Outcomes of a population-based series of early breast cancer patients with micrometastases and isolated tumour cells in axillary lymph nodes

Axillary lymph node staging is traditionally important to provide prognostic information to guide further treatment. However, the relevance of isolated tumour cells (ITC) or micrometastases in axillary nodes and the need for adjuvant treatment remain uncertain. Data from 18 370 patients with pT1-2 breast cancer with pN0, pN0i+ or pN1mi were analysed. The primary end point was 5-year disease-free survival (locoregional recurrence, distant metastases or contralateral breast cancer). Five-year disease-free survival was 89.9% [95% confidence interval 89.5% to 90.4%]; and did not differ significantly between groups. After adjusting for prognostic factors (including treatment), patients with ITC had a comparable risk (hazard ratio = 1.12) as patients with node-negative disease, while patients with micrometastases had a 38% higher risk of recurrence. Patients with ITC and node-negative breast cancer appear to have similar prognosis, and those with micrometastases have a 38% higher risk of tumour recurrence. However, considering that disease-free survival is already high, we are reluctant to advise chemotherapy in all patients with ITC or micrometastases. In future, genomic tumour characteristics might predict the propensity of dissemination from the primary cancer better than the status of the axillary lymph nodes.