Axillary observation alone versus sentinel node biopsy: past, present and future perspectives

The evolution of axillary surgery in breast cancer has led from complete axillary dissection (AD) to sentinel node biopsy (SNB). It has not stopped yet but continues with a progressive de-escalation of surgical procedures aiming at axillary conservation. In parallel, the meaning of axillary surgery has changed as well. Over time, the dual role of both a therapeutic and a staging procedure has decreased leaving room to other modalities to treat and stage breast cancer. Although, the gold standard for axillary staging in early breast cancer remains SNB, the idea that axillary surgery could be even omitted has been proposed. The concept of abandoning axillary surgery is revolutionary but not new. Historical literature provides interesting data on patients who did not receive any axillary treatment at all with no impact on their survival. Starting from this, several ongoing trials are working to demonstrate that in selected breast cancer cohorts the information deriving from axillary surgery is superfluous and "axillary observation" alone is as effective as SNB. Whilst surgery has been de-escalated to less invasive procedures, systemic treatment, radiotherapy, multigene assays and advanced imaging modalities have gained ground in the management of breast cancer. New research is expected to help select the subgroups of patients for whom axillary surgery is not necessary anymore. This is a qualitative review reporting the most relevant literature data from historical trials on the omission of axillary surgery to the most recent and ongoing ones.