Exact Sciences' Cologuard®: What It Is and How It Works

While it is estimated that over 150 thousand people in the United States will be diagnosed with colorectal cancer (CRC) in 2023, the likelihood of successful CRC treatment depends on how early it is detected and diagnosed. In fact, the global overall survival rate has shown gradual improvements thanks to a combination of better early detection options and treatment plans.

Nonetheless, successful advocacy of CRC screening especially in asymptomatic or average-risk individuals is highly dependent on patient compliance. Particularly for colonoscopies, which are known to be reliable in detecting cancerous lesions or precancerous polyps in the colon and rectum, there are many barriers to compliance, and patients are often reluctant to go through with the procedure unless other symptoms are present. Besides fear, the lack of knowledge, bowel preparation and possibly the discomfort and pain that accompanies the procedure were described by patients to be the leading deterrents.

A bid to improve patient compliance has led to the development of several new colorectal cancer screening tests, of which Cologuard^® is one of the presently FDA-approved kits. There is much debate about Cologuard^® being a potential colonoscopy alternative, but how certain are we about this? In this article, we cover the ins and outs of Cologuard®, including how it works and if it could serve as a reliable colonoscopy replacement.

Developed and manufactured by Exact Sciences, Cologuard^® is a stool-based colorectal cancer screening kit that detects the presence of DNA and hemoglobin (the protein found in red blood cells) in stool samples. Use of the Cologuard^® test kit is recommended for individuals aged 45 and above who are at average risk of colorectal cancer and do not present any of the symptoms.

Cologuard^® is also an easy-to-use and non-invasive test kit, and can be done at home without a doctor’s supervision. The stool sample can be easily collected using the provided sample container and toilet bracket. A preservative solution is also supplied to help maintain the stability of the sample. To send the sample for analysis, a pickup can be scheduled with UPS on the same day or the next day after the sample is collected. Thereafter, results of the test will be sent to the patient’s healthcare provider within two weeks.

In clinical trials, Cologuard^® proved to be reliable in detecting colorectal cancer. Compared to FIT, Cologuard^® detected colorectal cancer with a sensitivity of 92% compared to 74% for FIT.

While Cologuard^® appears reliable in detection, it still has a ways to go in specificity. Compared to a colonoscopy, which can detect up to 95% of large polyps or precancerous lesions, Cologuard^® is only able to detect 42%. In addition, there is also a likelihood of false negative or false positive results with the Cologuard^® test.

While a negative result indicates that no DNA or blood was found in the stool sample, false negatives may be possible in earlier stages of colorectal cancer development. On the other hand, a positive result means that blood or DNA has been detected. While the chances of precancerous growths or tumors are high, positive results may be caused by other non-cancer related reasons.

Patients who receive negative results are advised to consult their healthcare provider on whether another round of screening is required, while those who test positive will need a follow-up diagnostic colonoscopy to confirm the presence or absence of precancerous or cancerous growth.

Given that it is possible to receive false positive or negative results and the detection rate is not 100%, a colonoscopy may still be needed after a Cologuard^® test. It is important to remember that the Cologuard^® will only provide preliminary information on the presence or absence of cancer, but does not function as a preventative measure. Further steps are still required to remove the polyps and run a biopsy for more definitive results.

If you are not showing any symptoms, or are at average risk of colorectal cancer, Cologuard^® is an option to consider for routine screening, as the test only needs to be conducted once every three years. However, if you are predisposed to colorectal cancer as a result of hereditary, genetic, or environmental risk factors, then a screening colonoscopy is recommended over the Cologuard^® test. Ultimately, detecting the presence of cancer early is the goal, particularly given that the onset of colorectal cancer is getting earlier.

While Cologuard^® is not completely foolproof or 100% sensitive or accurate, it remains a non-invasive screening method that may enable earlier colorectal cancer diagnosis and treatment.