In previous research also funded by Exact Sciences, Cologuard has been shown to have a higher sensitivity, yet a lower specificity, than FITs.9 In a prospective study of approximately 10,000 patients, Cologuard had a 92% sensitivity for detecting CRC, compared with 73.8% with a FIT. Meanwhile, the specificity rate was 87% for Cologuard, compared with 95% for a FIT.
Some gastroenterologists have raised concerns about the possibility of false-positive tests with Cologuard, particularly for older individuals, although the tool could be a useful screening option particularly for those at the highest risk for colonoscopy complications. Individuals who test positive require follow-up screening with colonoscopy, and if they test negative but have symptoms, they should also follow up with their physician, Dr Yarden said.
An important question is the extent to which such home-based screening methods influence survival outcomes. Dr Yarden noted that it isn’t clear how many individuals who test positive with Cologuard tests actually do follow up that test with a colonoscopy, which research has demonstrated to reduce risk of death.10
Dr Limburg agreed that this question about what happens after a Cologuard test warrants further study. “If somebody does a stool-based test at home, they sometimes don’t follow through with their colonoscopy, even with a positive result. So there are challenges all the way along that screening continuum,” he said.
A modeling study by the US Preventive Services Task Force estimated the impact of different screening methods on life-years gained, projecting that colonoscopy every 10 years had similar benefits to a yearly FIT or other home-based screening methods.11
However, as Dr Limburg explained, that study made unrealistic assumptions, such as an 100% adherence rate across a patient’s lifetime.
To evaluate the impact of Cologuard screening on use of diagnostic colonoscopy, CRC incidence, and mortality, Exact Sciences Corporation launched a clinical study
(ClinicalTrials.gov Identifier: NCT04124406) last year in collaboration with the Mayo Clinic. Known as the Voyage study, it aims to enroll 150,000 adults in the US who are prescribed Cologuard. “We are going to follow this group of patients for at least 7 years to measure those endpoints so that we can get at [those] questions,” Dr Limburg said.
Disclosure: Several authors of the Weiser et al. study reported financial relationships with molecular diagnostic companies. For a full list of disclosures, please refer to the original studies.
- Cyhaniuk A, Coombes ME. Longitudinal adherence to colorectal cancer screening guidelines. Am J Manag Care. 2016;22(2):105-111.
- Weiser E, Parks, PD, Swartz RK, et al. Cross-sectional adherence with the multi-target stool DNA test for colorectal cancer screening: Real-world data from a large cohort of older adults. J Med Screen. 2020;0(0) 1–7.
- Exact Sciences. Exact Sciences and Mayo Clinic initiate 150,000 patient, 7-year study to evaluate real-world impact Of Cologuard®. Published October 14, 2019. Accessed March 27, 2020.
- Naber KS, Knudsen AB, Zauber AG, et al. Cost-effectiveness of a multitarget stool DNA test for colorectal cancer screening of Medicare beneficiaries [published online September 4, 2019]. PLOS One. doi:10.1371/journal.pone.0220234
- Exact Sciences. Cologuard® helps more people get screened in a cost-effective way [press release]. Published September 10, 2019. Accessed May 05, 2020.
- Jensen CD, Corley DA, Quinn VP, et al. Fecal immunochemical test program performance over 4 rounds of annual screening. Ann Intern Med. 2016;164(7):456-463.
- Hassan C, Giorgi Rossi P, Camilloni L, et al. Meta-analysis: adherence to colorectal cancer screening and the detection rate for advanced neoplasia, according to the type of screening test. Ailment Pharmacol Ther. 2016;36(10):929-940.
- Singal AG, Gupta S, Skinner CS, et al. Effect of colonoscopy outreach vs fecal immunochemical test outreach on colorectal cancer screening completion: A randomized clinical trial. JAMA. 2017;318(9):806-815.
- Imperiale TF, Ransohoff DF, Itzkowitz, et al. Multitarget stool DNA testing for colorectal-cancer screening. N Engl J Med. 2014;370:1287-1297.
- Pan J, Xin L, Ma Y, et al. Colonoscopy reduces colorectal cancer incidence and mortality in patients with non-malignant findings: A meta-analysis. Am J Gastroenterol. 2016;111(3):355–365.
- Knudsen AB, Zauber AG, Rutter CM, et al; US Preventive Task Force. Estimation of benefits, burden, and harms of colorectal cancer screening strategies: Modeling study for the US Preventive Services Task Force. JAMA. 2016;315(23):2595-609.