PET with O-(2-18F-Fluoroethyl)-L-Tyrosine in peripheral tumors: first clinical results

O‐(2‐18F‐Fluoroethyl)‐L‐Tyrosine (18F‐FET) PET has shown promising results in brain tumor diagnosis. The aim of this prospective study was to evaluate 18F‐FET PET in comparison with 18F‐FDG PET in patients with peripheral tumors. METHODS: Forty‐four consecutive patients with suspected malignant tumors underwent 18F‐FET PET and 18F‐FDG PET within 7 d. Whole‐body PET studies were performed 1 h after intravenous injection of 370 MBq of 18F‐FET or 18F‐FDG. Six patients were excluded from the analysis because a malignant tumor could not be verified. In 38 patients (7 with colorectal cancer, 6 with pancreatic cancer, 9 with head‐neck cancer, 4 with lymphomas, 3 with lung cancer, 3 with ovarian cancer, 4 with breast cancer, and 2 with prostatic cancer), 18F‐FET PET and 18F‐FDG PET were compared. RESULTS: 18F‐FET was positive in only 13 of 38 patients (8 with head‐neck cancer, 3 with breast cancer, and 2 with lung cancer), whereas 18F‐FDG exhibited increased uptake in 37 of 38 patients. All squamous cell carcinomas were found to be 18F‐FET‐positive tumors (8 head‐neck cancer and 2 lung cancer), whereas most adenocarcinomas were found to be 18F‐FET‐negative tumors. In patients with colorectal cancer, pancreatic cancer, ovarian cancer, prostatic cancer, and lymphomas, no increased 18F‐FET uptake could be identified. All lesions that exhibited increased 18F‐FET uptake also showed increased 18F‐FDG uptake. No additional lesion was identified by 18F‐FET PET but not by 18F‐FDG PET. A subgroup analysis of patients with head‐neck carcinomas allowed a better distinction between malignant and inflammatory tissues with 18F‐FET than with 18F‐FDG. CONCLUSION: 18F‐FET is inferior to 18F‐FDG as a PET tracer for general tumor diagnosis. Our preliminary results suggest rather selective uptake of 18F‐FET in squamous cell carcinomas. Compared with 18F‐FDG PET, 18F‐FET PET may allow a better distinction between tumors and inflammatory tissues in patients with squamous cell carcinomas.