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Colorectal cancer: Overview

Created: ; Last Update: January 26, 2017; Next update: 2020.

Introduction

Colorectal (bowel) cancer is one of the more common forms of cancer in many countries, including Germany. Colorectal cancer is cancer of the colon (the large intestine, also called the large bowel) and 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 not all polyps will become cancerous – and if they do, the process can take 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 largely depend on the stage of the cancer. For early-stage colorectal cancer, the tumor just needs to be surgically removed. At 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 the transition back to the workplace easier.

Symptoms

Colorectal cancer often doesn't cause any symptoms at first, so it may remain unnoticed for a while. But sometimes it may lead 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.

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.

Causes

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. Often they 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). 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 with colorectal cancer doubles the risks listed in the following table. Other factors like diet, diabetes or being overweight have less of an influence.

Prevalence

The risk of colorectal cancer also 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 this is wrong. 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

AgeNumber of men who will develop colorectal cancer in the next ten yearsNumber of men who will die of colorectal cancer in the next ten years
507 out of 10002 out of 1000
5513 out of 10004 out of 1000
6018 out of 10006 out of 1000
6524 out of 10009 out of 1000

Table: Risk of colorectal cancer in women

AgeNumber of women who will develop colorectal cancer in the next ten yearsNumber of women who will die of colorectal cancer in the next ten years
505 out of 10001 out of 1000
558 out of 10002 out of 1000
6010 out of 10003 out of 1000
6514 out of 10005 out of 1000

Looking at their entire lifetime, about 32 out of 1,000 men and 26 out of 1,000 women will die of colorectal cancer.

Outlook

Colorectal cancer develops gradually over a period of many years. Non-cancerous (benign) growths in the mucous lining of the colon (large intestine) 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 reach 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.

Diagnosis

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 – the passage may be constricted or there may be tissue blocking the way. 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 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 estimating the chances that treatment will be successful.

Positron emission tomography (PET) is also used sometimes if colorectal cancer comes back again following treatment.

Screening

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 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. Statutory health insurers cover the costs of this test for men and women over the age of 50.
  • Colonoscopy for endoscopic examination of the large intestine. Existing polyps can be removed during this procedure. People with statutory health insurance in Germany are entitled to two free colonoscopies: the first after the age of 55, and the second 10 years later.The options may be different in other health care systems. If polyps are removed during the first colonoscopy, repeating the screening examination sooner is usually recommended.

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

A third possibility for screening is having a sigmoidoscopy, where only a specific portion of the large intestine is examined. But this test 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 (or when) they have already been screened for the condition.

Prevention

Colonoscopy allows doctors to remove polyps before they become cancerous. But even a colonoscopy can't guarantee that you won't get colorectal cancer.

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 this advice has ever been scientifically proven to actually prevent colorectal cancer.

Some studies have already tested whether the long-term use of drugs like acetylsalicylic acid (the drug in “Aspirin”) can prevent bowel 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.

Treatment

Surgery is performed to remove as much of the cancer as possible. In some cases, no further treatment is needed for early-stage tumors. If the cancer is at a more advanced stage, 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 also 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

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

Sources

  • Deutsche Gesellschaft für Gastroenterologie, Verdauungs- und Stoffwechselkrankheiten (DGVS). Kolorektales Karzinom. S3-Leitlinie. June 2013 (AWMF-Leitlinien; Volume 021-007OL).
  • Robert Koch-Institut (ed) und die Gesellschaft der epidemiologischen Krebsregister in Deutschland e.V. (ed). Krebs in Deutschland 2005/2006. Häufigkeiten und Trends. Berlin: 2010.
  • 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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