cancer written on a newspaper

How to prevent colon and rectal cancer

Colon cancer usually goes unnoticed for a long time. Symptoms appear when the tumor has reached a certain size. It can then interfere with the passage of food debris. As a result, bowel movements change (constipation, diarrhea), and there is often blood in the stool.

Like any cancer, the tumor weakens the entire body. Therefore, nonspecific complaints, such as poor performanceunwanted weight loss, and possibly mild fever, may also occur.

If the tumor has already spread to other organs at an advanced stage (metastasis), additional symptoms may appear.

But be careful: the mentioned symptoms are not a clear sign of colon cancer, they can also have other causes. You should always consult your doctor.

This is especially true when relatively young people experience possible symptoms of colon cancer, as it is extremely rare in them.

Colon Cancer: Symptoms

Changes in bowel movements

Many patients alternately suffer from constipation and diarrhea because the tumor contracts the intestine: feces initially accumulate in front of the tumor.

It is then liquefied by bacterial decomposition and excreted as sometimes foul-smelling diarrhea. This alternation of constipation and diarrhea is also called paradoxical diarrhea and is a classic warning sign of colorectal cancer.

Colorectal cancer (colorectal carcinoma) refers to a malignant tumor of the colon or rectum that usually arises from benign intestinal polyps. So far, the only cure for colorectal cancer is surgery. Other methods, such as chemotherapy or radiation therapy, often support treatment.

If the unwanted stool is also excreted when gasses disappear, it may also be an indication of colon cancer. It occurs when the muscular tension of the anal sphincter is reduced.

The reason for this may be deep colon cancer, which cuts through the muscle and therefore interferes with its function.

In people over 40, any changes in stool habits that last three weeks should be checked with a doctor.

Blood in the stool

A malignant tumor is not very stable, which is why it often bleeds. In colorectal cancer, this blood is excreted along with feces. Blood mixtures are found in the stool in most patients with colorectal cancer.

This mixture of blood are sometimes visible to the naked eye.

The color indicates the location of the tumor: If colon cancer is found in the rectum area, blood in the stool appears red (fresh blood). In other cases, the stool is black due to older (darker) blood.

Dark stools indicate bleeding in the upper digestive tract (stomachduodenum).

Many patients with colorectal cancer excrete so little blood that they are not noticeable in the stool. These  “invisible” blood mixtures are also known as occult blood. It can be demonstrated with certain tests ( for example, a blood culture test ).

Despite its frequency, blood in the stool is not a specific sign of colorectal cancer. There may also be other causes. Most of the blood residue in the stool is due to hemorrhoids.

The blood is usually bright red in color and is stored in the stool. Blood from bowel cancer, on the other hand, mixes mainly with feces due to bowel movements.

In addition to hemorrhoids, sources of bleeding in the esophagusstomach, or duodenum are also possible causes of bleeding in the stool, such as a stomach ulcer).

General symptoms of colorectal cancer

Colon cancer can also impair a person’s general condition. For example, those affected feel unusually tired and weak and are not as efficient as usual. Also, fever can be a sign of colon cancer.

In addition, it may happen that you begin to suffer from anemia. Since iron is necessary for the formation of the red blood pigment (hemoglobin), anemia arises as a result of an iron deficiency.

It manifests with symptoms such as paleness, poor performance, fatigue, and, in severe cases, shortness of breath.

Another sign of colorectal cancer in advanced stages is the weight loss is not desired. Doctors speak of tumor cachexia: due to cancer, the body breaks down a large amount of fat and muscle mass. The patients seem increasingly emaciated.

two kids with colon cancer

More signs of colorectal cancer

If colon cancer has spread to other parts of the body (metastasized), additional complaints may occur. It often forms daughter tumors in the liver (liver metastases).

This can cause pain in the upper right abdomen, jaundice, or increased liver values in the blood. Pulmonary metastases are not uncommon in colon cancer.

Colon cancer can also continue to grow in the intestine and can damage the intestinal wall or surrounding tissue.

A large tumor, for example, can narrow the intestine so that food scraps can no longer pass. This creates a bowel obstruction (ileus), a serious complication of colon cancer.

In some cases, patients report severe bowel sounds and bloating. Of course, both can also occur in healthy people. However, when such symptoms accumulate, they are sometimes signs of colorectal cancer.

With the additional growth of the tumor, it can break through the intestinal wall and peritonitis. If cancer cells in the abdominal cavity spread to the peritoneum, these are known as peritoneal carcinomatosis.

