Utility of Quantitative SPECT/CT Lymphoscintigraphy in Guiding Sentinel Lymph Node Biopsy in Head and Neck Melanoma.

To investigate the use of advanced SPECT/CT quantification in guiding surgical selection of positive sentinel lymph nodes (SLNs) in head and neck melanoma. We retrospectively reviewed data from patients with cutaneous head and neck melanoma who underwent lymphoscintigraphy with SPECT/CT prior to SLN biopsy (SLNB). Quantification of radiotracer uptake from SPECT/CT data was performed using in-house segmentation software. SLNs identified using SPECT/CT were compared to SLNs identified surgically using an intraoperative γ-probe. A radioactivity count threshold using SPECT/CT for detecting a positive SLN was calculated. One hundred and five patients were included. Median number of SLNs detected was 3/patient with SPECT/CT and 2/patient with intraoperative γ-probe. The hottest node identified by SPECT/CT and intraoperative γ-probe were identical in 85% of patients. All 20 histologically positive SLNs were identified by SPECT/CT and γ-probe. On follow-up, all nodal recurrences occurred at lymph node levels with the hottest node identified by SPECT/CT and either the hottest or second hottest node identified by γ-probe during SLNB. Using our data, a SPECT/CT radioactivity count threshold of 20% would eliminate the unnecessary removal of 11% of SPECT/CT identified nodes and 12% of intraoperatively detected nodes. Utilizing SPECT/CT quantification, we propose that a radioactivity count threshold can be developed to help guide the selective removal of lymph nodes in head and neck SLNB. Furthermore, the nodal level containing the hottest node identified by SPECT/CT quantification must be thoroughly investigated for SLNs and undergo careful follow-up and surveillance for recurrence.