Sentinel lymph node biopsy using dye alone in patients with initial clinical N1 breast cancer receiving neoadjuvant therapy: A multicenter diagnostic trial (Northern Breast Cancer Collaboration Group NBCG-002).

[BACKGROUND] Both domestic and international guidelines recommend using dual tracers and retrieving at least three sentinel lymph nodes (SLNs) for SLN biopsy (SLNB) in patients who are downstaged from clinical N1 lymph node status (cN1) to clinical N0 status after neoadjuvant therapy (NAT). However, because of various limitations, most hospitals in China still perform SLNB using a single blue dye. This discrepancy between guidelines and real-world practice warrants further reflection.

[METHODS] Adult women who had clinical cT1-cT4, cN1, M0 breast cancer scheduled who were for NAT were eligible. After NAT, patients underwent sequential SLNB and axillary lymph node dissection, with SLNs identified using single dye. The primary end point was the false-negative rate (FNR) of single-dye SLNB.

[RESULTS] Among 432 patients from 12 centers, single-dye SLNB succeeded in 393 of 432 (90.97%). Pathology revealed node metastases in 201 of 393 patients. The FNR was 8.96% (18 of 201 patients; 95% upper confidence limit, 12.02%). The FNR was lower in women aged 60 years and younger (3.80% vs. 27.91%; p < .0001), and in those with a body mass index (BMI) <25 kg/m (4.20% vs. 14.47%; p = .0151), with four or more SLNs (5.19% vs. 16.67%; p = .0152), and with estrogen receptor-negative tumors (3.52% vs. 12.93%; p = .0242). BMI ≥25 kg/m (odds ratio, 5.68; 95% confidence interval, 2.05-18.33; p = .0006), estrogen receptor-positive tumors (odds ratio, 3.49; 95% confidence interval, 1.15-12.72; p = .0264) were independently associated with a false-negative SLNB. Examining a greater number of SLNs was independently associated with a lower FNR (odds ratio, 0.65; 95% confidence interval, 0.45-0.90; p =.0088). In hormone receptor-negative/human epidermal growth factor receptor-positive patients, the FNR was 0%.

[CONCLUSIONS] Single-dye SLNB after NAT in patients initially diagnosed with cN1 breast cancer yielded a clinically acceptable FNR. When four or more SLNs were identified, an additional benefit was observed in patients who had a BMI <25 kg/m and negative estrogen receptor status.