Rectal cancer

Rectal cancer usually develops from cells of the mucous glands in the wall of the rectum. In terms of tissue, there is talk of a so-called adenocarcinoma.

Rarely, rectal cancer develops from other types of cells. If, for example, the supporting tissue cells degenerate into cancer cells, sarcoma develops.

In contrast, a neuroendocrine tumor arises from so-called neuroendocrine cells. These come from the nervous system and release hormones and other messenger substances.

Rectal cancer usually surgically removed. Depending on the stage of the tumor, patients also receive radiation and/or chemotherapy.

Colon cancer: causes and risk factors

Colon cancer usually arises from benign growths of the intestinal lining. In many people, these so-called intestinal polyps remain harmless. In others, on the other hand, they develop into colorectal cancer.

The polyps of the colon generally arise from cells of the mucous glands in the intestinal wall. This makes them a so-called adenoma.

Colorectal cancer, which develops from these benign adenomas, is one of the adenocarcinomas (carcinoma = cancerous tumor). Colon polyps and cancer tumors resulting from other cell types develop less frequently.

The development of normal intestinal mucosa, the formation of polyps, and the development of colon cancer are slow: it takes years.

It is triggered by various risk factors. Among other things, certain nutritional and lifestyle habits and hereditary factors are among the possible causes of colorectal cancer.

Diet and lifestyle

A diet low in fiber, high in fat, and high in meat (especially lots of red meat and processed sausages) increases the risk of colon cancer. These foods pass through the intestines more slowly than plant-based fiber-rich foods.

Lack of exercise and being overweight also promote the development of colon cancer. Also, alcohol and nicotine increase the risk of colorectal cancer (and other cancers).

man smoking

Genetic factors

In some cases, colon cancer runs in families. It can be seen that first-degree relatives (parents, children, siblings) of patients with colorectal cancer develop this type of cancer more frequently than other people.

There are genetic predispositions that do not directly increase the risk of colorectal cancer but make those affected more sensitive to risk factors for colorectal cancer (such as foods rich in meat).

The combination of inheritance and lifestyle is the trigger for the development of colon cancer.

On the other hand, there are genetic changes (mutations) that directly promote the formation of a malignant tumor in the intestine. Some inherited diseases are known to increase the risk of colon cancer.

Two examples:

  • HNPCC (hereditary non-polyposis colon cancer syndrome or Lynch syndrome): This is the most common form of hereditary colorectal cancer. Due to mutations, various repair systems for genetic material are defective. This significantly increases the risk of colon cancer and other cancers (such as cancer of the uterus, ovaries, and stomach).
  • FAP (Familial Adenomatous Polyposis): In this rare disease, innumerable polyps form throughout the intestine. Colon cancer is very likely to develop from them over the years. For this reason, those affected should have regular checkups for colon cancer from childhood. Preventive intestinal sections are often surgically removed to prevent colon cancer in FAP.

Other risk factors for colorectal cancer

Age also has a major impact: the older you are, the higher your risk of colon cancer. 90 percent of all colon carcinomas occur after age 50.

Genetically rarer colon cancer, however, often occurs at a young age. For example, people who develop colon cancer at the age of 30 can generally find typical genetic changes.

Colon cancer risk also increases if someone has an inflammatory bowel disease. People with ulcerative colitis are particularly affected: their colon is chronically inflamed.

The greater the inflammation and the longer the duration of the disease, the greater the risk of colon cancer.

Colon cancer risk may also increase in Crohn’s disease. This is especially true if chronic inflammation affects the large intestine (but is generally limited to the last section of the small intestine).

People with type-2 diabetes have elevated blood insulin levels in the early stages of the disease. According to doctors, they are responsible for the fact that the risk of colon cancer increases approximately three times.

Insulin generally promotes the growth and multiplication of cells, including cancer cells .

Protective factors of colon cancer

In addition to the aforementioned risk factors for colorectal cancer, there are also influencing factors that protect against cancer. This includes regular physical activity and a diet high in fiber and low in meat.

Exercise and fiber stimulate bowel movements. Food waste is transported faster through the intestine. This means that toxins in the stool can act on the intestinal lining, reducing the risk of colon cancer.

Colon cancer: exams and diagnosis

If you suspect you have colorectal cancer, you should first contact your family doctor. If confirmed by a colonoscopy, you will be referred to a gastroenterology specialist.

