Sentinel Lymph Node Biopsy after Neoadjuvant Chemotherapy in Breast Cancer Patients with Positive Nodes Using Low-Cost Dual Dye Technique: Identifying Factors Associated with Adequate False Negative Rate Threshold.

Background: In this study, we evaluated the feasibility of the sentinel lymph node (SLN) identification rate (SLN-IR) of fluorescein-guided sentinel lymph node biopsy (SLNB) in combination with methylene blue dye (MBD) and factors which can lead to a false negative rate (FNR) threshold of 10%. Methods: This was a prospective cross-sectional non-randomized validation study in patients with post-neoadjuvant chemotherapy (NACT) clinically node negative axilla who were node positive prior to start of NACT. Patients underwent validation of SLNB using fluorescein (and blue LED light) and MBD. Axillary dissection was performed irrespective of SLNB histology. SLIN-IR and FNR were assessed and compared with various molecular subtypes. Results: The SLNs were identified in 102 out of 120 (85%) post-NACT patients. The median number of sentinel lymph nodes identified was 2 (range 1-3). The SLN-IR using MBD was 85%, FD was 82.5%, and combined MBD FD was 85%. Two or more SLNs were removed in 72 patients and 11 patients had tumor in the rest of the axilla, resulting in an FNR of 17.4%. An FNR was 25% in case only one SLN was found, and it was 11.42% if two or more than two SLNs were excised. Conclusions: This cohort study found that use of low-cost dual dyes in patients with positive axillary disease, rendered cN0 with NACT, with 2 or more negative SLNs with SLNB alone, results in an FNR of 11.4%. Her 2 positive and TNBC with 2 or more negative SLNs are associated with an FNR of <10%. However, the number of such patients was small and further studies with larger sample size are warranted to confirm these findings.