Although the number of overall colorectal cancer cases has dropped in the U.S. in the last decade, one group, young adults, has seen an increase in the colorectal cancer rate. Every year since 1992, the number of people diagnosed with the disease before age 50 has increased by 2 percent, and cancer experts don’t yet understand why.

“Hopefully research will give us some insight into what is going on,” Edith P. Mitchell, MD, of Thomas Jefferson University’s (TJU) Kimmel Cancer Center, told Health Imaging, adding that it’s unclear whether the rate change has been caused by advancements in diagnostic methods or whether there’s been an actual increase in the number of colorectal cancers among younger adults.

Whatever the cause, the rate of colorectal cancer in young adults has increased to the point where nearly 10 percent of new diagnoses are in patients younger than 50. Most of these patients were diagnosed in their forties, but the disease has been found in patients in their twenties and thirties.

Another troubling recent finding is that when colorectal cancers are diagnosed in younger patients, they are more likely to be at an advanced stage of the disease. A study published Feb. 13 online in Archives of Internal Medicine found 63 percent of colon cancers and 57 percent of rectal cancers are stage III or IV at diagnosis. Less than half of later-onset colorectal cancers are diagnosed at stage III or IV (Arch Intern Med 2012;172:287-289).

The higher percentage of advanced stage colorectal cancers at diagnosis in younger patients could be linked to perceptions of the disease as an elderly affliction. The average age to be diagnosed with colon cancer is 71, so when symptoms such as rectal bleeding or abdominal pain present themselves in younger patients, clinicians might tend to dismiss the idea that cancer is to blame.

Because radiologists are not usually the first to diagnose colon cancer, Mitchell said they might not have a large role in changing diagnostic practice, but they should be aware that younger individuals with colorectal cancer might not mesh with perceptions held by payors.

“The important thing for radiologists would be the notion that certain individuals, because of their age, may be denied radiology procedures by insurance companies,” she said.

Mitchell said it’s too early to overhaul screening guidelines because of the uptick in colorectal cancer cases among younger patients, but certain risk factors should be considered. For instance, although it’s recommended that most people not begin colorectal cancer screening until age 50, the American College of Gastroenterology tweaked its guidelines to suggest that African Americans begin screening at age 45, since the disease tends to occur earlier in this group

About 25 percent of people with colon or rectal cancer have a family history of the disease, according to TJU. A smaller fraction, about 5 percent, of overall cases are due to genetic syndromes like hereditary nonpolyposis colorectal cancer, also called Lynch syndrome. When a person is diagnosed with colorectal cancer, their children should begin screening 10 years prior to the age at which the parent was diagnosed.

In addition to what is currently known about risk factors for the disease, Mitchell said research is being conducted to determine biomarkers in younger patients and detail any differences in the types of colon cancers that are evaluated.

Overall, colon and rectal cancers are the third leading cause of cancer death in the country, with more than 140,000 new cases diagnosed each year, according to TJU.