5）PET，PET/CT

Survey of Colorectal Cancer Using PET or PET/CT

要旨　大腸癌はFDGが良好に集積する腫瘍の1つである．しかし，PETは空間分解能に劣るため，小さい癌の検出には限界がある．早期大腸癌の検出能も十分でなく，特に平坦型の形態をとる早期癌の検出は難しいが，ポリープ状の形態をとるものは時としてFDGの点状集積として描出される．最近の本邦における全国規模の多施設共同研究の結果によると，FDG-PETによるがん検診の有効性が示されている．この報告では，PET検診で最も高頻度に発見されたのが大腸癌であった．いまだにPET検診の有効性に対する疫学的なエビデンスは不十分であるが，FDG-PETががん検診において一定の役割を担うことは確かであろう．

　Colorectal cancer is one of the tumors that shows strong accumulation of FDG. But due to the limitation of spatial resolution, small cancer is difficult to detect on PET. Detectability of early colorectal cancer is also inadequate on PET, especially a tumor showing flat type is difficult to depict though polypoid type is sometimes revealed as a hot spot of FDG accumulation.

　A recent report from Japan, that analyzed nationwide multi-institutional data, described the usefulness of “FDG-PET cancer screening”. In this report, colorectal cancer was the most frequently found malignancy. This report showed notable evidence that FDG-PET have a definite role to play in cancer survey, though epidemiological evidence based on high-level studies are still inadequate.