Colon cancer: causes, treatment, course


Colorectal cancer is one of the most common types of cancer and death in the western industrialized nations. Meanwhile, several risk factors have been identified that increase the likelihood of colorectal cancer (colorectal cancer). In addition to the genetic predisposition, these include nutritional and lifestyle factors.

Warning signal: blood in the stool

In most cases, colon cancer causes no discomfort. Only late, often when the tumor has already formed metastases, it comes to performance degradation, weight loss and stool changes. The most obvious warning sign blood in the stool should therefore always be clarified thoroughly after the age of 55, as it is highly suspicious to be associated with a colorectal carcinoma.

The diagnosis is usually carried out by a gastroenterologist, who examines the stool for hidden blood in addition to a palpation of the rectum. If suspicious findings are detected, a colonoscopy is performed in which a tissue sample (biopsy) is taken from the intestinal tissue.

If a colorectal carcinoma can be detected, the extent of the tumor is first determined. Based on this can then be decided which treatment method is the most appropriate. In any case, the focus is on the operation, which can optionally be followed by Chemotherapy or radiation. The success of therapy depends decisively on the time of the diagnosis: the sooner, the better the chance of recovery.

Frequency & distribution

Every year, around 60,000 new people in Germany develop colon cancer. Colorectal carcinoma is the third most common male form of cancer after prostate and lung cancer, the second most common form of cancer in women and the second most common cause of cancer death. The typical age of onset is after the age of 50, with early-onset forms often being more aggressive.

50% of the colorectal carcinomas are located in the rectum, in the rectal area, the remaining 50% are distributed over the remaining areas of the colon: 30% of the carcinomas are located in the sigmoid colon, 10% each in the transverse colon and in the descending colon and jejunum 5% in the ascending colon or cecum. The frequency of localization thus increases with the distance from the center of the body.


The exact causes of cancers of the colon and rectum are not yet fully understood, but a number of risk factors related to the occurrence of colorectal cancer have been identified. The most important are:

Genetic disorders affecting the intestine such as:

  • familial adenomatous polyposis (FAP)
  • the hereditary non-polypous colon carcinoma syndrome (HNPCC)
  • the Gardener syndrome
  • Family members with colorectal carcinoma

Lifestyle factors like:

  • Smoke
  • alcohol
  • overweight
  • lack of exercise
  • meaty and high-fat, but low-fiber diet

Other diseases that are associated with an increased risk of colorectal cancer include:

  • chronic inflammatory bowel diseases such as ulcerative colitis and Crohn's disease
  • Breast, ovarian, or stomach cancer
  • Diabetes mellitus type 2

Age: over 40 years

Colorectal cancer develops when cells of the intestinal mucosa degenerate and divide uninhibitedly. The above factors may favor this process, especially if several risk factors are present at the same time.

Colon cancer usually does not develop suddenly, but over a long period of time. Most years pass until the tumor becomes noticeable and spreads to other organs. For this reason, early detection examinations are very important, since precursors of the intestinal tumors can be detected and removed relatively easily.

Read also:
Everything worth knowing about the causes and risks of colorectal cancer


Both colon and rectal carcinomas develop in most cases creeping for years without causing discomfort. When symptoms do appear, they are often very nonspecific and are attributed to other, more likely, causes.

Possible complaints that can occur in colon cancer are:

1. Changes in the bowel movement:

  • Constipation and diarrhea in change
  • Blood in the stool or slimy blood deposits
  • frequent bowel movement or frequently changing stool frequency
  • thin, pencil-like chairs
  • unwanted stool discharge, which often occurs in connection with flatulence
  • bad smelling stools

2. Intestinal spasms that occur repeatedly and over a prolonged period


3. Dark to black colouration of the stool


4. general symptoms:

  • Weight loss, fever, night sweats
  • performance penalty
  • Tiredness, paleness, loss of appetite

In half of cases, colorectal carcinomas occur in association with hemorrhoids. For this reason, blood excretions with the stool should always be examined in a colonoscopy even in the presence of hemorrhoidal disease. Only in this way can a colon carcinoma be safely excluded.

Read also:
Questions and answers on the symptoms of colon cancer


If symptoms such as weight loss, changes in bowel movements or blood in the stool, you should always consult a doctor. In a detailed interview (history) asks this risk factors for a colorectal carcinoma and inquires about family members suffering from colorectal cancer.

