Retrospective study comparing imaging modalities for axillary response after neoadjuvant systemic therapy in locally advanced breast cancer

A retrospective study at Icahn School of Medicine at Mount Sinai (New York, NY) evaluated the efficacy of different imaging modalities for identifying residual lymphadenopathy after neoadjuvant systemic therapy (NST) in a contemporary cohort of locally advanced breast cancer (LABC) patients. The study included 101 patients (T3-4, N1-3 or any T stage with N2-3 disease) undergoing NST followed by surgical axillary staging from 2018 to 2023 (inflammatory breast cancer was excluded). Post-NST imaging included US (n=57), MRI (n=53), and PET/CT (n=45). US had the highest sensitivity of 71% and positive predictive value of 70%. PET/CT had the highest specificity of 73% and negative predictive value of 70%. MRI had the lowest performance in all diagnostic measures. There was a significant relationship between complete imaging response (CIR)-pathologic complete response (pCR) concordance and pretreatment nodal status. Higher N stage was associated with CIR-pCR concordance with cN3 disease having the highest odds compared with cN1 disease. Absence of lymphovascular invasion was associated with CIR-pCR concordance. The authors conclude that post-NST imaging provides valuable information on treatment response in LABC.