What Causes The Colon Cancer? All About Colon Cancer

Colon cancer (colorectal cancer) is a malignant tumor of the colon or rectum. It usually develops from benign intestinal polyps. Chances of recovery exist through an operation. Other methods such as chemotherapy or radiotherapy often support the treatment. Here you can read everything you need to know about the topic: How do you recognize colorectal cancer? What causes the colon cancer? What are it’s risk factors? How is colon cancer treated? What are the chances of recovery?

What is colon cancer?

Colon cancer is an uncontrolled growth of cells in the colon and/or rectum. Most colorectal cancers start as a growth on the inner lining of the colon or rectum, called a polyp. Some types of polyps can turn into cancer over time (usually many years), but not all polyps turn into cancer.

Colorectal tumors can originate in each of the three layers of the colon: mucosa, muscle, and serosa.

This type of cancer is one of the most common in the world and also one of the easiest to diagnose. In addition, cure rates are high if it is detected early and it takes a long time to develop.

Colon cancer can grow in three ways:

• Local growth : In this case the tumor deeply invades all layers of the wall of the digestive tract. First of all, the malignant tumor grows from the mucosa, expands through the serosa and reaches the muscle layers.

• Lymphatic spread : When the tumor penetrates the wall of the intestine, it can reach other organs using the network of lymphatic vessels that allow access to multiple lymph node regions. One of the characteristics of this diffusion is that it is carried out in an orderly manner, first reaching the nearby nodes until reaching the most distant ones.

• Hematogenous spread : Here the tumor uses the bloodstream to spread cancer cells to the liver, lungs, bones and brain, mainly.

What causes the colon cancer?

What causes the colon cancer

The main risk factors related to this disease are the following:

• Age : Most colon cancer cases occur in people between the ages of 65 and 75, and people between the ages of 50 and 65 are considered intermediate risk. Cases that are diagnosed before the age of 35-40 are usually due to the fact that the patient has a genetic predisposition to suffer from this pathology.

• Diet : Colon cancer appears to be associated with high-fat, low- fiber diets. In this sense, numerous investigations are currently being carried out.

• Heredity : In colon cancer, genetics plays an important role, since there is the possibility that it is transmitted hereditarily and predisposes the person to suffer from the disease. However, this can be detected and allow the cancer to be treated early.

• Medical history : It has been shown that those who have a greater predisposition to this disease are people who have or have had polyps (benign growth) of the colon or rectum, ulcerative colitis (inflammatory bowel disease), breast, uterine or ovarian cancer.

• First or second degree relatives who have also had colon cancer.

• Lifestyle : There are certain factors that depend on lifestyle and that predispose to the appearance of colon cancer, such as, for example, obesity, sedentary lifestyle, smoking and excessive alcohol consumption.

In people who have some type of inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease, the risk of developing the disease is increased.

Symptoms of colon cancer

Colon cancer has a long history and its symptoms can vary depending on the location of the tumor in the large intestine. The most frequent complaints appear in the advanced phase of the disease.

However, these symptoms are not exclusive to colon cancer and can occur in other pathologies such as hemorrhoids or certain digestive disorders. Specialists recommend seeing a doctor as soon as they appear to facilitate a proper diagnosis. The most common are:

Changes in bowel rhythm

Patients who have colon cancer may have diarrhea in some cases and constipation in others. The second possibility is common in those people who, prior to the disease, had a normal intestinal rhythm. However, the most frequent is that the patient suffers from periods of constipation combined with periods in which he suffers from diarrhea.

Blood in the stool

The most frequent symptom of this malignant tumor is that the patient presents blood in the stool. The color of the blood can be red or black. The presence of red blood occurs mainly when the person has tumors of the most distal part of the colon and rectum. In the case of black blood, this color appears because the blood is digested and comes from closer sections of the colon, giving rise to black bundles known as melena. If this symptom is not diagnosed early and the patient does not receive the appropriate treatment, it can worsen and lead to the appearance of anemia. In these cases, the patient may suffer from dizziness, tiredness or have the sensation of shortness of breath, among other symptoms.

On the other hand, the patient can detect that their stools change in size and are narrower. This occurs because the intestine is narrowing.

If the tumors are located in the distal part of the colon, the patient may also have a feeling that the bowel movement is not complete and that the evacuation is incomplete.

