By LOUISE CARR, Associate Editor and Featured Columnist
Not all cancers can be detected before they get serious but colon cancer is an exception. Because colon cancer, the third most common cancer and the third leading cause of cancer death in the US, progresses slowly from benign growth through to invasive tumor, it is possible to spot it and stop it in its tracks. Early screening for colon cancer is often in the form of a colonoscopy.
A colonoscopy can save lives, so wouldn’t it be better if it was carried out as often as possible? The standard recommendation in the US is for a colonoscopy every 10 years after the age of 50. But should you be getting one more often – every five years, or three years? Are there any risks involved in colonoscopy?
What is a Colonoscopy?
During a colonoscopy the doctor inserts a thin, bendy tube called a colonoscope into the back passage. The tube has a minute camera on the end and the doctor uses it to look for small growths inside your bowel called polyps. If these are found, they are removed for testing. The actual colonoscopy procedure takes around 30 minutes but the entire appointment takes longer.
But how often should you have a colonoscopy, exactly?
American Cancer Society Recommendations for Colonoscopy
The American Cancer Society recommends tests for colorectal (colon) cancer to start at age 50 for both women and men at average risk of colon cancer. One of these tests is the colonoscopy, and the Society recommends testing every 10 years. People with an increased risk of colon cancer should have colonoscopies begin before the age of 50 – an increased risk could be due to a personal history of polyps or colon cancer, inflammatory bowel disease, or a family history of colon cancer or polyps. In the case of family history of colon cancer, colonoscopy should be every five years.
In the UK, a system of colon cancer screening limits the use of colonoscopies to people aged 60 to 74 years who show abnormal results on a regular Fecal Occult Blood Testing screen.
The UK’s National Health Service says that 16 out of every 20 people with an abnormal result will have a colonoscopy and out of those 16 people, 8 will show nothing abnormal, 6 will have polyps, and 2 will have cancer (on average).
What Are the Benefits of Colonoscopy?
A 2014 study from the American Cancer Society is one of many pieces of research to demonstrate the benefits of colonoscopy.
The study (Colorectal Cancer Statistics, 2014) shows colonoscopy leads to a dramatic reduction in colon cancer incidence in Americans older than 50.
Following the widespread uptake of regular colonoscopies in the US in the last 10 years, the incidence of colon cancer has dropped by 30 percent. Between 2000 and 2010 the rate of colonoscopy tripled from 19 percent to 55 percent among adults aged between 50 and 75. American Cancer Society researchers aim to increase the screening rate to 80 percent by 2018.
And a 2012 study from the Memorial Sloan-Kettering Cancer Center shows that the removal of precancerous polyps from the bowel during a colonoscopy can cut the risk of dying from colon cancer by half. If adenomatous polyps, the most common growths seen during colonoscopy, are not removed, experts say, they grow into cancers that kill.
So Why Not Do It More Often?
If a procedure is proven to cut deaths from a preventable form of cancer by more than half, wouldn’t it be wiser to test people more often than the standard 10 years apart, in order to catch even more precancerous growths before they become a problem?
However, a colonoscopy is not without its risks.
Side effects are relatively common as a result of the procedure and some of them are serious.
According to a 2010 study from the University of Washington, up to 33 percent of patients report at least one minor digestive symptom after colonoscopy. This could be cramping, abdominal pain, excess gas, or nausea.
But complications can be more serious - a 2008 study from the Kaiser Permanente Center for Health Research, Portland, Oregon shows the overall serious adverse event rate is 2.8 per 1,000 colonoscopies.
Serious side effects include damage to the intestinal wall including perforation, infection, and bleeding. The sedative medicine can sometimes cause heart or breathing problems, according to the American Society for Gastrointestinal Endoscopy, 2011.
Plus, of course, it’s relatively expensive.
A 2014 study by Dr. Thomas Sequist at Partners HealthCare as part of the Choosing Wisely project reveals that some patients are getting a colonoscopy too often, putting them at unnecessary risk and also raising costs in the healthcare system.
Eighty-six percent of patients at the Harvard Vanguard Medical Associates physicians group were screened for colon cancer during the 2000s, with most of the patients receiving follow-up colonoscopies far earlier than the 10 recommended years.
For patients with precancerous polyps, the recommendation is to test within three to five years but patients in the study were also tested too soon – experts say there is no need, as polyps grow very slowly.
However in many cases, doctors are simply saying “I might as well do it” since there are few risks of serious side effects. But Sequist estimates the cost of over testing in the study amounted to nearly $1.3 million.
Everyone’s an Individual Case
Surveillance colonoscopy is both underused and overused, studies show, and how often patients receive a colonoscopy should be aligned with their personal risks, according to a 2010 study from the University of Pittsburgh School of Medicine.
In the study, surveillance colonoscopy – where a colonoscopy is performed to monitor people with a history of polyps, is not being carried out in relation to this risk. There is an “overuse of surveillance colonoscopy among low-risk patients and under-use among high risk patients,” according to researchers.
Are There Alternatives to the Colonoscopy?
Colonoscopy is the standard test for colon cancer but there are other less expensive, less invasive tests to consider including the virtual colonoscopy and the test of a stool sample for abnormal cells.
A 2008 study led by researchers at the Mayo Clinic Arizona shows that virtual colonoscopy, where a non-invasive x-ray looks for precancerous growths, is 90 percent as effective as colonoscopy at finding large growths, but not very effective at finding small growths.
The recommendation for the virtual colonoscopy is for a test very five years, which could cause problems with accumulated X-ray exposure although this has not been significantly tested.
Colonoscopy remains the most effective test for picking up colorectal cancers. According to a 2013 study from the Harvard School of Public Health 40 percent of all colon cancers could be prevented if Americans underwent regular colonoscopy screening. But the recommendation of colonoscopy every 10 years for those with an average risk remains the same. There is no concrete evidence that testing more frequently brings benefits to the population.