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  • Writer's pictureDoç.Dr.Mutlu Ünver

What is Colon Cancer? Symptoms and Treatment Methods | Assoc.Prof.Dr.Mutlu Unver Izmir, Turkey

Updated: Mar 3

Colon cancer is an abnormal cell growth that starts in the last part of the digestive system, the large intestine, called the colon. The colon is the first and longest part of the digestive system and is important for the body to digest food.

Colon cancer, which usually affects older adults, can occur at any age. It is usually caused by polyps, which start as small clumps of cells within the colon. Polyps are usually not cancerous, but some can develop into cancer over time.

Colon Anatomy

Polyps are usually asymptomatic, so doctors recommend checking for polyps in the colon with regular screening tests. Detecting and removing polyps can help prevent colon cancer.

If colon cancer develops, there are a range of treatment options. These include surgery, radiation therapy, chemotherapy, targeted therapies and drug treatments such as immunotherapy.

Colon cancer is sometimes referred to as colorectal cancer, which includes cancer of the colon and rectal cancer that starts in the rectum.

What Causes Colon Cancer?

Colorectal cancer is usually caused by polyps that start in the lining of the colon or rectum. These polyps include "adenomatous polyps" (adenomas), "hyperplastic polyps", "inflammatory polyps", "sessile serrated polyps (SSP)" and "conventional serrated adenomas (TSA)".

Adenomatous polyps:

These polyps can sometimes develop into cancer and are therefore considered a precancerous condition. There are three different types: tubular, villous and tubulovillous.

Hyperplastic polyps and inflammatory polyps:

They are not usually precancerous, but more frequent check-ups for colorectal cancer screening may be recommended in people with large hyperplastic polyps.

Sessile serrated polyps (SSP) and traditional serrated adenomas (TSA):

These polyps are usually treated like adenomas because they have a higher risk of cancer.

Factors that increase the likelihood of a polyp developing into cancer include the size of the polyp (greater than 1 cm), the number of polyps (more than 3), and the presence of dysplasia after removal. Dysplasia refers to a condition in which cells appear abnormal but do not develop into cancer.

Types of Cancer in the Colon and Rectum

  • Adenocarcinoma: Most colorectal cancers are of this type. These cancers start in cells that produce mucus to lubricate the inside of the colon and rectum. Doctors usually refer to this type when they talk about colorectal cancer. Some subtypes of adenocarcinoma, such as stony ring and mucinous, may have a worse prognosis than other subtypes.

  • Carcinoid tumours: They start from special hormone-producing cells in the intestine.

  • Gastrointestinal stromal tumours (GISTs): They start from special cells in the colon wall called Cajal's interstitial cells. Some are benign and not cancerous. They can be anywhere in the digestive system, but are rare in the colon.

  • Lymphomas: Cancers of cells of the immune system. They usually start in the lymph nodes, but can also be in the colon, rectum or other organs.

  • Sarcomas: They start in the blood vessels, muscle layers or other connective tissues in the wall of the colon and rectum. Sarcomas of the colon or rectum are rare.

How does colorectal cancer spread?

Colorectal cancer can spread through the wall of the colon or rectum over time when cancer forms in a polyp. The wall of the colon and rectum consists of many layers. Cancer usually starts in the mucosa, the innermost layer, and can grow outwards through other layers.

Once cancer cells are in the wall, they can move into the blood vessels or lymph vessels (small channels that carry waste and fluid). From here they can spread to nearby lymph nodes or to distant parts of the body.

The stage (degree of spread) of colorectal cancer is determined by how deep it grows in the wall and how far it has spread outside the colon or rectum.

Colon Cancer Symptoms

Symptoms of colon cancer can vary from person to person and may not be present at first. However, when they do occur, they can often depend on the size of the cancer and which part of the large intestine it is in.

Symptoms of colon cancer can be the following:

  1. Sudden change in bowel habits, for example more frequent diarrhoea or constipation.

  2. Rectal bleeding or blood in the stool.

  3. Constant cramping, gas or pain in the abdomen.

  4. A feeling that the bowel does not empty completely after a bowel movement.

  5. A constant feeling of weakness or tiredness.

  6. Unexplained weight loss.


Symptoms and Signs of Colon Cancer

Risk Factors for Colorectal Cancer

There is no single established risk factor for the development of colorectal cancer; heredity, environmental and lifestyle factors all play a role.

Research shows that there is a strong association between male gender and increasing risk with advancing age. In men, the risk of developing colorectal cancer is approximately 1.5 times higher than in women.

People aged 65 years and older are almost three times more likely to be diagnosed with colorectal cancer than people aged 50 to 64 years and about 30 times more likely than people aged 25 to 49 years.

On average, the age at diagnosis for colon cancer is 68 years for men and 72 years for women, while the average age for rectal cancer is 63 years for both sexes.

What's New in Colorectal Cancer Research?

Research in the field of colorectal cancer continues continuously. Scientists are investigating the causes and prevention methods of colorectal cancer, more effective ways to detect cancer early, and ways to improve treatment options. Here are some of the latest research:

Reducing the risk of colorectal cancer

Many studies have focused on understanding the causes of colorectal cancer. The hope of these studies leads to the discovery of new prevention methods.

