Fluorodeoxyglucose Positron Emission Tomography for Melanoma Staging: Refining the Indications

Melanoma patients with advanced disease are often considered for major therapeutic surgical interventions. Accurate identification of all sites of metastatic disease is critical, because only patients rendered completely free of disease are likely to experience disease-free intervals or a potential survival benefit from surgery. Metabolic imaging with fluorine 18–labeled deoxyglucose (FDG)-positron emission tomography (PET) has recently become more widely applied in a variety of human malignancies. Several reports show FDG-PET to be a more sensitive indicator of metastatic melanoma than conventional diagnostic imaging modalities, particularly in patients with recurrent disease. However, various design shortcomings in early reports may have overestimated the utility of PET. Recent studies focusing on specific clinical scenarios are providing information to develop guidelines for the effective use of PET in patients with melanoma. In this issue of Annals of Surgical Oncology, Brady et al. provide a thoughtful report of their investigations of the clinical utility of preoperative PET imaging in patients planned for surgery for high-risk or recurrent/metastatic melanoma. Their work provides further evidence that PET has a role in management of the complex advanced melanoma patient. Although this study showed FDG-PET to be more sensitive than conventional imaging for detection of metastatic disease, the combination of PET and conventional imaging had a greater effect on clinical decision making than either modality alone. The authors showed that the addition of PET to computed tomographic (CT) imaging affected clinical decision making in one third of patients. Collectively, this and other studies show that properly selected patients with metastatic/recurrent melanoma may benefit from adjunctive PET imaging. Should FDG-PET imaging be obtained in all melanoma patients? The collective literature clearly does not support this practice. Prospective studies of preoperative FDG-PET imaging in stage I and II melanoma patients do not show a significant clinical effect. FDG-PET imaging is very unlikely to upstage early-stage melanoma patients already staged by conventional staging protocols that include sentinel node biopsy. Our group found that PET was only 21% sensitive for identification of occult regional lymph node metastases compared with sentinel node biopsy. Preoperative FDG-PET was not useful in predicting the histology of the residual lymph node basin after a positive sentinel node. Most importantly, FDG-PET rarely predicts the presence of occult distant metastases in this population. Increased FDG uptake at a site of possible distant metastatic disease was 10 times more likely to be false positive than true positive. Despite increasing use of FDG-PET in melanoma, it is important to point out that FDG-PET is not generally considered to be the single most sensitive Received December 2, 2005; accepted December 20, 2005; published online February 24, 2006. Address correspondence and reprint requests to: Jeffrey D. Wagner, MD, Wagner and Associates Plastic and Reconstructive Surgery Consultants, Suite 570, 8040 Clearvista Parkway, Indianapolis, IN 46256; E-mail: jdwagner@insightbb.com.