Clinical Value of Single-photon Emission Computed Tomography Combined With Computed Tomography for Sentinel Lymph Node Identification in Melanoma.

Abstract

Melanoma is the deadliest form of skin cancer and has the ability to metastasize widely. Accurate diagnosis of sentinel lymph nodes (SLN) is crucial to its management. The gold standard for SLN identification is planar lymphoscintigraphy. Recently, single-photon emission computed tomography combined with computed tomography (SPECT/CT) has been used as a hybrid method to map lymphatic drainage networks. We aim to better characterize the utility of this tool in head and neck melanoma by evaluating its effectiveness in the preoperative setting for melanoma patients undergoing sentinel lymph node biopsy (SLNB). We performed a retrospective chart review at the West Haven Veterans Affairs Hospital. Inclusion criteria were patients with melanoma with a thickness greater than 0.75 mm and SPECT/CT use before operative sentinel lymph node excision. Exclusion criteria included clinically palpable lymph nodes, evidence of distant metastatic disease, melanoma with a Breslow depth less than 0.75 mm, and melanoma in situ. Our primary endpoints were correlation with intraoperative findings and whether the test had any influence on the operative plan. Thirty-five patients between 2011 and 2017 met our criteria. SPECT/CT correlated with the sentinel node biopsy based on intraoperative lymphoscintigraphy in 30 (86%) of 35 cases, and there were no changes to the operative plan after SPECT/CT was performed. Sentinel lymph nodes were correctly identified in all 35 cases. The role of SPECT/CT in SLNB is uncertain. According to some studies, SPECT/CT can help decision making and change surgical approach in up to 35% of patients. However, other studies have reported questionable correlation with intraoperative findings and no added intraoperative value in over 50% of patients. We have demonstrated that preoperative SPECT/CT was consistent with intraoperative findings in 86.0% of cases but did not change the surgical approach for the SLNB. Surveillance over a period of 12 months did not reveal any signs of melanoma recurrence. A possible advantage of SPECT/CT is potentially decreasing costs by lowering operative time. However, financial cost in the literature suggests SPECT/CT is costlier than lymphoscintigraphy and therefore this must be weighed against any potential benefit. Overall, we did not find that SPECT/CT gives added value when compared with lymphoscintigraphy.