Abstract PD7-08: Less is not necessarily more: A propensity matched national analysis on effect and outcome of sentinel lymph node biopsy omission
Authors: Cao Lifen , Miller Megan E , Rothermel Luke D , Montero Alberto J , Towe Christopher W , Shenk Robert 
Published: March 2022

Abstract
Background: Routine sentinel lymph node biopsy (SLNB) has been recommended against by Choosing Wisely© Foundation due to its low value in clinical node negative, hormone receptor positive breast cancer patients age≥70 years old. We used the National Cancer Database (NCDB) to examine the effect of SLNB omission and outcomes in this population. We hypothesized that SLNB would be beneficial in this population.Methods: The National Cancer Database was queried for women diagnosed with primary unilateral invasive clinical stage T1N0M0 hormone receptor positive, HER-2 negative breast cancer from 2012-2017. Patients age ≥ 70 years old with Charlson Score ≥1 who underwent partial mastectomy and received hormonal therapy were included in the study cohort. Patients received neoadjuvant therapy or underwent upfront axillary lymph node dissection (ALND) were excluded. A 1:3 propensity match with replacement was performed to compare SLNB omission vs. SLNB group controlling age, race, comorbidities, insurance and facility. Overall survival was analyzed using stratified multivariable Cox proportional hazard regression analysis.Results: Of 14,150 patients, 1,928 (13.6%) omitted SLNB and 12,222 (86.4%) underwent SLNB, including 1,545/12,222 (12.6%) who proceeded to ALND. Central portion tumor location (OR=1.77, P=0.001), clinical T1c (OR= 2.49, P&lt;0.001) and lymph-vascular invasion (OR=7.46, P&lt;0.001) were significant associated with positive pathological lymph node involvement in SLNB group. Among the 1,397 patients of positive nodal status with SLNB, 87.7% received radiation therapy and 19.3% received chemotherapy. Propensity matching reduced bias between the groups, generating 1,903 SLNB omission and 5,703 SLNB patients for analysis. After match, the SLNB omission group was less likely to receive chemotherapy (1.1% vs. 3.0%, p&lt;0.001) or radiation therapy (28.9% vs. 60.8%, p&lt;0.001). Omitting SLNB was associated with inferior overall survival (3-year 83.7% vs. 90.6%, 5-year 66.4% vs. 76.1%, p&lt;0.001). Omitting SLNB was also associated with inferior survival in multivariate cox regression (HR=1.64, p&lt;0.001). Chemotherapy (OR=0.51, p=0.020) and radiation therapy (OR=0.85, P=0.007) were associated with superior overall survival.Conclusions: SLNB remains to be of importance in cT1N0M0 HR+HER2- patients of age 70 years. Pathologic staging affects decisions on adjuvant treatment and SLNB omission is associated with inferior survival. In this population, SLNB might need to be re-implemented, especially in patients with high likelihood of nodal involvement.
Citation Format: Lifen Cao, Megan E Miller, Luke D Rothermel, Alberto J Montero, Christopher W Towe, Robert Shenk. Less is not necessarily more: A propensity matched national analysis on effect and outcome of sentinel lymph node biopsy omission [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD7-08.