Some actual aspects of tumor induction and promotion

Summary Quantitative data on chemical carcinogenesis illustrate how difficult it is to decide whether there are thresholds for complete carcinogens. With tumor promoters there probably are safe levels, but these are difficult to determine. The results recorded in the experiments of Fibiger, in which tumors of the stomach were seen, could have been caused by the tumor-promoting effects of a biological agent.The Journal of Cancer Research and Clinical Oncology publishes in loose succession Editorials and Guest Editorials on current and/or controversial problems in experimental and clinical oncology. These contributions represent exclusively the personal opinion of the authorDedicated to Professor Hermann Druckrey on the occasion of his 80th birthday