Colorectal cancer screening, 2021: An update
The American Cancer Society now recommends screening for colorectal cancer starting at age 45 years, not 50. The best colorectal cancer screening test is the one that the patient will complete. Colonoscopy and the multitarget stool FIT-DNA test (Cologuard) are the screening tests most likely to detect precancerous lesions and colorectal cancer.
Multitarget stool FIT-DNA test (Cologuard)
The multitarget stool FIT-DNA test is a remarkable innovation in cancer screening combining 3 independent biomarkers associated with precancerous lesions and colorectal cancer.14 The 3 test components include14:
- a fecal immunochemical test (FIT) for hemoglobin (which uses antibodies to detect hemoglobin)
- a test for epigenetic changes in the methylation pattern of promoter DNA, including the promoter regions on the N-Myc Downstream-Regulated Gene 4 (NDRG4) and Bone Morphogenetic Protein 3 (BMP3) genes
- a test for 7 gene mutations in the V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS).
In addition, the amount of the beta-actin DNA present in the stool specimen is assessed and used as a quantitative control for the total amount of DNA in the specimen.
In one large clinical study, 9,989 people at average risk for colorectal cancer were screened with both a multitarget stool FIT-DNA test and a stool FIT test.15 Positive test results triggered a referral for colonoscopy. Among this cohort, 1% of participants were diagnosed with colorectal cancer and 7.6% with a precancerous lesion. The sensitivity of the multitarget stool FIT-DNA test and the FIT test for detecting colorectal cancer was 92.3% and 73.8%, respectively. The sensitivities of the multitarget stool FIT-DNA test and the FIT test for detecting precancerous lesions were 42.4% and 23.8%, respectively. The specificity of the FIT-DNA and FIT tests for detecting any cancer or precancerous lesion was 90% and 96.4%, respectively.15 The FIT test is less expensive than the multitarget stool FIT-DNA test. Eligible patients can order the FIT test through a Quest website.16 In June 2021 the published cost was $89 for the test plus a $6 physician fee. Most insurers will reimburse the expense of the test for eligible patients.
The multitarget stool FIT-DNA test should be performed every 1 to 3 years. Unlike colonoscopy or CT colonography, the stool is collected at home and sent to a testing laboratory, saving the patient time and travel costs. A disadvantage of the test is that it is more expensive than FIT or guaiac testing. Eligible patients can request a test kit by completing a telemedicine visit through the Cologuard website.17 One website lists the cost of a Cologuard test at $599.18 This test is eligible for reimbursement by most insurers.
Ensure patients are informed of needed screening
Most obstetrician-gynecologists have many women in their practice who are aged 45 to 64, a key target group for colorectal cancer screening. The American Cancer Society and the USPSTF strongly recommend that people in this age range be screened for colorectal cancer. Given that one-third of people these ages have not been screened, obstetrician-gynecologists can play an important role in reducing the health burden of the second most common cause of cancer death by ensuring that their patients are up to date with colorectal screening. ●