Thorough investigation

This is followed by a complete physical examination, during which inter alia your abdomen is scanned and scanned and to which a palpation examination of the rectum (digital-rectal examination) belongs. Also, a laboratory diagnostic blood test should be performed at the first doctor contact. Individual altered values ​​(such as anemia) can strengthen the suspected diagnosis of colorectal cancer.

Using a Haemoccult test® (Guaiac test), blood in the stool can be detected, which may be an indication of colorectal carcinoma. The test is usually carried out at home following the doctor's visit: on three consecutive days, a small amount of stool must be spread over a filter paper and then dripped with hydrogen peroxide. If there is blood in the stool, the hydrogen peroxide on the filter paper turns blue. The test may indicate colorectal cancer but may be positive after eating raw meat or bleeding in the esophagus, stomach or hemorrhoids.

Colonoscopy creates certainty

If your doctor considers a colorectal cancer to be likely based on the studies listed above, he or she will recommend colonoscopy or refer you directly to a gastroenterologist for further investigation.

Colonoscopy is the gold standard of colon cancer diagnostics. Using this method, the entire colon can be examined for changes. A colonoscopy can be performed on an outpatient basis in a doctor's office or clinic; inpatient treatment is usually not necessary.

In preparation, it is important that your gut is completely empty. For this reason, you must drink a laxative that is dissolved in water the day before the examination to cleanse the intestines and speed up their emptying. On the day of the examination you must not eat anything and only drink a little clear liquid so that the examiner can see the intestine completely. If you are afraid of the examination, contact your doctor in advance. He will give you a light tranquilizer just before the procedure that will provide fatigue and relaxation.

Journey through the intestine

During the examination, the doctor will introduce you a flexible tube (colonoscope) of rectal into the intestine. At the top of the tube are a small light source and a camera connected to a monitor in the treatment room. This allows the doctor to view the entire colon and, at the same time, to take samples from various suspicious intestinal sections (biopsy) in order to examine them histologically (under the microscope). Furthermore, small outgrowths from the intestinal mucosa (polyps) can be removed directly. Polyps are benign but can develop into colon cancer for many years.

All in all, colonoscopy takes no longer than 25 minutes. Various complications such as bowel wall injury or bleeding are very rare. In many outpatient centers, your doctor will explain the findings to you immediately after the examination.

Further examinations after the diagnosis

If the diagnosis of cancer in the colon or rectum is confirmed during the initial examinations, further examinations must be performed to determine the stage of the disease. The aim is to find out at which points the tumor is located, how deep it penetrates into the intestinal wall and whether it has already formed dislocations (metastases) in other organs. Typical sites of metastasis are liver and lung.

The following examinations can be performed for staging, the classification of the tumor extent:

  • Ultrasound examination of the abdomen or liver to detect liver metastases
  • X-ray examination of the thorax for the detection of lung metastases
  • Ultrasound examination of the intestinal wall to estimate the tumor depth
  • Determination of the tumor marker CEA (carcinoembryonic antigen) from the blood. The value is increased in colon cancer in many cases, but may also be changed in other diseases and thus does not provide evidence of the presence of the disease. However, it can be determined over the course again and again, with a drop in the value speaks for a therapeutic success.

Here you can learn more about:
Questions and answers about early detection and diagnostics


The staging of colorectal carcinoma is based on the TNM classification, which is a widely used method for the systematic classification of malignant tumors.The TNM classification allows an estimation of the prognosis of the respective carcinoma and offers an important element in the selection of the appropriate therapy.

T, N and M stand for:

  • T (= tumor): the extent and behavior of the tumor
  • N (= Nodus): the infestation of regional (near the tumor) lymph nodes
  • M (= metastatic key): the presence of tumor-distant metastases (distant metastases)

The numbers following the letters give information on the size of the tumor as well as on the pattern of involvement of the lymph nodes.

TNM classification of colorectal carcinoma

Tis The tumor is located only on the inner surface of the intestinal wall (<1/3 of the intestinal wall is invaded by the tumor).
T1 The tumor has already penetrated into the middle third of the intestinal wall.
T2 The tumor has penetrated into the last third of the intestinal wall.
T3 The tumor crosses the intestinal wall and has affected the surrounding fatty tissue.
T4 The tumor has passed the intestinal wall and invaded the peritoneum (T4a) or other organs (T4b).
N1 1-3 regional lymph nodes are affected.
N2a 4-6 regional lymph nodes are affected.
N2b > 7 regional lymph nodes are affected.
M1a Distant metastases are found in only one organ (for example the liver).
M1b Distant metastases are found in more than one organ (for example, lung and liver).

