The Utility of Preoperative PET/CT in Patients with Clinically High-Risk Melanoma

Melanoma is a lethal skin cancer and accounts for the highest mortality rate caused by cutaneous malignancies. Prognosis is dependent on stage. Patients with "thick" melanomas of 4-mm Breslow depth or greater are at increased risk for nodal metastases. Positron emission tomography/computed tomography (PET/CT) may be an underutilized imaging study for preoperative clinical staging in those with T4 melanoma.

This was a single-institution retrospective analysis of adult patients with biopsy-proven T4 predominantly cutaneous melanoma (> 4 mm tumor thickness) who underwent preoperative PET/CT at a single National Cancer Institute (NCI)-designated cancer center between 1 January 2010 and 30 December 2022. Patients were excluded if there was clinical evidence of locoregional or distant metastatic disease at time of preoperative PET/CT.

A total of 94 patients met inclusion criteria. They were predominantly male (n = 56, 59.6%) and Caucasian (n = 83, 94.3%) with an average body mass index (BMI) of 27.97 and median age of 69.5 years. A total of 69.7% of patients had tumor ulceration on biopsy and 2% had microsatellitosis. Positive PET/CT scans were found in eight patients (8.5%), which changed clinical management in seven of the eight patients. When comparing PET/CT results to sentinel lymph node biopsy (SLNB) results, sensitivity was 15.4%, specificity was 94.1%, positive predictive value was 50%, and negative predictive value was 74.4%.

Patients with T4 melanoma without clinical suspicion of nodal disease do not have a high rate of occult metastases on preoperative PET/CT. We argue that clinical exam remains the most important tool for preoperative workup in these patients, but that PET/CT may be considered on the basis of patient-specific factors.