Colon Cancer: Symptoms, Causes, Risks, Diagnosis, Treatment, Outlook and Prevention

Woman with Colon Cancer


There are many types of cancer, and one of the most common is colon cancer, which affects the large intestine. This type of cancer is the most common form of gastrointestinal cancer. Rectal cancer, on the other hand, affects the rectum and together with the colon cancer, they form colorectal cancers.

The cases of colon cancer usually start with the formation of noncancerous or benign clumps of cells dubbed as adenomatous polyps. These benign cancer cells may become malignant, leading to colon cancers.

The World Cancer Research reports that colon cancer is the third most common cancer in the world, with about 1.4 million new cases in 2012. An estimated 95 percent of colorectal cancers are considered adenocarcinomas. The other types are adenosquamous and mucinous carcinomas.

In the United States, the National Cancer Institute reports that the number of new cases of colorectal cancer was 40.1 per 100,000 people each year, which includes both men and women. An estimated 14.8 per 100,000 deaths are recorded for men and women every year. In 2014, about 1,317,247 people were living with colon and rectal cancer in the United States.


A person with colon cancer may report signs and symptoms including:

  • Blood in the stool
  • Recurrent diarrhea and constipation
  • Change in bowel habits like diarrhea, constipation or changes in the consistency of the stools
  • Abdominal pain and cramps
  • Feeling that the bowel does not empty completely
  • Fatigue
  • Weakness
  • Unexplained weight loss

In some cases, colon cancer is also detected during screening procedures. The most common clinical presentations include the presence of rectal bleeding, iron deficiency anemia and intestinal perforation or obstruction.


The exact cause of colon cancer is still unclear, but there are some studies that suggest cancer develops when healthy cells in the large intestine become abnormal and mutate. These cells replicate or multiply faster than they should. When this happens, it leads to cell accumulation which in turn, becomes polyps or tumors.

Precancerous Growths

When the abnormal or mutated cells accumulate in the lining of the large intestine, they form polyps, and these growths can eventually become cancerous. Normally, these polyps are removed through surgery. However, untreated polyps may lead to malignancy.

Inherited Gene Mutations

Inherited gene mutations predispose a person to cancer. When a person has an inherited gene that predisposes him or her to colon cancer, she has an increased risk of developing the illness. The most common forms of inherited colon cancer are Hereditary nonpolyposis colorectal cancer (HNPCC) and Familial adenomatous polyposis (FAP).

These gene mutations do not guarantee that you’ll develop colorectal cancer, but they can increase your chances.


Many studies have shown a link between an increased risk of colon cancer and a typical Western diet. This type of diet is low in fiber and high in fat. The studies have shown that when people move from one location that the diet is low in fat and high in fiber to a place where the Western diet is common, the risk of colon cancer in these individuals increase dramatically.

4Risk Factors

Though everyone may develop colon cancer, some people are predisposed to developing it than others. The exact reason is still unclear, but some factors may increase the likelihood of developing colon cancer including:


The disease is most common in people who are 50 years old and above. The chance of getting colon cancer increases with each decade. However, colon cancer can still occur in younger people, but this rarely happens.


Scientists do not know why but men are at a greater risk of developing colon cancer than women. However, both men and women are equally at risk of developing the disease.


Colon cancer may occur more in African-Americans than other races.

History of Polyps  

 A person who has a history of polyps but was non-cancerous has a greater risk of developing colon cancer. An adenoma makes colorectal cancer more likely.

Family History

 A person whose family members or relatives have colon cancer, they’re more likely to develop colon cancer. The risk is higher if the relatives are immediate family members like parents, siblings or child.


A low-fiber and high-fat diet may increase the risk of developing cancer. There is ongoing research in this area, and some studies suggest that those who are fond of eating red meat and processed meat have increased risk too.


 Having a sedentary lifestyle with lack of exercise and physical activity may increase the risk of colon cancer. Smoking and excessive consumption of alcohol may increase the risk too.


People who are obese or overweight have an increased risk of colon cancer. In fact, those who are obese with colon cancer have an increased risk of dying from the disease than people with normal weight.

Radiation Therapy for Cancer

 Those individuals who underwent radiation therapy for another type of cancer may have an increased risk of developing colon cancer.


People with diabetes have an increased risk of developing colon cancer.


