Radiotracer technique optimization for breast cancer internal mammary sentinel lymph node biopsy

Abstract

Background and purpose: The modified injection technique developed in Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences has significantly improved the visualization rate of internal mammary sentinel lymph nodes (IMSLN), however there is still a gap between the visualization rate of IMSLN obtained by this technique and that of axillary sentinel lymph nodes (ASLN). The study aimed to further improve the IMSLN visualization rate and promote the widespread use of internal mammary sentinel lymph node biopsy (IM-SLNB) by optimizing the modified injection technique. Methods: A total of 159 patients with primary breast cancer were enrolled in a prospective group and divided into the optimized radiotracer technique group (group A, n=81) and the modified injection technique group (group B, n=78). In group A, 99mTc-sulfur colloid was injected averagely into parenchyma in the gland's three most abundant regions under ultrasound guidance (total radioactive intensity 1.0-1.3 mCi; 0.8-1.0 mL/point). In group B, 99mTc-sulfur colloid was injected averagely into the parenchyma of the breast at 6 and 12 points under ultrasound guidance (total radioactive intensity 1.0-1.3 mCi; 0.8-1.0 mL/point). Single photon emission computed tomography (SPECT)/computed tomography (CT) lymphoscintigraphy was performed preoperatively, and the sentinel lymph nodes were detected intraoperatively by γ probe. In this study, we evaluated the differences in IMSLN and ASLN visualization rates between the groups, and also analyzed the factors that may affect the IMSLN visualization rate. Results: There was no statistically significant difference in visualization rate of IM-SLN measured by preoperative SPECT/CT between the two groups (P=0.806). The intraoperative visualization rate of IM-SLN was significantly higher in group A than in group B (87.65% vs 70.51%, P=0.008). Analysis of subgroups showed that the intraoperative visualization rate of IMSLN was 92.31% and 83.33% (P=0.315) in group A patients aged ≤50 years and >50 years, respectively, and the intraoperative visualization rate of IMSLN was significantly higher in group B patients aged ≤50 years than in patients aged >50 years (81.58% vs 60.00%, P=0.037). The median in vitro radioactivity count of IMSLN was significantly higher in group A than in group B (160.50 vs 59.00, P=0.005). Conclusion: The optimized radiotracer technique can effectively increase the lymphatic drainage and uptake in the internal mammary region of the radiotracer, which can significantly improve the visualization rate of IM-SLN without affecting the visualization rate of ASLN, and is conducive to the promotion and application of IM-SLNB.

Keywords

• |breast cancer|internal mammary sentinel lymph node|sentinel lymph node biopsy|modified radiotracer technique