Colorectal cancer, also known as colon cancer, carcinoma of the colon or bowel cancer is cancer that develops in the colon.
The colon is the last section of the large intestine, a tube-like organ that ends at the anus.
According to Centers for Disease Control and Prevention (CDC), Colorectal cancer is the third most common cause of cancer deaths in both men and women worldwide.
In the United States, it is responsible for about 52,580 deaths annually.
Colon cancer most often occurs in people who are 60 years and older, but there are also cases in younger people.
The 5-year relative survival rate for people with colorectal cancer is about 75%, and less than half of those with colorectal cancer will be alive after 10 years.
What Causes Colon Cancer?
The exact cause of colon cancer cancer isn’t known.
However, colorectal cancer is strongly associated with chronic inflammation.
Environmental factors such as: – a high-fat diet and poor hygiene, have been linked to an increased risk of developing colorectal cancer.
Other risk factors include smoking, a family history of the disease, and age.
Signs and Symptoms of Colorectal Cancer.
The signs and symptoms of colorectal cancer can be vague, and diagnosis is often delayed because bowel cancer is often found at an advanced stage.
The colon may be invaded by cancer cells, but the colon itself appears normal.
Because of the lack of a specific tumor marker, it is possible that your doctor may not know you have colorectal cancer if there are no symptoms.
Your symptoms may differ depending on the stage of the disease and the location of the cancer.
Early Symptoms of Colorectal Cancer
- Unexplained change in bowel habits
- Excessive straining during bowel movements that occur more than once a day
- Gas (flatulence) or bloating
- A feeling of fullness in the abdomen after eating
- Gastric stasis (stasis of food in the stomach)
- Bruising or bleeding from rectum or anus (rectal bleeding)
- Bleeding from rectum which occurs during a bowel movement.
Signs of Colorectal Cancer
- Changes in bowel movements: Changes in bowel movements could indicate the presence of carcinoma of the colon, especially during or after a meal.
- Constipation: is a common symptom of colorectal cancer, but it can also occur due to a number of factors including a change in diet, stress, medication, pregnancy, or ageing.
- Blood in the stool: Blood in the stool may occur as a result of bleeding in the colon, diverticulitis, or polyps. It could also reflect cancer.
- Stool that is dark or tarry: Dark or tarry stools may indicate a problem such as blood, cancer, or inflammation.
Symptoms usually occur after 1 to 2 weeks.
Bleeding from the anus generally occurs during a bowel movement and may be accompanied by abdominal pain and cramping.
The color of stool may change from green to yellowish-brown or blackish-purple with blood in it before development of hemorrhage.
It’s important to have an examination at this time every 3 months for 6 months to monitor for blood in your stool
How Colorectal Cancer Develops
There are three stages of colorectal cancer development:
- Precancerous: In this stage, the abnormal cells of the colon are located at the surface of the colon without invading the inside of the organ. It is estimated that up to 5% of the population may have pre-cancerous changes in the colon.
- Adenoma in situ: Adenomas begin as pre-malignant polyps but do not invade the surface of the colon. Adenomas are estimated to be about 2% of the population.
- Invasive: When cancerous cells invade the inside of the colon, this is called intestinal cancer.
Colon cancer starts when normal cells change into cancer cells.
Certain risk factors may increase the chances that cells will begin to grow out of control.
This can include genetic mutations, exposure to environmental factors such as a high-fat diet and poor hygiene, and age.
One risk factor is a diet high in fat, red meat and a diet low in vegetables, fruits and fibre.
People who have a high-fat diet and also have impaired microbiota – the collection of microorganisms that live in the gut, may have a higher risk of colorectal cancer.
Risk factors for colorectal cancer
The cause of colorectal cancer is not known.
It appears that certain dietary, biological and environmental factors may increase your risk of developing colorectal cancer.
Risk factors for colorectal cancer include: –
- Smoking: People who smoke are at a higher risk of colorectal cancer.
- A family history of the disease: People with a close family member who had carcinoma of the colon are at a higher risk of developing the disease themselves.