Abdominal pain or discomfort

Abdominal pain and discomfort are very common. This is because the tumor partially obstructs the intestinal tube and pain and a situation similar to that of colic occurs. In some cases the closure of the tube can be completed and an intestinal obstruction occurs, in these situations it is necessary for the patient to receive urgent surgical medical care.

Unexplained weight loss, loss of appetite, and constant tiredness

Like other diseases related to the stomach, colon cancer, especially when it is in an advanced state, presents these symptoms.

Types of colon cancer

In 90-95% of cases, adenocarcinoma is the most common type of colon cancer . It is located in the mucosa that lines the interior of the colon and rectum. The less frequent types are the following:

Lymphoma : It is the cancer of the defense cells of the intestine and stomach.

Sarcoma : This tumor arises in the muscle layer of the digestive tract.

Carcinoid tumors : Occurs in the hormone-producing cells of the digestive system.


Diagnosis of colon cancer

One of the main advantages of colon cancer is that it is one of the few types that can be diagnosed before the person has symptoms and even before the polyps turn into cancer.

The most reliable screening test is a fecal occult blood test that finds out if there is blood present or not. The patient obtains the sample at home and delivers it to his health center to be analyzed and interpreted by a specialist. This test is recommended, as a general rule, every two years from the age of 50.

If it comes back positive, a colonoscopy will then be done to see the source of the bleeding. This test is used to detect and remove polyps in the same act, in order to prevent the tumor from developing and, where appropriate, becoming malignant.

Once there is suspicion that there may be an injury to the colon, the doctor should take a medical history, perform a physical examination and a digital rectal examination. Several techniques are used to detect colon cancer:

Digital rectal examination : It is a physical examination that the doctor performs by inserting a finger into the anus to detect abnormalities in the lower part of the digestive system, such as blood, abnormal lumps or if the patient feels pain.

Sigmoidoscopy : It is an exploration that consists of introducing a tube through the anus that transmits light and image, and which is called an endoscope. With it you can examine the rectum and the final part of the colon (about 60 cm), and detect some of the polyps that may be there.

Colonoscopy : It is an exploration similar to sigmoidoscopy, but the tube used is longer and allows the entire colon to be covered. It facilitates the taking of tissue samples (biopsy) in areas where a tumor is suspected, and then a study is carried out with a microscope. It is usually performed under sedation and the risk of complications is very low.

Genetic study : If there is a family history or the possibility of hereditary cancer is suspected, it is advisable to carry out a genetic study to detect abnormalities . If there are genetic alterations in the family, colon and rectal examinations should be started at an early age (20 years) and continued periodically.

Double contrast barium enema : It consists of a series of x-rays of the colon and rectum that are taken after the patient has been given an enema with a white calcareous solution containing barium to radiologically show the interior in detail of the colon and rectum.

In recent years, the technique known as liquid biopsy, which may be especially useful in colon cancer, has been intensively investigated. This is a test done on a blood sample to look for cancer cells that are circulating in the blood or for DNA fragments from tumor cells that are circulating in the blood. When its use is standardized, it can be used to detect cancer early, plan treatment or determine its effectiveness, among other things.

Prevention of colon cancer

In all types of cancer there are risk factors that make people who are exposed to them more likely to develop a malignant tumor.

Colorectal cancer research has shown that in some types, tumors originate from polyps (small, benign lumps). Early detection and removal of these polyps can help prevent the onset of the disease.

Another cause of the appearance of colon cancer is the genetic predisposition that the person has. This is due to various alterations in certain genes, therefore, individuals with relatives who have or have had this pathology should go to medical examinations periodically.

There are different syndromes that predispose the malignant tumor to appear. The most common are two:

Familial colonic polyposis

This syndrome only causes 1 percent of colon cancers. Familial colonic polyposis appears during adolescence causing multiple polyps in the rectum and colon. The cause of the appearance is the mutation of the APC gene, which is transmitted from parents to children. This gene can be inherited by both girls and boys.

Hereditary non-polyposis colorectal cancer

This type of cancer accounts for between 3 and 5 percent of rectal and colon tumors. The main difference from the previous syndrome is that patients do not have polyps.

Some unhealthy habits can also influence the onset of the disease, so following the advice below can be very beneficial:

• Do not abuse alcohol or tobacco : Tobacco increases the risk of developing polyps that can be precursors of the disease. Regarding alcohol, its consumption favors the growth of the cells of the mucosa of the colon. This growth gives rise to polyps.

• Control overweight : Obesity and excess calories in the diet should be avoided. Performing physical exercise on a regular basis helps prevent a sedentary life and favors the onset of the disease.

