Fluor-18-fluorodeoxyglucose positron emission tomography (FDG-PET) in malignant melanoma. Diagnostic comparison with conventional imaging methods.

PURPOSE: To assess the diagnostic value of fluor-18-fluorodeoxyglucose positron emission tomography (FDG-PET) in screening for melanoma metastases.

MATERIAL AND

METHODS

The case records of 94 melanoma patients who had been examined by whole-body FDG-PET between 1995 and 1999 were evaluated retrospectively. Forty patients showed evidence of lymphogenous and 42 of hematogenous metastasis. The maximal interval between PET and the diagnostic procedure under comparison was 2 weeks. Confirmation of the findings was based on histology or the clinical or radiological course.

RESULTS

In 24 patients, all diagnostic examinations including CT had been performed within 2 weeks from PET. In no case did PET change the staging. In 13 patients, PET agreed with morphological diagnosis in the number of metastatically invaded organs. This included 3 patients without metastases. The estimated number of organs invaded by metastases was higher with PET in 5 patients and higher with morphological imaging techniques in 6 patients. Among the PET findings with higher or equivocal counts of organs with metastases there were 2 confirmed false-positive findings.

CONCLUSION

In a selected patient population, FDG-PET was found to be inferior to CT for diagnosing lung and liver metastases. The supplementary use of FDG-PET is not generally of value once metastasis has been established.