Bowel cancer

Bowel cancer is one of the most common cancer diseases in Germany. The term bowel cancer applies to two types of cancer: colon cancer and rectal cancer. This article offers an overview of the risk factors, screening, and diagnosis and treatment options.

At a glance

  • Bowel cancer is also known as colorectal carcinoma.
  • The term applies to two types of cancer: colon cancer and rectal cancer.
  • In early stages of the disease, bowel cancer seldom causes symptoms.
  • In Germany, there is a statutory program for bowel cancer screening.
  • Some people have a genetic or familial risk of bowel cancer.
  • Bowel cancer is treated, when possible, by an operation, and if necessary, chemotherapy, radiation, or targeted drugs.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Bowel cancer: doctor standing at a hospital bed bending down to a man sitting up in the bed. Both men are looking at each other.

What is bowel cancer?

Bowel cancer, also known as colorectal carcinoma, is a disease in which malignant tumors grow in the colon or rectum. The rarer diseases small intestine cancer and anal cancer are not considered types of bowel cancer.

Ein Kreisdiagramm zeigt die Verteilung von Darmtumoren: 1/3 der Darmtumoren liegen im Enddarm, 2/3 der Darmtumoren liegen im Dickdarm.

Das Diagramm zeigt die Verteilung von Darmtumoren. Etwa zwei Drittel der Darmtumoren liegen im Dickdarm und ein Drittel im Enddarm.

In most patients, bowel cancer develops when mucosal cells in the intestine turn into cancer cells. At first, benign tumors grow, which over a longer period of several years develop into cancer. In the pre-cancerous stage, mushroom-shaped, raised growths known as intestinal polyps often grow. Although most intestinal polyps are harmless, some can degenerate. 

Important: Even less common types of cancers such as gastrointestinal stromal tumors (GIST), MALT-lymphoma or neuroendocrine tumors can develop in the intestines. However, medical specialists do not categorize these cancer types as bowel cancer.

What are the symptoms of bowel cancer?

Most people with bowel cancer do not have symptoms for a long time. The following warning signs can indicate a tumor in the colon or rectum:

  • digestive problems such as frequent, loud intestinal noises and bloating, the latter with sudden bowel movement, or frequent nausea or the feeling of being full despite having eaten little
  • change in stool habits, such as frequent stool urgency, increased constipation, repeated alternation between constipation and diarrhea
  • pain during bowel movement or abdominal pain in the form of cramps, even after emptying the bowels
  • abnormal stool, such as blood in the stool that colors it red or black, mucous in the stool, particularly foul smelling or pencil-thin stool  

Some of these symptoms can also indicate the presence of other, benign bowel diseases. If symptoms last more than a few weeks, and particularly, if typical risk factors for bowel cancer are present, a visit to the doctor is recommended. General Practitioners can already narrow down what is causing the symptoms and, if necessary, initiate further diagnostic steps with specialists. 

What can cause bowel cancer?

Bowel cancer, like most cancers, develops due to genetic changes. Normal somatic cells turn into malignant cancerous cells and start to grow uncontrollably.

These genetic changes occur randomly over the course of one’s life, however they can be inherited. Carriers of these types of gene alterations have an increased risk of bowel cancer.

The risk of bowel cancer also increases if bowel cancer occurs frequently in the family without a known hereditary condition. Close relatives of bowel cancer patients also have a significantly higher risk of bowel cancer. 

For detailed information about hereditary and familial bowel cancer, see the Cancer Information Service of the German Cancer Research Center website (in German). 

What risk factors contribute to possible bowel cancer?

In addition to hereditary and familial risks, there are other risk factors that contribute to bowel cancer: 

Chronic inflammatory bowel diseases also increase the risk of bowel cancer.  

How common is bowel cancer?

In Germany, bowel cancer is one of the commonest types of cancers. It is the third most commonly diagnosed tumor disease in men and the second most in women.  

Important: The risk of bowel cancer increases with age. While women are on average diagnosed at the age of 76, men are on average diagnosed at the age of 72.

What can be done to prevent bowel cancer?

