Epidemiological Studies on Biliary Tract Cancer in Niigata, Japan

在过去十年中对胆道癌（BTC）进行了流行病学研究，理由是我们居住的新潟县的死亡率被发现是日本最高的。本研究是BTC流行病学研究的一部分。本研究的目的是通过使用动物模型来检验一个多因素的因果关系假设。具体而言，我们在多因素因果假设的基础上设计了一种方案，将一种可疑的化学物质氯硝芬（CNP）喂给经过胆囊手术的金仓鼠，使其患上“实验性胆结石”。设5个试验组，分别为：1组：胆结石+正常饮食，2组：胆结石+ CNP(5000ppm)， 3组：阳性致癌物3-甲基胆蒽(3- mc) +正常饮食，4组：3- mc + CNP(5000ppm)， 5组（对照组）：假手术+正常饮食。每组选用起始时9-10周龄的雌性金仓鼠20只。1、2、5组试验周期为72周，3、4组试验周期为17周。第2组在试验第17周停止CNP治疗，其余试验期采用正常饮食，因为与对照组相比，体重增加受到影响。试验72周，1、2、5组各死亡3只。在第3组和第4组中，17周内没有一只死亡。牺牲时（1、2、5组72周，3、4组17周），1、2组肝脏增生性结节分别1例、2例。关于胆囊癌的发生，正在进行组织病理学检查，检查结果的细节将在其他地方公布。

Epidemiological studies of biliary tract cancer(BTC) have been conducted over the last decade, the rationale being that the deaths rates in Niigata Prefecture where we live were found to be the highest in Japan. The present study was conducted as a part of the epidemiological studies on BTC.The aim of the present study is to test a multifactorial causation hypothesis by making use of an animal model. In details, we designed a protocol on the basis of multifactorial causation hypothesis where a suspected chemical, chlornitrfen(CNP) is given to golden hamsters whose gallbladders are surgically operated to have "experimental gallstone".Five experimental groups were established as follows ; Group 1 : gallstone + normal diet, Group 2 : gallstone + CNP(5000ppm), Group 3 : positive carcinogen, 3-methylcholanthrene (3-MC) + nomal diet, Group 4 : 3-MC + CNP(5000ppm), Group 5(Control Group) : sham-oparation + nomal diet. Twenty female golden hamsters (9-10 weeks age at the time of initiation were used in each group. The periods of experiments were 72 weeks in the groups of 1,2 and 5, and 17 weeks in the groups of 3 and 4. CNP treatment in the group 2 was stopped at the 17th weeks and normal diet was introduced in the rest of the experimental period, since the body weight increase was affected as compared with the control group.During the course of experiment for 72 weeks in the groups of 1,2 and 5, three animals each were dead. In the groups of 3 and 4, none of them died for 17 weeks. At the time of sacrifice(72 weeks in groups of 1,2 and 5, and 17 weeks in the groups of 3 and 4), 1 and 2 cases of hyperplastic nodules in the liver were found in the groups of 1 and 2, respectively. In regards to the occurence of gallbladder cancer, the histopathological examination was being conducted and the details of the findings will be appeared elsewhere.