Colorectal cancer increases among 20-49 age group

New diagnoses of colorectal cancers, which have been on the decline for years among those over 50, are increasing dramatically among those between the ages of 20 and 49, new research has found.

By the year 2030, the rate of new diagnoses among the under-50 set can be expected to nearly double, even as that rate declines by a third among those over 50, who generally get routine screening for the disease, according to an epidemiological study by researchers at the MD Anderson Cancer Center in Houston.

The jump in youthful cancer risk isn’t unique to cancers of the colon or rectum: New diagnoses of breast cancer, too, are rising among younger women. The reasons for the jump in either cancer aren’t entirely clear.

But when it comes to colorectal cancer, the researchers have their suspicions: increasing obesity, sedentary lifestyles and the widespread embrace of a Western diet that’s high in processed foods and red meat and low in fruits and vegetables all may be contributing to the rate of new diagnoses in young people, they wrote.

Given the rising incidence of such cancers in young people, physicians seeing younger patients with potential symptoms of colorectal cancer should not dismiss their suspicions, the authors wrote.

The study was published Wednesday in the journal JAMA Surgery.

Colorectal cancer is still a disease of aging. Close to 90 percent of the 136,830 new cases diagnosed in 2014 in the United States are expected to be in those over 50. And between 2007 and 2011, the median age of diagnosis was 68.

But new diagnoses have grown fastest among adults between 20 and 34, a group in which the disease was virtually unheard of until fairly recently. Between 1975 and 2010, new diagnoses in this group grew by roughly 2 percent per year.

Among those 35 to 49, a pool that accounts for about 7 percent of colorectal cancer diagnoses over the study’s 35 years, rates of new diagnoses increased by a more modest 0.4 percent.