Carbon-11-methionine PET imaging of choroidal melanoma and the time course after carbon ion beam radiotherapy.

UNLABELLED The aim of this study was to assess the feasibility of MET-PET as an evaluation method of the therapeutic effect of carbon ion beam radiotherapy. PATIENTS AND METHODS Twenty-four choroidal melanoma patients who were treated with a carbon ion beam underwent at least three MET-PET scans before and after therapy. The uptake was visually and semiquantitatively evaluated on the basis of the tumor-to-brain ratio (TBR). RESULTS The accumulation was significantly decreased at 6 months or more after therapy and disappeared in 50% of the patients at 12 months after therapy. The baseline TBR, 1, 6, 12 and 24 months after therapy averaged 1.88+/-0.65, 1.73+/-0.52, 1.08+/-0.42, 0.67+/-0.27 and 0.65+/-0.30, respectively. TBR was significantly decreased at 6 months or more after therapy. CONCLUSION MET-PET may be an alternative method for evaluating the effect of radiotherapy.