Comparison of the value of percutaneous contrast-enhanced ultrasound and conventional sentinel lymph node tracing methods in diagnosis of sentinel lymph nodes of breast cancer
Authors: Zhao Mengfan , Wu Bin , Li Linfang , Liang Bin , Zhou Peng , Bi Lusha 
Published: April 2023

Abstract
Since the advent of sentinel lymph node biopsy for breast cancer in the 1990s, this technique has become a hot spot in the research field of breast cancer. We can accurately evaluate the staging of axillary lymph node in this way and avoid axillary lymph node dissection for those patients with negative axillary lymph nodes, also can improve their quality of postoperative life. After nearly 30 years of research and development, sentinel lymph node biopsy has become the standard surgical method for breast cancer patients with clinical negative axillary lymph nodes. Nowadays, sentinel lymph node biopsy mainly uses radioisotope, blue dye or fluorescence dye to detect the sentinel lymph nodes. Although these methods have high diagnostic value of sentinel lymph node, they can not evaluate the sentinel lymph node status before operation. Recently, contrast-enhanced ultrasound has been proved to be useful in the preoperative diagnosis of sentinel lymph nodes in breast cancer. The purpose of this study is to compare the diagnostic efficacy of percutaneous contrast-enhanced ultrasound and three kinds of tracing methods in sentinel lymph node biopsy of breast cancer. Methods: A total of 50 patients with early invasive breast cancer who were treated in the Department of Breast Surgery, Affiliated Hospital of Southwest Medical University from October 2020 to April 2021 were collected. Percutaneous contrast-enhanced ultrasound and indocyanine green combined with methylene blue were applied to sentinel lymph node biopsy, respectively. According to the postoperative pathological results, the detection rate and the number of sentinel lymph nodes detected by contrast-enhanced ultrasound, blue staining, fluorescence and double tracer methods were compared. The diagnostic sensitivity and specificity of each group were analyzed, and the corresponding accuracy were calculated, ROC curve was made to analyze the diagnostic efficiency of sentinel lymph nodes. Results: All 50 patients successfully completed percutaneous contrast-enhanced ultrasound examination and sentinel lymph node biopsy. At least one sentinel lymph node was found in 47 patients by contrast-enhanced ultrasound, 48 patients by methylene blue staining, and 49 patients by indocyanine green fluorescence method and double tracer method, respectively. There was no significant difference in the detection rate between contrast-enhanced ultrasound group and other groups. 81 sentinel lymph nodes were detected in contrast-enhanced ultrasound group, 87 in methylene blue group, 141 in indocyanine green fluorescent group, and 146 in double tracer group. The average number of sentinel lymph nodes detected in contrast-enhanced ultrasound group (1.62 ± 0.72) was not significantly different from that in methylene blue staining group (1.74 ± 0.69) (P = 0.400), but there was statistical difference compared to indocyanine green fluorescent group (2.82 ± 0.86) and double tracer group (2.92 ± 0.80) (P = 0.00). The sensitivity, specificity and accuracy of contrast-enhanced ultrasound group in the diagnosis of metastatic sentinel lymph node were 82.4%, 90.9% and 88.0%, respectively; 94.1%, 90.9% and 92.0% of methylene blue staining group; 94.1%, 93.9% and 94.0% of indocyanine green fluorescence method group; 94.1%, 93.9% and 94.0% of double tracer method group. Conclusion: Both contrast-enhanced ultrasound and traditional sentinel lymph node tracing methods have high diagnostic efficiency in sentinel lymph node biopsy. Compared with the traditional sentinel lymph node tracing methods, contrast-enhanced ultrasound can not only locate the sentinel lymph node before operation, but also predict the nature of the sentinel lymph node, which is a promising sentinel lymph node examination method.