Preventing Colorectal Cancer through Screening

Despite being one of few cancers that are actually preventable through screening, colorectal cancer continues to be the third most commonly diagnosed cancer and second most common cause of cancer death in the U.S. Better awareness and options for screening are leading to a decline in cases and mortality rates from this cancer.

Colorectal cancer forms on the lining of the colon (large intestine) or rectum, which make up the last part of the gastrointestinal tract. Almost all colorectal cancer develops from small growths known as polyps, some of which can develop into cancer over a period of several years.

Risk factors

One of the most important risk factors is a personal history of certain types of polyps or colorectal cancer. Other factors that can increase risk include inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease that can lead to potentially cancerous changes. Risk also increases with age. “Our patients are usually over the age of 60, but there is an increase in colorectal cancer among people under 50 and it’s not fully clear why that is,” says Srinivas Joga Ivatury, MD, MHA, division chief of Colon and Rectal Surgery in the Gastrointestinal Oncology Program at Dartmouth’s and Dartmouth-Hitchcock’s Norris Cotton Cancer Center (NCCC).

Family history and genetics are also important risk factors. People with family members who have had colorectal cancer or polyps are at risk for developing colorectal cancer, as are those with certain hereditary syndromes, such as Lynch Syndrome. Genetic testing can be considered for patients who are younger, or who have a strong family history of colon or rectal cancer or other potentially related cancers such as endometrial or ovarian cancer. Medical oncologist, Bradley A. Arrick, MD, PhD, MHCM, who directs NCCC’s Familial Cancer Program, notes, “Genetic testing is often covered by insurance and may be very informative for the tested individual as well as the other family members.”

Health habits such as smoking, diet, exercise and obesity all play a role in risk as well, with smoking being the most important of these—possibly even more of a risk factor than family history.

How to screen

Colonoscopy is one way to not only detect colorectal cancer early, but also to prevent colon cancer from forming. A colonoscopy prevents cancer by allowing polyps to be painlessly removed from the lining of the colon before they can potentially develop into cancer.

“We use colonoscopy to test people at increased risk because there’s a greater chance of finding colorectal polyps than if a person is at average risk, where several other screening test options, including colonoscopy, would also be appropriate,” explains Lynn F. Butterly, MD, a gastroenterologist and researcher at Dartmouth-Hitchcock and NCCC. “For those at average risk, we generally begin screening at age 50. However, this recommendation will likely soon change to age 45, due to the increase in colorectal cancer among people under 50.”

In 2018, the American Cancer Society (ACS) recommended that the age to begin screening for average risk people be lowered from age 50 to age 45. The New Hampshire Colonoscopy Registry, together with the ACS, published a study in January 2021 demonstrating that people age 45–49 have a similar risk of potentially precancerous polyps or colorectal cancer as those age 50–54, for whom screening is recommended. Several preventative societies, including the US Preventive Services Taskforce, are now considering lowering the recommended age to begin regular screening to 45. “People under 50 have historically not been recommended to be screened, which may be contributing to why incidence is rising in this group,” notes Ivatury. Meanwhile, the incidence of colorectal cancer is going down for people over age 50 who are having regular colonoscopies.

For people without symptoms who are at average risk of colorectal cancer, meaning they are age 50 and don’t have any personal or family history of colorectal cancer or polyps, one of the stool-based tests is also a good option and can be done at home. “We recommend people talk with their providers about which screening option is right for them,” says Butterly.

Screening challenges

One challenge is getting people to actually do screening, which saw a severe decline since the beginning of the COVID-19 pandemic. The National Comprehensive Cancer Network and ACS cite studies that found that during the peak of the pandemic, rates of colorectal cancer screening dropped by as much as 80 percent and rates of diagnosis, meaning patients with colon cancer were identified and could begin needed treatment, dropped by nearly 50 percent.

“I’ve heard anecdotally some practices increasing the use of stool-based tests that people can do themselves at home. I’m less concerned with which screening method is used and more concerned that people are actually getting screened, whatever the method,” says Ivatury. Positive results of a stool-based test must be followed up with colonoscopy.

Although New Hampshire and Vermont have quite good rates of screening, Ivatury notes it can always be better. “The more we screen, the more we can find polyps and reduce the incidence of colorectal cancer because we are addressing it before it becomes problematic.”

NCCC encourages patients and our community to fit life-saving cancer screenings, including those for colon and rectal cancer, back into your regular routines. Please talk with your primary care provider who can help you get scheduled.