Background: No prior studies have investigated the performance of Tc-99m tilmanocept (TcTM) in sentinel lymph node (SLN) biopsy for breast cancer since FDA-approval in March 2013. We sought to investigate the sensitivity and performance in a variety of clinical scenarios.
Methods: Our institution adopted the use of Tc-99m tilmanocept for routine use in May 2013 for breast cancer SLN biopsy in clinically node-negative patients. We assessed the effect of neoadjuvant chemotherapy, use of lymphoscintigraphy and compared one-day versus two-day preoperative injection protocols on sensitivity of detecting a SLN and on total number of removed nodes. Patients received a 0.1ml injection of either 0.5mCi TcTM on day of surgery or 0.1ml injection of 2.0mCi TcTM on day prior to surgery by a nuclear medicine radiologist. Performance and use of lymphoscintigraphy was optional. Intraoperatively, patients received a 2-3ml injection of vital blue dye (VBD) immediately prior to incision. A negative binomial count model was used to assess univariate and multivariate factors influencing the number of removed SLNs with TcTM and VBD. A p-value < 0.05 was used for statistical significance.
Results: Between May 2013 to June 2016, 617 clinically node-negative patients underwent SLN biopsy with TcTM and VBD. A SLN was identified intraoperatively in 100% of patients. On average, 3.0 SLNs (SD 1.8) were removed per patient. Sixty-seven (10.9%) patients were injected with the two-day protocol and 91 (14.7%) patients underwent neoadjuvant chemotherapy. At least one positive-node was detected in 95 (15.4%) patients. Overall, radioactive nodes were identified in 609 (98.7%) patients, blue nodes in 550 (89.1%) patients and both radioactive and blue nodes in 543 (88.0%) patients. There was no statistical difference in the number of removed nodes in patients receiving neoadjuvant chemotherapy, undergoing the “two-day” injection protocol or with the use of lymphoscintigraphy. On multivariate analysis: operating surgeon, age and presence of positive nodes affected the number of removed SLNs.
Conclusion: TcTM reliably identifies SLNs in clinically node-negative breast cancer patients undergoing SLN biopsy. The use of neoadjuvant chemotherapy does not alter the number of removed SLNs. Furthermore, the injection of TcTM can be performed on the day before surgery or the day of surgery without the use of lymphoscintigraphy.