早期胃癌のリンパ節微小転移とEMR適応拡大

The Indication for Endoscopic Mucosal Resection in Early Gastric Cancer from the Viewpoint of Lymph Node Micrometastasis

要旨　早期胃癌に対して，内視鏡的粘膜切除術(EMR)，縮小手術，定型手術を選択する上でリンパ節転移の有無は最も重要な因子である．近年の分子生物学的，遺伝子学的解析でリンパ節微小転移の存在が明らかとなってきた．粘膜癌では2cm以上から微小転移がみられ，粘膜下層癌ではその頻度はさらに高くなる．微小転移の観点からみると，現時点でEMRの適応拡大に関しては注意が必要である．今後，基礎的にはリンパ節微小転移の着床，増殖機序の解明，主病巣の転移能の評価の確立が必要である．臨床的にはsentinel node navigation surgeryの確立と微小転移の術中診断に関する各方法の評価が必要である．早期癌では根治は絶対条件であり，微小転移診断に基づくsentinel node生検を併用したEMRの適応拡大は機能温存と根治性を兼備した治療になりえると考えられる．

　The presence of lymph node metastasis is the most important factor influencing the decision about which treatment strategy should be selected from among endoscopic mucosal resection (EMR), less invasive surgery or standard gastrectomy with lymphadenectomy. The presence of lymph node micrometastasis (LMM) has been elucidated by biological and molecular methods. LMM has been found in mucosal cancers larger than 2 cm in size and the incidence of LMM has increased among submucosal cancers. At present, it is prudent to extend the indication for EMR from the viewpoint of LMM. It is fundamentally necessary to elucidate the origin and growth of LMM and to estimate the metastatic potential of primary tumor. It is clinically essential to establish sentinel node navigation surgery and to assess intraoperative diagnosis for LMM by various methods. Curability is most important for treatment of early gastric cancer. In the near future, the extension of the indication for EMR may be established by sentinel node biopsy based on the diagnosis of LMM. EMR in combination with sentinel node biopsy could be the ideal treatment guaranteeing curability and stomach preservation.

　1) Department of Surgical Oncology and Digestive Surgery, Graduate School of Medical Sciences, Kagoshima University, Kagoshima, Japan