The application of contrast-enhanced ultrasound for sentinel lymph node evaluation and mapping in breast cancer patients

BACKGROUND: To retrospectively investigate the application of contrast-enhanced ultrasound on sentinel lymph node (SLN-CEUS) for SLN evaluation and mapping in breast cancer patients. METHODS: Patients diagnosed with breast cancer at the First Affiliated Hospital of Sun Yat-sen University from June 2019 to March 2021 were conveniently evaluated by SLN-CEUS. The results of SLN-CEUS and B mode-ultrasound (BUS) were collected and compared. For patients who only underwent SLN-CEUS, we conducted a 1:1 propensity score matching (PSM). The diagnostic parameters, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), false negative rate (FNR), false positive rate (FPR), and proportion of undetermined diagnoses were compared between the SLN-CEUS and BUS cohorts. The identification rate and FNR of sentinel lymph node biopsy (SLNB) were also assessed. RESULTS: There were 327 patients in each of the SLN-CEUS and BUS cohorts. Among the entire cohort, both NPV [90.2% (95% CI, 85.4–93.5%) vs. 83.5% (95% CI, 77.8–88.0%), P=0.048] and accuracy [80.7% (95% CI, 76.5–85.0%) vs. 73.7% (95% CI, 68.9–78.5%), P<0.001] of SLN-CEUS were significantly higher than those of BUS. In non-neoadjuvant treatment (NAT) patients, the NPV [94.7% (95% CI, 89.9–97.4%) vs. 85.5% (95% CI, 79.1–90.2%), P=0.007] and accuracy [87.6% (95% CI, 83.2–92.0%) vs. 76.0% (95% CI, 70.4–81.5%), P<0.001] of SLN-CEUS were significantly higher than those of BUS. In NAT patients, no difference in diagnostic efficacy was found. The proportion of undetermined diagnoses of SLN-CEUS was significantly lower than that of BUS (5.8% vs. 15.3%, P<0.001). The identification rate of SLN-CEUS in overall patients, non-NAT patients, and NAT patients was 94.2%, 96.3%, and 89.9%, respectively. The FNR of SLNB with the blue-dye tracer in combination with SLN-CEUS in overall patients, non-NAT patients, and NAT patients was 7.3%, 4.0%, and 12.5%, respectively. CONCLUSIONS: Compared to BUS, SLN-CEUS is a better technique for diagnosing SLNs in early breast cancer patients, showing superiority in multiple diagnostic parameters. However, the diagnostic value of SLN-CEUS in NAT patients is still undetermined. SLN-CEUS is a promising mapping method in SLNB, with a high identification rate and a low FNR when used in combination with a blue-dye tracer.