48P - The impact of preoperative axillary ultrasound on the false negative rate of sentinel lymph node biopsy in post neoadjuvant chemotherapy breast cancer patients

Background

Sentinel lymph node biopsy (SLNB) in post-neoadjuvant chemotherapy (NACT) has demonstrated a higher false negative rate (FNR) compared to early breast cancer. This might result from a non-uniform pattern of tumour regression in SLN and Non-SLN within the axilla. SLNB can assess SLN alone by itself, but preoperative axillary ultrasound (AUS) can also determine the characteristics of Non-SLN. We studied whether axillary staging in post-NACT patients could be improved by combining AUS and SLNB to reduce false negative cases.

Methods

It was a single-centre, prospective study that was conducted between September 2020 and June 2022. All Post-NACT, clinically node-negative(cN0) patients who were scheduled for surgery were enrolled and underwent AUS. AUS normal node patients underwent SLNB using fluorescein and methylene blue followed by Axillary Lymph Node Dissection (ALND). We evaluated the AUS's Positive Predictive Value (PPV), Negative Predictive Value (NPV) and FNR in cN0 patients. The FNR of SLNB was calculated in patients who had cN0 and AUS normal nodes.

Results

cN0 was found in 62 patients out of 136 post-NACT patients.AUS had PPV and NPV of 90.6% and 76.6%, respectively. The FNR for AUS alone was 19.4% (7/36). Loss of fatty hilum was found to have a PPV of 89.3% and a sensitivity of 70%, making it the most reliable marker of nodal metastasis. Methylene blue allergy was observed in 1 patient. The FNR of SLNB was 8.6% (2/23) for the patients who had been selected for SLNB based on AUS normal nodes.

Conclusions

AUS alone or SLNB alone is insufficient to determine axilla node-negative status and can't omit ALND because each has a high FNR (>10%). If AUS findings are considered for selecting patients for SLNB, it reduces its FNR to below 10% and improves the accuracy of axillary staging in post-NACT patients.

Clinical trial identification

Clinical Trials Registry (India) number- CTRI/2020/10/028337.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.