Visualization rate of internal mammary sentinel lymph nodes with modified technique of radiotracer injection.

Abstract

99 Background: Even though the 2009 AJCC incorporated the internal mammary sentinel lymph node biopsy (IM-SLNB) concept, there has been limited change in surgeons practice patterns due to the low visualization rate of the internal mammary sentinel lymph nodes (IM-SLNs) with the conventional injection technique (average 13%, 0~37%). In this prospective study, different radiotracer injection techniques were evaluated to achieve a relative high visualization and detection rate of IM-SLNs (NCT01642511). Methods: The 190 patients enrolled in this study were divided into three groups according to the study period and radiotracer (99mTc-labeled sulfur colloid) injection technique. Group A: conventional technique (radiotracer injection only into the tumor quadrant) for the initial 58 cases; Group B: two-quadrant injection at the 6 and 12 o’clock positions, 2.0~3.0 cm from nipple in the latter 132 cases. Group B was then separated into two groups according to the radiotracer injection volume: Group B1, low volume (<0.5ml/point, n=41); Group B2, high volume (≥0.5ml/point, n=91). Radiotracer was injected into the parenchyma under the ultrasonographic guidance for all patients. IM-SLNB was performed for patients with IM-SLNs visualized on preoperative lymphoscintigraphy and/or detected by intraoperative gamma probe. Results: Group B was associated with a significantly higher IM-SLNs visualization rate (76.5%, 101/132) compared to Group A (15.5%, 9/58, P=0.000), and Group B2 with the highest visualization rate (86.8% vs. 53.7% Group B1, P=0.000). All techniques had the same visualization rate of the axillary SLNs (P=0.915). The visualization rate of IM-SLNs was related to the patient’s age (P=0.037) and injection volume (P=0.000). The successful rate of IM-SLNB was 92.3%, and arrived 100% after 20 cases learning curve. The postoperative IM-SLNB complications were 0. Conclusions: Modified technique of radiotracer injection (Qiu's injection technique: two-quadrant, high volume and ultrasonographic guidance) significantly improved the visualization rate of IM-SLNs, provided an effective technique to evaluate the status of internal mammary, and would promote research on the IM-SLNB.