ATNEC: A multi-centre, randomised trial investigating whether axillary treatment can be avoided in T1-3N1M0 breast cancer patients with no residual cancer in the lymph glands after neoadjuvant chemotherapy (clinicaltrials.gov: nct04109079)

Abstract Background: For patients who are node positive to start at presentation and are found to have a complete nodal tumour response (ypN0) post neoadjuvant chemotherapy (NACT), we do not yet know whether local axillary therapy can be modified based on the response to NACT. ATNEC randomised trial specifically address axillary management following NACT in patients with proven axillary node metastases. Methods: Design: ATNEC is a phase III, randomised (1:1), multi-centre trial, with embedded economic evaluation. Patients with proven axillary node metastases on needle biopsy receive NACT followed by sentinel node biopsy (SNB). If the sentinel nodes have converted to benign (ypN0), ATNEC randomly assigns patients to axillary treatment (nodal radiotherapy or axillary nodal clearance) vs. no axillary treatment (without further surgery). 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 nodal disease on SNB - is non-inferior to axillary treatment in terms of disease free survival, and reduces the risk of lymphoedema at 5 years. Stratification: Institution, type of 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). Inclusion criteria:. • Age ≥ 18. • Male or female. • T1-3N1M0 breast cancer at diagnosis (pre-NACT). • FNA or core biopsy confirmed axillary nodal metastases at presentation. • ER and HER2 status evaluated on primary tumour. • Received standard NACT as per local guidelines. • Imaging assessment of the axilla at completion of NACT. • Dual tracer SNB after NACT and at least 3 nodes removed (sentinel nodes and marked node). o If a single tracer is used, the patient is eligible if the involved node is marked before NACT and at least 3 nodes removed (including the marked node). o If axillary node sampling is performed following failed localisation of sentinel nodes, patient is eligible if at least 3 nodes removed (including the marked node). o If node is not marked, or marked node is not removed, patient is eligible if the histology report shows evidence of down-staging with complete pathological response in at least one node and at least 3 nodes removed. • No evidence of nodal metastases post NACT (ypN0). Exclusion criteria:. • Bilateral invasive breast cancer. • SNB prior to NACT. • Previous ipsilateral axillary nodal surgery. • Previous cancer within last 5 years or concomitant malignancy. Radiotherapy Quality Assurance: ATNEC has in-built radiotherapy QA programme that is coordinated by National Radiotherapy Trials QA (RTTQA) group. Target accrual: 1900 Number of sites: 100 Trial Status: Recruiting. Trial is open to new sites. 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, Andrea Marshall, Duncan Wheatley, Natalie Hammonds, Shama Puri, Tara Homer, Luke Vale, Roeum Butt, Romaana Mir, Janice Rose, Helen Teresa Edwards, Samreen Ahmed, Abeer Shaaban, Beatrix Elsberger, Julie Bruce, Sophie Gasson, Valerie Speirs, Jacqui Shaw, Helen Higgins, Janet Dunn. ATNEC: A multi-centre, randomised trial investigating whether axillary treatment can be avoided in T1-3N1M0 breast cancer patients with no residual cancer in the lymph glands after neoadjuvant chemotherapy (clinicaltrials.gov: nct04109079) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT1-04-01.