Accuracy of Tumor Bed Biopsy for Predicting Pathologic Complete Response After Chemotherapy Among Women With Breast Cancer: Complete Responders in the Breast Study

PURPOSE: With the advent of taxanes and targeted agents in neoadjuvant chemotherapy (NACT) for breast cancer, the rates for pathologic complete response (pCR) have been steadily increasing. Surgery in these women serves as a biopsy to confirm or negate a pCR. METHODS: All newly diagnosed patients with nonmetastatic breast cancer, planned for NACT, were screened. Eligible patients with a complete or near-complete response to NACT as seen on a mammogram and ultrasound (US) were recruited. A magnetic resonance imaging was performed for these patients for documentation. US-guided core biopsies of the tumor bed (Core Bx) using a 14G needle was performed (minimum four in number), and the results were compared with the final histopathology report after surgery for standard performance parameters. RESULTS: This study recruited 65 women of whom 94% were node-positive, and 60% were hormone receptor-negative. The pCR rate was 41.5% and 53.8% for the whole cohort and the hormone receptor–negative subgroup, respectively. The false-negative rate (FNR) for Core Bx was 42.1% (95% CI, 26.3 to 59.2), with a negative predictive value of 59.0% (95% CI, 42.1 to 74.4). Among the hormone receptor–negative tumors, the FNR was 44.4% (95% CI, 21.5 to 69.2) with a negative predictive value of 70.4% (95% CI, 49.8 to 86.2). CONCLUSION: The Complete Responders in the Breast study results suggest that ultrasound-guided 14G core needle biopsy of the tumor bed may not be a reliable predictor of pCR in the breast. These results highlight the importance of further research into the omission of surgery in the breast after chemotherapy. This study is registered with Clinical Trials Registry of India (CTRI/2018/01/011122).