What’s the harm in earlier screening for colorectal cancer?

Last week, the American Cancer Society released a new guideline recommending that regular screening for colorectal cancer (CRC) start at 45 for patients with average risk, rather than the current recommended age of 50. The guideline update is based on studies from last year that found a rise in the incidence of CRC among people younger than 50.

While cancer advocacy groups are cheering the news, few reports have examined both the costs and benefits of lowering the age of screening, or whether this would be a wise use of health care resources.

What’s the risk?

In 2016, the US Preventive Services Task Force updated their recommendations for CRC screening. They did not recommend regular screening for people with average risk under 50, because the risk of having CRC was so low in this age group that the costs of screening would not outweigh the benefits.

Since then, new data has come to light that shows an increased risk of CRC for younger people. According to a 2017 study, from 2000 to 2013, the incidence of CRC increased by 22% among people under 50, while it decreased in older age groups. The mortality rate from CRC increased by 13% for younger people during this time period as well.

These numbers sound worrisome, but it’s important to remember this increase is relative to a small absolute risk for someone under 50. As Kevin Lomangino writes in Health News Review, the lack of explanation makes the problem sound much more common than it actually is. The rate of CRC for people under 50 was 5.9 out of 100,000 people in 2000, increasing to 7.2 out of 100,000 people in 2013 – that’s a change from 0.0059% to 0.0072%. For comparison, the incidence of CRC among people age 60-64 is about 50 out of 100,000, or nearly 7 times as high.

With the rise in incidence of CRC among younger people, the impulse to screen more is understandable. However, it will take many more colonoscopies in this age group to result in a benefit, compared to other groups with higher risk. Few reports in the media mention this issue, which leaves out an essential part of the calculation of risks and benefits of screening in younger age groups.

What’s the benefit?

The American Cancer Society determined that screening should be started at 45 by applying the updated incidence data to the same models that the USPSTF used for their recommendation. We took a look at the updated analysis from the ACS to see how big of a difference the new data made.

In the 2016 USPSTF analysis, for a cohort of 1000 people, moving the screening age from 50 to 45 would result in 14 life-years gained* (one fewer person dying from CRC), but 827 more colonoscopies in total. In the ACS analysis with new data, moving the screening age from 50 to 45 would result in 25 life-years gained (two fewer people dying from CRC) with 810 more colonoscopies in total.

This was not the massive benefit we expected to see. Even with the increased risk of CRC, lowering the screening age only saves 25 life-years, which, divided between the entire cohort, is just 9 more days per person. To put this in context, screening for CRC with a fecal blood test starting at age 50 saves 244 life-years, or prevents 22 deaths from CRC, compared with no screening.

Another important point that Lomangino makes in his piece, is that modeling based on new incidence data is not the same thing as conducting a clinical trial of screening with real patients. As Dr. Andrew Wolf, who led the ACS guideline development group, told HealthDay, “It’s not certain that screening at age 45 will save more lives” because “most trials of screening have not included people younger than 50.” The true benefit of screening people under 50 is therefore still uncertain.

*In this analysis, life-years gained is a net measure that takes into account potential complications from colonoscopies.

What’s the harm?

Most of the media coverage around the guideline update did not mention the small size of the net benefit or the potential harms of screening thousands of additional people for CRC. Complications of colonoscopies include adverse reaction to anesthesia, bowel perforation, abdominal pain, and bleeding. In a 2016 study from the Yale Center for Outcomes Research and Evaluation, 1.6% of patients who had a colonoscopy later experienced a complication within 7 days that was serious enough to send them to a hospital. That’s not a high risk, but it’s much greater than the probability of actually having CRC at age 45.

There are other ways to screen for CRC that are less invasive and less expensive than colonoscopies, which the ACS also endorsed. Taking an at-home fecal blood test every year to detect CRC can be very effective, saving nearly as many lives with fewer total colonoscopies than having colonoscopy screenings every ten years. This would be an effective method for patients who want to start screening early, but want a less invasive option.

The financial cost of screening should also be a consideration when choosing when and how to screen for CRC. Insurers may not cover CRC screening for patients under 50, which means patients would be on the hook for more of the cost. And the cost of is substantial; colonoscopies can range from a few hundred dollars to more than $10,000. Fortunately, home fecal blood tests can cost as little as $8, but here’s the catch: if the test is positive, the follow-up colonoscopy is categorized as a “diagnostic colonoscopy” and patients can be charged a copay for the test or have to pay from their deductible, even if their insurance covers preventive colonoscopies. This is another example of practices that may be rational at the individual or enterprise level, but make no sense at a system level.

What’s the point?

Many advocates of the new guideline are hopeful that the updated guidelines will raise awareness of the risk of colon cancer for young people and the importance of screening. In articles covering the guideline change, several young survivors of colorectal cancer shared stories of how their doctors ignored their symptoms or how they didn’t recognize the signs of potential cancer.

Learning the symptoms, risk factors, and preventive measures for CRC is extremely valuable both for patients and clinicians. We certainly need to continue to share these stories, educate both patients and doctors on CRC, and encourage better doctor-patient communication. Let’s spread the word: Young people can get colon cancer, and their symptoms should not be dismissed!

But as we draw attention to the increased rates of CRC in young people, we shouldn’t ignore the crisis that already exists – the many Americans over 50 who have never been checked for colon cancer and are at greater risk. Currently, only about 63% of Americans above 50 get screened for colon cancer at all, and that number drops to only 25% of uninsured Americans above 50.

Could the resources we will spend screening asymptomatic average-risk 45-year olds be put to better use? With 810 additional colonoscopies from screening people at age 45, at a conservative $1000 each, that’s $810,000 we could theoretically use to provide free screening tests, create an awareness campaign, invest in preventive care in underserved areas, or target uninsured people. 

If we are concerned about saving lives, we should direct resources toward helping uninsured and high-risk patients get the care they need, and educating doctors and patients on symptoms and prevention of CRC.