There are two ways to lower the personal risk of disease:

A healthy lifestyle

Avoiding known risk factors lowers the risk of bowel cancer. Medical specialists recommend:

  • not smoking.
  • limiting alcohol consumption.
  • regular physical activity.
  • a healthy body weight.
  • a diet rich in fiber.
  • a diet low in red meat and processed meat products. 

Important: Even people who lead a healthy lifestyle can develop bowel cancer. However, by avoiding risk factors that are in one’s own control, the individual risk of bowel cancer is reduced. 

Removing benign tumors

A colonoscopy is available for the early detection of bowel cancer. It allows doctors to not only detect possible benign tumors early on, but also remove them as a preventative measure.  

What options are available in Germany for the early detection of bowel cancer?

Statutory screening for bowel cancer in Germany starts at age 50. Those with health insurance receive a letter recommending an early detection screening. Participation is voluntary and information about the advantages and disadvantages of screening can be provided at a doctor visit. 

Annual stool test from 50 to 54, colonoscopy from 55 repeated every 10 years, alternatively stool test every two years from 50, colonoscopy after 10 years, alternatively annual stool test from 50 to 54 and stool test every 2 years from 55.

Investigations under German statutory bowel cancer screening program.

There are two reliable procedures for detecting bowel cancer and its pre-stages:

  • A colonoscopy is currently the most reliable method of early detection. It is an early detection method that allows doctors to detect benign tumors early on and remove them.
  • A stool test looks for blood in the stool that is not visible to the eye.

For more detailed information about screening for bowel cancer, for example, in relation to the benefits and drawbacks of the various tests, see the patient brochures published by the Joint Federal Committee (G-BA) for women and men.


More than half of those with bowel cancer are over the age of 70 at the time of diagnosis. Those at risk of hereditary and familial bowel cancer often become ill much earlier, typically before their 50th birthday. Therefore, medical specialists recommend a colonoscopy for those who have close relatives (e.g. parents, siblings, and children) with the disease. The procedure should be performed as early as 10 years before the earliest age of bowel cancer onset in the family. Family members to whom this applies should therefore request more information at their annual check-up.

Those with bowel cancer in the family can also refer to a center for hereditary bowel cancer. More information is available through the German Consortium of Familial Bowel Cancer.

Important: You should see a doctor immediately and not wait for a preventative screening appointment if you have acute symptoms, for example, blood in the stool.

Do you want to know more about screening for bowel cancer and learn about the advantages and disadvantages? Visit the Cancer Information Service of the German Cancer Research Center website for more information (in German).

How is bowel cancer diagnosed?

A colonoscopy is the most important examination used to determine if bowel cancer is present. Doctors use a camera to examine the intestines and determine if the intestinal mucosa has undergone noticeable changes. At the same time, they take tissue samples from suspicious areas (biopsy).

The biopsy samples are then examined at a lab. What happens if the analysis indicates that the samples are cancerous tissues? Additional tests are necessary.

These additional tests provide information about how advanced the disease is. They help doctors plan for the best treatment possible and can include:

  • determining if endogenous substances that point to cancer are present in the blood (tumor markers)
  • an ultrasound of the abdomen
  • X-rays of the chest
  • computed tomography (CT)
  • positron emission tomography (PET)

Patients with rectal cancer must have additional tests performed, including:  

  • palpation examination
  • rectoscopy (rigid proctoscopy)
  • magnetic resonance imaging (MRI) of the pelvis
  • pressure test of the sphincter muscle
  • ultrasound examination of the rectum from inside

How is bowel cancer treated?

If treatment of a patient with bowel cancer is being considered, the type of treatment depends on the patient’s general health, the individual tumor, and the results from the preliminary examinations.

Treatment for bowel cancer without metastases 

If the tumor has not yet spread to other organs, an operation is the most important treatment measure for colon cancer and rectal cancer.

During the operation, the surgeon removes the tumor to the greatest extent possible. The associated section of the intestine and surrounding lymph nodes are also removed. If all of the tumor tissue can be removed, there is a chance of recovery.

