Risk and Clinical Benefit of Chemotherapy and Intensive Endocrine Therapy for Luminal B1 Early-stage Breast Cancer

Breast cancer is the most common female malignancy in the world, and the leading cause of cancer-associated mortalities among women. Hormone receptors (HR) including ER and PR are the main prognostic factor for breast cancer patients. Breast cancer subtype was defined by ER, PR, HER2 and Ki67 status since the definition of intrinsic subtypes for breast cancer. Breast cancer which ER are positive have less aggressive and better long-term prognoses than other breast cancer subtype. Luminal B1 was definited as ER Positive, PR positive \<20%, or Ki-67 ≥20% , and HER2-Negative. Although standard therapy to HR positive breast cancer is endocrine treatment, evidence reported that Luminal B1 breast cancers with lower PR expression are less sensitive to tamoxifen than luminal A breast cancers with higher PR expression, and the specific mechanism is not clear. We previously had a clinically analysed, and we found the Luminal B1 breast cancer had a significant proportion with 38%. Whether we need standard chemotherapy or chemotherapy based intensive endocrine therapy for those patients? In our research, we divided the patients with ER positive, PR negative, and HER-2 negative into two groups. One groups will be treated with 8 cycles of chemotherapy (EC×4-T×4). The other received 4 cycles of chemotherapy (TC×4) then will be given the intensive endocrine therapy (Goserelin acetate+Tamoxifen for young patients/Letrozole for postmenopausal patients). The primary endpoint is to assess disease-free survival (DFS) and overall survival (OS) in different regiments, the secondary endpoint is to assess the expression of female hormone levels. The correlation of the expression of female hormone levels with the clinical outcomes, so that the investigators could optimize adjuvant treatment regiment with luminal B1 breast cancer.