Is axillary dissection unnecessary in patients with a positive sentinel lymph node?

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Recently, the American College of Surgeons Oncology Group (ACOSOG) reported the results of the Z-0011 trial [1, 2]. The data indicated that axillary lymph node dissection (ALND) could be safely omitted in selected patients with a positive sentinel lymph node (SLN) who undergo breast conservation therapy (BCT) with wholebreast irradiation and appropriate systemic therapy. However, questions have been raised regarding the Z-0011 results and whether we should change clinical practice [3]. The historic role of ALND in breast cancer includes (a) assessment of nodal status, (b) prevention of axillary recurrence, and (c) the possibility of survival benefit from the removal of positive axillary nodes [4]. In 1985, however, 10-year outcomes from the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-04 study were published and showed that clinically node-negative patients showed no survival advantage with immediate ALND compared to observation and delayed ALND if clinical nodal disease developed [5]. Twenty-five followup study also confirmed that ALND does not reduce the incidence of systemic recurrence or improve survival [6]. Nevertheless, patients with an untreated axilla had a significantly greater risk of axillary recurrence compared to those who either received axillary radiotherapy or underwent ALND. Therefore, this landmark study did not lead to the abandonment of ALND, although it was extremely influential in our thinking about breast cancer biology [3]. In practice, ALND had remained in use as a reliable method of assessing nodal status and preventing axillary recurrence [4]. In the last decade of the twentieth century, SLN biopsy appeared to allow the reliable staging of patients as nodepositive or node-negative. Fewer lymph nodes are removed with SLN biopsy, allowing more focused histopathological analysis, including multiple sectioning with hematoxylin– eosin (H&E) staining supplemented with immunohistochemical staining. More intense examination has led to increased identification of micrometastases in the lymph nodes [7]. As SLN biopsy is more accurate than ALND, it has replaced the latter method for assessing axillary nodal status in clinically node-negative patients. Therefore, the role of ALND has been limited to the prevention of axillary recurrence. ALND is highly effective in preventing axillary recurrence irrespective of the clinical nodal status [4]. However, the Z-0011 study demonstrated a remarkably low rate of axillary recurrence in SLN-positive patients who did not undergo ALND. Axillary recurrence rates were similar between each arm with 4 (0.9 %) patients in the SLN biopsy group compared with 2 (0.5 %) in the ALND group. SLN biopsy would be a preferable procedure if it could achieve locoregional control as effective as that of ALND without adversely affecting survival [2]. Nevertheless, there are limitations to the Z-0011 trial. As many surgeons were unwilling to randomize patients because they considered it unethical not to perform ALND, the trial was closed early without accruing sufficient numbers of patients, and may lack statistical power to show whether ALND is always necessary if the SLN is positive. In this study, moreover, the eligibility requirements M. Noguchi (&) Department of Breast and Endocrine Surgery, Kanazawa Medical University Hospital, Uchinada-daigaku 1-1, Kahoku, Ishikawa 920-0293, Japan e-mail: nogumasa@kanazawa-med.ac.jp