Why are more people under 50 getting colon cancer?


by Lawrence Schiller, MD

Mar 30, 2016

Colorectal cancer typically affects older adults, usually over age 50, but according to recent studies, the percentage of colorectal cancer cases in younger patients is increasing.

Recommended screenings for men and women are typically initiated at age 50 to find and remove premalignant polyps, and thereby reduce the risk of cancer.

We know early screening has decreased cancer rates in the screened population and this may be shifting the relative risk to a younger population, but some suggest we’re overlooking younger adults who may be at risk.

The recent claim that colon cancer is affecting more young adults is from a 13-year retrospective study of colorectal cancer diagnoses. The analysts observed the age of onset and relating screening and treatment. Of the 258,024 patients with colorectal cancer, 15 percent were less than 50 years old and more often presented with advanced disease that needed aggressive treatment.

“Colon cancer has traditionally been thought of as a disease of the elderly,” said study lead author Samantha Hendren, MD, an associate professor of surgery at the University of Michigan in Ann Arbor. “This study is really a wake-up call to the medical community that a relatively large number of colon cancers are occurring in people under 50.”

But how accurate are these claims?

Cancer still rare in younger patients

The colonoscopies I perform for young individuals are usually for reasons other than cancer screening, including chronic diarrhea, severe pain or bleeding. They rarely show polyps or tumors.

Surgeons see a different population of patients.

“Over the last couple years, I’ve probably seen an average of one patient every two months that is 50 years old or younger with colon cancer,” said Laurie Novosad, Chief of Surgery and Medical Director of surgical services at Baylor Scott & White Medical Center – McKinney. “Generally, these patients have rectal bleeding and have either self-diagnosed themselves with hemorrhoids or have been told that they have hemorrhoids. However, most of my cancer patients are older and come to see me because they have been discovered to have cancer by other means and need surgery.”

In my gastroenterology practice, it’s pretty uncommon to find cancers in younger patients without specific risk factors like a family history of cancer or a personal history of longstanding inflammatory bowel disease. I occasionally see patients like that, but the vast majority of people with colon cancer are older, in their late 50s, 60s and 70s.

Colon cancer develops over time

Colorectal cancer usually is found in older adults in part because it takes a long time to develop polyps and for polyps to turn cancerous, so patients diagnosed with cancer naturally will be older. The common sort of polyp (a tubular adenoma) may take 10 years to turn into cancer. Even in people with less common types of polyps that may more rapidly turn into cancer, it takes months or years to go down that road.

Not enough evidence to change screening recommendations

If younger adults are at a higher risk for colorectal cancer than we thought, it might make sense to lower the age for starting screening. But modeling suggests that this would not be cost-effective; the frequency with which clinically important lesions would be found is too low. It is better to focus our resources on the older population, where the impact is likely to be greater.

Remember, colon cancer screening is a bit different than other cancer screenings that people are used to. Unlike a mammogram, where you’re looking for a cancerous tumor, we’re looking for polyps before they go bad. The important thing to recognize is that when we do the screening exams, we very rarely find cancer.

By removing polyps before they go bad with regular screening, colorectal cancer is highly preventable.

It may be true that we will be seeing relatively more cancers in younger people, but our focus must remain on the population at greatest risk, those over 50.

Current screening recommendations

Screenings for colorectal cancer are not based on symptoms, but on age and risk factors.

  • Guidelines suggest starting screening colonoscopies at age 50, if there are no risk factors or family history.
  • African-Americans should start screening at age 45, as the prevalence of polyps is higher in that population.
  • Patients with inflammatory bowel disease affecting the colon should be screened starting after 8—10 years of illness as they are at higher risk of developing colon cancer after that time.
  • If you have a parent, sibling or child with colon cancer, your screenings should start at age 40, or 10 years younger than the age of the affected family member at diagnosis.
  •  For example, if your mother was diagnosed with colon cancer at age 50, you would start at age 40. But, if your mother was diagnosed at 45, you would start at age 35.

“Not having a family history of colon cancer does not mean a person is not at risk,” Dr. Novosad said. “Only one in 10 patients diagnosed with colon and rectal cancer has a family history. The vast majority of patients, including patients diagnosed under age 50, do not have any family history of colon or rectal cancer.”

The best bet for concerned young adults is to talk to your doctor to identify any special reasons to consider an earlier screening exam.

Future of colon cancer screening

The rising incidence of colon cancer in young adults may be related to changes in dietary habits or other environmental factors.

“We are starting to see a generation growing into their 30s and 40s who grew up on fast food and highly processed food, with low fiber intake,” Dr. Novosad said.

As this rise continues, we’re searching for better ways to detect and treat colon cancer. For patients young and old, research is underway at Baylor Scott & White Research Institute to bring game-changing testing and treatment methods to the colorectal cancer field.

Download our free colorectal treatment guide.

Learn more about colon cancer care at Baylor Scott & White Health.

About the Author

Lawrence Schiller, MD, is the Chair of the Institutional Review Boards for Human Subject Protection at Baylor Scott & White Research Institute in Dallas. He received his medical degree from Jefferson Medical College and has been in practice for more than 40 years.

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