Localizing Positive Axillary Lymph Nodes in Breast Cancer Patients Post Neoadjuvant Therapy.

Introduction: Multiple trials demonstrated the feasibility of sentinel lymph node biopsy (SLNB) after neoadjuvant chemotherapy. Those trials reported > 10% false-negative rate; however, a subset analysis of the Z1071 trial demonstrated that removing the clipped positive lymph node (LN) during SLNB reduces the false-negative rate to 6.8% post neoadjuvant chemotherapy. This study examines the factors that might contribute to the ability to identify the clipped nodes post neoadjuvant therapy (NAT).

Materials And Methods: Breast cancer patients with biopsy-proven metastatic axillary LN who underwent NAT, converted to N0, had preoperative localization, and then SLNB between 2018 and 2020 at a single institution were identified. A retrospective chart review was performed. Demographic and preoperative variables were compared between localization and nonlocalization groups.

Results: Eighty patients who met inclusion criteria were included. A total of 39 patients were localized after NAT completion (49%). Only half of the patients with ultrasound-detectable marker clips were able to be localized. Minimal LN abnormality was seen in imaging after NAT completion in 39 patients and is significantly associated with localization; 26 (67%) were localized (Odds Ratio 4.31, P = 0.002, 95% Confidence Interval 1.69-10.98).

Conclusions: Our study suggests that radiologically abnormal LNs on preoperative imaging after NAT completion are more likely to be localized. Nodes that ultimately normalize by imaging criteria remain a significant challenge to localize, and thus localization before starting NAT is suggested. A better technology is needed for LN localization after prolonged NAT for best accuracy and avoids repeated procedures.