Impact of delayed-SLNB in patients with low-risk invasive breast cancers with upfront SLNB omission: a retrospective hypothetical simulated analysis

Abstract Introduction Sentinel lymph node biopsy (SLNB) is performed to facilitate decision-making on adjuvant treatments for invasive breast cancer. Recently, SLNB omission has been shown to be non-inferior in low-risk patients. We aimed to investigate the impact of delaying SLNB (d-SLNB), if axillary staging was omitted upfront. Method A retrospective hypothetical simulated analysis. Patients who had breast surgery and SLNB between 2019 and 2021 were included. Low-risk invasive cancers were identified: over 65 years, luminal A-like, T1, cN0, Grade 1 to 2. Outcome analyses were based on the Actual clinical setting compared to two different hypothetical Scenarios: a) upfront SLNB omission only, and b) upfront SLNB omission with d-SLNB. Primary endpoints were proportion of patients suitable for SLNB omission, outcome of d-SLNB and changes in adjuvant treatments. Secondary endpoint was surgical costs. Result Of 712 patients, 205 (30%) had low-risk invasive cancers and would have been eligible for SLNB omission. In Scenario A, 25 (12%) patients with SLN metastases would have been missed. If Scenario B was applied, the false negative rate of SLNB would reduce from 25 (12%) to 12 (6%) patients, p<0.001. On average, adjuvant therapies were given to 73% (Actual clinical setting) vs. 27% (Scenario A) vs. 55% (Scenario B), p<0.001. Based on 100 patients, d-SLNB was associated with an incremental cost of 55,000 EUR. Discussion Upfront SLNB omission in low-risk invasive cancers was associated with missed SLN metastases. However, d-SLNB could reduce the false negative rate and provide more information to guide adjuvant treatments, but with additional costs.