- Change in the stool color: From black or dark grey to grey or white
- Chronic inflammation of the colon: A long history of ulcerative colitis or Crohn’s disease
- Reduced immune system as a result of aging: People who are older are at a higher risk of developing colorectal cancer than those who are younger.
- Diet high in red meat
Diagnosis of Colorectal Cancer
Your doctor will ask about your symptoms and medical history and perform a physical exam.
Tests may include blood tests, a stool sample for stool analysis, a colonoscopy with biopsy, or magnetic resonance imaging (MRI).
Colonoscopy with biopsy – During a colonoscopy, your doctor will look at your entire colon using a colonoscope.
A colonoscope is a thin, flexible tube used to examine the colon and rectum.
The doctor may also need to perform a biopsy on a sample of your stool.
Biopsy is a procedure where a small piece of tissue is removed for examination under a microscope.
If a tumor is detected during the exam, the doctor may choose to perform a more thorough biopsy.
Treatments for Colorectal Cancer
If you have been diagnosed with colorectal cancer, you should consult a doctor as soon as possible for treatment options.
You may be offered surgery, radiation therapy, or a combination of both.
The type of treatment you receive will depend on the stage of the cancer.
Depending on your specific situation, your doctor may prescribe one or more of the following:
The goal of surgery is to remove the cancer from the colon and/or rectum.
While some surgeries can be done through a small incision (open surgery), others require a larger incision.
There are many different types of colon surgery, and each has benefits and risks.
The type of surgery you have depends on a variety of factors, including the stage of your cancer.
A chemotherapy drug is given through a vein (intravenously), usually every three weeks for four to six months.
Some people have a single treatment, while others may have repeated treatments.
Read Also: Chemotherapy Side Effects and Prevention.
This type of treatment uses high-energy rays to kill off cancer cells.
Radiation therapy is delivered through an outside skin shield or by a machine that is inserted into a patient’s body.
The treatment is usually given once a week for as long as 12 weeks.
The most common radiation therapy used to treat cancer is called “external beam” or “external-beam radiotherapy.”
This type of treatment uses very high-energy rays that can penetrate the skin and through the air, reaching deep into the body.
Stem cell transplant
Stem cell transplant is a form of cancer treatment in which doctors remove stem cells from a donor and inject them into the colon or rectum of the person with colorectal cancer.
Stem cells are cells that can develop into many different types of cells in the body.
These cells can help the body fight cancer by making new blood cells, immune cells, and cells that destroy cancer cells.
A stem cell transplant may be an option for some people with advanced colorectal cancer.
Stem cell transplants from donors do not work for everyone.
It is important to talk with your doctor about the risks and benefits of a stem cell transplant.
Prognosis of Colorectal Cancer
Unfortunately, the outlook for people with advanced colorectal cancer is generally poor.
If the cancer is located in the rectum, the 6-month survival rate is only 6%, and less than 3% of people live for more than 5 years after diagnosis.
However, there are things you can do to improve your survival rate.
For example, if you have colorectal cancer, try to maintain a healthy weight, eat a diet high in fibre and vegetables, and drink less soda pop and alcohol.
Colorectal cancer is the third most common cause of cancer in both men and women worldwide.
Death rates have been declining steadily over the past two decades and are now at an all-time low.
Bowel cancer is strongly associated with chronic inflammation.
Certain risk factors, such as a high-fat diet, may increase the chances of developing the disease.
Early signs and symptoms of colorectal cancer may include constipation, blood in the stool, and an excessive straining during bowel movements.
If you have symptoms of colon cancer, talk to your doctor. Early diagnosis and treatment can lead to a better prognosis, and even cure.
- American Cancer Society guideline for colorectal cancer screening. (2020). cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/acs-recommendations.html
- Colorectal cancer risk factors.(2020). cancer.org/cancer/colon-rectal-cancer/causes-risks-prevention/risk-factors.html
- Survival rates for colorectal cancer. (2021). cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/survival-rates.html
- Centers for Disease Control and Prevention. Colorectal Cancer Statistics (n.d). cdc.gov/cancer/colorectal/statistics/index.htm