Colorectal cancer (also termed colon or bowel cancer) is the third most prevalent type of cancer both in men and in women, taking the lives of approximately 400,000 people annually worldwide (including 50,000 people per year in the United States). It results when tumors form in the lining of the large intestine's colon or rectum. Since the year 2000, the number of cases and mortality rates of patients having colorectal cancer have risen dramatically among young and middle-aged adults in the United States. Specifically, in adults younger than age 50, the incidence rate of colorectal cancer has increased by 22%, with an accompanying 13% increase in the death rate from this condition. These statistics are surprising because the rates among persons more than 50 years of age have been dropping, predominantly because of their adoption of healthier lifestyle habits (such as smoking less and eating less red meat) and improvements in medical screening and treatment protocols. Thus, the rise of colorectal cancer in the younger population is a troubling shift. See also: Cancer; Colon; Digestive system; Gastrointestinal tract disorders; Intestine; Oncology; Tumor

Light micrograph of an adenocarcinoma of the colon. Almost all colorectal cancers are primary adenocarcinomas. The tumor cells have made several acini (saclike structures) containing mucinous material and inflammatory cells. (Credit: Steve Gschmeissner, Science Photo Library/Alamy Stock Photo)

If colorectal cancer is detected, it is highly treatable. Most colon cancers initially develop as abnormal growths (polyps) on the inner wall of the colon or rectum. Some of these polyps may become cancerous as the abnormal cells continue to accumulate mutations. However, colonoscopy examinations and associated blood tests can diagnose colon cancer in its early stages, resulting in a good prognosis and survival rate for individuals who undergo prompt surgery and additional treatment. See also: Chemotherapy and other antineoplastic drug treatments; Mutation; Surgery

The question for researchers to unravel is why younger adults are becoming more prone to colorectal cancer. Investigators have focused on several harmful trends and lifestyle changes found among modern-day youths and young adults. The chief culprits under suspicion include the epidemic of obesity, increased sedentary behaviors, and unhealthy eating habits, especially the consumption of highly processed foods. See also: Epidemic of obesity; Food manufacturing; Nutrition; Obesity; Public health