食道扁平上皮癌のリスク因子と高リスク群の絞り込み

Risk Factors and High-risk Groups for Esophageal Squamous Cell Carcinoma in Japan

要旨

本邦の食道扁平上皮癌は，食道・頭頸部・胃に多発重複発癌するfield cancerizationが特徴である。飲酒，喫煙，野菜果物の摂取不足，萎縮性胃炎，痩せがリスク因子だが，ADH1B低活性型とALDH2欠損型の遺伝子多型でエタノールとアセトアルデヒド（AcH）への長時間高濃度の曝露が起き，食道はAcHが蓄積しやすく発癌しやすい。1日30g以上飲酒するALDH2欠損者は特に危険である。フラッシング質問紙法と飲酒・喫煙・野菜果物摂取を含む問診で，食道癌と二次癌のリスク評価ができる。高リスク群の食道ヨード染色はさらに評価を高める。リスク因子に男女差はない。AcH病には粘膜メラノーシス，MCV値増大，大球性貧血，白血球減少があり食道癌に併発しやすく発癌マーカーになる。治療前の禁酒が骨髄回復のため推奨される。禁酒・減酒・禁煙でリスクは下がる。食道癌患者にはアルコール依存症疑いの人が多く，Alcohol Use Disorders Identification Test（AUDIT）などの問診による飲酒問題の包括的評価が推奨される。

　Esophageal squamous cell carcinoma in Japan is characterized by field carcinogenesis, in which multiple, overlapping carcinomas occur in the esophagus, head and neck, and stomach. The risk factors for esophageal squamous cell carcinoma are alcohol consumption, smoking, insufficient intake of fruits and vegetables, atrophic gastritis, and emaciation. Prolonged exposure to high concentrations of ethanol and acetaldehyde (AcH) occurs in ADH1B hypoactive and ALDH2 deficient genetic polymorphisms, and the esophagus is prone to AcH accumulation and carcinogenesis. ALDH2-deficient individuals who drink more than 30g of alcohol per day are at particular risk. Risk assessment for esophageal cancer and secondary cancers can be done using the Flushing Questionnaire and questionnaires that include alcohol consumption, smoking, and fruit and vegetable intake. Esophageal iodine staining in high-risk groups further enhances the assessment. Risk factors do not differ between men and women. AcH disease includes mucosal melanosis, increased MCV, macrocytic anemia, and leukopenia, which are likely to occur with esophageal cancer and are markers of carcinogenesis. Abstinence from alcohol prior to treatment is recommended for bone marrow recovery. Abstinence from alcohol, reduction in alcohol consumption, and smoking cessation reduce the risk. Many patients with esophageal cancer are suspected to be alcohol dependent based on AUDIT, and a comprehensive assessment of drinking problems is recommended.