At-Home Colon Cancer Testing Vs. Colonoscopy

Colon cancer is the third most common cancer diagnosed in both men and women each year in the United States. There are screenings that are used to look for colorectal cancer before a person has any symptoms or signs. Home-based stool tests and colonoscopy both screen for similar things, but they take two different approaches to detecting colorectal cancer.

In this article, Franciscan Health cancer experts discuss the differences between colonoscopy and at-home tests and what types of colon cancer screening may be best for you.

What Is A Colonoscopy?

A colonoscopy is a short procedure allows the doctor to look inside the entire rectum and colon while a patient is under anesthesia. A flexible, lighted tube called a colonoscope is inserted into the rectum and the entire colon to look for polyps or colorectal cancer.

Physicians who perform colonoscopy still regard colonoscopy as the “gold standard,” since it has the highest detection rate of small tumors and polyps.

"This is an important but underappreciated benefit of colonoscopy," said Ben Tsai, MD, a colorectal surgeon with Franciscan Physician Network Indiana Colon & Rectal Specialists in Indianapolis. "With colonoscopy, we are able to completely remove polyps or biopsy suspicious lesions."

What Are At-Home Stool/Fecal Tests?

There are several types of at-home stool/fecal tests. With each type of test, a patient provides a stool sample which is sent to a lab for review. There may be specific instructions of things to avoid eating or medication to stop prior to the test, so be sure to review all instructions carefully. Results are provided to your primary care physician in about two weeks.

There are three main types of at-home tests to screen for colon cancer:

Fecal DNA Test

A fecal DNA test is the newest type of at-home colon cancer screening, and looks for abnormal DNA as well as blood in your stool sample.

Fecal Immunochemical Test (FIT)

A FIT test looks for blood in your stool.

Fecal Occult Blood Test (FOBT)

A fecal occult blood test also looks for the presence of blood in your stool using a substance galled guaiac.   

What Are Limitations Of At-Home Stool Tests?

At-home stool-based tests are limited in their ability to detect polyps, and the test does not differentiate between cancer and benign polyps. This can result in a positive stool test that creates unnecessary worry. Some of these positive test patients will have completely normal colonoscopy exams; some will have polyps that are easily removed with colonoscopy; and a small fraction will have cancer.

Positive At-Home Stool Test

A positive at-home stool test means that DNA and/or hemoglobin (blood) biomarkers that may be associated with colorectal cancer were found in the stool. Note that not all at-home tests check for both DNA and blood in the stool. If the stool-based test turns out positive, the next step for the patient is to have a colonoscopy to rule out cancer.  

Negative At-Home Stool Test

A negative at-home stool test means that the home test did not detect significant levels of DNA and/or hemoglobin biomarkers in the stool that are associated with colorectal cancer. 

How Often Are At-Home Stool Tests Recommended?

At-home fecal immunochemical tests (FIT) and fecal occult blood tests (FOBT) are yearly tests, while the recommendation of fecal DNA testing varies from yearly to every three years. Any positive test results shown on these at-home stool tests require immediate follow-up with colonoscopy for further diagnosis. Colonoscopy, on the other hand, is suggested every 10 years or as recommended by your physician based on risk factors and findings. 

Why Use An At-Home Test For Colon Cancer Screening?

Because at-home stool-based tests are easier to complete, many patients opt for this method since some type of colorectal cancer screening is preferred to none at all. Current estimates suggest that only 70 percent of eligible patients get a colon cancer screening of any kind.

Challenges that may lead to someone delaying a colonoscopy include work schedules, having no driver to bring you home after an appointment, potential out-of-pocket expenses for colonoscopy prep and more.

“When you look in the real world, it is hard to get some people to a colonoscopy,” said Naina Mahngar, MD, medical oncologist at Franciscan Health Michigan City. “You could do a stool test, and it's pretty accurate for invasive cancers. But again, the gold standard is a colonoscopy if you're able to do it, because not only are you checking for cancer, but at the same time you can get rid of polyps and the pre-cancerous cells in the process.”

At-Home Test vs. Colonoscopy: Which One?

Colonoscopy has the highest detection rate of small tumors and polyps, and it is the one cancer screening that can prevent colon cancer by removing precancerous polyps.

"By removing polyps, this can prevent a cancer from growing, and this is one of the best cancer prevention methods we have," said Michael Eaton, MD, radiation oncologist and medical director of cancer services at Franciscan Health Cancer Center Indianapolis.

If You Are At Average Risk For Colon Cancer

Colonoscopy remains the first recommendation for all eligible, average-risk patients, and stool-based testing is an option if patients are unwilling or unable to proceed with colonoscopy initially.

If You Are At High Risk For Colon Cancer Or Have Symptoms

High-risk patients or people with colon cancer symptoms should undergo colonoscopy without at-home stool-based testing.

“At-home stool tests are never going to be a replacement for someone who's high risk for cancer,” Dr. Mahngar said. “So if you have multiple family members with a history of colon cancer, if you have any bowel disease like Crohn's Disease or ulcerative colitis, if you have a personal history of colon cancer, or if you're higher risk for colon cancer or pre-cancer, we would want to skip straight to a colonoscopy rather than doing an at-home test.”

Does Insurance Cover Colon Cancer Screenings?

Commercial insurance and Medicare provide coverage for screening colonoscopies and at-home tests, but patients must choose one or the other (not both, unless an at-home test results in a positive stool sample). Commercial insurance and Medicare also recently began providing coverage at no cost for follow-up colonoscopies after a positive at-home stool test. Be sure to check with your insurance provider prior to any testing to confirm your coverage.

What matters most is that all patients undergo age-appropriate colon cancer screening of some type and adhere to routine surveillance depending on their specific circumstances.

What If My At-Home Test Indicates I Need More Testing?

If your at-home stool test warns of a possible colon cancer, a diagnostic colonoscopy is the next step. Unfortunately, only about half of people who undergo a stool test to screen for colon cancer follow up with a colonoscopy when that test warns of a possible cancer, according to a new study in JAMA Network Open.

"If you have a positive stool-based test, you're at roughly 10 times higher risk of having colon cancer, so that it makes it very urgent that you would go in," said study-co-author Jeff Mohl, director of research and analytics for the American Medical Group Association.

Detection and removal of precancerous polyps can significantly reduce the incidence of the cancer and deaths caused by it.

HealthDay News contributed information to this article.