The doctor will first talk to you in detail to collect your medical history. It also collects information that will help you better assess the likelihood of colon cancer.

Possible questions from the doctor in the anamnesis interview are:

  • Has your digestion changed (for example, constipation or diarrhea)?
  • Have you noticed traces of blood in your stool?
  • Does anyone in your family already have colon cancer?
  • Does anyone in your family suffer or have other types of cancer such as breastovarian, or cervical cancer?
  • Have you inadvertently lost weight?
  • Do you smoke and drink alcohol? How often do you eat meat?

Physical exam

The doctor will then physically examine you. Among other things, he will listen to your stomach with the stethoscope and feel it with his hands. With colon cancer, the tactile exam can sometimes be painful.

A particularly important test for suspected colon cancer is the so-called digital rectal exam (DRE). It is not uncommon for colon cancer to develop in this section.

Stool blood test

A stool sample is often used to check for blood in the stool that is not visible to the naked eye (hidden blood).

Immunological stool test (i-FOBT)

For some time now, doctors have been using the so-called Immune Stool Test (i-FOBT), which is very sensitive to blood in the stool.

You can distinguish between human and animal blood (when you eat raw meat) in your stool. This is done using antibodies that only bind to human blood.

However, this test says nothing about the source of human blood in the stool. For example, it could also be positive for nosebleedsbleeding gums, or hemorrhoid bleeds.

Conversely, not all intestinal tumors bleed, or at least not continuously. Even if the test is negative, cancer tumors may still be present in the intestine (false-negative result).

Therefore, colonoscopy is always the safest alternative.

the room of a hospital

occult blood test

The blood culture test used previously has been largely superseded by the immunological stool test. The blood culture test also begins with animal blood and some vegetables.

Patients who, for example, had eaten raw meat before taking a sample received a false-positive result. False negatives are possible if the patient has consumed too much vitamin C or if the cancerous tumor in the intestine is (just) not bleeding.

Whether it’s a stool immunoassay or a blood culture test: if colon cancer is suspected, a colonoscopy is also done.


Colonoscopy is the most significant test if you suspect you may have colon cancer. The intestine is examined with a tubular instrument (endoscope) equipped with a small camera and a light source. The inside of the intestine can be illuminated and viewed on a monitor.

As part of the colonoscopy, the doctor may also remove intestinal polyps with a loop. It is also possible to take tissue samples (bioscopy) from suspicious areas of the intestinal mucosa.

Tissue samples are examined histologically in the laboratory. In this way, colorectal cancer can be reliably identified or excluded.

The doctor gives the patient a laxative to prepare for the exam. Only when the bowel is emptied can it be well examined by colonoscopy.

Alternatives to colonoscopy

If normal colonoscopy cannot be performed for any reason, the doctor may switch to virtual colonoscopy or rectoscope/sigmoidoscopy.

In the case of virtual colonoscopy, a computed tomography (CT) is performed. From their images, a computer can calculate a three-dimensional image of the intestine and display it graphically.

In order for the intestinal wall to be evaluated safely, the patient must first empty their intestine completely with laxatives (as with a normal colonoscopy).

A disadvantage of virtual colonoscopy is that it does not provide as accurate a result as normal colonoscopy. Also, polyps cannot be removed or samples of tissue taken during the exam. Therefore, colonoscopy or surgery may still be necessary.

The sigmoidoscope is the reflection of the rectum with an endoscope. In sigmoidoscopy, the section of the rectum (S-shaped bowel loop) in front of the rectum is also examined with an endoscope.

Unlike normal colonoscopy, the entire colon is not examined. The result of the investigation is, therefore, limited.

New research on colorectal cancer

Once the diagnosis of colon cancer has been made, further tests should show how far cancer has progressed (stages of colon cancer):

  • Rectal ultrasound examination (ultrasound): Can be used to determine how far the tumor has spread in the intestinal wall.
  • Ultrasound (ultrasound) of the abdominal cavity: These ultrasounds are fixed in daughter metastases, especially in the liver. Other abdominal organs ( spleenkidneyspancreas ) are also examined.
  • Computed tomography (CT): Here we also look for metastases from colorectal cancer, for example in the lungs or liver. So-called CT angiography is also useful: Blood vessels can be visualized and evaluated very accurately using contrast media and CT.
  • Magnetic resonance imaging (MRI): Like CT, MRI also allows a very accurate representation of different tissues and organs. Here also metastases can be identified and the exact location and spread of the tumor (important for the operation) can be determined. The advantage of MRI is that, unlike CT, it does not work with X-rays.
  • Chest x-ray: A chest x-ray helps detect child settlements (metastases) in the lungs.

