A 52-year-old woman with ER+/PR+ HER2- invasive lobular carcinoma (T2N1M0) undergoes neoadjuvant chemotherapy followed by mastectomy. The resected specimen shows no residual invasive disease (pathological complete response). Which biological marker best predicts long-term outcome in this specific molecular subtype after achieving pCR?
- A Ki-67 proliferation index on pre-treatment biopsy
- B Oncotype DX recurrence score < 11 on pre-treatment biopsy
- C Residual Cancer Burden (RCB) score 0 ✓
- D Multigene assay PAM50 intrinsic subtype (Luminal A) of residual disease
Correct answer: C. Residual Cancer Burden (RCB) score 0
Explanation
The Residual Cancer Burden (RCB) scoring system, devised at MD Anderson, stratifies prognosis after neoadjuvant chemotherapy; RCB-0 (pCR, no residual disease) confers the best event-free survival. In ER+ lobular cancers pCR rates are lower than in TNBC, but when achieved, RCB-0 is the most validated outcome predictor across subtypes. Oncotype DX and Ki-67 are pre-treatment prognostic tools but do not predict post-neoadjuvant outcome as robustly. PAM50 on residual disease is investigational.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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Written and medically reviewed by the StethoPrep medical team.