Timing of Colorectal Cancer Screening Disputed

Laird Harrison

May 21, 2019

SAN DIEGO — A recommendation to lower the age of colorectal cancer screening to 45 years in adults at average risk, issued by the American Cancer Society (ACS) last year, could result in a waste of healthcare resources, specialists warn.

"I suspect we will see a lot of healthy 45-year-olds — such as kale-eating marathoners — getting tested," said Robert Schoen, MD, from the University of Pittsburgh.

Even though the incidence of the cancer is increasing in people younger than 50 years, the addition of this new 5-year cohort of people would absorb so many resources it, could "crowd out" older people who need it more, he explained.

Instead, Schoen — along with David Lieberman, MD, from Oregon Health Sciences University in Portland — say screening should start at 50 years unless the person is at elevated risk for colorectal cancer. The two specialists presented their viewpoint here at Digestive Disease Week 2019.

The overall incidence of colorectal cancer is increasing around the world, and the number of related deaths is expected to jump from 861,000 in 2018 to 1.1 million by 2030, Schoen reported.

But even with this increase, the incidence in people 45 to 49 years is still only about half that in people 50 to 54 years, said Schoen.

The most effective time to begin screening has been a matter of debate.

The US Preventive Services Task Force (USPSTF) estimated lifetime outcomes in a model cohort of 1000 40-year-old people. On the basis of the increase in colonoscopies required to save lives and the lack of data supporting for a younger starting point, the USPSTF endorsed colorectal screening starting at age 50.

USPSTF Estimated Lifetime Outcomes in a Model Cohort of 1000 40-Year-Old People
Outcome Screening From
45–75 Years, n
Screening From
50–75 Years, n
Lifetime colonoscopies required 4928 4101
Life-years saved 263 248
Deaths prevented 23 22

In contrast, ACS models — which estimated more lives saved than the USPSTF model but more lifetime colonoscopies required — led to the recommendation that screening start at 45 years (CA Cancer J Clin. 2018;68:250-281).

Schoen presented a comparison of the costs and benefits of three scenarios of colonoscopies done at 10-year intervals: screening starting at age 45; screening starting at age 55 for anyone not currently being screened; and screening starting at age 65 for anyone not currently being screened.

Compared with the current practice — screening starting at age 50 with many people not being screened — lowering the age of screening would increase healthcare costs and save only a few lives, results showed. In contrast, testing unscreened older people would not only save more lives, it would save money because so many fewer people would need cancer treatment.

"It's more efficient to use the resources to apply to the unscreened," said Schoen.

Still, screening at an early age might be cost-effective for people at high risk, said Lieberman. "The first step is to understand who is at risk and target interventions at those individuals."

High-risk Patients

It is not clear why colorectal cancer is increasing in people born in 1965 or later, he explained. Sedentary lifestyles, increased use of antibiotics, more industrial food processing, inflammation and atopy, ambient radiation, and other environmental exposures might all contribute.

It is clear that genes play a role, he said. The risk is more than twice as high in people with one first-degree relative diagnosed with colorectal cancer, and more than four times as high with two first-degree relatives. And black people are at higher risk for colorectal cancer than those in the general population of the United States.

Lieberman said primary care physicians and gastroenterologists should start taking family histories at age 40. And careful evaluation of lower gastrointestinal symptoms, such as bleeding, could identify patients younger than 50 years who are at high risk, he pointed out.

Smoking and a high body mass index should be investigated as risk factors, he added, whereas the use of aspirin or nonsteroidal anti-inflammatory drugs should be explored as factors that reduce risk. Premenopausal women are at a decreased risk, he pointed out.

Meanwhile, research is underway to develop genetic tests to identify people at high risk, the two specialists explained.

After the presentation, a member of the audience suggested that if screening is done using methods less expensive than colonoscopy, a lower age could save lives but not increase costs. "I don't think that denying screening to the 45- to 49-year-olds is going to do anything to increase the screening in the old folks," he said.

Schoen and Lieberman have disclosed no relevant financial relationships.

Digestive Disease Week (DDW) 2019: Session 4075. Presented May 20, 2019.

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