Taking Early Detection Further: Colon Cancer
Screening works: Since its introduction, significantly fewer people have died from colorectal cancer. Nevertheless, half of all eligible individuals do not undergo the screening. Expert Prof. Hermann Brenner discusses inadequate invitation letters, the limitations of AI in colonoscopy, and simple strategies for increasing participation rates.
Prof. Brenner, when it comes to colorectal cancer screening, people in Germany aged 50 and older can actually choose between two different options: They can undergo a colonoscopy twice in their lifetime, ten years apart—or take a fecal occult blood test every two years. Does this mean Germany is particularly well-positioned in this regard?
Since the introduction of preventive colonoscopy in 2002, we have indeed achieved a great deal: colorectal cancer mortality in Germany has declined by more than 30 percent, and the incidence rate by just under 30 percent—which is certainly better than in many other countries...
That sounds like a “but” is coming?
Whether a screening program can be effective depends crucially on the participation rate—and there’s still room for improvement in Germany. Based on health insurance billing data, it’s estimated that about 20 percent of those eligible undergo a screening colonoscopy within 10 years, and about 30 percent use the fecal occult blood tests. Combined, that brings us to about 50 percent.
That’s not too bad. But neighboring countries like Denmark and the Netherlands are showing us how it’s done: If you invite eligible individuals to take a stool test every two years, send the test tube along with an easy-to-understand explanation, and—ideally—even announce the entire process in advance via letter, you can achieve participation rates of up to 70 percent. Here, we only receive one “invitation letter” every five years, which, in my opinion, isn’t really worded in an inviting way.
An invitation plus a test kit sounds like a simple solution. Why isn’t this being implemented here? For cost-saving reasons?
Cost isn’t a valid argument, because it must be viewed in relation to the very high treatment costs for cancer that are avoided through screening. On the other hand, early detection definitely pays off. Colorectal cancer screening is one of the most cost-effective measures we have in the healthcare system!
But perhaps the situation here is like so often when it comes to prevention: today’s slightly higher costs are offset by massive savings that only materialize after a delay. We need to move beyond a perspective focused primarily on the current budget or the current legislative term.
Colorectal cancer screening is one of the most cost-effective measures we have in healthcare.
Prof. Dr. Hermann Brenner
There is often discussion that cancer screening should move away from a “blanket approach” toward a program more tailored to individual risks. What is the situation with colorectal cancer?
Yes, that could also make colorectal cancer screening more efficient in the future. For example, the intervals between two fecal occult blood tests could be made longer or shorter depending on the exact result of the stool test, since this result is a good indicator of colorectal cancer risk in the coming years.
Incidentally, according to the guidelines, first-degree relatives of colorectal cancer patients should undergo a colonoscopy by the age of 40 to 45 at the latest. This raises the question, however, of how well people are informed about this and whether primary care physicians even ask about family history. In any case, there is no billing code for providing this information.
During a colonoscopy, there is always a certain risk that small precancerous lesions—so-called adenomas or polyps—will be overlooked. Are there any techniques on the horizon that can assist doctors in evaluating the colon?
Yes, AI is also increasingly being used during colonoscopy to aid in the detection of polyps. However, much of this is still in the development stage. For example, there is also a certain risk that this could lead to overdiagnosis due to the detection of too many small precancerous lesions that pose only a very low risk. In the future, AI will certainly provide crucial support to pathologists in the histological evaluation of resected polyps and tumor tissue.
We also read a lot about new molecular markers, new tests—even blood tests?
So far, new markers have not yielded significantly better results than the immunological fecal occult blood test (iFOBT). Tests already approved and routinely used in the U.S. that combine the iFOBT with specific DNA or RNA markers in stool show no significant improvement in results, yet the cost per test is about 30 times higher. That is anything but cost-effective! Intensive research is also currently underway on blood tests, but they are still significantly inferior to stool tests at this time.
If you had the power to decide: Which area of development do you think should be given the highest priority because it promises the greatest health benefits for people?
Quite clearly: An efficient screening program in which people receive test tubes for fecal occult blood tests directly from their health insurance provider at home, along with information about the alternative option of colonoscopy. Anyone who opts for a colonoscopy won’t need another test for the next ten years. The option to choose between the two screening methods should be maintained, as this allows us to reach more people overall.
As head of the Department of Epidemiology and Aging Research at the DKFZ, Prof. Dr. Hermann Brenner has spent decades evaluating colorectal cancer screening programs. Since his retirement in 2025, he has served as scientific coordinator of the Cancer Prevention Graduate School of the DKFZ and German Cancer Aid.
Interview: Dr. Sibylle Kohlstädt, Press Spokesperson for the DKFZ