PET/CT

PET/CT for Small Intestine and Colorectal Neoplasm

要旨●現時点では大腸癌診断におけるFDG-PETの役割は病期診断（特に遠隔転移診断）と再発診断である．2010年から“早期胃癌を除く”すべての悪性腫瘍にFDG-PETが保険適用となったため，小腸癌やGISTなどの非上皮性腫瘍にも実施できるようになった．FDG-PETを用いたがん検診において，大腸癌は最も多く発見される癌である．感度は便潜血検査よりも優れており，スクリーニング検査として意義がある．現在の分子標的薬剤は治療効果が遺伝子変異に相関し，PETはそのイメージングバイオマーカーとして有望である．治療効果判定や予後予測を目的とした場合，FDG-PETは保険適用外であるが，今後エビデンスが得られればPETの用途がさらに広がるものと思われる．

　Currently, FDG（fluorodeoxyglucose）-PET（positron emission tomography）is being used to determine the stage of colorectal cancer, particularly screening of distant metastases, and to detect recurrence. Because FDG-PET is being covered under reimbursement since 2010 for all malignancies except early gastric cancer, it can be used for small intestinal cancer and non-epithelial tumors. Colorectal cancer is the most frequently found cancer in cancer screening programs that include FDG-PET. FDG-PET is a useful modality for cancer screening because the sensitivity of FDG-PET is superior to that of the FOBT（fecal occult blood test）. The response to molecular target therapy is closely correlated with gene mutations, and FDG-PET is suggested to be a promising imaging biomarker that reflects therapeutic effect.

　Although therapeutic monitoring and response prediction by FDG-PET are not currently covered under reimbursement, the available applications of PET will expand if supportive evidence is collected in the near future.