FDG positron emission tomography in isolated limb perfusion therapy in patients with locally advanced melanoma - Preliminary results

Purpose: Isolated limb perfusion (ILP) with high-dose chemotherapy and tumo r necrosis factor is being tested in clinical trials as a treatment for loc ally 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 distribut ion of lesions differs from that seen in previous studies. Methods: Nine patients with locally advanced melanoma were selected for ima ging of the entire body and extremities using FDG PET from a group of parti cipants in a clinical trial of ILP with melphalan tumor necrosis factor. Sc ans 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 an atomic images and physical examinations. Results: 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 lesion s (sensitivity rate, 88%). In contrast, 48 lesions were detected with the S P (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 no des in one patient. The accuracy rates of FDG PET and the SP were 83% and 6 5%, respectively. These results are comparable to those seen in previous st udies with patients who had disease confined primarily to the torso. All po st-therapy FDG-PET scans showed a reduction in the number of visualized lim b lesions, and diffuse uptake throughout the perfused limbs. The diffuse up take correlated with post-therapy limb inflammation. Conclusions: Non-attenuation-corrected FDG PET is more sensitive than the S P in detecting the extent of disease in candidates for ILP. The FDG uptake associated with post-therapy inflammation may reduce the contrast resolutio n of this technique and must be evaluated further.