Colorectal cancer in the family: Are earlier screening tests worth it?

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In Germany, everyone is offered a colonoscopy to screen for : men from the age of 50, and women from the age of 55. Many experts suggest that people should be offered a colonoscopy at an earlier age if they have close relatives who have (had) . But it's not clear whether this would actually have any advantages.

If a close blood relative has cancer, many people wonder whether they might be at higher risk of developing it themselves. With , the answer depends on their specific situation.

In some families develops in several people at a relatively young age. This happens most commonly in two inherited diseases: “hereditary nonpolyposis ” (HNPCC) and “familial adenomatous polyposis” (FAP). To help detect these diseases, it may be helpful to look for specific genes in family members who haven't had cancer. Families who are affected are offered special health care services. But these diseases are quite rare, and only a few families have them.

It is more common for someone's parents to develop in older age, for instance. This could mean that their children have a higher risk of developing too. In Germany, all men over the age of 50 and women over the age of 55 can have a colonoscopy to screen for . Whether people with a sister, brother or parent with should be entitled to this examination at a younger age is currently being debated.

In order to better assess the possible pros and cons of this idea, researchers at the Institute for Quality and Efficiency in Health Care (IQWiG, Germany) summarized the currently available research results related to the following questions:

1. How high is someone's individual risk of developing if a close blood relative developed this disease?
2. Is it worth doing screening tests sooner in people who are at greater risk?
3. When someone is asked whether their relatives have (had) , how reliable is their answer?

How high is the risk of developing colorectal cancer if a relative has had it?

The answer to the first question was relatively clear. The researchers found a total of seven studies that looked into whether the relatives of people with are also more likely to develop .

These studies suggest that people under the age of 55 are two to four times more likely to develop if they have a close blood relative who has had . This is only true for first-degree relatives, though – in other words, mainly parents, sisters or brothers. But it's not clear whether the increased risk is due to an inherited genetic predisposition, similar lifestyles, or a combination of both.

Is it worth doing screening tests sooner in people who are at greater risk?

The risk of is very low in young people, but it increases with age. So tests are offered to people aged 50 and over in Germany: Statutory health insurers cover the costs of one test for blood in stool (poo) per year in men and women between the ages of 50 and 54. If you are aged 50 or over (men) or 55 or over (women), you can decide to have a colonoscopy instead.

The risk is generally higher in people whose families have a history of , though. So it could be a good idea to offer them colonoscopies earlier. But colonoscopies can have disadvantages, too. The researchers at IQWiG specifically looked for studies on the benefits and harms of in younger people with in their family.

The results here are disappointing. Although there are studies that looked at the benefits and harms of the occult blood test and sigmoidoscopy (endoscopic examination of the lower part of the colon), they focused on older people and didn't take family risk factors into account. The IQWiG researchers found only two studies that looked into colonoscopies in people who had a family-related risk: The results of one of these studies couldn't be used. The other study had various flaws and didn't distinguish between younger and older people who had a family-related risk.

So it's not clear whether there are more overall advantages or disadvantages to doing tests in people under the age of 55 with close relatives who have (had) .

How reliable are the answers to questions about colorectal cancer in relatives?

Some experts suggest that doctors should routinely ask their patients whether any of their close relatives have had . But there's no guarantee that this question will be answered correctly because many people are embarrassed to talk about problems affecting that part of their body. Research has shown that people who have often don't talk about it with their family. This means that people might unintentionally give a wrong answer to the seemingly simple question, “Have any of your close relatives had ?”

So the researchers at IQWiG also tried to find out how reliable the answers to questions like that are. Their findings here were also sobering. Although there are questionnaires for this purpose, it's not clear how reliable the answers are. The IQWiG researchers didn't find any research on written questionnaires.

Worldwide, they only found one U.S. study and one Swedish study on interviews. In both studies, the participants were first asked about illnesses in the family. Then their answers were checked, for instance by looking at their relatives’ medical records. Some of the people who took part in the studies were a lot older than 55. The studies show that many people don't really know whether their family members have had :

  • In one of the studies, 47 out of 100 people who had a relative with didn't know about it, compared to 19 out of 100 people in the other study. The wrong answers led to doctors missing a family-related genetic predisposition (a "false negative” result). These people wouldn't have access to special offers.
  • Wrong answers were also given by people who didn't have a family-related predisposition: 6 out of 100 people in the studies said they had a relative with , although that wasn't the case. They possibly confused with another medical condition. So if their answers weren't checked, these people would be wrongly classified as having a higher risk of (a "false positive" result). If they were offered special health care services, they wouldn't benefit from them.

These studies also show that a seemingly simple question can have negative effects too: Someone who believes that their risk of cancer is higher based on the answer that they've given may already start worrying because of it. And not knowing about an existing risk can be a problem too: If you have a false sense of security, you might not make use of possibly important offers.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Assessment of the benefit of screening in persons under 55 years of age with a family history of colorectal cancer: Final report; Commission S11-01. 2013.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Colorectal cancer screening in persons with a relevant family history - Update: Rapid Report; Commission S17-01. 2018.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on September 13, 2021
Next planned update: 2024

Authors/Publishers:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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