The problem of digestive tract tumors presents multifaceted aspects which involve epidemiology, pathogenesis, histopathology, surgery and adjuvant multidisciplinary mo dality. Time trends in cancer mortality vary in the individual cancers. Mortality from stomach cancer shows a decreasing tendency in most countries, although Japan still has the highest incidence in the world. Intestinal other than rectum and pancreatic cancers have shown an increase in most countries, while mortality due to liver cell and gallbladder cancer vary greatly by locality. Since most cancers are considered to be related to en vironmental and lifestyle exposures, such as diet, smoking or excessive drinking, there is hope that action on these factors may serve to substantially reduce occurrence of the disease. Recent progress in early diagnosis has made it feasible to detect small and minute cancers, and these have proven possible to cure with relatively favorable results. The most important advancement has come from a multidisciplinary approach to cancer treatment, utilizing a balanced application of surgery, radiation therapy and chemo therapy. A considerable increase in the five-year survival rate has been realized in stomach cancer. While progress is being made in the practical treatment of this disease, it remains far better to prevent than to cure. For the first time immunization offers a unique op portunity to prevent liver cell cancer."

During the last decade a considerable body of knowledge has come into existence concerning a class of carcinogenic molecules chiefly represented by 4-nitroquinoline i-oxide. Original papers on this subject are numerous and widely scattered over many branches of science; it was felt that these papers should be reviewed and the knowledge brought together in one volume before it became too unwieldy. This we have attempted to do in this monograph. Our aim has been to include all relevant papers published to date, so that it may serve as an epitome of the present status of knowledge on this important subject. We have been fortunate in securing the cooperation of several colleagues who have contributed chapters, each dealing with one aspect of the subject. We have been doubly fortunate in that these contributors, like ourselves, were at one time or another members of the group belonging to the scientific staff of Dr. WARO NAKA HARA, Director of the National Cancer Center Research Institute, Tokyo, Japan."