PET/CT imaging: detection of choroidal melanoma

To determine the size of untreated choroidal melanomas resolved by whole body positron emission tomography fused with computed tomography (PET/CT).

50 consecutive patients with untreated choroidal melanomas underwent whole body PET/CT. A functionally fused helical CT scan and 18-fluoro-2-deoxyglucose (FDG) PET scans were employed. The tumours were identified (both quantitatively and qualitatively) and compared with clinical measurements derived from ophthalmoscopic, angiographic, and ultrasonographic imaging. Standardised uptake values (SUV) of more than 2.5 were considered positive.

Among the 50 patients with choroidal melanoma, PET/CT scan SUVs of more than 2.5 were noted in 14 (28%) tumours. No AJCC T1 class tumours, 33.3% of T2 melanomas, and 75% of T3 melanomas were physiologically identifiable on PET/CT. With respect to COMS group classifications, no small choroidal tumours, 33% of medium, and 75% of large melanomas were physiologically identifiable. The sole ring melanoma was identifiable on PET/CT imaging. The smallest tumour physiologically identifiable by PET/CT had basal dimensions of 3x5.9 and an apical height of 2.9 mm.

Though PET/CT was found to be capable of physiologically identifying certain medium (T2) and most large sized (T3) choroidal melanomas, physiological imaging was not completely dependent upon tumour size. Functionally fused PET/CT localised the tumours within the eye and assessed their physiological activity.