FDG Positron Emission Tomography in Isolated Limb Perfusion Therapy in Patients with Locally Advanced Melanoma

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Abstract
Isolated limb perfusion (ILP) with high-dose chemotherapy and tumor necrosis factor is being tested in clinical trials as a treatment for locally advanced extremity melanoma. The authors investigated the ability of F-18 fluorodeoxyglucose positron emission tomography (FDG PET) to determine the true extent of disease in patients with this condition, whose distribution of lesions differs from that seen in previous studies. Nine patients with locally advanced melanoma were selected for imaging of the entire body and extremities using FDG PET from a group of participants in a clinical trial of ILP with melphalan ± tumor necrosis factor. Scans were obtained without attenuation correction. Post-treatment scans were obtained in three patients 1 month after ILP. The findings in the FDG-PET scans were compared with those of a standard protocol (SP) that included anatomic images and physical examinations. Eighty lesions (74 malignant, 6 benign) were detected with FDG PET and the SP combined. Only malignant lesions were detected by both methods in the perfused limbs. Of the malignant lesions, FDG PET detected 65 lesions (sensitivity rate, 88%). In contrast, 48 lesions were detected with the SP (sensitivity rate, 65%). Twenty-six malignant lesions were seen only with FDG PET (35%), whereas nine malignant lesions were seen only with SP (12%). The six benign lesions included three false-positive mediastinal lymph nodes in one patient. The accuracy rates of FDG PET and the SP were 83% and 65%, respectively. These results are comparable to those seen in previous studies with patients who had disease confined primarily to the torso. All post-therapy FDG-PET scans showed a reduction in the number of visualized limb lesions, and diffuse uptake throughout the perfused limbs. The diffuse uptake correlated with post-therapy limb inflammation. Non–attenuation-corrected FDG PET is more sensitive than the SP in detecting the extent of disease in candidates for ILP. The FDG uptake associated with post-therapy inflammation may reduce the contrast resolution of this technique and must be evaluated further.