A Prospective Double-Blinded Randomized Controlled Trial Comparing the Intraoperative Injection of Technetium Tc 99m Tilmanocept with Technetium Tc 99m Sulfur Colloid in Breast Cancer Lymphatic Mapping

Abstract

Introduction. Technetium-labeled sulfur colloid (TSC) is a radiolabeled mapping agent commonly used for sentinel lymph node biopsy (SLNBx). Tilmanocept, a CD206 receptor-targeted mapping agent, has gained recent popularity due to potential advantages of rapid and quick uptake to the SLNs. The objectives of this study were to assess (1) the difference in the number of SLNs harvested using tilmanocept versus TSC and (2) the difference in time to transcutaneous localization when using an intraoperative injection approach. Methods. Patients undergoing breast conservation and SLNBx were consented and randomized to receive either 0.5 mCi of filtered TSC or 0.5 mCi of tilmanocept injected intradermally immediately after induction of anesthesia. Axillary transcutaneous gamma detector probe counts were taken at 1-minute intervals until a hot spot was identified. SLNs were then identified and excised. Additional nodes were excised if their counts per second (cps) were greater than 10% of the cps of the hottest SLN. The number of SLNs was based on both number of nodes collected intraoperatively and the number recorded in the final pathology report. Results. The study population consisted of 86 patients, 48 randomized to tilmanocept and 38 to TSC. There were no significant differences in patient or tumor characteristics between the two groups. Localization rates were 100% for both cohorts. The mean number of SLNs identified and removed was not significantly different ( $p=0.34$ , intraoperatively; $p=0.57$ , pathology reported). Time to transcutaneous localization was 3.3 ± 2.0 minutes for tilmanocept and 3.9 ± 2.3 minutes for TSC ( $p=0.19$ ). The average cps for the hottest node was 2,180.0 ± 2,460.5 in the tilmanocept group compared to 2,679.3 ± 2,687.5 in the TSC group ( $p=0.94$ ). Conclusion. There was no significant difference in the number of SLNs harvested or in the time to transcutaneous localization when using tilmanocept versus TSC as the radiolabeled mapping agents for intraoperative injection and mapping. Either agent can be used without any significant difference in performance.