UICC classification of tumor stages

The UICC classification summarizes the different manifestations or combination possibilities of the TNM classification and helps with therapeutic decision-making. Depending on how large the tumor is, how many lymph nodes are affected and if there are distant metastases, it can be decided which therapeutic approach should be followed, which therapy methods are used and if a cure is sought (curative approach) or a life extension or An improvement in quality of life should be achieved through therapy (palliative approach).

Stage 0 Tis
Stage I T1-T2 N0 M0
Stage IIA T3 N0 M0
Stage IIB T4a N0 M0
Stage IIC T4b N0 M0
Stage IIIA T1-2 N1 M0
T1 N2a M0
Stage IIIB T3-T4a N1 M0
T2-T3 N2a M0
T1-T2 N2b M0
Stage IIIC T4a N2a M0
T3-T4b N2b M0
T4b N1 M0
Stadium VIA every T every N M1a
Stadium VIB every T every N M1b


Here are some examples:
Questions and answers about the different stages of colon cancer


Individually tailored therapy

The therapy of colorectal carcinoma depends on the stage of the disease as well as on your general condition. In early stages, it is often sufficient to remove the tumor locally, while at later stages surgery and Chemotherapy often need to be used in combination. At the beginning of the treatment, it must always be decided whether a therapy should lead to healing (curative intention) or prolong the survival time only (palliative intention).

Important parameters that are included in the therapeutic decision are:

  • the growth rate (aggressiveness) of the tumor
  • how far the tumor has spread in the surrounding tissue
  • whether metastases were found
  • where the tumor is located (colon or rectal carcinoma)

1. Therapy of rectal cancer

The following table provides an overview of the different forms of rectal cancer therapy in the respective UICC stages. The exact explanation of the terms can be found below.

UICC stage therapy
0 Removal of the superficially modified intestinal tissue only locally through the anus (transanal local excision)
I depending on the aggressiveness of the tumor: transanal local excision or partial or complete removal of the rectum (rectum resection)
II previous radiation and chemo followed by rectal resection, followed by another dose of chemotherapy
III previous radiation and chemo followed by rectal resection, followed by another dose of chemotherapy
Via preliminary radiotherapy and chemotherapy followed by rectal resection and removal of each metastasis, followed by another dose of chemotherapy
VIb Palliative chemotherapy with transanal local excision to facilitate bowel movements


The treatment of rectal cancer may include the following sub-steps:

  • Neoadjuvant chemotherapy (chemotherapy before surgery for tumor reduction)
  • surgery
  • adjuvant chemoradiotherapy (combined chemo- and radiotherapy after surgery)

Not every therapeutic regimen includes all of these sub-steps. The therapy is chosen very individually in most cases and depends on the above mentioned tumor characteristics as well as on your general condition.

Sometimes helpful: Pre-operative treatment

Neoadjuvant chemotherapy is usually performed in UICC stages II and III. During therapy, the tumor significantly reduces in many cases, which can reduce the likelihood of tumor recurrence by as much as 50% upon completion of treatment. Typical chemotherapeutic agents used to treat colon carcinoma include:

  • Fluorouracil (5-FU)
  • oxaliplatin
  • folinic acid
  • capecitabine

Except for capecitabine, which can also be taken as a tablet, the drugs must be given via the vein and thus administered in the hospital.Classic side effects include hair loss, nausea, vomiting, diarrhea, and blood count changes that can occur with any of these medicines.

The whole cancer has to get out

Following neoadjuvant chemotherapy, surgery is performed. The surgery is the main therapeutic agent for the treatment of colorectal cancer. While in the early stages of the disease only the tumor tissue is removed (transanal local excision in the UICC stages 0 and I), in later stages complete intestinal sections (intestinal resection) with surrounding lymph nodes, lymph channels and blood vessels have to be removed.

The goal is always to recognize altered tissue and completely remove it by removing part of the colon. In the same surgical procedure, the open bowel ends can then be sutured together, so that the intestine again represents a continuous continuum (so-called end-to-end anastomosis).

Preservation of continence depending on the location of the tumor

In rectal cancer, it is important to maintain the function of the sphincter, which is close to the intestinal exit and is responsible for continence. Now and then it happens that the tumor is too close to the sphincter, or that it is even affected. Then a distance is mandatory. Since a chair control without a sphincter is not possible, an artificial intestinal outlet (anus praeter) must be permanently placed. The healthy part of the intestine, which is located in front of the operated site, is displaced outwards through the abdominal skin and sealed with a replaceable bag.

