# The outcome of selective delayed sentinel lymph node biopsy following upfront omission of axillary staging in low-risk invasive breast cancers: a retrospective hypothetical simulated analysis

## TL;DR

This study explores the benefits of delaying sentinel lymph node biopsy in low-risk breast cancer patients to avoid unnecessary surgery and guide treatment decisions.

## Contribution

The study introduces a hypothetical simulated analysis to evaluate the clinical and cost implications of delaying sentinel lymph node biopsy in low-risk breast cancer patients.

## Key findings

- 205 out of 712 patients were eligible for SLNB omission based on low-risk criteria.
- Delayed SLNB reduced the false negative rate from 12% to 6% compared to upfront omission alone.
- Adjuvant treatment rates dropped from 73% in actual practice to 27% with upfront omission.

## Abstract

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.

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 (≥ 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.

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.

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.