• Food : Specialists advise following a balanced diet and recommend the following guidelines.
• Do not abuse foods rich in fat.
• Reduce the consumption of fats so that they do not exceed 20 percent of the total calories in the diet, preferably consuming monounsaturated fats (olive oil) and polyunsaturated fats (fish oil).
• Reduce the intake of red meat.
• Increase the fish and chicken consumption.
• Incorporate foods rich in fiber into the diet since taking an amount of fiber of at least 25 grams daily, in the form of cereals and wholemeal bread, prevents the appearance of the tumor.
• Increase the intake of fruits and vegetables. Especially cauliflower, Brussels sprouts, broccoli, and legumes.

Treatments for colon cancer

To plan the right treatment, the doctor needs to know what stage of the disease the patient is in. Currently there are two systems that are used with the same frequency.

Scale types

TNM classification

This measures the three aspects that affect cancer. First, the T refers to the size of the primary tumor in the intestine; the N refers to the presence or not in the lymph nodes, while the M refers to the presence of distant metastases. Thus, five stages are distinguished:

• Stage 0 or carcinoma in situ : In this early stage the cancer is found in the most superficial layer of the mucosa, it does not pass through it and it does not affect the lymph nodes.

• Stage I : The cancer has spread to the wall of the rectum or colon without breaking through the muscle layer. At this stage the lymph nodes are also not affected.

• Stage II : The cancer has spread to the deepest layer of the colon, but not to the lymph nodes, which, throughout the body, produce and store cells capable of fighting infection. At this stage the tumor can invade surrounding organs.

• Stage III : The cancer has already spread to the nearby lymph nodes and organs.

• Stage IV : The cancer has reached other organs in the body (mainly it tends to invade the liver, bones and lungs).

Dukes or Astler and Coller classification

This scale uses the letters from A to D assessing how deep it goes into the colon wall :

• Stage A : At this stage are patients who have a lesion only in the mucosa and does not affect the lymph nodes.

• Stage B1 : The cancer is found in part of the wall of the rectum and colon but does not go beyond it, nor does it affect the nodes.

• Stage B2 : The tumor extends throughout the wall of the colon and rectum without invading the lymph nodes.

• Stage C : At this level, the cancer can partially or totally affect the wall and also the lymph nodes.

• Stage D : The cancer affects the entire wall and spreads to more distant organs.

Choice of treatment

After performing the tests that confirm the diagnosis, the specialist will determine the treatment. As in many other types of cancer, colon cancer requires multidisciplinary therapy to offer the patient the highest recovery rates. Specialists will decide on the appropriate treatment based on the patient’s condition, where the tumor is located, and the stage of the cancer.

In addition, the specialist will assess whether the patient suffers from other diseases that may hinder the treatment. All this implies that each patient will receive a treatment that is adapted to their particular circumstances. The most common treatments are chemotherapy and surgery.


Through an operation in the operating room, the part affected by the cancer is removed. Surgery is used at all stages of the disease. In fact, in stage A, it is the recommended treatment since in the rest of the stages the specialists advise applying surgery in combination with other treatments.

In this early stage, specialists may remove a polyp by colonoscopy for examination, and depending on the results, the cancer and a surrounding piece of healthy tissue will be removed, and any nodes in the area will be removed. Another possibility is, after removing part of the colon, to make an opening from the colon to the outside (colostomy), in which case the person will have to use a special bag for external use where the stool will be collected. The colostomy may be transient or permanent.


It consists of applying high-energy radiation to the affected area in order to destroy cancer cells. It only affects the area being treated and can be applied before surgery (to reduce the tumor and be able to remove it more easily) or after surgery (to finish destroying any cancer cells that may have remained).


It is the treatment by which drugs are administered with the aim of destroying cancer cells. It is done by inserting a tube into a vein (catheter) through which the drugs will be injected through a pumping system. It is usually administered after surgery.


Immunotherapy, which consists of stimulating or restoring the body’s own immune defenses, is being of great help in the treatment of various types of cancer. However, in colon cancer it is still very ineffective: only around 5% of patients with colorectal cancer can benefit from immunotherapy.

Targeted treatments

There are specific drugs against some colon or rectal cancers. For example, drugs have been developed for advanced tumors that have mutations in the BRAF gene.


According to data from CDC, approximately 54 percent of colon cancer patients survive more than five years. Although these figures vary depending on the stadium. Thus, the five-year survival in stage A is between 90 and 92 percent; in stage B, between 50 and 75%; in stage C from 25 to 55% and in stage D it is less than 8 percent.