An artificial bowel outlet may also be temporarily applied for better wound healing. After the surgical area has been healed, the intestine is then returned to the abdomen in a second operation, thus making the original intestinal passage possible again.

Here you can get more information:
Questions and answers about the artificial bowel issue

Following the tumor surgery, radiation, chemotherapy or a combination of both treatment methods (chemoradiotherapy) can be performed. Without neoadjuvant chemoradiation, UICC stage II can be followed by chemoradiotherapy 4 to 6 weeks after surgery. If neoadjuvant radiochemotherapy has been performed, adjuvant chemotherapy should always be added. All other possible cases have to be decided individually and can not be read from a schema.

2. Therapy of colon carcinoma

Operation always comes first

In contrast to rectal cancer, the colon is usually operated on directly, ie without prior chemotherapy. All tumors that either have no or exclusively operable liver or lung metastases are removed in curative intention. Similar to rectal cancer, the affected intestinal tract is removed and the two open ends joined together in an end-to-end anastomosis to restore the original intestinal passage.

The anus praeter is usually only used temporarily to relieve the freshly operated intestinal segment. A backward displacement of the intestine and a chair control are possible in most cases without any problems. If the tumor can not be removed by surgery (UICC stage IV), a permanent anus praeter can be placed and palliative chemotherapy can be connected.

After the operation

Following surgery, chemotherapy is often used. It should always be done in stage III according to UICC classification, optionally or after individual consideration in stages IIa and IIb. In stages 0 and I chemotherapy is not necessary; The cancer can be defeated by surgery alone.

In Stage IV, on the other hand, the combination of surgery and chemotherapy can no longer be cured. In this case, the treatment is limited to surgery to maintain intestinal transit and palliative chemotherapy, which can prolong life but not complete healing.

More on this topic can be found here:
Worth knowing about the stage-dependent treatment


After completing cancer treatment and discharge from the hospital, follow-up examinations must take place at regular intervals in order to detect tumor recurrence at an early stage. Follow-up appointments should be made at fixed intervals based on disease severity and surgical outcome. As a rule, there are only short intervals between appointments at the beginning of follow-up. Over time, however, these distances will lengthen.

A typical aftercare appointment may include some of the ingredients listed here:

  • detailed medical history
  • physical examination focusing on the operating area
  • regular colonoscopy
  • Ultrasound examinations of the abdomen and especially the liver
  • In the case of CEA-positive preliminary findings, the tumor marker can be used for follow-up
  • X-ray or a CT scan of the lung suspected metastases in the lungs

Read also:
Questions and answers about the topic of aftercare


Most colon cancers develop slowly, but then take an aggressive course. For this reason, early diagnosis and treatment of colorectal carcinoma is very important.The sooner the cancer is detected, the better the prognosis: While early forms can almost always be cured, there is little chance of recovery in metastatic colorectal cancer.

Provision is worthwhile!

Measured by the annually registered number of new colorectal cancer cases, the mortality rate has been steadily decreasing for several years. Reason for this are introduced screening measures, which are entitled to every health insurance from the age of 50 every year. The check-up includes a palpation of the rectum (digital rectal exam) and a test for blood in the stool. Alternatively, colonoscopy (colonoscopy) can be performed every 10 years from the age of 55. You should discuss with your doctor if you want a check-up and what form is right for you.

More information here:
Questions and answers about the course and prognosis


There are a number of factors that you can influence yourself, which can lower the risk of colorectal cancer. These include:

  • a healthy, balanced diet rich in fiber and whole foods and reduced in fat
  • a reduction of meat and an increase in vegetable consumption
  • quitting smoking
  • a reduction of overweight
  • regular physical activity

Other risk factors, such as first-degree relatives with colorectal cancer or inflammatory bowel disease, are unaffected.

Still, you can do something! Look for stool changes such as blood in the stool, changes in bowel habits, performance decline, fatigue, or weight loss. See a doctor if you find something different than usual and take the check-up!

Read also:
How to prevent colon cancer


Author: Lisa Wunsch


S3 Guideline Colorectal Carcinoma, DKG Cancer Society, German Cancer Aid:, last accessed: 10.06.17.

Center for Cancer Registry Data, RKI:, last accessed on 10.06.2017.

