Gastric and Colon Cancer Therapy in Accordance with the Pathological Carcinogenesis

Takeshi Oohara

The Third Department of Surgery, University of Tokyo

We have been investigating the histology of gastric ulcer, intestinal metaplasia and regenerated gastric mucosa in terms of the pathological background of carcinogenesis. Consequently, these three proved to interact with one another. In the process of regeneration of gastric mucosa, preintestinalization which proved to be related to carcinogenesis occurs at the early stage and then stable intestinal metaplasia takes the place of it. The experimental carcinogenesis using NMMG for chronic gastric ulcer or intestinal metaplasia and the pathological observation of healing process of human gastric ulcer, about 70% of which turns into intestinal metaplasia, can explain this interaction. Thus the regeneration of gastric mucosa-intestinalization system plays an important role not only as an initiator but also as a promoter of carcinogenesis. Another study we have concentrated on is a prospective randomized study to determine the clearance level of surgical operation for gastric cancer dependent on the pathological differentiation and the depth of cancer invasion. From the results so far, modified surgery proved to be effective for early cancers, but careful determination dependent on each grade of differentiation was suggested to be necessary for advanced cancers.
Concerning the pathological development of colon cancer, there are two theories dependent on the preceding status. "Adenoma-carcinoma sequence" which supports the presence of adenoma before cancer developes and "de novo carcinogenesis theory" which does not support it. According to our stepsectioning study of resected colon specimens of 38 colon cancer patients, 12 minute early cancers were discovered from macroscopically normal lesions. Six of them were cancers developed on adenoma and another six belonged to de novo cancers. There was a remarkable difference between cancer on adenoma and de novo cancer, the former one developed polyp like protruded lesion and invaded slowly. The latter one, appeared flat at the earliest stage, however, invaded vertically very fast. This fact is consistent with the results of another investigation into sm invasion rate of 32 early colon cancers less than 1 cm in diameter/Only 7.1% (1/14) of the cancer developed after adenoma invaded into sm layer, versus 55.6% (19.18) of de novo cancers showed sm invasion. For the treatment of colon cancer, one of the most important things is to know the relationship between macroscopical or pathological findings and the degree of vertical invasion of early cancer. Since de novo cancer is invading very fast even if it's diameter is small, the majority of advanced cancers are supposed to develop from this type of early cancers. Thus, it's significant to search for de novo cancer histologically and flattyped colon cancer macroscopically. Another thing we have to stress on is that advanced colon cancers cannot be prevented just by polypectomy.

Key words
gastric cancer; histogenesis, treatment, large intestinal cancer;histogenes, de novo cancer, adenoma-carcinoma sequence, intestinal metaplasia of the gastric mucosa

Reprint requests
Takeshi Oohara The Third Department of Surgery, University of Tokyo
3-28-6 Mejirodai, Bunkyoku, Tokyo, 112 JAPAN

Accepted
July 6, 1994

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