Some studies are investigating whether certain types of diet, nutritional supplements or medicines can reduce the risk of colorectal cancer.

For example, many studies have shown that painkillers such as aspirin can reduce the risk of colorectal cancer, but these drugs can have serious side effects. Researchers are currently trying to understand whether the benefits outweigh the risks for certain groups of people at high risk of colorectal cancer.

Early detection of colorectal cancer

Doctors are looking for more effective ways to detect colorectal cancer early by studying new screening methods, such as blood tests, and improving existing ones. Researchers are trying to determine which test or screening plan will work best.

They are also looking at ways to tell people that known routine screening tests are effective in reducing the number of deaths from this cancer and to encourage them to have these tests.

Testing colorectal cancer cells

When it comes to testing colorectal cancer cells, we know that not all cancers are the same. Researchers are studying genetic or protein changes in cancer cells to identify differences between colorectal cancers.

These studies can help us better understand the mechanisms by which colorectal cancer grows and spreads.

It can also help identify which types of cancer may respond better to certain treatments and which cancers are more likely to relapse after treatment. In this way, more personalised and effective treatment options can be developed.

Molecular tests to help plan treatment

In terms of molecular tests to help plan treatment, in some colorectal cancers, cancer cells may have changes in certain genes or proteins that can affect how they grow and how well they respond to certain cancer drugs.

When colorectal cancer is diagnosed, laboratory tests called biomarkers are sometimes routinely performed on cancer cells to look for specific gene or protein changes. The results of these biomarker tests can influence treatment options by showing whether certain medicines may benefit the person.

Some biomarkers are now routinely tested and others are being studied to determine if they can help improve colorectal cancer treatment.

Tests for cancer cells or DNA in the blood

Tests to look for cancer cells or DNA in the blood, researchers have found that the blood of individuals with colorectal cancer often contains cancer cells as well as fragments of cancer DNA. Taking blood and testing it for cancer (cells or DNA) is sometimes called a liquid biopsy.

Researchers are currently looking at whether liquid biopsy samples could be tested for specific gene or protein changes to help guide treatment, in the same way that tumour samples are tested. This type of test could be useful in cases where taking a blood sample is often much easier than removing a piece of tumour.

Tests for tumour cells or DNA in the blood also have other uses. For example, some new tests look for tumour DNA (ctDNA) circulating in the patient's blood. Such tests can be useful in some situations, such as after surgery, to determine whether there are any cancer cells left. However, there is still debate about the usefulness of these tests.

Researchers are also looking at whether ctDNA testing could be useful in detecting cancer recurrence after treatment has been completed. It is hoped that such a test could detect recurrence earlier than other imaging tests. However, more research is needed in this area.

Colorectal Cancer Treatments

Surgical Treatment in Colorectal Cancer

Surgeons continue to improve the surgeries used to treat colorectal cancers. However, rectal cancer surgery through the anus without cutting the skin is also being studied.

Another research goal is organ preservation, i.e. maintaining the body's normal functions. For example, doctors are investigating the optimal timing of surgery after chemotherapy to shrink the rectal tumour and how to get the best response in each patient.

In some cases, when colorectal cancer recurs, it can spread to the peritoneum (the thin lining of the abdominal cavity and organs inside the abdomen). These cancers are often difficult to treat. Surgeons are working on a procedure called hyperthermic intraperitoneal chemotherapy (HIPEC).

In this procedure, surgery is done to remove most of the cancer in the abdomen and then the abdominal cavity is flushed with heated chemotherapy drugs. This method is thought to be effective by putting the chemotherapy in direct contact with the cancer cells. However, more studies are needed to determine which patients it may help.

Another procedure being studied for colorectal cancer that has spread to the liver and cannot be removed by surgery is hepatic arterial infusion chemotherapy (HAIC). In this procedure, a pump or port is placed in the blood vessel in the liver that supplies the cancer, and the doctor puts chemotherapy drugs into the pump that are released directly into the liver and help kill the cancer cells. HAIC is usually given in combination with systemic chemotherapy and further research is needed to identify the most suitable candidates.

Chemotherapy for colorectal cancer

Chemotherapy is an important component of colorectal cancer treatment and doctors are constantly trying to make this treatment more effective and safer. The following methods are being tested in clinical trials:

  • Testing the effects of new chemotherapy drugs or drugs used in other types of cancer on colorectal cancer.

  • Combining known effective drugs to see if better results can be achieved against colorectal cancer.

  • Combining chemotherapy with other treatment modalities such as radiation therapy, targeted therapies and/or immunotherapy to determine the most effective combination.

  • Identify side effects of chemotherapy and investigate better ways to prevent and treat them.

Targeted therapy in colorectal cancer

Targeted therapy drugs work in a different way to standard chemotherapy drugs. These drugs target specific parts of cancer cells that are different from normal cells. Several targeted therapy drugs are already available to treat advanced colorectal cancer.

Researchers are continuing to work out how best to use these drugs and are looking for new targeted drugs.

Most cases of advanced colorectal cancer that has spread are now being studied to determine whether targeted drugs are treatment options by testing for mutations (changes) in certain genes (or the proteins they code for).

Questions about colorectal cancer

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