Session 4: Can sentinel lymph node biopsy after neoadjuvant systemic therapy be omitted in clinically-node negative triple negative breast cancer patients?

Purpose: To determine the node positivity rate at surgery after completion of neoadjuvant systemic treatment (NAST) in triple negative breast cancer (TNBC) patients who were classified as clinically-node negative (cN0) using pretreatment ultrasound.

Materials and Methods: This cohort study included TNBC patients who were enrolled in a single-institution IRB-approved clinical trial between 11/2015 and 1/2018 and were treated with NAST followed by standard-of-care breast and axillary surgery. Pretreatment ultrasound evaluation of the axilla was performed as part of the usual staging evaluation. cN0 is defined as either the absence of abnormal nodes during pretreatment ultrasound evaluation or if an axillary node was biopsied during pretreatment ultrasound evaluation but with benign, concordant pathology. Categorical variables were compared using Fisher’s exact test. Univariate and multivariate logistic regression analyses were performed to determine the relationship between clinical parameters and nodal status at the time of surgery. All tests were two-sided, and p-values ≤ 0.05 were considered statistically significant.

Results: The study included 198 patients with a median age of 55 years, range 24-78. There were 118/198 (59.6%) who were cN0 and 80/198 (40.4%) who were cN+ (clinically-node positive). Out of 118 cN0 patients, 98.3% (116) were ypN0 (node negative at surgery) while 1.7% (2/118) were ypN+ (node positive at surgery). For the 116 cN0/ypN0 patients, 62 (53.4%) achieved pCR while 54 (46.6%) did not. For cN+ patients, 58.8% (47/80) were ypN0 while 41.2% (33/80) were ypN+. The node positive rate at surgery was much higher in cN+ patients than cN0 patients (41.3% vs 1.7%, p< 0.001). Univariate analysis revealed that T3 and T4 were associated with positive node status at surgery (OR 7.67, 95% CI 2.14-29.68, p = 0.002; and OR 5.11, 95% CI 1.06-24.00, p=0.036) and that positive N stage was associated with positive node status at surgery (OR 40.72, 95% CI 11.73-257.49, p< 0.001). In multivariate analysis, positive N stage was associated with positive node status at surgery (OR 119.74, 95% CI 21.57-1419.93, p< 0.001).

Conclusion: For TNBC patients who were identified as cN0 using ultrasound, the probability of nodal positivity rate at surgery after NAST is less than 2%.

Clinical Relevance Statement: The results from this cohort add to growing evidence that support potential omission of sentinel lymph node biopsy after NAST in cN0 TNBC patients.