Cologuard: A Non-Invasive Screening Test for Colorectal Cancer – Advantages and Ongoing Research

1. Introduction

   1. Colorectal Cancer and Its prevalence

      Colorectal cancer also known as bowel or colon cancer refers to a malignancy that develops in the colon or rectum. It is known to originate from abnormal growths called polyps in the lining of the colon or rectum. Colorectal cancer is the most common type of cancer worldwide and is the most commonly diagnosed cancer in both men and women. According to the World Health Organization, it is estimated that 1.93 million new cases of colorectal cancer and 10 million deaths occurred globally in 2020. ⁽¹⁾ Also, higher mortality rates are observed in the developed countries.

      Colorectal cancer affects individuals of all ethnicities and ages and a majority of cases are diagnosed in individuals over the age of 50 years. Also, having a family history of colorectal cancer, inflammatory bowel disease can further increase the risk of developing the disease.

   2. Importance of Early Detection of Colorectal Cancer

   Early detection plays an important role in the prognosis and survival rate of colorectal cancer. If diagnosed at an early stage, the chances of successful treatment and cure are higher. Regular screening can be helpful in detecting precancerous polyps or early stages of cancers. This can further help in enabling timely intervention and reducing the risk of advanced disease.

2. Overview of Cologuard

1. What is Cologuard and its Purpose

Cologuard is a non-invasive screening test that can help detect colorectal cancer and precancerous polyps. ⁽²⁾ It is a combination of DNA analysis and fecal immunochemical testing (FIT) to analyze a patient’s stool sample for the presence of certain biomarkers associated with colorectal cancer.

The purpose of Cologuard is to provide alternate screening options for people with an average risk of colorectal cancer. It is issued for early detection and prevention by identifying abnormal DNA and blood biomarkers in the stool that may indicate the presence of colorectal cancer or precancerous polyps.

2. How Cologuard Works as a Non-Invasive Screening Test

Cologuard is a non-invasive alternative to other screening methods like colonoscopy. It uses a multitargeted approach to analyze DNA from cell shed in the stool. ⁽³⁾ It provides an option for colorectal cancer screening that is more convenient and less invasive.

A Cologuard test kit is provided to the patient, by a healthcare provider or through a direct consumer model. The sample is collected by the patient at home using a provider collection container and following the instructions provided. The sample is packaged and sent back to the laboratory for analysis.

The sample is tested for DNA mutations and alterations associated with colorectal cancer. The sample is also tested for the presence of blood in the stool which can be an indication of colorectal cancer or gastrointestinal issues.

A report is generated by the laboratory indicating whether the test is positive or negative. A positive test indicates a higher likelihood of colorectal cancer or precancerous polyps. However, it should be noted that a positive test does not indicate the presence of colorectal cancer or polyps. Further diagnostic evaluation through colonoscopy is recommended to confirm the finding and guide appropriate treatment decisions.

3. Who Can Go Ahead with Cologuard Procedure

The Cologuard screening test is suitable for adults who are at an average risk of the disease. According to the American Cancer Society, a person who is at an average risk of developing colorectal cancer should begin screening at the age of 45 years. ⁽²⁾ The screening should continue until 75 years of age. After this, the need for screening should depend on the person’s health, preference, and life expectancy.

However, Cologuard does not replace the diagnostic colonoscopy nor does it replace a surveillance colonoscopy in those at high risk of developing colorectal cancer. ⁽⁴⁾

3. Advantages and Limitations of Cologuard Compared to Other Screening Methods

Cologuard is a non-invasive screening method and as compared to other traditional screening methods offers several advantages.

• Non-Invasive: Cologuard is a non-invasive procedure. The stool sample needs to be collected at home and there is no need for any invasive procedure like colonoscopy. The individuals who are hesitant to or are unable to undergo colonoscopy are more comfortable with this technique.
• Convenient: As Cologuard can be performed at home, the individuals are given a chance to collect the stool sample at home in their own privacy and at the time that suits them. The convenience increases compliance rates.
• No Bowel Preparation Needed: Unlike colonoscopy, no bowel preparation is needed in Cologuard, which includes fasting or taking laxatives. This eliminates the inconvenience and discomfort associated with bowel cleansing.
• Low Risk of Complications:

Cologuard carries a lower risk of complications compared to colonoscopy.

The limitations of Cologuard include:

• False Positive result: Cologuard is associated with a high risk of false positive results. ⁽⁵⁾ This may cause unnecessary anxiety and additional follow-up procedures.
• Incomplete Detection: Cologuard can detect certain biomarkers associated with colorectal cancer, but it may not detect all the cases. Some colorectal cancers may not shed enough DNA or produce detectable blood markers. This may lead to false negative results.
• Need for Confirmatory Colonoscopy: If a Cologuard test is positive, further diagnostic evaluation may be needed to confirm the presence of colorectal cancer or precancerous polyps. A positive Cologuard test may ultimately lead to a colonoscopy which adds to the cost.
• Cost Considerations: The cost of Cologuard screening is higher as compared to the traditional methods.

Before going ahead with Cologuard screening it is important to discuss the advantages and limitations with a healthcare professional.

4. Advances and Ongoing Research in Improving Cologuard Accuracy

   Advances and ongoing research are being conducted to improve the accuracy of Cologuard as a screening test for colorectal cancer. Some of the key areas of focus in advances for Cologuard include:

   • Biomarker Discovery and Refinement: Identifying and evaluating additional DNA markers can help improve the sensitivity and specificity of Cologuard. By expanding the panel of biomarkers used in Cologuard, the test may get more accurate in detecting colorectal cancer and precancerous polyps.
   • Enhanced DNA Analysis: There is ongoing research that aims to improve the sensitivity and specificity of DNA analysis methods used in Cologuard. This may lead to improved detection of genetic abnormalities associated with colorectal cancer.
   • Blood-Based Biomarker Analysis: Enhancing the detection and analysis of blood-based biomarkers in the stool may enhance the accuracy of Cologuard in identifying colorectal cancer and other gastrointestinal conditions.
   • Machine Learning and Artificial Intelligence: Machine learning algorithms are being developed to increase the accuracy of Cologuard in distinguishing between normal and abnormal samples.
   • Comparative Study and Validation: Large-scale studies are being researched to evaluate the performance of Cologuard against other screening methods. ⁽⁶⁾

   Ongoing advances aim to refine Cologuard’s accuracy, enhance its sensitivity and specificity and improve its overall performance as a non-invasive screening test for colorectal cancer.

5. Conclusion

   Cologuard plays a significant role in the detection of colorectal cancer in the high-risk population. It offers a non-invasive screening option and addresses the challenges and limitations associated with traditional screening methods.

   The future lies in refining the biomarkers used, enhancing DNA analysis techniques, and improving blood-based biomarker detection.

   Cologuard serves as a valuable tool in the early detection of colorectal cancer and provides accessibility and compliance, particularly in the high-risk population. It has the potential to further improve accuracy, contributing to a better outcome and being helpful in reducing the mortality rates in the fight against colorectal cancer.

Also Read:

• Stages of Colorectal Cancer & Its Treatment, Prognosis, Survival Rate, Causes, Symptoms, Risks
• The Link Between Blood Infections and Colorectal Cancer