Abstract OT3-01-02: Preservation of axillary lymph nodes compared to complete dissection in T1-T2 breast cancer patients presenting 1-2 metastatic sentinel lymph nodes: A multicenter randomized clinical trial. Sinodar One Study

Introduction Sentinel lymph node (SLN) staging is currently used to avoid complete axillary lymph node dissection (ALND) in breast cancer (BC) patients with negative SLNs without jeopardizing survival or regional control. International guidelines keep recommending ALND in the presence of positive (+) SLNs. However SLN is the only site of axillary metastasis (MTS) in many cases (60%). Retrospective studies have also shown a low risk of locoregional relapse in patients with SLNs+ not receiving ALND.This latter finding was recently confirmed in a randomized trial comparing SLN biopsy (SLNB) alone with SLNB followed by ALND in patients with 1-2 SLNs+. However the observation of both similar relapse rate and survival in the 2 arms and the conclusion of a non-inferiority of SLNB compared to ALND require cautiousness because of some study limitations: premature enrollment cessation due to death rate lower than expected, short follow-up (6 years), small tumor size (≤2cm in 70% of cases), frequent presence of only microMTS in SLN (40%), prevalent use of “whole breast” adjuvant radiotherapy (>90%) which irradiates the breast but also the I° axillary level, thereby contributing to the low rate of regional relapse in the SLNB arm due to lymph node sterilization. Consequently further randomized trials with more precise selection criteria based on homogeneous clinico-pathological features and with longer follow-up are needed to confirm that performing only SLNB does not affect survival or relapse risk in patients with 1-2 SLNs+. Materials and Methods Primary and secondary aims of the present 2-arm randomized trial are to assess whether ALND omission in BC patients with 1-2 SLNs+ is associated with worse survival and/or increased rate of regional/distant relapse, respectively, thus evaluating whether SLNB is or is not inferior to ALND. Patients receive either conservative surgery or mastectomy and radiotherapy. They all undergo intraoperative SLNB and SLN evaluation, and are randomly assigned to either further dissection of level I-II axillary lymph nodes (standard ALND arm) or absence of any axillary surgery (experimental SLNB arm). According to International Guidelines post-surgery treatments. Eligibility criteria are: age 40-75 years; primary invasive T1-T2 tumor; axillary nodes clinically N0; no more than 2 SLNs presenting macroMTS at intraoperative or definitive histological evaluation; no distant MTS; no neoadjuvant therapy; no previous invasive BC, signed informed consent. Exclusion criteria are: in situ, inflammatory, contralateral BC; presence of only microMTS in the SLN+; pregnancy or breast feeding; comorbidity impeding adjuvant therapy. Follow-up controls foresee: clinical examination every 6 months for 5 years and yearly thereafter; annual mammography and breast echography; annual axillary echography for patients in the SLNB arm; additional laboratory and instrumental surveys in case of suspected onset of distant MTS. The primary endpoint is overall survival (OS). Secondary endpoints are disease-free survival (DFS) referring to distant MTS and to locoregional (ipsilateral breast or axillary, internal mammary or sopraclaveolar lymph nodes) disease recurrence. All analyses are performed both on all patients according to the Intention-To-Treat principle and excluding those patients who did not receive the axillary treatment randomly assigned. Citation Format: Corrado Tinterri, Emilia Marrazzo, Federico Frusone, Wolfgang Gatzemeier, Erika Barbieri, Andrea Sagona, Alberto Bottini, Valentina Errico, Alberto Testori, Giuseppe Canavese. Preservation of axillary lymph nodes compared to complete dissection in T1-T2 breast cancer patients presenting 1-2 metastatic sentinel lymph nodes: A multicenter randomized clinical trial. Sinodar One Study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT3-01-02.