In addition, in recent years, the survival prognosis for stage C patients receiving chemotherapy after surgery has improved considerably.

Side effects

Side effects vary depending on the treatment the patient receives, but most are temporary. The doctor must inform the patient about those that may appear.

• Surgery can cause pain and weakness in the affected area and temporary diarrhea. In addition, if the patient has had a colostomy , skin irritation may occur around the opening made.

• Chemotherapy affects both cancer cells and normal cells and can cause nausea, vomiting, hair loss (although hair always grows back), diarrhea and fatigue.

• Lastly, immunotherapy can cause flu-like symptoms , such as fever, chills, weakness, and nausea.

Control and monitoring of colon cancer

After treatment ends, the risk of the cancer coming back decreases over time. During the first three years it is advisable to carry out quarterly reviews. From the fourth and fifth year these revisions can be spaced out at six months and from the sixth year they can be carried out annually.

Follow-up tests include a careful general physical exam and a more specific rectal exam, a colonoscopy, and blood tests for tumor markers such as carcinoembryonic antigen (CEA). If symptoms or common test results suggest a recurrence of the cancer, chest x-rays, CT scans, and MRI tests may also be done. If you have any new or persistent symptoms, you should see your doctor right away.

Tumor markers

Carcinoembryonic antigen (CEA) is a substance found in the blood of some people with colon cancer. The carcinoembryonic antigen blood test is most often used with other tests to follow patients who have already had cancer and have received treatment. This test can provide early warning of the reappearance of cancer. Carcinoembryonic antigen may be present in the blood of some people who do not have colon cancer. Smoking can also increase the levels of this antigen. Therefore, it cannot be considered as a specific test to detect colon cancer.

How to reduce discomfort after performing diagnostic tests?

Although the tests to diagnose colon cancer are not painful, they can be uncomfortable for the patient and become difficult to tolerate in some cases. From the Spanish Association Against Cancer they give these recommendations to help the patient to pass the tests:

• First of all, they recommend that the patient be accompanied since talking to a close person will make it easier for the patient to be more relaxed.
• Next, they point out that the user should ask the doctor to explain what the tests will consist of to avoid imagining situations.
• Before performing the tests, they advise the patient to perform some relaxation exercise. . In addition, they emphasize that it is important that you focus solely on what is happening at each moment. After finishing the test they also advise that the patient perform some relaxation exercise.
• Finally, if you are nervous or anxious, it is advisable to talk to your doctor to let him know and to prescribe some medication that can improve this situation if he deems it appropriate.

Screening tests

There are different tests for early diagnosis. From the Medical-Surgical Center for Digestive Diseases, the following stand out:

• Fecal occult blood test: it is a good diagnostic test for screening on a large scale, but its sensitivity and specificity is relatively low, since blood in the stool is a symptom of other pathologies, such as hemorrhoids, anal fissures or IBD. If it is positive, it is not conclusive and requires a colonoscopy.

• Septin 9 test: blood test that excludes the possibility of colon cancer with 90% reliability. If it is positive, a colonoscopy is required to identify its location and possible extension.

• Virtual colonoscopy: allows visualization in 3D (the test is performed on a CT scan) of the colon in its entirety without the need for sedation as it is painless. If a polyp or other abnormality is detected, a traditional colonoscopy is required.

• Traditional colonoscopy. that it is the diagnostic test par excellence to prevent and diagnose early colorectal cancer. In addition, it is not only diagnostic because it is therapeutic since if a polyp is identified, it is removed immediately, eliminating the risk of developing cancer . The specialist indicates when a traditional colonoscopy is due.

Depending on each case, one type of test or another would be indicated, but as a general rule, tests should be done:

  1. Healthy older than 50 years : age is an unavoidable risk factor (but it can also appear in people of any age, although it is not usual). It must be repeated every 5 years.
  2. People with a family history : the age of performance decreases to 40 years and the periodicity of repetition continues to be every 5 years.
  3. Patients with intestinal polyposis : when one or more polyps are detected, there may be a genetic predisposition for more to appear. In this case, the colonoscopy depending on the type of polyp removed and is repeated as negative results are given.
  4. Patients with Inflammatory Bowel Disease : colonoscopy is recommended from the age of 40, repeating every 5 years.

Dr. Ashwani Kumar is highly skilled and experienced in treating major and minor general medicine diseases.