Impact of omission of completion axillary lymph node dissection (cALND) or axillary radiotherapy (ax RT) in breast cancer patients with micrometastases (pN1mi) or isolated tumor cells (pN0[i+]) in the sentinel lymph node (SN): Results from the MIRROR study

CRA506 Background: The Dutch MIRROR study is the largest cohort study on pN1mi and pN0(i+) in the SN era with long-term follow-up, central pathology review (6th AJCC-classification), and separate analyses on the use of adjuvant systemic therapy (AST). In patients not receiving AST, pN1mi and pN0(i+) as final N-stage were shown to be independent prognosticators for disease-free survival (SABCS 2008, #23, oral). As a substantial number of patients in the MIRROR study did not undergo cALND or ax RT, we questioned whether this policy was safe in patients with pN1mi(sn) or pN0(i+)(sn). Methods: Patients operated for breast cancer in all Dutch hospitals in the years 1998–2005, having favorable primary tumor characteristics, and having undergone an SN biopsy without macrometastases as final N-stage were included. For this present research question, patients were categorized by their SN-stage. Median follow-up was 4.7 years. The Kaplan-Meier method was used to estimate 5-year axillary recurrence (AR) rates, and C...