Can Highly Specific Ultrasound Criteria Obviate the Need for Sentinel Lymph Node Biopsy in Breast Cancer Patients with Axillary Lymph Node Metastasis?

Abstract

Background: Sentinel lymph node biopsy (SLNB) is primarily performed to detect axillary lymph node involvement and determine the need for surgical axillary lymph node dissection (ALND). However, the procedure is expensive and necessitates the use of radio-labelled colloids that are not readily available to a large number of patients. It also carries the risk of producing occasional false negative results. Objectives: This study aimed to define highly specific ultrasound parameters to ascertain axillary lymph node involvement as an alternative or complementary method to SLNB in selected patients who require ALND. Patients and Methods: In this prospective cross-sectional study, 256 patients with confirmed breast cancer were selected through non-probability purposive sampling. The selected patients were referred to Omid Hospital, a tertiary educational oncology center in Mashhad, Iran, from 2018 to 2022. This study identified highly specific cut-off points for ultrasound parameters to determine lymph node involvement in comparison with the histological diagnosis post-SLNB or ALND. Measurements were taken of the tumor size, the cortical thickness of the axillary lymph node, the short axis diameter of the node, and the count of lymph nodes with a cortical thickness of ≥ 3 mm. Results: Among 256 patients with a mean age of 46.41 ± 10.77 years, 202 (87.9%) had histologically confirmed metastatic adenopathy. The ultrasound cut-off values identified to define metastasis with high certainty were as follows: A tumor size > 50.5 mm (with 97% specificity), a difference in cortical thickness of ≥ 4.5 mm (with 100% specificity), a short axis diameter of the node > 12 mm (with 95% specificity), more than three lymph nodes with a cortical thickness of ≥ 3 mm (with 94.3% specificity), and a cortical thickness of ≥ 6 mm (with 95% specificity). Conclusion: Highly specific ultrasound findings can diagnose lymph node metastasis with a high degree of certainty and can used as an alternative method to SLNB. A difference of ≥ 4.5 mm between the cortical thickness of the suspected lymph node and the contralateral lymph node and a cortical thickness of ≥ 6 mm are ultrasound findings that can detect lymph nodes involvement, with a specificity ranging from 95% to 100%.