Changing Practices in Axillary Surgery After Neoadjuvant Breast Cancer Therapy: Insights From the EUSOMA European...

Sentinel lymph node biopsy (SLNB) after neoadjuvant treatment (NAT) is an increasing option for axillary surgery in patients responding to treatment, whether diagnosed as clinically node-negative (cN0) or node-positive (cN + ). This study evaluates SLNB trends in patients with NAT in a large European population.

Data sourced from EUSOMADB, collating prospectively collected data from certified European Breast Units, included 17,321 patients who have undergone NAT between 2010 and 2021. Of those, 9,226 and 8.095 are clinically N0 and cN1, respectively.

During the study period, for cN0 patients, there has been a significant increase in the proportion of cases with SLNB, rising from 86% in the 2010-2015 period to 94% in the 2016-2021 period. Consequently, a decline in direct axillary dissection (AD) has been shown in both periods, dropping from 14% to 6% (p < 0.001). Similarly, in cN+ patients, SLNB increased from 25% to 40%, while direct AD decreased from 75% to 60% (p < 0.001). Regarding immunohistochemistry subtypes, higher SLNB rates were reported in triple-negative and HER2-enriched tumors. Nevertheless, SLNB rates rose significantly across all immunohistochemical subtypes (p < 0.001) between both periods. Multivariate analysis identified as statistically significant predictors of SLNB: surgery period (second period), molecular subtype (HER2-positive, triple-negative), breast-conserving surgery and type of NAT.

This study evidences a substantial shift towards SLNB as the primary axillary surgery following NAT during the study period. This trend emphasizes a preference for less invasive procedures, likely due to the efficacy of neoadjuvant therapy in reducing axillary lymph node involvement.