Colonoscopies aren’t the most comfortable procedures, so it’s welcome news that not everyone may need the regular exams to stave off colorectal cancer after all.
According to research published in the Annals of Internal Medicine, people whose first colonoscopy is negative may be able to rely on less invasive cancer screening and bypass repeated colonoscopy tests without increasing their risk of developing cancer. And that switch could save as much as $3 billion in health care costs, according to the study, while at the same time reducing the medical harms of screening complications.
The results emerged from computer simulations of how likely cancer would develop based on data from the National Cancer Institute’s Surveillance Epidemiology and End Results (SEER) Program. The scientists created models of how likely colon cancer would develop beginning at age 60 among people with varying levels of risk for the disease if they followed different screening regimens starting at age 50, including colonoscopy once every 10 years, a CT scan of the bowel every five years, or a stool test for markers of colorectal abnormalities every year.
Although colonoscopy is the most accurate of the colon cancer tests, it’s also more expensive and carries a greater risk of side effects. The Annals study suggests that for the low-risk patients who had only one negative colonoscopy result, there would be no difference in their rates of dying of colorectal cancer whether they were screened with repeated colonoscopies or whether they took advantage of alternative and more frequent screening procedures (which are also cheaper and safer).
Currently the U.S. Preventive Services Task Force, an independent group of government-commissioned experts, strongly recommends that men and women aged 50-75 get routine colorectal cancer screening. It doesn’t recommend one screening method over another, but because it’s the most reliable, colonoscopy is the most common screening method in the U.S.
For patients, however, the procedure itself is a deterrent. To prepare for the test, patients need to clear the bowels with a combination of a liquid diet and laxatives sever hours before the exam. During the exam, which requires sedation, a doctor inserts a long, flexible tube into the rectum and into the large intestine. The discomfort is enough to keep people from following the recommended once-a-decade screening, potentially putting them at higher risk of being diagnosed with advanced forms of the disease.
Then there are the side effects and complications, which can result in hospitalization or death, that occur in roughly 25 per 10,000 colonoscopy procedures. And while that risk is extremely small, it does means that, across the millions of people who receive a colonoscopy, thousands of will experience debilitating side effects, such as a perforated bowel or diverticultisis, which involves inflammation or infection of the colon wall.
In fact, these risks are what convinced the USPSTF to advise against routine colorectal screening for most adults over age 75. Elderly people are still at risk of the cancer; in fact, they’re at even higher risk than younger adults. But the long-term benefits of invasive screening do not outweigh the short-term risks for those very elderly people who — even if they do successfully get diagnosed and recover from cancer — are more likely to die of other conditions.
The authors of the current study acknowledge that as newer, non-invasive screening procedures emerge in coming years, the calculus around the risks and benefits of screening could change. And the convenience of those tests over colonoscopy could boost the number of people who get screened. Two separate studies published earlier this year, for example, show that patients are much more likely to get colorectal cancer screening when the tests involve only a stool sample rather than an invasive colonoscopy.
(VIDEO: TIME Explains: Cancer Screenings)
The computer simulations announced this week cannot, of course, show with absolute certainty how well different screening procedures work in the real world. Balancing benefits and risks can often depend on personal priorities: whether you’d rather risk the complications from a more invasive procedure, or take the less invasive procedure and accept a higher risk of missing potentially precancerous polyps. But the data do support one conclusion: any of the screening procedures should be better than no test at all.