PETを用いた大腸スクリーニング検査

Fluorodeoxyglucose Positron Emission Tomography CT for Colorectal Cancer Screening

要旨●陽電子放出断層撮影（PET）は¹⁸F-フルオロデオキシグルコース（FDG）の集積を可視化する非侵襲的診断手法で，大腸癌では糖代謝亢進により異常集積を示しうる．無症候・平均リスク集団におけるPET/PET-CTの診断成績は概して感度が低く，特異度は高い．感度は病変径，肉眼型，遺伝子変異，糖代謝状態などにより修飾される．見かけの精度は分析単位（患者/病変），陽性の定義，SUVカットオフ値，集積部位との突合性，検査間隔などによって変動する．現時点で対策型検診の第一選択は免疫学的便鮮血検査（FIT）であり，PETは任意型検診における補完的役割にとどまる．近年，ラジオミクス解析が注目されており，今後の診断精度の向上が期待される．

　Positron emission tomography（PET）is a non-invasive imaging technique that visualizes ¹⁸F-fluorodeoxyglucose（FDG）uptake. Colorectal cancer（CRC）can show abnormal FDG accumulation due to increased glycolysis. In asymptomatic, average-risk populations, PET/PET-CT demonstrates low sensitivity and high specificity for CRC screening. Its diagnostic performance may depend on tumor size, macroscopic type, gene mutation, and glycemic status. Its apparent diagnostic yield varies with methodological factors, including the analysis unit（per-patient vs. per-lesion）, positivity criteria, SUV thresholds, spatial matching rules between PET findings and the reference test, and the PET-reference test interval. Currently, the fecal immunochemical test remains the first-line modality for population-based screening in Japan, while PET/CT has a limited adjunctive role in opportunistic settings. Recently, radiomics analyses have attracted much attention and may contribute to future diagnostic accuracy improvement.