Abstract OT-04-01: Axillary Management in T1-3N1M0 Breast Cancer Patients with Needle Biopsy Proven Nodal Metastases at Presentation after Neoadjuvant Chemotherapy - ATNEC (clinicaltrials.gov NCT04109079)

Abstract Background: Neoadjuvant chemotherapy (NACT) results in eradication of cancer in the axillary lymph nodes in 40% to 70% of patients. This has raised questions about the benefit of further axillary treatment in these patients with no evidence of residual disease in the lymph nodes. Trial design: A multi-centre phase III randomised controlled trial with embedded economic evaluation in which participants will be randomised in a 1:1 ratio. Study participants: T1-3N1M0 breast cancer patients aged 18 years or older, with needle biopsy proven nodal metastases, who after NACT have no residual cancer in the lymph nodes on dual tracer sentinel node biopsy and removal of at least 3 lymph nodes (sentinel nodes and marked involved node). Intervention: Participants in the experimental group will not receive further axillary treatment (axillary lymph node dissection [ALND] or axillary radiotherapy [ART]), after NACT and surgery. Participants in the control group will receive further axillary treatment (ALND or ART) after NACT and surgery, as per local guidelines. Stratification: Institution, type of breast surgery (breast conserving surgery (BCS) vs mastectomy), receptor status (triple negative vs HER2 positive vs ER status positive and/or PR status positive and HER2 negative) Eligible participants will be/should have:•Age ≥ 18•Male or female •T1-3N1M0 breast cancer at diagnosis (prior to NACT) •FNA or core biopsy confirmed axillary nodal metastases at presentation •Oestrogen receptor and HER2 status evaluated on primary tumour •Received standard NACT as per local guidelines (Patients undergoing neoadjuvant endocrine therapy as part of another clinical trial are eligible) •Ultrasound of the axilla at completion of NACT •Undergo dual tracer sentinel node biopsy after NACT and at least 3 nodes removed (sentinel nodes and marked node). If axillary node sampling is performed following failed localisation of sentinel nodes, patient will be eligible if at least 3 nodes removed (including the marked node) •No evidence of nodal metastases post NACT (isolated tumour cells, micro or macro metastasis) Participants will be excluded if they have any one of the following:•Bilateral invasive breast cancer•Sentinel node biopsy prior to NACT•Marked node not removed except where at least one node removed showsoevidence of down-staging with complete pathological response e.g. fibrosis or scarring and at least 3 nodes removed•Previous axillary surgery on the same body side as the scheduled targeted sampling•Any previous cancer within last 5 years or concomitant malignancy except basal or squamous cell carcinoma of the skin, in situ carcinoma of the cervix oin situ or stage 1 melanoma, contra- or ipsilateral in situ breast cancer Specific aims: To assess whether, omitting further axillary treatment (ALND and ART) for patients with early stage breast cancer and axillary nodal metastases on needle biopsy, who after NACT have no residual cancer in the lymph nodes on sentinel node biopsy, is non-inferior to axillary treatment in terms of disease free survival (DFS), and reduces the risk of lymphoedema at 5 years.Statistical methods: All analyses will be carried out on an intention-to-treat basis to preserve randomisation, avoid bias from exclusions and preserve statistical power. Target accrual: 1900, Number of sites: ~100 ClinicalTrials.gov: NCT04109079 Contact information: atnec@warwick.ac.uk Disclaimer: This study is funded by the National Institute for Health Research (NIHR) Health Technology Assessment (HTA) programme (Reference - HTA NIHR128311). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care. Citation Format: Amit Goyal, Sophie Cramp, Duncan Wheatley, Andrea Marshall, Shama Puri, Tara Homer, Luke Vale, Romaana Mir, Zohal Nabi, Janice Rose, Helen Teresa Edwards, Samreen Ahmed, Abeer Shaaban, Beatrix Elsberger, Julie Bruce, Sophie Gasson, Valerie Speirs, Jacqui Shaw, Helen Higgins, Janet Dunn. Axillary management in T1-3N1M0 breast cancer patients with needle biopsy proven nodal metastases at presentation after neoadjuvant chemotherapy - ATNEC (ClinicalTrials.gov NCT04109079) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-04-01.