The incidence of colorectal cancer is increasing among adults under age 55—and rising particularly fast among 20- to 29-year olds, according to a recent study in the Journal of the National Cancer Institute.
In the study, researchers analyzed data from 490,305 patients ages 20 and older who were diagnosed with invasive colorectal cancer (cancer of the colon or rectum) between 1974 and 2013. Data were obtained from the government’s Surveillance, Epidemiology and End Results (SEER) program, which tracks historical, population-based cancer incidence in the United States.
The research showed that during the late 1970s and early 1980s, rates of colon cancer declined in people younger than 50 while they increased among those over age 50. But this trend flipped during the period between the mid-1980s and 2013, when rates decreased among adults over age 55—likely due to increased use of colonoscopy and other screening methods—but increased among younger adults. The largest increase occurred in the 20-to-29 age group, which saw rates of colon cancer grow by 2.4 percent per year, followed by adults ages 40 to 49 (1.3 percent increase per year), 30 to 39 (1 percent increase per year), and 50 to 54 (0.5 percent increase per year).
Rates of rectal cancer in adults under 55 increased even more during the study period, with the youngest adults (ages 20 to 29) again seeing the greatest increase—a growth of 3.4 percent per year between 1974 and 2013. During the same time period, rectal cancer incidence among adults over age 55 decreased.
Based on the data, the researchers concluded that a person born in 1990 has double the risk of developing colon cancer, and quadruple the risk of developing rectal cancer, compared with someone born in 1950. (The current study didn't look at anal cancer, but data from the American Cancer Society show that it, too, is on the rise in the U.S. and around the world, likely due to the high incidence of HPV infection. This sexually transmitted virus is linked to the most common form of anal cancer, known as anal squamous cell carcinoma.)
What could account for the jump in colorectal cancer incidence among younger people? The researchers attributed it in large part to lifestyle factors, such as excess body weight, high consumption of processed meats and alcohol, low levels of physical activity, inadequate fiber consumption, and cigarette smoking. They also cited barriers to early diagnosis in young adults, including lack of awareness of the disease and lack of health insurance. This may lead young people experiencing symptoms of colorectal cancer—such as changes in bowel habits, rectal bleeding, blood in the stool, or unexplained weight loss—to delay or avoid seeing a doctor about the symptoms.
Clinicians, for their part, may be slow to presume colorectal cancer for adults in this age group, in whom absolute rates of the cancer are far lower than in older people. To give an example, a man in the U.S. has a 1 in 294 chance of developing invasive colorectal cancer before age 50; a woman, a 1 in 318 chance. After age 50, the rate jumps to 1 in 149 for men and 1 in 198 for women; after age 60, it’s 1 in 84 and 1 in 120 for men and women, respectively, and keeps increasing every decade thereafter.
What to do
Current colorectal cancer screening guidelines call for individuals at average risk to be screened at regular intervals beginning at age 50 until age 75; those who are at increased risk (including individuals with a family history of colorectal cancer or cancerous polyps) should be screened before age 50. The authors of the current study suggested that screening for colorectal cancer in all adults might be lowered to age 45. For a summary of screening options, see Colon Cancer Screening Choices.
Any person who is experiencing symptoms of colorectal cancer should seek medical attention. These include change in bowel habits, blood in the stool, rectal bleeding, abdominal pain, weakness and fatigue, and unintended weight loss. Early screening and diagnosis can lead to earlier detection, which in turn typically means that the cancer will be found at a much more curable stage.