Aspects of descriptive epidemiology and survival in colorectal cancer

World-wide cancer of the colon and rectum emerges as the third most frequent form of cancer in males and the fourth in females. Patients with colorectal cancer suffer from a considerable excess mortality during the first six to eight years after diagnosis, and the cure rate, which is in the order of 35-40% in the Swedish population, has remained largely unchanged over several decades. The incidence rates show a steep rise with age, marked international differences, increasing incidence in developing countries, adjustments in cancer risk within few decades in populations who move from low- to high-risk areas, and no consistent differences in relation to race. In addition, the incidence rates display a complex network of relationship to age, sex, segment of the large bowel and secular trends. These observations indicate that environmental factors play a predominant role in the development of colorectal cancer, that such factors may have specific influences in certain segments of the large bowel, and that they modulate the risk even in adult life.