FDG PET in early stage cutaneous malignant melanoma

Fluorodeoxyglucose positron emission tomography ( FDG PET ) is not recommended in early stage melanoma; however, a significant number of cases are referred to our institution for FDG PET . We refer to early stage disease as A merican J oint C ommittee on C ancer ( AJCC ) stage I and II , which includes all cases without metastases. A retrospective review was undertaken to determine the clinical utility of FDG PET in this patient group. Methods A retrospective study of FDG scans on all patients presenting to the WA PET Centre with early stage melanoma over a 5½ year period was undertaken. The positivity rate of the initial study for detection of malignant melanoma was determined. In patients with an initially negative FDG PET , the time from initial diagnosis to a positive surveillance study was determined. Both the initial positivity rate and time to a positive study were correlated with B reslow staging. Results Three hundred twenty‐two patients were included in the study, of which 74 had initial positive FDG PET scans (23%). Adequate follow‐up was available in 51 patients with the PET result confirmed as true positive in 37 (positive predictive value 73%). One hundred eight of 248 patients initially negative had follow‐up scans during the follow‐up period, of which 48 became positive. The 73% of recurrences were over 12 months post‐diagnosis. No correlation with Breslow thickness was demonstrated. Conclusion Despite FDG PET not being recommended for early cutaneous malignant melanoma, 27% of melanoma cases referred for FDG PET during the study period were AJCC stage I or II . Our results suggest FDG PET in early stage melanoma demonstrates occult disease in 17% of cases.