Patient Age and Tumor Subtype Predict the Extent of Axillary Surgery Among Breast Cancer Patients Eligible for the American College of Surgeons Oncology Group Trial Z0011.

BACKGROUND: The American College of Surgeons Oncology Group (ACOSOG) Z0011 trial established the safety of omitting axillary lymph node dissection (ALND) for early-stage breast cancer patients with limited nodal disease undergoing lumpectomy. We examined the extent of axillary surgery among women eligible for Z0011 based on patient age and tumor subtype.
METHODS: Patients with cT1-2, cN0 breast cancers and one or two positive nodes diagnosed from 2009 to 2014 and treated with lumpectomy were identified in the National Cancer Data Base. Sentinel lymph node biopsy (SLNB) was defined as the removal of 1-5 nodes and ALND as the removal of 10 nodes or more. Tumor subtype was categorized as luminal, human epidermal growth factor 2-positive (HER2+), or triple-negative. Logistic regression was used to estimate the odds of receiving SLNB alone versus ALND.
RESULTS: The inclusion criteria were met by 28,631 patients (21,029 SLNB-alone and 7602 ALND patients). Patients 70 years of age or older were more likely to undergo SLNB alone than ALND (27.0% vs 20.1%; p < 0.001). The radiation therapy use rate was 89.4% after SLNB alone and 89.7% after ALND. In the multivariate analysis, the uptake of Z0011 recommendations increased over time (2014 vs 2009: odds ratio [OR] 13.02; p < 0.001). Younger patients were less likely to undergo SLNB alone than older patients (age <40 vs ≥70: OR 0.59; p < 0.001). Patients with HER2+ (OR 0.89) or triple-negative disease (OR 0.79) (p < 0.001) were less likely to undergo SLNB alone than those with luminal subtypes.
CONCLUSIONS: Among women potentially eligible for ACOSOG Z0011, the use of SLNB alone increased over time in all groups, but the extent of axillary surgery differed by patient age and tumor subtype.