Detectable size of melanoma metastases to brain on PET/CT

Objective We aimed to determine at what size melanoma metastases become detectable by PET/CT. Methods We reviewed a total of 293 whole-body PET/CT studies performed on 212 patients for staging of melanoma where there was an MRI within a month of the PET/CT. MR and PET/CT were reviewed independently by separate readers. Results PET/CT revealed an overall incidental true-positive rate of 1% on a per-patient basis, consistent with other studies, with ‘hot’ lesions (more avid than brain parenchyma) visible at smaller sizes than ‘cold’ lesions. Conclusions PET/CT can detect metastatic melanoma lesions over about 2 cm in size, with hot lesions generally visible at smaller sizes.