Positron emission tomography (PET) with fluorine 18 fluorodeoxyglucose (FDG) is a functional imaging modality that can reliably help visualize malignant lesions in structures that are still macroscopically normal. In oncology, it has become a major clinical diagnostic and prognostic tool, which often leads to appropriate changes in patient treatment. It also helps in the early evaluation of the patients’ response to treatment. Positron emission tomography has been proven to be a very useful imaging tool in the evaluation of patients with melanoma specifically. Actually, melanoma was one of the first indications for which Medicare approved coverage for PET. The pooled estimates of FDG PET for the detection of metastasis are as high as 83% for sensitivity, 85% for specificity, 4.56 for positive LR, 0.27 for negative LR, and 19.8 for diagnostic OR.
In the advanced stages, FDG PET has proven to be an adjunctive imaging modality. FDG PET is very useful in helping detect deep soft-tissue metastases, lymph node metastases, and visceral metastases. Most lesions missed by using FDG PET are usually smaller than one centimeter in the lung, liver, or brain. The literature suggests that FDG PET could replace conventional imaging in staging of melanoma patients, except for brain MR and lung CT imaging.
When limited to sentinel lymph nose metastasis, the diagnostic performance of FDG PET is low for the detection of small nodal metastases and cannot replace the sentinel lymph node biopsy.
In conclusion, positron emission tomography is a very useful imaging technique in the evaluation of patients with melanoma.