In addition, the doctor regularly measures so-called tumor markers in the blood of patients with colon cancer. Tumor markers are substances that are increasingly formed by tumors and are released into the blood.

In the case of colon cancer, the “carcinoembryonic antigen” (CEA) can increase in the blood. However, it is not suitable for the early detection of colon cancer (healthy colon cells also produce CEA).

The CEA level helps to assess the course of the disease and the success of the therapy.

After surgical removal of the tumor, CEA values ​​fall within the normal range. If there is a relapse, the value increases again. By regularly determining the CEA value, a relapse can be recognized early.

If hereditary colorectal cancer is suspected (HNPCC, PAF, and other rare forms), genetic testing and advice are carried out. The patient’s genetic makeup is examined for characteristic genetic changes (mutations).

If the genetic test actually diagnoses hereditary colorectal cancer, the doctor may also offer genetic counseling and a genetic test to close family members (parents, siblings, children).

This is how you can determine if you also have a genetically increased risk of colon cancer. If so, regular colonoscopy checkups are helpful.

Colorectal Cancer Stages

Two systems are common for the classification of bowel cancer: first, there is the so-called TNM staging. It can be used for almost all tumors and describes the spread of the tumor.

It can be used to classify cancer into certain stages of colorectal cancer according to the UICC (International Union Against Cancer).

TNM staging

TNM is an abbreviation of the following three terms:

  • T for tumor: This parameter indicates the spread of the tumor. It is based on the so-called depth of infiltration (that is, how deep the tumor has penetrated the tissue).
  • N for nodes (lymph nodes): This parameter specifies whether and how many cancer cells are involved in the lymph nodes.
  • M for metastases (daughter tumors): This factor indicates whether and how many metastases are present in more distant parts of the body.

A numerical value is assigned for each of these three categories. The more advanced the disease, the greater the numerical value.

Colon cancer stages according to UICC

The UICC stages of colorectal cancer are based on the TNM classification. Depending on the extent of the tumor, colorectal cancer is assigned to a specific UICC stage in each patient. The patient’s prognosis can also be roughly estimated based on the UICC stage.

A patient with an advanced tumor (T4) according to the TNM classification is still in stage II of the UICC, as long as there are no child settlements in the lymph nodes or other organs (N0, MO). On the other hand, a patient with proven distant metastases (M1) is always in stage IV of the most severe colon cancer.

a support letter against colorectal cancer

Colon cancer: treatment

If colorectal cancer is discovered early, that is, before child settlements form in the body, it is often curable.

The exact therapy for colorectal cancer initially depends on which part of the intestine is affected. There are fundamental differences between the treatment of colon cancer and that of rectal cancer.

The exact therapy plan for colon cancer depends on several factors in individual cases: therefore, it matters where the tumor is, how large it is, and whether it has already spread to other parts of the body (tumor stage).

The patient’s age and general condition also influence therapy planning.


The most important treatment for colon cancer is surgery: the affected part of the intestine is cut with a margin of safety (that is, the surrounding tissue). The surgeon then sews the intestinal ends together.

In colon cancer, it is very rare to have an artificial intestinal leak permanently or temporarily.

Along with the affected section of the intestine, the adjacent lymph nodes are also removed. Both the intestine and the lymph nodes are carefully examined in the laboratory.

In the case of intestinal tissue, one checks to see if the tumor has been completely cut. By removing the lymph nodes, it is checked to see if the cancer cells have already spread.

In the early stages of the disease, surgery is usually sufficient as the only treatment: colon cancer can be cured by completely cutting the tumor. In more advanced stages, attempts are also made to remove the tumor as completely as possible.

Daughter’s tumors, such as liver metastases, can often be removed surgically. However, in individual cases, this largely depends on the location and number of metastases. Also, additional treatments for advanced colon cancer are usually needed.

Chemotherapy for colon cancer

With advanced colon cancer, many patients receive chemotherapy in addition to surgery.

This is because there is a very high risk of a relapse (recurrence) occurring despite the complete removal of the tumor – individual cancer cells have often already been distributed in the body. Therefore, chemotherapy is necessary.

