- Jennifer Middleton, MD, MPH
The United States Preventive Services Task Force (USPSTF) updated its recommendations for colorectal cancer (CRC) screening last month; it is now a B recommendation for adults aged 45-49 to be screened. (The previous A recommendation for adults aged 50-75 is unchanged.) An increasing prevalence of CRC in younger adults, along with more outcome data from screening younger adults, led to the new recommendation for adults aged 45-49:
[T]he USPSTF determined that beginning screening at age 45 years and continuing to the age of 75 years, for the following screening strategies, yielded a reasonable balance of benefits (life-years gained) and burdens or harms (number of colonoscopies): annual FIT, sDNA-FIT every 1 to 3 years, CT colonography or flexible sigmoidoscopy every 5 years, colonoscopy every 10 years, or flexible sigmoidoscopy every 10 years with annual FIT.
The USPSTF's statement was supported by a systematic review and a modeling study. The systematic review sought to answer: 1) how effective is CRC screening to lower rates of CRC cancer and/or mortality, 2) how accurate are the available screening modalities, and 3) what are the harms of CRC screening. The researchers found that 1) screening via the modalities listed above* decreases cancer rates and improves mortality, 2) several modalities* have reasonable data to support their use, and 3) most harms are due to colonoscopy; since persons with a positive screening test then require colonoscopy, colonoscopy's harms were applied by researchers to the other testing modalities (the article's Table 4 reviews these in-depth). The modeling study used three sophisticated microsimulation models and found that "screening for colorectal cancer with stool tests, endoscopic tests, or computed tomography colonography starting at age 45 years provides an efficient balance of colonoscopy burden and life-years gained."
The studies cited by the systematic review did not separately analyze their data for adults aged 45-49, and the modeling study is limited by the assumptions entered into the model by researchers. Criticism of the new recommendation for adults aged 45-49 centers around the lack of randomized controlled trials specifically examining this population. The capacity to accommodate this additional population segment is also of concern: "[r]eliance on colonoscopy for screening among individuals aged 45 to 49 years might crowd out approximately one-third of individuals aged 50 to 75 years whose [colorectal cancer] screening is not up-to-date, given limited endoscopy capacity in some communities." The new recommendations are also not an endorsement to ignore patients with concerning symptoms under the age of 45, since "[n]early half of patients with early onset CRC are diagnosed before age 45 years...as was the case for the actor Chadwick Boseman, who died from CRC at age 43 years. Symptoms of CRC...should be evaluated promptly with appropriate diagnostic tests."
As family physicians, we should both discuss the new recommendation with patients and also provide guidance regarding the choice of screening modality when appropriate. Although these 2020 AFP Practice Guidelines from the BMJ and the ACP refer to the 2016 USPSTF recommendation statement, their overviews of CRC screening options remain relevant and useful. The USPSTF's website also has this table reviewing the evidence base behind each screening modality.
* recommended screening modalities are annual Fecal Immunochemical Test (FIT), stool DNA-Fecal Immunochemical Test (sDNA-FIT) every 1-3 years, CT colonography or flexible sigmoidoscopy every 5 years, colonoscopy every 10 years, or flexible sigmoidoscopy every 10 years with annual FIT.