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

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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.

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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

( 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.


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  2. 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.
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