American College of Surgeons Oncology Group (ACOSOG) Z0011 demonstrated that eligible breast cancer patients with positive sentinel lymph nodes (SLN) could be spared an axillary lymph node dissection (ALND) without sacrificing survival or local control. Although heralded as a “practice-changing trial”, some argue that the stringent inclusion criteria limit the trial’s clinical significance. The objective was to assess the potential impact of ACOSOG Z0011 on axillary surgical management of Medicare patients and examine current practice patterns.

Medicare beneficiaries aged ≥66 with non-metastatic invasive breast cancer diagnosed from 2001–2007 were identified from the Surveillance, Epidemiology and End Results-Medicare database (n=59,431). Eligibility for ACOSOG Z0011 was determined: SLN mapping, tumor <5 cm, no neoadjuvant treatment, breast conservation; number of positive nodes was determined. Actual surgical axillary management for eligible patients was assessed.

12% (6,942/59,431) underwent SLN mapping and were node positive. Overall, 2,637 patients (4.4% (2,637/59,431) of the total cohort but 38% (2,637/6,942) of patients with SLN mapping and positive nodes) met inclusion criteria for ACOSOG Z0011, had 1 or 2 positive lymph nodes, and could have been spared an ALND. Of these 2,637 patients, 46% received a completion ALND and 54% received only SLN biopsy.

Widespread implementation of ACOSOG Z0011 trial results could potentially spare 38% of older breast cancer patients who undergo SLN mapping with positive lymph nodes an ALND. However, 54% of these patients are already managed with SLN biopsy alone, lessening the impact of this trial on clinical practice in older breast cancer patients.