Carbon-11-Methionine PET Imaging of Malignant Melanoma

The purpose of the study was to assess the feasibility of PET and L-[methyl-11C]methionine (11C-methionine) in the detection of malignant melanoma. Ten patients diagnosed with malignant melanoma (two with primary melanoma and eight with metastatic melanoma of the skin) but had no liver metastases underwent a PET study before starting cancer therapy. Dynamic scanning was performed for 40 min in seven patients and 10-20 min in three patients 25-45 min postinjection. Carbon-11-methionine PET detected all melanoma lesions greater than 1.5 cm (n = 22) in diameter, whereas five smaller pulmonary lesions were not detected. The average standardized uptake value of the untreated lesions was 6.3 +/- 2.1 (n = 19) and the uptake rate (influx constant) was 0.085 +/- 0.041 min-1 (n = 16). PET imaging with 11C-methionine is an effective method for visualizing melanoma. It may also be useful in measuring tumor metabolic activity in vivo.