Clinical trials and cancer risk in Japan.

This paper presents the results of a clinical trial with vitamin A that was performed in Japan for the treatment of various cancers. The results of epidemiologic studies on the relationship between food intake and development of lung cancer in Japan also are reported. Several Japanese groups are studying the combined effect of vitamin A and its derivatives and anticancer chemotherapeutic agents on the in vitro and in vivo growth of various cancer cells, however, few clinical trials of these combinations for cancer treatment have been conducted. The results of these few studies are reviewed.