To determine the clinical benefits of selective delayed sentinel lymph node biopsy in patients with low-risk invasive breast cancers if upfront sentinel lymph node biopsy was omitted: a retrospective hypothetical simulated analysis

Background Sentinel lymph node biopsy (SLNB) is performed to guide recommendations on adjuvant treatments for invasive breast cancer. However, studies have shown oncological safety without SLNB in low-risk patients. We aimed to determine the clinical benefits of delaying SLNB (d-SLNB), if upfront axillary staging was omitted in patients with low-risk invasive breast cancers. Methods and materials A retrospective hypothetical simulated analysis. Patients who had breast surgery and SLNB between 2019 and 2021 were included. Patients with low-risk invasive cancers were identified based on preoperative histopathology (³ 65 years, Luminal A-like, T1, cN0, Grade 1-2). Outcome analyses were based on the Actual clinical management 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 eligible for SLNB omission. In Scenario A, 25 (12%) patients with SLN metastases would have understaged. If Scenario B was applied, the false negative rate of axillary staging would reduce from 25 (12%) to 12 (6%) patients, p<0.001. On average, adjuvant treatments 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 per 100 patients. Conclusion Although upfront SLNB omission was associated with missed SLN metastases, majority of low-risk invasive cancers were SLN negative. Delayed-SLNB could provide additional useful information to guide adjuvant treatments.