Don’t ignore one of the best cancer screening tools available

Colorectal cancer kills an average of 52,000 people every year in the U.S., according to the American Cancer Society. Yet it is one of the few cancers that actually has numerous screening methods that can catch the disease in its earliest, most treatable stages.

A CDC survey in 2018 indicated that only 60 percent of Americans between the ages of 50 and 75 who are eligible for a colonoscopy actually get one. Another 11 percent in the survey had done a home stool test – either a FIT (Fecal Immunochemical Test) in the past year or a FIT DNA test in the past three years. That means that about 30 percent of Americans haven’t had any screening at all.

“It’s scary and frustrating,” said Falmouth gastroenterologist Joseph Cobb, MD. “It’s a preventable cancer. There aren’t too many cancers that, one, grow slowly and, two, grow from precancerous lesions like colon polyps. So, we can really interrupt the process by doing a colonoscopy.”

Since there has been an increase in the number of young people with colon cancer in recent years, the American Cancer Society changed its guidelines for screening to recommend that screening begin at the age of 45 instead of 50. The age for people with average risk to stop doing colonoscopies is 75.

How often you need to come back for a repeat colonoscopy depends on what the gastroenterologist finds, Dr. Cobb said. If no polyps are found, you don’t have to do a repeat screening for ten years. If polyps are found, the size, number and type determine how often you should be re-screened.

“We do it every ten years because we know it takes 12 to 15 years to grow colon cancer and a vast majority of colon cancers are going to start out as polyps,” he said. “So, no polyps, great – ten more years.”

The Prep

The day or night before a colonoscopy, patients need to do a prep to completely clean out their colon. Dr. Cobb recommends either using the MiraLAX powder mixed with two 32-ounce bottles of Gatorade that are taken six hours apart, or Dulcolax tablets, also taken with 32 ounces of Gatorade, six hours apart. The timing of the prep depends on what time your colonoscopy is scheduled.

“It used to be that you did everything at once,” Dr. Cobb said. “But the big thing about colonoscopy is how clean can you get the colon? By splitting the dose up, and waiting six hours between them, we find the colon gets cleansed much better.”

Colonoscopy

At Cape Cod Healthcare, colonoscopies are done under deep sedation with the drug propofol. That keeps the patient more comfortable than lighter sedation would and it wears off quickly afterwards so people feel better sooner. Dr. Cobb still advises patients to avoid driving, cooking and signing legal papers on the same day as their colonoscopy, but they should be fine to do activities like taking a walk.

Colonoscopies are booked on the half hour. If there are no polyps, it only takes about 15 minutes. It takes five minutes or less to thread the scope up to the cecum, which is the last part of the colon. Then the scope moves slowly down on the way out, looking for polyps. Any polyps that are at least a centimeter in size are removed on the spot. Polyps that are smaller than one centimeter almost never harbor cancer.

“Some polyps are too big to be removed with the scope,” Dr. Cobb said. “But those are exceptions to the rule. With those folks we do biopsies and then we send them up to a surgeon to have that part of the colon removed.”

Home Testing

Colonoscopies are 95 percent effective in finding precancerous polyps, but Dr. Cobb recommends home stool testing for the 30 percent of people who are not doing any testing and who are resistant to colonoscopies. A FIT test detects the presence of blood in the stool. It is repeated every year. It is about 79 percent effective at detecting colon cancer.

A FIT DNA test, tests for both the presence of blood and also looks for genetic abnormalities called abnormal DNA methylation. It is repeated every three years.

Cologuard is the most commonly used FIT DNA test and it is a great test, Dr. Cobb said. It can detect 92 percent of all colon cancers. The biggest down side of it is that 30 percent of people over the age of 70 abnormally methylate their DNA. That can lead to a high number of false positives in that age group that could cause a lot of unnecessary anxiety.

If a patient gets a positive result for either type of home stool test, they need to get a follow-up colonoscopy.

“The FIT is the only one that has actually been shown to decrease mortality,” Dr. Cob said. “It’s ironic that we’ve been doing a ton of colonoscopies and we have evidence that colonoscopies lower the chance of getting cancer, but in the only well-done double-blinded randomized study, having a FIT test lowers your chance of dying of colon cancer.”