Age

18–any

Sex

ALL

Healthy volunteers

Not accepted

Histologically confirmed invasive breast cancer.
Hormone receptor-positive (ER positive and/or PgR positive) and HER2-negative disease:
ER positive: ≥1% positive cells or Allred score ≥3.
PgR positive: ≥1% positive cells or Allred score ≥3.
HER2 negative: IHC 0, 1+, or 2+ with no ISH amplification.
Advanced or recurrent breast cancer (unresectable, recurrent, or Stage IV).
Age ≥18 years at registration.
ECOG Performance Status of 0-1.

Symptomatic visceral metastases or deemed unsuitable for endocrine therapy.
Prior endocrine therapy or chemotherapy for metastatic/recurrent disease.
Prior CDK4/6 inhibitor exposure (perioperative or metastatic setting).
Adjuvant endocrine therapy within 35 days before study start.
Active malignancy other than allowed exceptions (e.g., resected skin cancers, ≥5-year disease-free cancers).
Hypersensitivity to ribociclib, anastrozole, or their components (including soy/peanut allergy, sugar intolerances).

Ribociclib for HR-positive HER2-negative Metastatic Breast Cancer