Objective: PET with a novel tracer, L-[3-¹⁸F]-α-methyl tyrosine (¹⁸F-FMT), has been studied in lung cancer. We evaluated ¹⁸F-FMT PET for therapy response in comparison with ¹⁸F-FDG PET.
Subjects and methods: Eighteen patients with lung cancer underwent PET studies with ¹⁸F-FMT and FDG before and after chemoradiotherapy. Uptake of tracers was measured by standardized uptake value (SUV) in the primary tumor and the mediastinal lymph node. The ratio of the lymph node maximum SUV (SUV(max)) to that of the primary tumor and the SUV(max) of the primary tumor itself were correlated with the survival time estimated by Kaplan-Meier method. Metabolic response, as determined by the changes in the tracer uptake, was compared with Response Evaluation Criteria in Solid Tumors (RECIST) for therapy response.
Results: Agreement of therapeutic response evaluated by RECIST was noted in 10 (56%) of 18 patients evaluated with FDG PET and in 16 (89%) of 18 patients evaluated with ¹⁸F-FMT PET (p = 0.025). In nine patients with partial response, partial metabolic response was observed in eight (89%) by use of FDG PET and in nine (100%) by use of ¹⁸F-FMT PET. In nine patients with stable disease, stable metabolic disease was observed in two (22%) by use of FDG PET and in seven (78%) by use of ¹⁸F-FMT PET (p = 0.056). Fluorine-18-FMT PET revealed that the prognosis of the group with a lymph node-to-primary tumor SUV(max) ratio greater than or equal to 1 was significantly better than that in the group with a ratio of less than 1.
Conclusion: Fluorine-18-FMT is a promising PET tracer for monitoring response to chemoradiotherapy and for predicting the prognosis of patients with lung cancer.