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Colorectal cancer: Overview

Created: ; Last Update: April 5, 2018; Next update: 2021.


Colorectal (bowel) cancer is one of the more common forms of cancer in many countries, including Germany. The name "colorectal cancer" is used to describe bowel cancer that starts in the colon (the large intestine) or the rectum. Cancer of the small intestine is very rare.

Colorectal cancer almost always develops from growths called colorectal polyps that form in the lining of the colon. But by no means do all polyps become cancerous – and if a polyp does become cancerous, it takes many years. One way to prevent colorectal cancer is to have a colonoscopy, which also allows doctors to remove polyps.

Having colorectal cancer can be a life-changing experience. What happens after the diagnosis has been made will depend on various factors, including the stage of the cancer. In early-stage colorectal cancer, the tumor just needs to be surgically removed. In advanced stages, additional treatments may be considered, such as chemotherapy or radiation therapy.

In Germany, high-quality medical care is available for people who have cancer. There are also a number of sources of support, for instance to help cope with the disease emotionally and make it easier to go back to work.


Colorectal cancer often doesn't cause any symptoms at first, so it may remain unnoticed for a while. Sometimes it leads to abdominal pain or a change in bowel movements. By this we mean that the frequency of bowel movements or the usual time of day when you go to the toilet may change, or you might start having constipation or diarrhea. Black or very dark stool may be caused by traces of blood and could also be a sign of colorectal cancer. When colorectal cancer has reached a more advanced stage it can also cause weight loss, nausea and loss of appetite.

But it's important to keep in mind that these symptoms could have any number of other causes. Most of the time there is no serious underlying condition or the symptoms are signs of another, non-cancerous health problem, such as enlarged hemorrhoids or inflammatory bowel disease.


Colorectal cancer arises when cells in the mucous lining of the intestine change (mutate) and then multiply out of control. This growth pushes the cells into surrounding tissue. There are a number of possible causes of these kinds of changes, including pollution or radiation. But they often simply occur by chance. The body’s immune system can normally deal with these malignant cells, but not always. As we grow older, mistakes in cell division increase while the body’s ability to repair these problems decreases. This is why most types of cancer are more common in older people.

In most people who have colorectal cancer, no clear cause can be found. About 5 out of 100 people with colorectal cancer have a genetic form: either familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC, or Lynch syndrome). These two types are more likely to start at a younger age.

Risk factors

There are factors that can slightly increase the risk of developing colorectal cancer. For instance, people who have chronic inflammatory bowel conditions such as Crohn's disease and ulcerative colitis are at greater risk of getting colorectal cancer. Having parents or siblings who developed colorectal cancer doubles the risks listed in the following table. Other factors like diet, diabetes or being overweight have less of an influence.


The risk of colorectal cancer increases with age: Many people who have colorectal cancer are already over 75 years old. Colorectal cancer is very rare in anyone under the age of 50.

It is sometimes considered to be a disease that typically affects men, but that's not true. Although it is indeed more common in men and often starts at an earlier age, women can also develop colorectal cancer.

The following tables show the probabilities of getting colorectal cancer within the next ten years for people of certain ages. These are averages for specific age groups – but different people also have different personal risk factors.

Table: Risk of bowel cancer in men

Age Number of men who will develop colorectal cancer in the next ten years Number of men who will die of colorectal cancer in the next ten years
50 7 out of 1,000 2 out of 1,000
55 13 out of 1,000 4 out of 1,000
60 18 out of 1,000 6 out of 1,000
65 24 out of 1,000 9 out of 1,000

Table: Risk of colorectal cancer in women

Age Number of women who will develop colorectal cancer in the next ten years Number of women who will die of colorectal cancer in the next ten years
50 5 out of 1,000 1 out of 1,000
55 8 out of 1000 2 out of 1,000
60 10 out of 1,000 3 out of 1,000
65 14 out of 1,000 5 out of 1,000

About 32 out of 1,000 men and 26 out of 1,000 women will eventually die of colorectal cancer.


Colorectal cancer develops gradually over a period of many years. Non-cancerous (benign) growths in the mucous lining are the first stage. These growths aren't yet considered to be dangerous. The medical term for them is polyps or adenomas. Some of them look like small wart-like mounds, while others look somewhat like small mushrooms with stems. Colorectal polyps become increasingly common with age. About one third of all adults over the age of 55 have at least one colorectal polyp.

The great majority of these polyps stay small and don't pose any threat. But some continue growing for several years, and some turn malignant (cancerous).

If a polyp turns malignant, there's a risk that the cancerous cells will grow deeper into the wall of the colon. If the tumor continues to grow, it could spread to other organs, such as the liver. When cancer cells spread like this it's called “metastasis.” There are a number of different factors that will influence how the cancer develops over time. If a smaller, localized, early-stage tumor can be removed, the prognosis (outlook) is good: Most people then recover fully after surgery. If the cancer is more advanced, the chances of complete recovery drop. And if metastatic tumors are discovered, full recovery can usually no longer be expected. In that case, the aim of treatment is to slow down tumor growth and help maintain a good quality of life for as long as possible.

