Colorectal Cancer: Epidemiology, Etiology, and Molecular Basis

Abstract

Colorectal cancer (CRC) is a disease with a major worldwide burden. It is the fourth most frequently diagnosed malignancy in both sexes with almost 1 million people developing CRC annually. CRC is the third most common cause of cancer death in the world, responsible for 630,000 deaths annually. In the United States, CRC is the third most common cancer in men and women and the second most common cause of cancer death overall. The worldwide incidence of CRC is increasing. Before 1985, the age-adjusted incidence of CRC in the United States had been increasing; however, since this time, the rates have declined an average of −1.6% per year (Fig. 23.1). This reduction has been mainly confined to the Caucasian race and is largely limited to a decrease in the incidence of distal cancers. The recent decrease in incidence in the United States may be attributable to screening, specifically screening with flexible sigmoidoscopy, although other factors are likely to have influenced this trend. Currently, the overall probability of an individual developing CRC in United States over a lifetime is almost 6%. From a population perspective, age is the most important risk factor for CRC. CRC is predominantly a disease of older individuals; 90% of cases are diagnosed over the age of 50. The risk of CRC continues to increase with age (Fig. 23.2).