Positive Ultrasound-guided Lymph Node Needle Biopsy in Breast Cancer may not Mandate Axillary Lymph Node Dissection

Background. The ACOSOG Z0011 (Z11) trial demonstrated that in patients with nonpalpable axillary lymph nodes (LN) and one to two positive sentinel LN (SLN), axillary LN dissection (ALND) is unnecessary.JAMA 305:569-575, [(2011)], Ann Surg 264:413-42, [(2016)] The Z11 trial did not require preoperative axillary ultrasound (axUS). In many centers, preoperative axUS is part of the standard workup of a newly diagnosed breast cancer patient, but in light of the Z11 results, its role is now questioned. Methods. We retrospectively analyzed newly diagnosed breast cancer patients at two institutions. Inclusion criteria were patients with (1) no palpable lymphadenopathy, (2) abnormal axUS, (3) axillary LN metastasis confirmed preoperatively by axUS-lymph node needle biopsy, (4) no neoadjuvant therapy, and (5) ALND. LN disease burden was dichotomized as N1 versus N2-3. We examined relationships between clinicopathologic factors, including axUS characteristics, and LN disease burden. Results. Of 129 included cases, 67 had N1 disease (51.9%) and 62 had N2-3 disease (48.1%). Factors significantly associated with N1 disease were tumor size <= 2 cm (p = 0.012), nonlobular histology (p = 0.013), and one suspicious LN on axUS (p = 0.008). For patients with both tumor size on imaging <= 2 cm and one abnormal LN on axUS, only 27% had N2-3 disease (p = 0.007). Conclusions. More than half of patients without palpable adenopathy but with preoperative US-guided biopsy proven axillary LN metastases had N1 disease. For patients with both tumor size <= 2 cm and only 1 abnormal LN on axUS, 73% had N1 disease. This suggests that such patients, if they are otherwise analogous to Z11 patients, may undergo attempt at SLNB.