Use of low-dose technetium Tc 99m sulfur colloid to locate sentinel lymph nodes in melanoma of the head and neck: preliminary study.

OBJECTIVES/HYPOTHESIS: Because sentinel lymph nodes are the first lymph nodes that drain a primary cancer site, results of sentinel lymph node (SLN) biopsy indicate status of the regional lymph nodes. Preoperative lymphoscintigraphy and intraoperative combined application of the handheld gamma probe and blue-dye technique (i.e., the "combined technique") was used previously to accurately identify the SLN, mostly in melanoma of the extremities and trunk and, sometimes, in melanoma of the head or neck, which is anatomically complex. Because of this complexity, melanoma in the head or neck is inherently problematic to treat: Localization of the SLN can be difficult or impossible because the primary cancer site can be near or overlapping the nodal basin. The objective of the present study was to determine the technical modifications and other considerations that can make SLN localization feasible in cases of melanoma occurring near or overlapping the nodal basin in the head or neck.

STUDY DESIGN/METHODS: In a retrospective study of clinical records containing our database of melanoma diagnoses made between January 1996 and December 1999, we identified 27 patients diagnosed with stage I or II primary melanoma of the head or neck with clinically negative neck nodes who also had had preoperative lymphoscintigraphy. Of the 27 patients (17 male and 10 female patients; mean age, 54 y), 24 had SLN biopsy by intraoperative localization using both the handheld gamma probe and the blue-dye technique.

RESULTS: Among the 27 patients who had SLN mapping, a median Breslow thickness of 1.8 mm was noted. Sentinel lymph node was noted at preoperative lymphoscintigraphy in 26 (96%) of the 27 patients. Activity of technetium Tc 99m (Tc-99m) sulfur colloid injected ranged from 10 to 1000 microCi (0.37 to 37 megabecquerel [MBq]). Intraoperative use of the combined technique for sentinel lymphadenectomy was successful in 92% of patients. Sentinel lymph nodes were identified in all 14 patients who received Tc-99m sulfur colloid at an activity level less than 60 microCi (2.2 MBq); mean activity level of injected TC-99m sulfur colloid was 28 microCi (1.04 MBq). Sentinel lymph nodes were identified in 8 (80%) of 10 patients who received Tc-99m sulfur colloid at an activity level greater than 100 microCi (3.7 MBq); mean activity of injected Tc-99m sulfur colloid in these patients was 482 microCi (17.8 MBq). A mean number of 1.4 sentinel lymph nodes per patient was identified at preoperative lymphoscintigraphy, and a mean number of 3 sentinel lymph nodes per patient was identified intraoperatively using the combined technique. Tumor recurrence was seen in 2 (10%) of the 19 patients who had cancer-free SLN at mean follow-up of 18 months (range, 1 to 47 mo). Sentinel lymphadenectomy of the parotid region did not injure the facial nerve in any patients.

CONCLUSIONS: For patients with primary melanoma that is near or overlaps the nodal basin in the head or neck, SLN biopsy can be accurately performed using Tc-99m sulfur colloid at low activity levels (10 microCi to 60 microCi [0.37 to 2.2 MBq]. However, background radiation from the primary injection site can incorporate the SLN, making localization at preoperative lymphoscintigraphy difficult if not impossible; therefore, the high doses commonly used for melanoma of the extremities and trunk (500 to 2000 microCi [18.5 to 74 MBq]) should not be used for melanoma of the head or neck if the primary site is near or overlaps the nodal basin. In addition, absorption of Tc-99m sulfur colloid by salivary glands increases background radiation in the nodal basin; therefore, use of the handheld gamma probe for intraoperative localization of SLN can be problematic in regions where lymph nodes are adjacent to or within the substance of the salivary gland (i.e., the submandibular and parotid glands).