The goal of this investigator-initiated, open-label, phase II clinical trial is to evaluate the efficacy and safety of neoadjuvant chemotherapy combined with endocrine therapy in patients with hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative, Ki67 \> 20% invasive breast cancer.
The main questions it aims to answer are:
What is the objective response rate (ORR) assessed by Response Evaluation Criteria in Solid Tumours (RECIST) version 1.1 criteria at the completion of neoadjuvant treatment?
What are the changes in Ki-67 proliferation index, pathological tumor response, pathological complete response (pCR) rate, disease-free survival (DFS), and safety profile?
Participants will receive standard anthracycline- and taxane-based chemotherapy with letrozole. The chemotherapy regimen was either six cycles of docetaxel, epirubicin, and cyclophosphamide (TEC) every 3 weeks or four cycles of epirubicin plus cyclophosphamide followed by four cycles of a taxane (EC→T). The investigator could replace docetaxel or paclitaxel with nanoparticle albumin-bound paclitaxel (nab-paclitaxel), depending on the patient's clinical features and treatment tolerance.
Patients took letrozole 2.5 mg orally once daily throughout neoadjuvant systemic therapy. Premenopausal patients also received ovarian function suppression with leuprorelin acetate (3.75 mg) subcutaneously every 28 days, from the start of neoadjuvant treatment until definitive surgery. A safety assessment will be conducted for each treatment cycle in the patient. During the neoadjuvant therapy phase, tumor assessment will be performed at least after 4 cycles and preoperatively; postoperatively, assessments will be conducted every 3 months using imaging modalities to evaluate the tumor status until disease progression, death, or completion of 3 years postoperatively occurs. Following surgery, all patients will receive adjuvant therapy selected by the investigator based on their individual clinical condition.
Eligible patients were aged ≥18 years
Histologically confirmed estrogen ER-positive, HER2-negative breast cancer with a Ki67 proliferation index >20%.
ER-positivity was defined as nuclear staining in ≥1% of tumor cells by immunohistochemistry (IHC). HER2-negative disease was defined as an IHC score of 0 or 1+, or an IHC score of 2+ with negative fluorescence in situ hybridization(FISH).
Patients were required to have stage I-III operable or locally advanced breast cancer according to the eighth edition of the American Joint Committee on Cancer staging system.
Previous chemotherapy or endocrine therapy for breast cancer;
Pregnancy or lactation;
Severe or uncontrolled infection;
Clinically significant cardiovascular disease, including New York Heart Association class III or IV heart failure, unstable angina, or myocardial infarction within 6 months before enrollment;
Single group
NaCET: For chemotherapy, the TEC or EC-T regimen is selected; for endocrine therapy, letrozole is administered; for premenopausal patients, an LHRH agonist-goserelin or leuprolide
DrugPatients received NaCET consisting of standard anthracycline- and taxane-based chemotherapy administered concurrently with letrozole. The preferred chemotherapy regimen was TEC, comprising docetaxel, epirubicin, and cyclophosphamide, administered every 3 weeks for six cycles. A sequential EC→T regimen, consisting of four cycles of epirubicin plus cyclophosphamide followed by four cycles of a taxane, was also permitted. At the investigator's discretion, nab-paclitaxel could be substituted for docetaxel or paclitaxel according to individual patient characteristics, treatment tolerance, and clinical considerations. Letrozole was administered orally at 2.5 mg once daily throughout the entire neoadjuvant chemotherapy period. Premenopausal patients additionally received ovarian function suppression with leuprorelin 3.75 mg subcutaneously every 28 days, beginning at initiation of neoadjuvant treatment and continuing throughout the preoperative treatment period.
Objective Response Rate (ORR)
ORR defined as the proportion of patients whose best radiological response during neoadjuvant treatment was complete response (CR) or partial response (PR) according to RECIST version 1.1.
pCR
pCR defined as no residual invasive disease in the breast or axillary lymph nodes (ypT0/is ypN0)
Pathological Response
Pathological response defined as Miller-Payne grade 3-5
Paired change in Ki67 between biopsy and surgery
The Ki-67 labeling index was visually assessed independently and in a blinded manner by two breast pathologists according to specific instructions. The average value obtained from both observers was used as the final value for each case. For pCR patients, the postoperative Ki-67 value was replaced by the minimum value of 0.01.
Disease-Free Survival (DFS)
Disease-free survival (DFS) is defined as the time from definitive surgery to the first occurrence of invasive disease recurrence (local, regional, or distant), contralateral invasive breast cancer, or death from any cause. Patients alive without any of these events will be censored at the date of last known disease-free status. Tumor assessments will be performed every 3 months post-surgery for up to 3 years, using imaging modalities (MRI, CT, or ultrasound) as per clinical practice.
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