各种癌症死亡率(或发病率)在不同国家或地区间的相关性研究,常可为癌症病因学研究提供一些新的线索或检验已有的假设。研究前提是假定二个或二个以上癌症死亡率或发病率在一些国家或地区都是比较高,而在另一些国家或地区又都是低的,亦即在地理分布上有其相关性,提示这二个或二个以上的癌症可能存在着一个或一个以上的共同 The correlation studies of various cancer mortality (or morbidity rates) in different countries or regions can often provide new clues or test existing hypotheses for the study of cancer etiology. The premise of the study is to assume that two or more cancer deaths or morbidities are relatively high in some countries or regions and low in other countries or regions, that is, geographically relevant. Prompt that two or more cancers may have one or more common