There is a trend towards de-escalation in early breast cancer axillary surgery. In the American College of Surgeons Oncology Group (ACOSOG) Z-0011 trial, observation was shown to be non-inferior in terms of overall survival to complementary axillary lymph node dissection (cALND) in patients with up to two sentinel lymph node (SLN) metastases. The study included patients with T1-T2 invasive breast cancer, clinically node negative, undergoing breast-conserving surgery with SLN biopsy, followed by systemic therapy and radiotherapy. The aim of our study was to evaluate the impact of applying these ACOSOG Z-0011 inclusion criteria in routine practice.
This retrospective observational study was conducted in a French comprehensive cancer center where patients treated for breast cancer with primary surgery were prospectively included between 2010 and 2016. Patients meeting ACOSOG Z-0011 inclusion criteria were analyzed.
Among the 1900 included patients, 1497 (79 %) met the ACOSOG Z-0011 criteria before surgery. Of these, 390 (20 %) had one or two metastatic SLN and could have avoided cALND. Out of these patients, 319 (81 %) presented cT1 tumors. During the study period, cALND was performed in 320 (82 %) patients and was free of metastases in 80 % of cases, having an impact on eligibility for adjuvant chemotherapy in only 3 (0.8 %) patients.
In situations of primary breast cancer surgery, use of ACOSOG Z-0011 criteria could reduce the rate of cALND by 20 %. Further studies are needed to help select patients for whom abstention from any axillary surgery would be reasonable.

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