Which subgroup of breast cancer is most responsive to hormone therapy?

• A. Luminal A
• B. Basal
• C. Luminal B
• D. HER2-Enriched

Answer: (A)

Hormone therapy works best when the tumor cells rely on estrogen signaling for growth. The subgroup with tumors that are estrogen receptor–positive and progesterone receptor–positive, and HER2-negative, with low proliferation, depends most on this pathway. Because they express hormone receptors strongly and aren’t driven by HER2 or by high cell division, blocking estrogen signaling with endocrine therapies like tamoxifen or aromatase inhibitors yields the strongest, most consistent response.

Other subtypes don’t fit as well: basal tumors are typically triple-negative and lack hormone receptors, so hormone therapy isn’t effective; luminal B tumors are ER-positive but have higher proliferation and can be HER2-positive, making them less uniformly responsive to hormone therapy; HER2-Enriched tumors overexpress HER2 and are usually ER-negative, so they respond better to HER2-targeted treatments rather than endocrine therapy.