Patients with colon cancer typically undergo chemotherapy after the operation, especially if the lymph nodes were affected. This supplementary treatment is intended to lower the probability of the cancer returning and also kills any tumor cells still in the body.

Patients with colon cancer often receive radiation before the operation, typically combined with chemotherapy. Then another round of chemotherapy is administered. These measures are intended to lower the probability of the cancer returning, shrink the size of the tumor prior to operation, and make it possible for the sphincter muscle to be preserved if the tumor is deeply seated. Pre-treatment can also make the tumor disappear completely. Currently, there is discussion as to if an operation is still necessary in such cases. What if an operation was the first stage of treatment? Then chemotherapy or radiation therapy follows.

Treatment for metastasized bowel cancer

If metastases have already formed, operation is an option only for select patients: if complete removal of all tumor clusters and a full recovery is possible or if the tumor in the intestine is causing serious symptoms.

If an operation is not possible, the patient receives chemotherapy often in combination with targeted drugs. Patients with bone metastases often receive additional radiation to help alleviate symptoms caused by the metastases.

Do you want to learn more about the various treatment options for bowel cancer and possible treatments and side effects? Visit the Cancer Information Service of the German Cancer Research Center’s website for a detailed description of the treatments described above, their effectiveness, and side effects (in German). The website also includes information about what is available to help with distressing symptoms.

The difference between a primary tumor and a metastasis

The video below explains the difference between a primary tumor and a metastasis.

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What happens after the treatment of bowel cancer?

Medical rehabilitation

Cancer treatment can be physically and mentally exhausting. Medical rehabilitation (rehab) after cancer therapy aims to help patients regain their strength. It is also designed to help them cope with the consequences of the disease and its treatment as best as possible.

Rehab focuses on the patient’s personal history with the disease and any existing limitations. Possible measures for those affected by bowel cancer are: 

  • dietary consultation that focuses on the specific needs of bowel cancer patients.
  • consultation provided by an ostomy therapist who can help patients with an artificial stoma.
  • psycho-oncological consultation that can help if worry and anxiety become overwhelming.  


Aftercare for patients with bowel cancer helps prevent a relapse and identify long-term effects from treatment early on. Once treatment has been completed, patients are examined regularly, initially at short intervals, then at longer ones. However, if experiencing symptoms, patients can visit the doctor more frequently.

Follow-up appointments usually include: 

  • a physical exam
  • determining if endogenous substances that point to cancer are present in the blood (tumor markers)
  • an ultrasound of the abdomen
  • colonoscopy 

Patients with colon cancer may receive additional examinations.

What if the cancer cannot be cured?

That is when monitoring and regular care can help to identify distressing symptoms early on and alleviate them. The aim is to maintain the patient’s quality of life for as long as possible.

What is life like with or after bowel cancer?

It is not always easy for patients to return to their daily lives when they have or have had bowel cancer. This is because cancer and the associated treatments can come with long-term effects.

Each situation is different and therefore it is not possible to identify one single solution that helps patients deal with the disease and the possible effects of treatment. In the beginning, bowel cancer affects:

  • diet
  • stool incontinence
  • an artificial stoma

Those affected must relearn how to return to a normal meal schedule in small steps and how to live with a stoma or stool incontinence.

For most people, these situations normalize after a while so that they are able to return to their daily lives. If this is not the case, it is important to speak to a doctor about additional options.  

What are suitable points of contact for information about bowel cancer?

When treating bowel cancer, doctors from different fields work together closely. Hospitals with extensive experience in treating bowel cancer patients can have this confirmed with certification. The German Cancer Society (DKG) regularly checks their compliance with certain professional requirements.

You can find the addresses of the certified centers on the OncoMAP website. 

Do you have further questions about dealing with the condition in everyday life and additional support options? You can find information about this on the website of the Cancer Information Service of the German Cancer Research Center (in German).

For all questions related to bowel cancer, contact the Cancer Information Service at 0800 - 420 30 40 (toll free) or email 

In cooperation with the Cancer Information Service of the German Cancer Research Center (Krebsinformationsdienst des Deutschen Krebsforschungszentrums).

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