It usually takes about five years to know if the cancer is completely gone. The chances of the cancer coming back depend on various factors, including its stage at the time it was treated.


If your doctor thinks you may have colorectal cancer, a colonoscopy is usually done first. This involves using a specialized endoscope (called a colonoscope) to examine the entire large intestine. Tissue samples can be taken and tested for cancer in a laboratory. It usually takes a few days to get the results back. Sometimes it's not possible to examine the entire intestine using an endoscope – for instance, because the passage is too narrow or blocked by scar tissue. In that case, computed tomography (CT) or magnetic resonance imaging (MRI) can be used to examine the bowel.

In order to see whether the cancer has already spread beyond the bowel, an abdominal ultrasound, an x-ray of the torso and a digital rectal examination (feeling the rectum with a finger) are carried out. If your doctor thinks there are signs of metastasis, other tests can be performed to gather more information, such as a CT of the abdomen or chest.

Before treatment starts, blood is taken to test for a specific tumor marker called carcinoembryonal antigen (CEA). This test can be helpful for assessing the chances that treatment will be successful.

If colorectal cancer comes back again following treatment, positron emission tomography (PET) is also used sometimes.


It is possible to detect colorectal cancer at an early stage, and it can even be prevented effectively. For this reason, German statutory health insurers offer members the opportunity to have colorectal cancer screening. The screening is intended for people who don't have any signs of colorectal cancer and aren't at any special risk of getting it. People who have chronic inflammatory bowel diseases are advised to be screened more often. Ulcerative colitis and Crohn's disease are two examples of such diseases.

The statutory health insurers offer two types of colorectal cancer screening:

  • Fecal occult blood test (FOBT) to discover any traces of blood not visible to the naked eye. In Germany, statutory health insurers cover the costs of this test for people from the age of 50: once a year for men and women between the ages of 50 and 54, and then every two years for people aged 55 and over – unless you decide to have a colonoscopy.
  • Colonoscopy for an endoscopic examination of the large intestine. Any polyps that are discovered can be removed during this procedure. Women with statutory health insurance in Germany are entitled to two free colonoscopies: the first from the age of 55, and the second 10 years later. Men are already entitled to a first colonoscopy from the age of 50, and then the second colonoscopy can also follow 10 years later. The options may be different in other health care systems. If polyps are removed during the first colonoscopy, people are usually advised to come back for another colonoscopy sooner.

In Germany, colorectal cancer screening is intended for people between the ages of 50 and 75 without any particular risk factors for colorectal cancer.

There is a third possible screening examination known as a sigmoidoscopy, where only the lower part of the large intestine is examined. But this examination isn't covered by statutory health insurers in Germany when performed for screening purposes.

Generally speaking, people who have symptoms always have access to free diagnostic tests – regardless of whether they have already been screened for the condition, or when they were last screened.


There are a lot of recommendations concerning how to prevent this disease: These include getting enough exercise, eating a lot of fruits, vegetables and fiber, and avoiding too much red meat and alcohol. But none of these measures have ever been scientifically proven to actually prevent colorectal cancer.

Some studies have already looked into whether the long-term use of drugs like acetylsalicylic acid (the drug in “Aspirin”) can prevent colorectal cancer. But using these drugs in this way is not recommended because it isn't clear whether they actually prevent colorectal cancer, and they can cause side effects.


Surgery is performed to remove as much of the cancer as possible. In early stages, further treatment may not be needed. If the cancer is at a more advanced stage, further treatments like radiation therapy or chemotherapy are options.

Everyday life

Even successful treatment of colorectal cancer is often followed by a period of uncertainty because you have to wait a few years to be sure that the cancer is gone for good.

Advanced colorectal cancer can have a major impact on your quality of life. Many people feel weak for quite some time after treatment and may not be as active as they used to be. It takes time to come to terms with the diagnosis, the treatment and its effects.

If cancer is found in the rectum and surgery is needed, it isn't always possible to keep the sphincter muscle. Then an artificial opening of the bowel (stoma) is needed. It can take some time to get used to not being able to fully control bowel movements and deal with having an artificial opening. Many people feel embarrassed about it at first, and may start avoiding others.

Although having colorectal cancer can really turn your life upside down, over time many people find a way to cope and still manage to live a fulfilled life.

Further information

When people are ill or need medical advice, they usually go to their family doctor first. Read about how to find the right doctor, how to prepare for the appointment and what to remember.

There are many sources of support for people with colorectal cancer, including self-help groups and information centers. But different regional facilities are often organized quite differently. Our list can help you find and make use of local services in Germany.


  • Deutsche Gesellschaft für Gastroenterologie, Verdauungs- und Stoffwechselkrankheiten (DGVS). S3-Leitlinie Kolorektales Karzinom. AWMF-Registernr.: 021-007OL. November 2017. (Leitlinienprogramm Onkologie). [PubMed: 29141269]
  • Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Invitation and decision aid for bowel cancer screening: Final report; Commission P15-01. (IQWiG reports; Volume 451).
  • 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. 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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