Can we avoid axillary dissection in the micrometastatic sentinel node in breast cancer?

There is considerable interest in foregoing axillary dissection (AD) when the sentinel node (SN) is positive in early breast cancer, particularly when involvement is minimal (micrometastases or isolated tumor cells). To address this issue we analyzed outcomes in patients with a single micrometastatic SN who did not receive AD. We selected 377 consecutive patients treated at the European Institute of Oncology between 1999 and 2007 for invasive breast cancer. Classical and competing risks survival analyses were performed to estimate prognostic factors for axillary recurrence, first events and overall survival. Median age was 53 years (range 26-80); median follow-up was 5 years (range 1-9). Most (91.8%) patients received conservative surgery; 209 (55.4%) had only one SN (range 1-8). Five-year overall survival was 97.3%. There were 10 local events, 2 simultaneous local and axillary events, 6 axillary recurrences and 12 distant events. The cumulative incidence of axillary recurrence was 1.6% (95% CI 0.7-3.3). By multivariable analysis, tumor size and grade were significantly associated with axillary recurrence. The high five-year survival and low cumulative incidence of axillary recurrence in this cohort provide justification for the increasingly common practice of foregoing AD in women with minimal SN involvement, and suggest in particular that AD can safely be avoided in women with small, low-grade tumors. Nevertheless, a subset of patients might be at high risk of developing overt axillary disease and efforts should be made to identify such patients by ancillary analyses of the results of ongoing or recently published clinical trials.