Colorectal cancer

At a glance

  • Colorectal cancer typically develops from benign growths called polyps in the lining of the colon (the large intestine) or the rectum.
  • Most of these polyps remain small and harmless, but some can develop into cancer over the years.
  • In Germany, people between the ages of 50 and 75 are offered stool tests and colonoscopies to screen for this cancer.
  • Colonoscopies allow polyps to be found and removed right away.
  • People sometimes find this procedure unpleasant, though, and it also has risks.


Photo of an elderly man talking with his son

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

Colorectal cancer usually develops from growths called colorectal that form in the lining of the colon or . But by no means do all turn into cancer – and if they do, it takes many years. One way to prevent is to have a colonoscopy, which also allows doctors to remove .

Having can really turn your life upside down. What happens after the has been made will depend on various factors, including the stage of the cancer. In early-stage , surgery to remove the tumor is enough. In more advanced stages, other treatments such as chemotherapy or radiation therapy may be needed too.

There are many sources of support for people with , 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 (belly) pain or a change in bowel movements. For instance, 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 (hard poo) or diarrhea (runny poo), or both at different times. Black or very dark stool may be caused by blood and could also be a sign of . When has reached a more advanced stage it can also cause unintended 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. It is usually something harmless or the symptoms may be caused by another, non-cancerous health problem, such as enlarged hemorrhoids or an of the bowel.


Colorectal cancer arises when cells in the mucous lining of the intestine change (mutate) and then grow out of control and into surrounding tissue. These changes in the cells usually happen by chance. The body’s can normally deal with 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 , no clear cause can be found. But about 5 out of 100 people with have a genetic form: either or hereditary nonpolyposis (HNPCC, or Lynch syndrome). These two types are more likely to start at a younger age.

Risk factors

Certain things increase the risk of somewhat. These include:

Other factors like diet, diabetes or being overweight have less of an influence.


The risk of increases with age: Many people who have 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 .

The following tables show the likelihood of getting 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 in men
Age Number of men who will develop in the next ten years Number of men who will die of 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 in women
Age Number of women who will develop in the next ten years Number of women who will die of 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 develops gradually over a period of many years. Non-cancerous (benign) growths in the mucous lining are the first stage. Known as , these growths aren't yet considered to be dangerous. They are very common in older people: About one third of all adults over the age of 55 have at least one colorectal polyp.

Some look like warts or small hills. Others look like mushrooms with a stalk. The great majority of stay small and don't pose any threat. But some continue growing for several years, and some turn into cancer (malignant).

If a polyp becomes malignant, it grows deeper into the wall of the bowel and turns into cancer. As the cancer progresses, cancer cells may spread to other organs such as the liver and form tumors (metastases) there.

A number of different factors can influence how the cancer develops over time. If a smaller, localized, early-stage tumor can be removed, the (outlook) is good: Most people then recover fully after surgery. If the cancer is already at a more advanced stage, the chances of complete recovery are lower. If metastatic tumors are discovered, full recovery can usually no longer be expected. In that case, the aim of treatment is to slow down the progression of the disease 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 , a colonoscopy is usually done first. This involves using a special tube with a small camera at the end () to examine your 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 large intestine using an – for instance, because the passage is too narrow or blocked by scar tissue. In that case, (CT) or (MRI) can be used to examine the bowel.

In order to see whether the cancer has already spread beyond the bowel, the doctor does an ultrasound scan of the abdomen, an x-ray of the torso and a digital rectal examination (feeling the with a finger). 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 comes back again following treatment, positron emission tomography (PET) is also used sometimes.


It is possible to detect at an early stage, and it can even be prevented effectively. For this reason, German statutory health insurers offer their members the opportunity to have .

In Germany, screening is intended for people between the ages of 50 and 75 without any particular risk factors for . People who have a higher risk – for example, because they have a chronic inflammatory bowel disease – are advised to be screened more often.

The statutory health insurers offer two types of :

  • Fecal occult blood test (FOBT): A sample of stool (poop) is examined for traces of blood that can't be seen by just looking at it. 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 they decide to have a colonoscopy.
  • Colonoscopy: The entire large intestine is checked for cancer and . Any that are discovered can be removed immediately. Women with statutory health insurance in Germany are entitled to two free colonoscopies: the first from the age of 55, and the second ten years later. Men are already entitled to the first colonoscopy from the age of 50, and a second one ten years later as well. These options may be different in other health care systems. If several, larger or abnormal were removed during the first colonoscopy, people are usually advised to repeat this examination more often.

There is a third possible 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 purposes.

As a general rule, 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 about how to prevent : These include getting enough exercise, eating a lot of fruits, vegetables and fiber, and avoiding too much alcohol and red or processed meat. But none of these measures have ever been clearly proven to actually prevent .

Some studies have looked into whether the long-term use of drugs like acetylsalicylic acid (the drug in medications like “Aspirin”) can prevent . This is not currently recommended because it's not clear whether they really do prevent cancer, and they can have side effects.


Surgery is performed with the aim of removing all of the cancer, if possible. In early stages, further treatment may not be needed. If the cancer is at a more advanced stage, treatments like chemotherapy or radiation therapy are options.

Everyday life

Even successful treatment of 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.

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 , the treatment and its effects.

If cancer is found in the 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, especially at first, and may start avoiding others.

Although having can really turn your life upside down, over time it's often possible to find a way to cope with it and still manage to live a fulfilled life.

Further information

You will find more information about and the various treatment options in Germany on the website of the German Cancer Information Service (Krebsinformationsdienst) and in the patient information accompanying the German clinical practice guidelines. They also provide information about places you can turn to for help, such as support groups and information centers.

You can also read our information about how to find the right doctor, how to prepare for the appointment and what to remember.

Adelstein BA, Macaskill P, Chan SF et al. Most bowel cancer symptoms do not indicate colorectal cancer and polyps: a systematic review. BMC Gastroenterol 2011; 11: 65.

Deutsche Gesellschaft für Gastroenterologie, Verdauungs- und Stoffwechselkrankheiten (DGVS). S3-Leitlinie Kolorektales Karzinom. AWMF-Registernr.: 021-007OL. 2019.

Händel MN, Rohde JF, Jacobsen R et al. Processed meat intake and incidence of colorectal cancer: a systematic review and meta-analysis of prospective observational studies. Eur J Clin Nutr 2020; 74(8): 1132-1148.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Invitation and decision aid for bowel cancer screening: Final report; Commission P15-01. 2016.

Jellema P, van der Windt DA, Bruinvels DJ et al. Value of symptoms and additional diagnostic tests for colorectal cancer in primary care: systematic review and meta-analysis. BMJ 2010; 340: c1269.

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. 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.

Comment on this page

What would you like to share with us?

We welcome any feedback and ideas - either via our form or by We will review, but not publish, your ratings and comments. Your information will of course be treated confidentially. Fields marked with an asterisk (*) are required fields.

Please note that we do not provide individual advice on matters of health. You can read about where to find help and support in Germany in our information “How can I find self-help groups and information centers?

Über diese Seite

Updated on September 13, 2021

Next planned update: 2024


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

How we keep you informed

Follow us on Twitter or subscribe to our newsletter or newsfeed. You can find all of our films online on YouTube.