The Yield of SPECT/CT for Anatomical Lymphatic Mapping in Patients with Melanoma

The hybrid single-photon emission computed tomography camera with integrated CT (SPECT/CT) fuses tomographic lymphoscintigrams with anatomical CT data. SPECT/CT shows the exact anatomical location of a sentinel node and may detect additional drainage. The purpose of this study was to explore its potential in patients with melanoma. We studied 85 patients with melanoma with conventional lymphoscintigrams that were difficult to interpret (51 patients), that showed an unusual drainage pattern (33 patients), or with nonvisualization (1 patient). Forty-one patients had melanoma on an extremity, 31 on the trunk, and 14 in the head and neck region. SPECT/CT was performed following late conventional imaging without reinjection of the radiopharmaceutical. Conventional imaging suggested 214 sentinel nodes in 84 of the 85 patients (99%). SPECT/CT showed these same nodes and 12 extra sentinel nodes in seven patients (8%). Ten of these additional nodes were harvested, of which three nodes of two patients harbored metastases. There was a clear advantage of SPECT/CT in 30 patients (35%), resulting in a different incision in 17 patients, an incision at another site in 8, and an extra incision in 5 patients. The value was questionable in 19 patients (22%) in whom sentinel nodes were more clearly visualized by SPECT/CT, although the incision remained unchanged. There was no additional value of SPECT/CT in 36 patients (42%). SPECT/CT detects additional drainage and shows the exact anatomical location of sentinel nodes in patients with inconclusive conventional lymphoscintigrams. SPECT/CT facilitates surgical exploration in difficult cases and may improve staging.