Which molecular abnormality, when overexpressed, guides targeted therapy in many breast cancers?

Which molecular abnormality, when overexpressed, guides targeted therapy in many breast cancers?

• A. BRCA1 mutation status
• B. Estrogen receptor positivity
• C. ALK rearrangement
• D. HER2 overexpression

Answer: (D)

In breast cancer, HER2 overexpression identifies tumors that respond to targeted anti-HER2 therapy. When the HER2 gene is amplified, the receptor drives excessive growth signaling, but this same overexpression makes the cancer vulnerable to drugs like trastuzumab and other anti-HER2 agents, improving outcomes. Other options reflect different concepts: BRCA1 mutation status relates to DNA repair and is treated with PARP inhibitors in mutation-containing tumors; estrogen receptor positivity guides endocrine therapy; ALK rearrangements are not a common driver in breast cancer. The direct targeted-fixation in many breast cancers is HER2 overexpression.

In breast cancer, HER2 overexpression identifies tumors that respond to targeted anti-HER2 therapy. When the HER2 gene is amplified, the receptor drives excessive growth signaling, but this same overexpression makes the cancer vulnerable to drugs like trastuzumab and other anti-HER2 agents, improving outcomes. Other options reflect different concepts: BRCA1 mutation status relates to DNA repair and is treated with PARP inhibitors in mutation-containing tumors; estrogen receptor positivity guides endocrine therapy; ALK rearrangements are not a common driver in breast cancer. The direct targeted-fixation in many breast cancers is HER2 overexpression.