レーザー内視鏡による癌の診断と治療

抄録

It is said that in our century, the appearance of the lasers was, in the area of scientific techniques one of the most important discoveries. The introduction of lasers to endoscopy, with all their special characteristics such as the coherence, targeting ability, high power, high intensity, conver-gence, high interference, ultra short light pulse gen-eration and other unique qualities, provided a useful and powerful mean for the diagnosis and treatment of cancer. We are reporting a recapitulation of the research done on the endoscopic use of lasers. In the field of diagnostic approach the cancer's fluorescence was discovered. When we irradiated an excised specimen of gastric or colon cancer with a 514.5nm argonlaser beam, we observed, through a VO -55 filter, the fluorescence corresponding to the can-cer focus. We found two types of fluorescence, a yellow-orange and a red one. In the case of early gastric cancer, the IIc group showed a yellow-orange fluorescence which was often significantly stronger than the intrinsic fluorescence of the normal mucosa. On the contrary, it was found that in the case of the elevated type of early gastric cancer its fluorescence was lower than that of the normal mucosa. Also a red fluorescence was often observed in decayed parts of colon cancer. In order to investigate that fluorescence we measured the fluorescent spectrum of a cancer tissue using a fluorescence analyzer. The yellow-orange fluorescence observed in the cancer focus, showed a biphasic spectrum at 5$0nm and 600nm a pattern similar to that of the normal mucosa. At the histological examination the fibrotic compo-nent of the muscularis mucosa as well as the inner elastic layer of the vessels showed a strong yellow fluorescence. The existence of the muscularis mucosa at the area of the mucosal lesion may be the source of the strong fluorescence that can be detected in the undifferentiated, depressed, early gastric can-cer focus. On one hand, the red fluorescence had a peak at 630nm and we supposed that it looked like the fluo-rescence of the porphyrin derivatives. In order to detect and to analyze the fluorescence spectrum we created a laser beam transporting system and we tried a variety of analyzers. In vivo, white coat, mucus, bleeding and other factors have a great influ-ence on the intensity of the fluorescence thus dimini-shing it and providing poor results. Till now the usefulness of its clinical application has not been evaluated. We started using YAG-laser tissue coagulation as a therapeutic method. The elevated, differentiated type of early gastric cancer, less than lcm, showed a 100% 5-year survival rate in contrast to the depressed, undifferentiated type of early gastric can-cer which showed a high rate of recurrence and demanded a retreatment (Table 1). Concerning the problem of metastasis to the lymphnodes, we found that the early, differentiated adenocarcinoma less than lcm, limited to the mucosa (ul-), was not accompanied by lymphnode metastasis (Table 2 ). If we seek a complete cure we have to look for a small gastric cancer. In order to achieve the complete tissue coagulation, we investigated, both basically and clinically, the efficacy of thermotherapy. Using nude mice, bearing tumor from implanted cancer cells, we evaluated the type, the distance and the temperature of the laser, the adjuvant cancer drugs, the HPD treatment as well as various other factors; we developed the equipment and started using it clinically. As a result the single use of lasers proved to be not satisfactory and in its place, a combination of photoradiation therapy and adjuvant chemotherapy was shown to be effective (Table 3). Recently, HPD, photophrin I and II, metal porphyr-ine derivatives, from pheophorbides, the pheophor-bide A, PH1126, from phthalocyanines, the zinkphth-alocyanine made their appearance and are under basic research investigation.