レーザー療法による胃癌の内視鏡的治療の現況

Present Status of Endoscopic Therapy for Gastric Cancer Mainly by Laser Irradiation

要旨　内視鏡による胃癌病巣の治療の展開について，レーザー内視鏡法による治療を中心に，現状と問題点を述べた．現在のレーザー療法はNd-YAGレーザーを中心とする光凝固法と，腫瘍親和性光感受性物質とargonレーザーまたは色素レーザーのコンビネーションによる光化学療法がある．早期胃癌病巣に対しては，強力な光エネルギーを用いたNd-YAGレーザーによる光凝固法が有利で，粘膜下組織までの癌組織は凝固壊死に陥らせることができる，一方，進行胃癌病巣に対し，Nd-YAGレーザーでは深部までの照射は穿孔の危険性がある．光化学療法は，この点，癌細胞だけの破壊となり正常組織には影響がない．したがって理論的には筋層，漿膜下層への浸潤癌組織に対しても安全に治療が行われる．しかし長時間のレーザー照射を必要とすること，光感受性物質のヘマトポルフィリン誘導体による日光皮膚炎などの副作用の問題がある．レーザー療法による胃癌の治療は，始まったばかりと言えるし，その適応についても制限がある．しかし大切なことは，レーザー療法というのはレーザー内視鏡法でなければできない特異性を持った療法である，という認識である．レーザー療法の今後の展開は，内視鏡医のこの認識の如何によると考えている．

　Authors studied the development of endoscopic therapy for gastric cancer mainly by laser irradiation and evaluated its present status and problems.

　Laser therapy today includes photocoagulation mainly with the use of Nd-YAG laser and photodyna-mic therapy which is done in combination with the light sensitivity materials with tumor affinity and Argon laser or Dye laser. For the nest of early gastric cancer, photocoagulation is advantageous by using Nd-YAG laser with strong light energy and can put cancer cells within the submucosal layer into coagulation necrosis. On the other hand, it is dangerous to use Nd-YAG laser for the nest of advanced gastric cancer because irradiation to deeper layer has risk of perforation. Photodynamic therapy is advantageous at this point in destroying only cancer cells without any influence to the normal tissue. Therefore, it is possible to perform safely the therapy for the cancer tissue infiltrating to the proper muscle or subserosa. However, there are some problems, that is, it needs long time laser irradiation and has side effects such as dermatitis solaris caused by light sensitive material by hematoporphyrin derivative.

　Endoscopic therapy for gastric cancer using laser irradiation has just been put into practice and has now yet limitation in its indication. But what is important is the recognition that laser therapy is a specific therapy which is impossible to perform without laser endoscopy. The development of laser therapy from now on depends on how endoscopists think about this problem.