Comparison of Clinical Efficacy Between Letrozole + Ribociclib and Fulvestrant + Letrozole + Ribociclib in Hormone Receptor Positive, HER2 Negative Metastatic Breast Cancer

Inclusion Criteria

• •Female ≥ 19 years of age
• •Histologically confirmed unresectable, locally advanced or metastatic invasive breast cancer with hormone receptor positive/HER2 negative
• •No previous history of systemic endocrine or chemotherapy for metastatic, advanced breast cancer.
• •If the patient has received AI as adjuvant endocrine therapy, the treatment free interval (TFI) should be more than 12 months after the end of adjuvant endocrine therapy. If the patient has received tamoxifen for adjuvant endocrine therapy, TFI less than 12 months will be allowed.
• •ECOG PS 0-2
• •Patients should have measurable or evaluable lesion based on RECIST version 1.1
• •Patients should have adequate organ function:
• •* ANC (absolute neutrophil count) ≥ 1.5 × 109/L
• •* Platelet ≥ 100 × 109/L
• •* Serum Hb ≥ 9.0 g/dL
• •* INR ≤1.5
• •* Serum creatinine ≤ 1.5 X ULN
• •* ALT \& ALT \<2.5 X ULN, if patients have hepatic metastasis, ALT \& ALT \<5.0 X ULN is allowed
• •* Total serum bilirubin \<1.5 X ULN, if patients have hepatic metastasis, Total serum bilirubin \<3.0 X ULN is allowed.
• •In the case of childbearing potential, patients who can adhere to appropriate contraception during the study period and for at least 6 months after the end of study treatment.
• •Patients who understand the contents of the clinical trial and are cooperative with the process of the clinical trial.