Use of fluorine-18 fluorodeoxyglucose positron emission tomography in the detection of silent metastases from malignant melanoma

Correct staging is crucial for the management and prognosis of patients wit h malignant melanoma. The aim of this prospective study was to compare stag ing by whole-body positron emission tomography using fluorine-18 fluorodeox yglucose (F-18-FDG) with staging by conventional methods. Thirty-eight pati ents with malig- nant melanoma of clinical stage II (local recurrence, intr ansit and regional lymph node metastases) or III (metastases to other sites than in stage II) were included in the study. The results of the PET scans were compared with those obtained by clinical examination, computed tomogr aphy, ultrasound, radiography, and liver function tests and histology or cl inical follow-up. With F-18-FDG PET we found for all foci a sensitivity of 97% and a specificity of 56%, compared with 62% and 22%, respectively, when using routine methods. For intra-abdominal foci, the sensitivity and speci ficity were 100% for both F-18-FDG PET and routine methods. Corresponding f igures for pulmonary/intrathoracic foci were 100% and 33%, respectively. Of the patients included in this study, 34% would not have been staged correc tly by conventional methods alone. We conclude from this study that F-18-FD G PET is a sensitive method superior to conventional methods for detecting widespread metastases from malignant melanoma. Mutilating surgery of no ben efit can thereby be avoided. F-18-FDG PET is useful as a supplement to clin ical examination in melanoma staging.