Introduction: Dual-agent mapping for sentinel lymph node (SLN) biopsy generally involves a radiotracer and a dye. Tc-99m sulfur colloid (TcSC) and Tc-99m tilmanocept (TcTM) are the two most common radiopharmaceutical agents used in the United States for SLN biopsy in breast cancer. However, limited data exists that compares operative performance characteristics between the two radiotracers. We sought to compare the number of surgical removed nodes between patients undergoing SLN with TcSC or TcTM.
Methods: We retrospectively reviewed the use of TcSC and TcTM in clinically node-negative breast cancer patients at our institution since 2010. Patients receiving TcSC typically received 2-4 intradermal peritumoral injections of 0.5mCi on day of surgery or 2.0mCi on day prior to surgery. Patients receiving TcTM received a single intradermal peritumoral injection of 0.5mCi on day of surgery or 2.0mCi on day prior to surgery. Intraoperatively, patients received 2-3ml of isosulfan blue dye immediately prior to incision. The mean number of removed SLNs between TcSC + blue dye and TcTM + blue dye was compared with a t-test. The proportion of node-positive patients was assessed with a chi-squared test. A multivariate negative binomial count model was constructed to assess patient and surgical covariates on number of removed nodes.
Results: Since 2010, 1062 clinically node-negative patients underwent SLN biopsy with TcSC + blue dye (n=522) or TcTM + blue dye (n= 540). Overall, the mean number of removed SLNs was 3.0 (SD 1.8). Additionally, 162 patients (15.8%) had at least one positive SLN. The mean number of nodes did not differ between TcSC + blue dye (2.97) vs. TcTM + blue dye (2.94), p = 0.80. The proportion of node-positive patients did not differ between groups, TcSC + blue dye (16.1%) vs. TcTM + blue dye (15.6%), p= 0.88. On multivariate modeling, patient age, surgeon and presence of positive nodes were significantly associated with the number of removed SLNs, however, radiotracer agent did not affect the number of removed SLNs.
Discussion: The number of removed SLNs did not differ between radiopharmaceutical agents in clinically node-negative breast cancer patients. The dual technique of radiopharmaceutical plus blue dye with these two pharmaceutical appear statistically equivalent. Further study is needed to compare the efficacy of the radiopharmaceuticals when used as a single agent.