J. Siewert: Surgery, Springer Verlag, 2006.

G. Herold: Internal Medicine, Herold Verlag, 2017.


Comment: The most important questions and answers about colon cancer

Colon cancer is today curable in many cases. And even in advanced cases, life expectancy has improved significantly. This is partly due to preventive examinations and well-functioning early detection, but also to improved therapeutic options.

Third most common cancer in Germany

Every year over 60,000 people in Germany receive the diagnosis of colon cancer. It is mostly about the colon, which makes it the third most common place of origin for tumors in the body. A predominantly preferred location are the lower intestine sections (rectum and sigma). According to statistics, more than 6 out of every 100 Germans suffer from colon cancer during their lifetime. Most of them (90%) are older than 50 years. The first diagnosis is on average most frequently made at the age of 65 years.

Many colon cancer cases could be avoided

Our 10 most important tips for colon cancer

Continue reading...

The dangerous thing about colon cancer is that it does not make itself felt for a long time. This also applies to other tumors. But not all are as easy to avoid as colon cancer. The number of people affected could in all likelihood be much lower,

  • if more people would pay attention to a healthier lifestyle and diet. Our immune system is constantly and everywhere in the body with the elimination of cancer cells and those who could be, busy. Therefore, it should be our concern to minimize the risk factors for degeneration of the colon mucosa and to promote the body's own defenses. This works, as most of us are more or less aware, especially about a healthy, u.a. High-fiber diet, nicotine-free, less alcohol and more exercise, good sleep and a mindful, stress-reducing lifestyle.
  • if more people use the recommended colorectal cancer screening more. Fortunately, colon cancer can be avoided by medical intervention. Namely, if it is already removed in the preliminary stage, as a benign intestinal polyp (adenoma) in the context of a colonoscopy.

Very good healing prospects in the early stages - but mostly recognized later

And even if a colon carcinoma has already formed, a complete cure is possible. This is especially true at the beginning of the disease process. In stage I the 5-year survival rate is about 95%, in stage IV only 5%, always dependent on different individual factors.

The sad news is: the median 5-year survival rate is only 40-60%. Why? Because the most common finding at diagnosis is Stage III. The findings in jargon are "T3 N +". This means that the local tumor is already quite large (T3) and there is already a lymph node involvement (N +). This is not a death sentence for the person affected. With a mere operation as in the early stages, it is then no longer done.

The medical procedure in this case regularly provides for chemotherapy following the operation. Sometimes even before (medically: neoadjuvant) to reduce the size of the tumor. Chemotherapy is used to support the surgical procedure for complete tumor removal (rehabilitation). This is considered necessary in more advanced stages to eliminate residual cancer or scattered cancer cells that are not recognizable to the surgeon as such. The use of cancer drugs may be combined with radiation therapy (chemoradiotherapy). If unfavorable chances of recovery are concerned above all with relieving symptoms, this is called palliative chemotherapy.

Decide in peace for the best treatment offer

Of course, if you've got the diagnosis of colon cancer, that's a shock that needs to be digested first. This takes time, as well as the subsequent collection of important information. Incidentally, the health insurance funds support your claim to a second medical opinion by paying them.

In this situation, it is important for you to know: A colon cancer usually grows slowly and is, with a few exceptions, not an emergency. Therefore, do not let yourself be pressured by the upcoming decisions. Especially not in the selection of a suitable hospital. It has been scientifically proven that the healing success increases with the quality and experience of the surgeon.

The largest treatment experience and the highest quality standards are usually found in a certified colon cancer center. The bundled competence is also necessary if your colon cancer has already metastasized. A cure is then difficult, but not excluded in principle. The best therapeutic options should at least be available as an option.

How is it possible without a colon? And with artificial intestinal exit?

Of course, in the surgery Next to the cancer removal is the goal in the foreground to get as much of the intestine and the normal digestive processes. But that does not always succeed. Sometimes more or less the entire colon has to be removed and sometimes an artificial bowel outlet has to be laid. In many cases this is and will be less dramatic after getting used to it than initially feared. Of course, there are also many questions here. Is it possible to live "normally" after removal of the large intestine? Can an artificial bowel issue be reversed?

Answers to these and many more questions about the colorectal cancer, its treatment and follow-up and of course the recommended prevention can be found on this portal. We hope to be able to help you with this and look forward to your comments and any further questions.

Author: Dr. Hubertus Glaser