18: SLNB in low-risk breast cancer in patients ≥70 years: practice patterns and trends in a national cohort

In its 2016 Choosing Wisely guidelines, the Society of Surgical Oncology recommended against routine sentinel lymph node biopsy (SLNB) for women 70 years and older with early-stage, low-risk breast cancer based on evidence that axillary staging in this cohort does not impact mortality. We sought to identify the impact of these guidelines on receipt of SLNB and to identify factors associated with SLNB receipt and nodal positivity. 


Methods:

Women 70 years and older with hormone receptor-positive, HER2-negative invasive breast cancer, with tumors 2 cm and smaller (T1a-c), and without clinical nodal disease (N0) were identified using the National Cancer Database (2010-2020). Predictors of SLNB and node positivity were identified by univariable analysis and multivariable logistic regression. Annual percent change (APC) in proportion of patients undergoing SLNB was calculated via log-linear regression (Joinpoint analysis).

 


Results:

161,196 women met inclusion criteria. The median age was 76 years (interquartile range 72-80), and 90% of patients were White. Overall, 82% of patients underwent SLNB; 84% before guidelines (BG) vs. 80% after guidelines (AG) (p< 0.001). By Joinpoint regression, the rate of SLNB decreased after 2016 with an APC of -2.4% (p< 0.001), Figure 1.

Factors associated with receipt of SLNB AG included age 70-75 vs. >75 (OR 3.5, 95% CI 3.3-3.6), fewer comorbidities by Charlson-Deyo Combined Comorbidity score (CDCC) (3 vs. 0: OR 0.6, 95% CI 0.5-0.7), patient race (OR 1.1, 95% CI 1.0-1.2 for Black vs. White) and ethnicity (OR 1.2, 95% CI 1.0-1.30 for Hispanic vs. non-Hispanic), treatment at a non-academic center (OR 1.7, 95% CI 1.6-1.7),  urban vs. metropolitan setting (OR 1.4, 95% CI 1.3-1.5), mastectomy vs. lumpectomy (OR 1.9, 95% CI 1.8-2.0), and lymphovascular invasion (LVI) (OR 1.2, 95% CI 1.1-1.4). Patients with all factors present had 87% rate of SLNB compared to 55% without any factor (p< 0.001).

The rate of SLN positivity was 7% BG and 8% AG (p< 0.001). Factors associated with SLN positivity included Black race (OR 1.2, 95% CI 1.1-1.3), higher CDCC (OR 1.3, 95% CI 1.1-1.4 for 3 vs. 1), mastectomy (OR 1.10, 95% CI 1.04-1.16), and LVI (OR 6.8, 95% CI 6.4-7.2). LVI was present in 6% of patients and SLN positivity in this group was 29%.





Conclusions:

Despite decreasing trends concordant with current recommendations, most women over 70 with low-risk breast cancer continue to undergo SLNB nationally. These findings illustrate an important opportunity for improving uniformity in care and more selective use of SLNB in this otherwise low-risk population based on prevalence of nodal metastasis.