Comparison of [99mTc] tilmanocept and [99mTc] sulfur colloid for identification of sentinel lymph nodes in clinically node-negative breast cancer patients.

Abstract

11098 Background: Receptor-targeted (CD206) [99mTc] tilmanocept is a radiopharmaceutical specifically engineered for sentinel lymph node (SLN) identification that has recently completed phase III clinical trials. The agent has been compared to vital blue dye in prior studies, but has not yet been compared to radio-labeled sulfur colloid. We compared the performance of [99mTc]tilmanocept vs. filtered [99mTc]sulfur colloid (fTcSC) in two cohorts of clinically node-negative breast cancer patients (BCP) who underwent SLN mapping at a single institution. Outcomes were degree of SLN localization and % positive nodes among those removed. Methods: The [99mTc]tilmanocept cohort was composed of UCSD-specific patients pooled from two phase III clinical trials (Jun 2008-Jun 2009, Jul 2010-Apr 2011); the fTcSC cohort was composed of consecutive BCP undergoing SLN mapping at UCSD (Mar 2011-Feb 2012). Demographic, lymph node-specific, and cancer characteristics were compared between groups. A zero-inflated binomial model compared %-positive nodes among nodes removed. Results: There were 85 vs.120 patients in the [99mTc]tilmanocept and fTcSC cohorts, respectively. The groups did not differ in demographic or clinicopathologic factors predictive of axillary metastatic disease (age, race, cancer stage, histologic subtype and grade, hormone and HER2-Neu status or presence of lymphovascular invasion). The [99mTc]tilmanocept group had significantly fewer SLNs removed (mean 1.9 vs. 3.9, p<0.001), achieved higher gamma counts/node (28 vs. 1.6 kcps, p<0.001), and detected a significantly higher percent of tumor-positive SLNs (73% vs. 49%, p=0.016) while identifying the same rate of node-positive patients (24% vs. 18%, p=0.4). Conclusions: [99mTc]Tilmanocept identified the same rate of node positive patients and removed fewer SLNs compared to fTcSC among BCP with similar risk of axillary metastatic disease. These data suggest that [99mTc]tilmanocept more precisely targets true SLNs and may minimize morbidity while maintaining or improving the accuracy of axillary staging in clinically node-negative breast cancer patients.