with HR-positive, HER2-negative breast cancer: A prospective, multicenter, randomized two-group, non-controlled phase 2 clinical trial.

Abstract

TPS625 Background: The combination of CDK4/6 inhibitors (CDK4/6i) with endocrine therapy has significantly improved progression-free survival and overall survival in patients with HR-positive, HER2-negative advanced breast cancer (BC), revolutionizing the treatment landscape. However, previous CDK4/6i neoadjuvant studies have predominantly focused on postmenopausal populations, leaving a gap in preoperative treatment for early HR-positive, HER2-negative premenopausal BC patients. Therefore, the present trial is conducted to investigate the efficacy of dalpiciclib, exemestane and goserelin as neoadjuvant therapy in premenopausal women with HR-positive, HER2-negative BC. Methods: This is a multicenter, randomized two-group, non-controlled phase 2 clinical trial. Key eligibility criteria include: Patients aged 18 years or older with no prior treatment, an ECOG performance status of 0-1, at least 1 measurable lesion, and clinical stage II-III HR-positive, HER2-negative premenopausal invasive BC. Initially, all enrolled patients will receive two cycles of treatment with docetaxel, doxorubicin, and cyclophosphamide (TAC). Subsequently, patients with complete response (CR) or partial response (PR) will receive an additional four cycles of TAC, whereas patients with progressive disease (PD) will undergo surgery or treatment options decided upon by the investigators. Those with stable disease (SD) will be randomly assigned 1:1 to either an experimental group receiving 16 weeks of dalpiciclib, exemestane, and goserelin (dalpiciclib: 125 mg daily for 21 days followed by 7 days off, exemestane: 25 mg daily for 28 days, goserelin: 3.6 mg every 28 days) or a standard chemotherapy group receiving four more cycles of TAC. Treatment response is assessed according to RECIST 1.1 criteria. Surgery will be performed after completion of the planned neoadjuvant treatment, followed by radiation therapy and systemic treatment according to local guidelines or the investigators' choices. The study's primary endpoint is the objective response rate (ORR) of the experimental group. Secondary endpoints include the ORR, residual cancer burden, preoperative endocrine prognostic index, event-free survival, and safety of both. Using Simon's two-stage optimal design and assuming a 40% response rate as desirable in the experimental group, at least 13 responses among a total of 43 patients were required to meet the primary endpoint. The trial will be terminated if fewer than 3 patients respond in the first stage. Considering an 80% SD rate post two neoadjuvant TAC cycles and a 10% attrition, the sample size was ultimately set at 119. The trial is actively recruiting. Clinical trial information: NCT06009627 .