POSNOC - A Trial Looking at Axillary Treatment in Early Breast Cancer

POSNOC is a pragmatic, randomised, multicentre, non-inferiority trial. Aim For women with early stage breast cancer and one or two sentinel node macrometastases, to assess whether adjuvant therapy alone is no worse than adjuvant therapy plus axillary treatment, in terms of axillary recurrence within 5 years. Stratification: Institution, Age (\<50, ≥50), Breast-conserving surgery (BCS) or mastectomy, Estrogen receptor (ER) status (positive, negative), Number of positive nodes (1, 2), Intra-operative sentinel assessment using OSNA (yes, no). Interventions The study will compare adjuvant therapy alone with adjuvant therapy plus axillary treatment (axillary node clearance (ANC) or axillary radiotherapy (ART)). Sample Size: 1900 participants Follow-up: Participants will be followed up for 5 years. Adjuvant Therapy: All participants will receive adjuvant systemic therapy (chemotherapy and/or endocrine therapy). All participants may receive breast/chest wall radiotherapy. Axillary and supraclavicular fossa radiotherapy is not allowed when randomised to adjuvant therapy alone.