Prospective, Multicentric Registry Study Evaluating the False-negative Rate of Targeted Axillary Dissection (TAD) in Primary Breast Cancer With Initially ≥ 3 Suspicious Lymph Nodes Under Neoadjuvant Systemic Therapy (SenTa 2)

Patients with triple-negative breast cancer (TNBC) or human epidermal growth factor receptor 2 (HER2) positive breast cancer achieved pCR rates of 50-70% following NST. In the multicenter prospective SenTa study (NCT03102307), the axillary pCR rate after the end of NST in 473 initially cN+ patients was 60.3%. Therefore, less invasive surgical techniques have been investigated to avoid the morbidity associated with ALND. One of these minimally invasive methods called TAD involves the combined intraoperative excision of the pre-NST marked most suspicious lymph node (target lymph node, TLN) and sentinel lymph nodes (SLNs). In a pooled analysis of 13 studies including 521 patients who had undergone TAD, the FNR of TAD was 5.2%.

The FNR of TAD in breast cancer patients with high initial lymph node (LN) involvement (≥ 3 clinically suspicious LNs) has so far hardly been investigated. In a very small cohort, a FNR of 0% was obtained for patients with 1-3 suspicious LNs (cN1, n = 10), 33% for patients with 4-9 suspicious LNs (cN2, n = 3) and 100% for patients with 10 or more suspicious LNs (cN3, n = 2). In addition, patients with high lymph node involvement are often excluded from some larger studies evaluating TAD or other axillary surgical approaches. In consequence, the FNR of TAD LNs in comparison to LNs obtained during ALND in the patient group with ≥ 3 clinically positive LNs needs to be evaluated in a larger cohort, since extensive initial LN involvement is associated with a higher probability that a false-negative result of TAD could cause one or more involved LNs to be left in the axilla, if only TAD and not ALND is performed.