Definition
Luminal A and Luminal B are molecular subtypes of breast cancer, classified based on hormone receptor (HR) status, HER2 status, and proliferation markers (Ki-67). These subtypes help guide treatment decisions and prognosis.
Subtype Characteristics
| Feature | Luminal A | Luminal B |
|---|---|---|
| Hormone Receptors | ER-positive, PR-positive (usually high) | ER-positive, PR variable (often lower than Luminal A) |
| HER2 Status | Usually HER2-negative | Can be HER2-negative or HER2-positive |
| Proliferation (Ki-67) | Low (<20%) | High (>20%) |
| Grade | Usually low (Grade 1–2) | Higher (Grade 2–3) |
| Aggressiveness | Less aggressive | More aggressive |
| Prognosis | Favorable | Intermediate to poor compared to Luminal A |
| Treatment Implications | Endocrine therapy is mainstay; chemo often not needed | Endocrine therapy + chemotherapy considered (especially if HER2-positive or high Ki-67) |
Pharmacist-Relevant Points
- Endocrine therapy: Aromatase inhibitors (AI), tamoxifen, fulvestrant depending on menopausal status.
- CDK4/6 inhibitors: Often combined with endocrine therapy in HR+/HER2- advanced/metastatic disease (more relevant for Luminal B due to higher proliferation).
- Chemotherapy: More commonly indicated in Luminal B because of higher proliferation and worse prognosis.
- HER2-targeted therapy: If Luminal B is HER2-positive, agents like trastuzumab, pertuzumab, or T-DM1 may be used.
- Monitoring and counseling: Focus on endocrine therapy adherence, side effects, hematologic monitoring if chemo is used, and drug interactions with targeted agents.