Medical groups differ on when to start colon and rectal cancer screening. Here's why
Posted November 4, 2019 5:20 p.m. EST
CNN — Conflicting recommendations on when and how average-risk adults should get screened for colon and rectal cancer could leave you confused -- but new guidance aims to make sense of it all.
The American Cancer Society recommends to start regular screening at age 45, while other recommendations have stuck with recommending to start at age 50. The Canadian Task Force on Preventive Health Care recommends not using colonoscopy as a primary screening test, while other recommendations do.
A new guidance statement from the American College of Physicians or ACP, published in the journal Annals of Internal Medicine on Monday, examines that discord and offers new insight into what to follow based on the latest evidence.
"When we do a guidance statement, we are essentially looking at other organizations' guidelines and taking a deeper dive into their process and why might they have come to slightly different conclusions -- some of that is how they look at data or what definitions they might use," said Dr. Robert McLean, president of the ACP and a practicing internist and rheumatologist at Northeast Medical Group of Yale New Haven Health in Connecticut.
"The conclusion is you should be starting screening at age 50. Between 50 and 75, you should be getting some type of screening test for colorectal cancer," he said about the guidance statement. "The options are colonoscopy, the flexible sigmoidoscopy and FIT test or just a FIT test every two years."
A FIT, or fecal immunochemical test, which can be used at home, checks for hidden blood in the stool, which can be an early sign of cancer. Flexible sigmoidoscopy and colonoscopy procedures are more invasive screening methods that allow a physician to look inside of the rectum and colon for signs of cancer.
"Any of those three are good screening modalities," McLean said.
The great debate on when and how to screen for colorectal cancer
ACP's guidance statement involved analyzing colorectal cancer screening recommendations, published between 2014 and 2018, from six organizations: American College of Radiology, Canadian Task Force on Preventive Health Care, US Preventive Services Task Force, American Cancer Society, Scottish Intercollegiate Guidelines Network and the US Multi-Society Task Force on Colorectal Cancer.
The analysis specifically focused on adults at "average risk," meaning adults who are currently show no symptoms of colorectal cancer and are not at higher risk due to having a personal or family history of colon or rectal polyps.
The analysis showed that, based on their methodology and evidence provided, recommendations from the Canadian Task Force on Preventive Health Care and US Preventive Services Task Force rated highest for strength.
Based on all of the recommendations analyzed, the guidance statement concluded that average-risk adults age 50 to 75 should get regularly screened for colorectal cancer using either a FIT or high-sensitivity fecal occult blood test every two years, colonoscopy every 10 years, or flexible sigmoidoscopy every 10 years plus FIT every two years.
"If you're at average risk, there's no recommendation at this point from us or from a number of other organizations to continue screening after the age of 75," McLean said.
He added that beginning screening earlier than age 50 "has not convincingly demonstrated that benefits exceed harms," based on the analysis.
Yet the new guidance statement could be a source of confusion for some clinicians and the general public because of the methods used, Dr. Richard Wender, chief cancer control officer for the American Cancer Society or ACS, said in an email on Monday. He added that the data from some of the trials referenced in the guidance statement "are all somewhat older" and "some should be judged as being out of date."
"No trials evaluated beginning screening prior to age 50," he said in the email. "Thus, the ACP methods permit no clear pathway to ever recommend a change in starting age, as the ACS did last year."
Last year, the American Cancer Society updated its guidelines for colon and rectal cancer screening to recommend that adults at average risk get screened starting at age 45 instead of 50.
Those updated guidelines, published in CA: A Cancer Journal for Clinicians, also referenced six screening test options for adults, ranging from noninvasive stool tests to visual exams like colonoscopy, depending on the patient's preference and the availability of the test.
Risk at 45 'now virtually the same as the risk at age 50'
The American Cancer Society's guidelines were released after a separate study showed that rates of colon and rectal cancer deaths were increasing among adults younger than 55 in the United States.
After declining overall from 1970 to 2004, colorectal cancer death rates among 20- to 54-year-old adults in the United States climbed by 1% annually from 2004 to 2014, according to the study published in the medical journal JAMA in 2017.
"The risk of colorectal cancer in people age 45 is now virtually the same as the risk at age 50 when some of the clinical trials were first conducted," Wender said in the email.
"While relying on trials is an important and conservative approach to determine the efficacy of screening, once that efficacy is established, we need to move beyond the trials when we need to update a screening guideline based on new data, such as evidence of changing risk of disease.," he said. "Using other approaches, like modeling, adds to the precision of guidelines."
In an editorial accompanying the new ACP guidance statement on Monday, Dr. Michael Pignone of the University of Texas at Austin's Dell Medical School also noted the importance of using modeling when making screening recommendations.
"Cost-effectiveness modeling can offer additional guidance" on the questions about colorectal cancer screening that "are difficult to answer," he wrote in the editorial.
"Cost-effectiveness analyses support a qualified recommendation to adopt an earlier starting age for screening only if the screening rate in persons aged 50 to 75 years is already high," Pignone wrote.
"They also reinforce the most important point in all of the major guidelines: Any recommended form of screening in the 50- to 75- year age range is likely to be very cost-effective (if not cost-saving) compared with no screening and should be strongly encouraged," he wrote. "As we consider how best to proceed at the margins, it is important not to lose sight of the strong consensus supporting screening for this age group."
Patients who are confused about their screening options are advised to talk to their doctors about their risk factors and when and how to get screened for colorectal cancer.