Purpose: In the ACOSOG Z0011 trial, patients with primary breast cancer and 1-2 tumor-involved sentinel lymph nodes (SLNs) undergoing breast-conserving surgery had no oncological outcome benefit after axillary lymph node dissection (ALND), despite a relevant rate of non-SLN metastases of 27%. According to the St Gallen expert consensus, and NCCN and ASCO clinical guidelines, ALND may be avoided in patients who meet all ACOSOG Z0011 inclusion criteria. This recommendation can also be extended to patients undergoing mastectomy, with 1 or 2 positive SLNs and an indication for chest wall radiation, in whom axillary radiotherapy can be proposed as an alternative to completion ALND. The aim of this study was to assess non-compliance with the NCCN and ASCO clinical guidelines and Z0011 criteria, namely the rate of performance of completion ALND when it was not recommended, and the rate of failure to perform completion ALND when recommended.

Methods: Data were prospectively analysed from T1-2 N0 breast cancer patients undergoing an SLN procedure and treated at the Georges-François Leclerc Cancer Center between November 2015 and May 2017. Factors associated with non-compliance treatment decisions were identified using logistic regression.

Results: Among 563 patients included, 122 (21.7%) had at least one positive SLN. ALND was not recommended for 76 patients (62.3%), and was recommended in 46 patients (37.7%). The rate of non-compliant treatment was 32% (39/122) overall: ALND was performed despite not being recommended in 16/76 patients (21.1%) and was not performed in 50% of patients in whom it was recommended (23/46). By multivariate analyses, lymphovascular invasion ((Odds Ratio (OR)=6.1; 95% confidence interval (CI): 1.4-26.7; P=0.02)) and only one SLN removed (OR=9.1; 95%CI: 2.2-33.3; P=0.002) were associated with performance of completion ALND when not recommended. Conversely, >1 SLN removed (OR=5.1; 95%CI: 1.2-22.2; P=0.03) was associated with the failure to perform completion ALND when recommended.

Conclusion: Almost one third of patients with invasive breast cancer receive treatment that is not in compliance with recommendations regarding completion ALND.