Viability of sentinel lymph node biopsy in breast carcinoma after neoadjuvant therapy: analysis of outcomes in a 10-year follow-up

Introduction: Neoadjuvant treatment (NAT) in early-breast cancer patients allows new possibility of less aggressive surgical treatment and offers a challenge in reducing the extent of axillary surgery in both clinically node-negative patients and node-positive patients. However, if the assessment of tumor response to the breast is widely standardized, the management of the axilla in breast cancer remains controversial mainly in the group of patients with positive lymph nodes prior to neoadjuvant treatment, which convert to clinically negative axilla (cN0) after treatment. In these cases, the use of sentinel node biopsy (SNB) is still debatable, since the false-negative rate (FNR) is significantly higher (13-14%). Objective: The purpose of this large retrospective monoinstitutional study, with a long follow-up, is to evaluate the viability of SNB by analyzing the prognosis of patients with breast cancer undergoing NAT, who report had clinically negative (cN0) or positive (cN+) lymph nodes and remain or converted to ypN0. Therefore, were analyzed the rates of Axillary recurrence (AR) rate, distant disease-free survival (DDFS) and overall survival (OS). Methods: This study was developed at the European Institute of Oncology, Milan (IEO-Milan) from 2000 to 2015. We analyzed 688 consecutive patients with clinical breast disease stage 1-3 (cT1-3), who were divided into 2 groups: Group 1 (n = 466, 67,7%), composed by women without axillary disease (cN0) who remained cN0 after NAT and; Group 2 (n = 222, 32,3%), with axillary disease (cN +) and who became cN0 after the neoadjuvant treatment. The clinical positive sentinel node was demonstrated by imaging exams or by fine needle aspiration (FNA). Both groups of patients underwent SNB with the identification of at least one sentinel node (SN), independent of the TAD method. Axillary dissection was not performed when the transoperative pathology of the SN was negative for metastases. SNB was performed using only our standard technique with technetium-labeled colloid. NAT, TAD and Adjuvant nodal radiotherapy were applied according to IEO guidelines. Results: After a median follow-up of 9.2 years (IQR 5.3-12.3), the 5 and 10-year overall survival were 91.3% (95% CI, 88.8-93.2) and 81.0% (95% CI, 77.2-84.2) in the whole cohort respectively; Group 1 - 92.0% (95% CI, 89.0-94.2) and 81.5% (95% CI, 76.9-85.2) in those initially cN0 respectively; Group 2 - 89.8% (95% CI, 85.0-93.2) and 80.1% (95% CI, 72.8-85.7) in those initially cN1/2 respectively. Axillary failure occurred in 1.8% of the initially cN1/2 patients and 1.5% of the initially cN0 patients. The 10-year cumulative incidence of distant events was slightly higher for cN1/2 patients (16.6%) compared to cN0 (13.1%), although this difference was not statistically significant (p=0.148). No differences in the cumulative incidence of loco-regional events (local, axillary and other regional, analyzed separately) in the patients groups studied. Conclusion: These results achieved confirm the preliminary data obtained in the 5-year follow-up of this same group of patients and this large study confirmed that standard SNB is an effective method for staging the axillary status data after NAT and corroborates its indication for cN1/2 patients who become cN0 in this context. There were no worse outcomes in this group of patients (Group 2). (author)