SENTINEL LYMPH NODE DETECTION USING TECHNETIUM 99M SULFUR COLLOID TARGETED TO CRANIOCERVICAL LYMPHOCENTERS IN NORMAL DOGS

V.M. Sadler, D.V.M., E.R. Wisner, D.V.M., L.S. Hinton, D.V.M., M.A. McLoughlin, D.V.M., B. Leroy, D.V.M., S.E. Weisbrode, V.M.D, Ph.D. The Ohio State University, College of Veterinary Medicine, Columbus, OH 43210

Introduction: Historically, the diagnosis of regional lymph node metastasis in dogs with head and neck tumors has been made by palpation and biopsy of enlarged lymph nodes. For cancer staging, selective lymphadenectomy, or sentinel node biopsy, has been shown to be an effective and accurate alternative to radical regional lymph node dissection in human patients with breast cancer and malignant melanoma. The purpose of this study was to develop a method for selective lymph node biopsy by coupling the sentinel node concept with a technique of intraoperative gamma probe localization using an interstitially delivered particulate lymphotropic radiopharmaceutical.

Methods: Eight normal, conditioned adult Beagle dogs were used to evaluate lymphatic drainage patterns from four superficial sites on the head. The identities of the sentinel lymph node(s), and non-sentinel nodes from each of the four sites were determined preoperatively using dynamic and static lymphoscintigraphy; and intraoperatively using a hand-held gamma probe and injectable isosulfan blue dye. The radioactivity level of the sentinel lymph nodes, the nonsentinel lymph nodes, and the surrounding tissues was determined with a well counter.

Results: Lymphatic drainage patterns and nodal radiopharmaceutical uptake were consistent for each injection site. Dynamic lymphoscintigraphy documented anomalous lymph nodes, or unexpected lymphatic drainage in 3 of 32 injections performed. The hand-held gamma probe corroborated gamma camera findings, and definitively localized the sentinel lymph nodes and the second echelon nodes. Sentinel lymph nodes were associated with a higher level of radioactivity when compared to non-sentinel lymph nodes and the surrounding tissue. The use of isosulfan blue dye enhanced localization of the lymph nodes intraoperatively.

Conclusion: Lymphoscintigraphy, when used in combination with the hand-held gamma probe and isosulfan blue dye provided accurate localization of sentinel lymph nodes following injection of Technetium 99m Sulfur Colloid on four superficial sites on the head. The techniques used may provide a reliable method for accurate cancer staging in patients with cancers of the head and neck.