Breast cancer
Progression after CDK4/6i + ET for HR+ HER2- MBC. What now?

Emily (52 years old)

A 52-year-old woman presents with gradual fatigue and weight loss.

Assessment summary:

  • No family history of breast cancer
  • ECOG PS: 0
  • Medical history:
  • 10 years ago: diagnosis stage IIA breast cancer in left breast (3.2 cm). Tumour biology: ER 90%, PgR30%, HER2 IHC 1+, G2 
    • Treated with breast conserving surgery, negative sentinel lymph node
    • Gene expression profiling: low risk
    • Treated with 5 years of adjuvant tamoxifen
  • 2 years ago (8 years after diagnosis breast cancer): presence of 3 bone metastases. Biopsy bone lesion: breast cancer, NST, ER 60%, PgR 30% HER IHC 1+, G2
    • Treatment with riboclicib + OFS + letrozole started
    • Tumour regression in control imaging

Today, she is postmenopausal and experiences disease progression.

  • Imaging: progression of bone lesions, new lesions in liver (N=2) and mediastinal lymph nodes
    • Biopsy of liver metastasis: breast cancer, NST, ER 50%, PgR 30%, HER2 IHC 1+, G2
  • Haematology and biochemistry: all values normal
  • Somatic PIK3CA mutation status: PIK3CA mutated
  • Somatic ESR1 mutation status (on liquid biopsy): ESR1 mutated
  • Germline BRCA mutation status: wild type

Which option would you choose for this patient?