Early diagnosis of colorectal cancer is important as it gives you the best chance of a good prognosis. Early detection of polyps and other abnormal cell growth in the large intestine may lead to the early initiation of treatment. This prevents metastasis or the spread of cancerous cells to the other parts of the body.

The doctor will perform physical examination and interview for medical and family history. Other diagnostic tests include:

Blood Tests

The doctor may run some blood tests to determine the cause of the symptoms and to rule out other conditions. However, there is no single blood test to detect colon cancer, but some test like liver function tests and complete blood count may help detect other conditions that may be causing your symptoms.


This procedure uses a scope to examine the inside of the colon. A long and flexible tube with a video camera is inserted into your colon. The doctor can see the recording in real time via a monitor. This test will examine the entire colon and rectum. If any suspicious areas are detected, the doctor can get tissue samples to perform a biopsy.

Imaging Tests

CT scan and MRI can detect any abnormal growth inside the large intestine. These procedures provide 3D images or cross-sectional images of the colon to determine any tumor or polyps.

The Stages Of Colon Cancer

The American Cancer Society provides the criteria for the staging of colon cancer. The stages depend on the extent of where the tumor is located. The more tissues or organs affected, the more severe the stage is.

Stage 0 – Colon cancer is staged at 0 when it is still in the early stages. This is called carcinoma in situ, which means that cancer has not grown beyond the inner layer of the colon or rectum.

Stage 1 – This stage of cancer means that the tumor has grown through the mucosa of the colon but has not spread to nearby lymph nodes.

Stage 2a – The stage 2a of colon cancer means that the tumor or cancer cells have grown into the outermost layer of the colon but has not affected them.

Stage 2b – cancer has grown through the wall of the colon but has not affected the nearby organs.

Stage 2c – This stage of colon cancer involved the growth of cancer through the colon wall and attached itself to nearby tissues or org.ans

Stage 3a – This stage of cancer has grown through the mucosa, submucosa, and muscles. About one to three lymph nodes are affected but not the nodes themselves.

Stage 3b – cancer has affected the outermost layers of the colon and through the visceral peritoneum but has not affected nearby organs. About one to three lymph nodes have been affected but have not spread to distant sites.

Stage 3c – In this stage of cancer, the tumor has grown through the wall of the colon, which includes the visceral peritoneum. It has affected around 4 to 6 nearby lymph nodes.

Stage 4a – cancer has spread to one distant organ such as the lung or liver.

Stage 4b – cancer has spread to one distant organ – liver or lung or a distant group of lymph nodes. It has also affected parts of the lining of the abdominal cavity.


The treatment of colon cancer relies on the stage or severity of the illness. For people who have the early stages of colon cancer, surgery is the main treatment.


Surgery is the removal of the tumor and some surrounding healthy tissue. For the early stages of the disease, this is the most common treatment. Called surgical resection, the procedure removes part of the healthy colon or rectum, including nearby lymph nodes to prevent further spread of the cancer cells.

Aside from surgical resection, other surgical procedures for colon cancer include laparoscopic surgery, colostomy for rectal cancer and radiofrequency ablation.

Radiation Therapy

Radiation therapy is the use of high-energy x-rays to kill cancer cells, and it’s used for colon cancer because the tumor will come back near where it has first started.


Chemotherapy is a treatment procedure wherein drugs are used to kill cancer cells. This procedure help curbs the cancer cells’ ability to grow and divide. A doctor that specializes in treating cancer, a medical oncologist, is the one who will administer these drugs.

7 Outlook

Each person has a different response to treatment. Some may respond to surgery alone. However, the survival rate for people diagnosed with colon cancer depends on the severity and extent of cancer at the time of diagnosis.

The outlook of colon cancer depends on the stage of cancer, the number of lymph nodes involved, if the cancer cells have spread to other organs, and the quality of the surgery done.


You can take steps to reduce your risk of colon cancer including:

  • Get screened for colon cancer
  • Eat a nutritional diet which is low in fat and high in fiber such as fruits and vegetables
  • Avoid eating processed meat and red meat
  • Drink alcohol in moderation
  • Avoid smoking
  • Maintain a healthy weight
  • Prevent diabetes by maintaining a healthy weight and reducing the consumption of added sugars