Colon cancer is the third most common kind of cancer in men and women and the second leading cancer cause of death, but it doesn’t have be.
Screening tests find abnormal growths such as precancerous polyps so they can be removed before cancer develops. We asked Bonnie A. Ewald, MD, a gastroenterologist from Lahey Hospital & Medical Center, to discuss different screening options.
“Colonoscopy is typically the recommended form of screening because not only can it detect colon cancer, but it also detects and removes precancerous polyps which can eventually become colon cancer. While there are risks to undergoing colonoscopy, the risk of significant adverse events is less than 0.3 percent,” she said. “But there are other screening options that can be considered.”
The commercial sounds compelling: get a prescription from your doctor and test yourself for colon cancer in the privacy and comfort of your own home. But is an at-home/mail-in test enough?
“Stool-based screening methods detect microscopic blood and DNA in stool which can indicate colorectal cancer,” Ewald said. But stool based screening is only indicated for average risk patients. Therefore it is not indicated for patients with a family history of colon cancer, personal history of polyps, and symptoms such as rectal bleeding.
“The benefits of stool samples are that there is no requirement for colon preparation, it can be done in the comfort of your own home, and there is no risk of procedure based complications. The downsides include the detection rate being slightly lower than colonoscopy, the test is not meant for detection of precancerous polyps, and false positives occur causing patients concern, requiring colonoscopy,” she said.
Radiographic methods include CT colonography, which uses a CT scan to detect polyps or cancer that are larger than 6 mm.
Also known as a virtual colonoscopy, this method uses X-rays and computers to produce images of the entire colon, which are displayed on a computer screen for the doctor to analyze.
“The benefits of CT colonography include a decreased potential for procedural complications. The patient is required to undergo colonoscopy preparation and if any lesion is found, repeat preparation for diagnostic colonoscopy is required,” she said. “Downsides include radiation exposure and inability to detect flat lesions which may be precancerous or cancerous. Findings outside of the colon are also not unusual.”
This third option may sound like the colonoscopy of the future. “Capsule colonoscopy uses a small camera, which is swallowed, to take images of the colon for detection of polyps or cancers,” Ewald said. “This option is not yet widely available.”
The most important thing to know about colon cancer screening is that it saves lives, she said.
“People should be screened because it decreases mortality of colon cancer. With screening, cancers can be detected in earlier stages and precancerous polyps can be detected and removed before they become cancerous,” Ewald said.
For information about colon cancer screening and information on when you should be screened, register for our upcoming Conversations on Cancer event.