Early-onset gastrointestinal cancer: An epidemiological reality with great significance and implications

During the last few years, epidemiological data from many countries suggest that the incidence and prevalence of many cancers of the digestive system are shifting from the older to the younger ages, the so-called "early-onset cancer". This is particularly evident in colorectal cancer and secondarily in other malignant digestive neoplasms, mainly stomach and in a lesser degree pancreas, and biliary tract. It should be emphasized that data concerning digestive neoplasms, except for those referring to the colon and stomach, could be characterized as rather insufficient. The exact magnitude of the shift in younger ages is expected to become clearer shortly, as long as relevant epidemiological data from many parts of the world would be available. The most important question concerns the etiology of this phenomenon, since its magnitude cannot be explained solely by the better diagnostic methodology and the preventive programs applied in many countries. The existing data support the assumption that a number of environmental factors may play a primary role in influencing carcinogenesis, sometimes from childhood. Changes that have appeared in the last decades related mainly to eating habits, consistency of gut microbiome and an increase of obese people interacting with genetic factors, ultimately favor the process of carcinogenesis. Even these factors however, are not entirely sufficient to explain the age-related changes in the frequency of digestive neoplasms. Studies of the individual effect of each of the already known factors or factors likely to be involved in the etiology of this phenomenon and studies using state-of-the-art technologies to accurately determine the degree of the population exposure to these factors are required. In this article, we attempt to describe the epidemiological data supporting the age-shifting of digestive malignancies and their possible pathogenesis. Finally, we propose some measures regarding the attitude of the scientific community to this alarming phenomenon.