The patient receives special anticancer drugs, called cytostaticsThey inhibit the growth of cancer cells or directly damage them, causing them to perish.

Cytostatics are administered at regular intervals, either as an infusion or in tablet form. The therapy lasts for about half a year.

The cytostatic act on all growing cells. This includes not only cancer cells, but also many healthy cells, for example, in the lining of the digestive tract and hair root cells.

Possible side effects of chemotherapy include nausea, vomiting, diarrhea, and hair loss.

Radiation therapy for colorectal cancer

Radiation therapy is particularly important for colorectal cancer if the tumor is in the rectum (rectal cancer). Conversely, it is not standard for colon cancer (colon carcinoma).

At most, it can be helpful in specifically fighting bone or brain metastases.

Targeted medication

In some cases, advanced colon cancer is also started with targeted therapy: the patient receives medications that target the specific characteristics of the tumor.

Therefore, they are only suitable for patients whose tumor has these characteristics. This can be determined by carefully examining a sample of the tumor in the laboratory.

An example of targeted drugs is the so-called EGFR receptor antibodies (such as cetuximab or panitumumab). In nine out of ten cases of colon cancer, coupling sites (receptors) for epidermal growth factor (EGFR) are found on the surface of tumor cells.

This can be prevented with EGF receptor antibodies: the drugs occupy the EGFR coupling sites. The growth factor can no longer couple: tumor growth slows down.

Other targeted drugs that can be used in certain cases of colorectal cancer are VEGF antibodies (such as bevacizumab): the abbreviation VEGF stands for “vascular endothelial growth factor”.

This substance ensures that new blood vessels are formed (angiogenesis), which supply the tumor with nutrients and oxygen.

Antibodies against VEGF are called angiogenesis inhibitors: they inhibit growth factor VEGF, and therefore the new formation of tumor-promoting blood vessels. The cancer tumor no longer receives enough blood to spread further.

Colon cancer: disease course and prognosis

The course of the disease and the prognosis for colorectal cancer depend crucially on the stage at which the tumor is discovered and treated. Also, the quality of surgical care also plays an important role.

The treatment is closely followed, that serves to detect a possible relapse (relapse) as soon as possible.

Follow-up exams

The treating physician will develop an individual follow-up care plan for each colon cancer patient – the patient must appear at regular intervals for follow-up exams over a five-year period.

These examinations include, for example, a doctor-patient consultation, a physical examination, the determination of the CEA tumor marker in the blood, a colonoscopy (colposcopy), ultrasound examinations of the abdominal cavity, and a CT scan of the abdominal cavity and the chest.

The doctor informs the patient when the examination should be performed.

Recovery possibilities

Whether colon cancer is curable depends crucially on the stage of the disease. If the tumor is discovered and treated early, it is curable. However, the chances of a cure decrease the more advanced the tumor is.

If the peritoneum is spread over a large area (peritoneal carcinosis), the median survival time of patients is even less than for other metastases (for example, in the liver).

Life expectancy

Colon cancer life expectancy has increased in recent years. This is due to the preventive program that was introduced: from a certain age, regular check-ups for colon cancer are planned.

Therefore, colorectal cancer can often be discovered at an early stage. The best therapy options also contribute to increasing the life expectancy of patients with colon cancer.

In general, the life expectancy of colon cancer depends on the stage of the disease. It is usually administered with the so-called five-year survival rate. This is the percentage of patients who are still alive five years after diagnosis. The prerequisite for this is, of course, that the treatment has taken place.

Final stage

Unfortunately, people with colon cancer at the highest stage have a very poor prognosis with a five-year survival rate of only about five percent.

In this situation, healing (healing therapy approach) is generally no longer possible. Patients then receive palliative treatment. The main objective is to alleviate the patient’s symptoms and thus improve their quality of life.

Sometimes chemotherapy is also used to try to prolong survival, but colon cancer patients should be aware that chemotherapy will not cure them.

At this stage, life expectancy is approximately 12 months without treatment and up to 24 months with treatment.

Colon Cancer Screening

Colon cancer is often only recognized when it is advanced. So the chances of a cure are not as good as in the early stages.

So checkups are very important. This is especially true if someone has known risk factors for colorectal cancer, such as being overweight or a family history of cancer.

As part of the legal screening for colon cancer, health insurance companies pay for certain tests at certain intervals for patients age 50 and older. This includes, for example, a stool test for “hidden” blood and a colonoscopy.

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