A 55-year-old woman with a 1.8 cm ER-positive, HER2-negative invasive ductal carcinoma undergoes breast-conserving surgery with negative margins. Sentinel lymph node biopsy is negative. She is postmenopausal. Which adjuvant therapy is indicated in addition to radiotherapy and endocrine therapy?
- A Adjuvant chemotherapy (AC regimen)
- B Trastuzumab
- C No further systemic therapy is required if Oncotype DX RS is low ✓
- D Tamoxifen
Correct answer: C. No further systemic therapy is required if Oncotype DX RS is low
Explanation
For ER-positive, HER2-negative, node-negative breast cancer with low Oncotype DX recurrence score (less than 26 per TAILORx), chemotherapy can be safely omitted in postmenopausal women. Radiotherapy and endocrine therapy (aromatase inhibitor) are indicated. Trastuzumab is for HER2-positive disease. AC chemotherapy would not be added if RS is low. Tamoxifen is for premenopausal women, though she is postmenopausal.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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