Home Tests for Colorectal Cancer Don’t Beat Colonoscopy for Prevention
March 6, 2020
Colorectal cancer has a high cure rate – especially when caught early – yet it remains the third deadliest cancer for men and women in the United States. It doesn’t help that many people avoid getting a colonoscopy, which is by far the best way to find colorectal cancer early or prevent it altogether.
Home screening tests using a stool sample have gotten better in recent years. But they are much less effective than colonoscopies at finding abnormal tissue growths called colon polyps, which can develop into colorectal cancer if not removed. And if the home test is positive, you still need to have a colonoscopy.
“Colonoscopy is generally recommended as the best screening test, especially for people who have a history of colorectal cancer in their close family,” says Frederick Weber Jr., MD, a gastroenterologist and professor in the UAB Medicine Division of Gastroenterology and Hepatology. “But as I tell all of my patients, the best test is the one that will get done.”
March is National Colorectal Cancer Awareness Month, so we spoke with a team of UAB Medicine specialists to highlight the latest advancements in screening, treatment, and prevention, including the at-home FIT tests.
About Colorectal Cancer
Cancer is caused by DNA changes that make cells divide uncontrollably and spread to surrounding tissue. Colorectal cancer is a general term that includes both colon cancer and rectal cancer. Both conditions affect the large intestine, the lowest part of the digestive system. Colon cancer can start anywhere in the large intestine, and rectal cancer starts in the last several inches of the large intestine (the rectum).
The American Cancer Society estimates that one in 21 males and one in 23 females in the country will develop colorectal cancer during their lifetime, usually after age 50. Nearly 148,000 new cases are projected for 2020, and over 53,000 deaths. Many more will develop non-cancerous polyps. The exact cause of colorectal cancer is not known, but genetic factors play a role, and it may run in families. However, 80% of people who develop colorectal cancer have no family history of the disease. Diets high in red meat or processed foods may slightly increase the risk.
Colon polyps are the most common cause of colorectal cancer, and they are removed when discovered during a colonoscopy, if possible. A colonoscopy is an exam in which a long, flexible tube with a camera on the end is inserted into the rectum to view the inside of the colon. This device also includes instruments that enable doctors to remove most polyps during the exam.
“Colon polyps are quite common, but only a small percentage of them ever become cancerous,” says UAB Medicine colorectal surgeon Greg Kennedy, MD, PhD, director of gastrointestinal (GI) surgery. “By removing all of them, that’s how we’re able to prevent colorectal cancer. If they never have a chance to develop into cancer, it eliminates the need for treatment and surgery and the risks that go along with that.”
For colon cancer, the primary treatment is surgery to remove the affected section of the large intestine. For rectal cancer, chemotherapy and radiation therapy may be used along with surgery. Today, most colorectal cancer surgeries are performed using minimally invasive laparoscopic techniques, which require only small incisions (cuts) and a short hospital stay. About 60-65% of patients need treatment in addition to surgery – usually chemotherapy.
The survival rate for colorectal cancer depends on many factors, including how early it was caught and whether it has spread. The five-year survival rate is 60-70% for typical cases and as high as 95% if detected and treated early.
“Having colorectal cancer once increases your risk of getting it again, especially if the cancer was in an advanced stage,” says Ravi Paluri, MD, MPH, an oncologist in the UAB Medicine Division of Hematology and Oncology. “The standard of care is that an oncologist should monitor you for at least five years after treatment.”
Dr. Weber says colonoscopy is the “gold standard” for colorectal cancer screening and the only test that allows doctors to remove the polyps as part of the exam. He and many other experts recommend a colonoscopy every 10 years starting at age 50 for people with normal risk, or beginning at age 40 for those who have a close family history of colorectal cancer or large polyps. In recent years, many doctors have begun recommending the exam starting at age 45 for patients with normal risk factors.
If the polyp is very large or too deeply embedded to remove it during a colonoscopy, surgery is needed to remove that section of the colon. But this is becoming less common with advancements in colonoscopy instruments. A new colonoscopy technique called endoscopic mucosal resection (EMR) has made it possible to remove even large polyps that previously would have required surgery.
“EMR is a specialized technique that isn’t done by all gastroenterologists, so we treat a large number of referred patients who have polyps that were too large for their doctor to remove,” Dr. Weber says. “At UAB, we can remove them with a colonoscopy rather than having to operate.”
Other Physical Screening Tests
- Flexible sigmoidoscopy: Similar to a colonoscopy, this exam is cheaper and less invasive than a colonoscopy but doesn’t allow doctors to see as much of the colon, so it is less effective at finding polyps or colon cancer. It is generally recommended every five years starting at age 50. With or without regular home stool tests, a flexible sigmoidoscopy is considered to be the best alternative for people who do not wish to have a colonoscopy.
- CT colonography, or “virtual colonoscopy”: This test uses X-rays to look inside the large intestine for large polyps or colon cancer. It is sometimes used when parts of the colon couldn’t be seen clearly during a colonoscopy, due to the patient’s anatomy or other reasons.
- Wireless capsule endoscopy: The patient swallows a small capsule containing a wireless camera, and images are captured over several days as it makes its way through the digestive system. Those images are recorded on a device worn by the patient and later downloaded and reviewed by a doctor. It is highly effective at finding polyps and colorectal cancer, but the technology isn’t widely used for this purpose at this time.
Home Screening Tests
There are several types of home screening kits, which require the patient to collect a small stool sample that is sent to a laboratory for testing. These tests are only approved for people age 45 and up who have never been diagnosed with colorectal cancer and have average risk factors. Though convenient, they are less effective than physical testing methods such as colonoscopy. These at-home tests include:
- Fecal immunochemical test, or FIT test: Designed to detect blood in the stool that isn’t visible with the naked eye. It is recommended every year.
- FIT-DNA test (Cologuard): Similar to the standard FIT test but designed to also detect altered DNA in the stool caused by colorectal cancer. It is recommended every three years.
- Guaiac fecal occult blood test (gFOBT): This is another type of stool test that has mostly been replaced by the more accurate FIT tests.
“Even if done year after year, these home stool tests are not as good as having a colonoscopy, but they are still better than doing nothing,” Dr. Weber says. “And if your test is positive, you must then have a colonoscopy to evaluate your condition, otherwise there’s no benefit to having the screening in the first place.”
Click here to learn more about colon cancer or to make an appointment with a UAB Medicine gastroenterology specialist.