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Colon cancer occurs when cells in your large intestine grow out of control. Treatment can vary by the stage and type of colon cancer.

What is colon cancer?

Colon (colorectal) cancer starts in your colon (large intestine), the long tube that helps carry digested food to your rectum and out of your body.
 
These cancers can also be called colon cancer or rectal cancer, depending on where they start. Colon cancer and rectal cancer are often grouped together because they have many features in common.
 
Colorectal cancer often begins as a growth called a polyp inside the colon or rectum. Finding and removing polyps can prevent colorectal cancer.
 
Healthcare professionals recommend regular colorectal cancer screenings for adults aged 45–75.

Stages

There are different ways of assigning a stage to cancer. The stages indicate how far cancer has spread and the size of any tumors.
 
In colon cancer, the stages develop as follows:
 
Stage 0: Also known as carcinoma in situ, at this point, the cancer is in a very early stage. It has not grown farther than the inner layer of the colon and will usually be easy to treat.
Stage 1: Cancer has grown into the next layer of tissue.
Stage 2: Cancer has reached the outer layers of the colon but has not spread beyond the colon.
Stage 3: Cancer has grown through the outer layers of the colon and reached one to three lymph nodes. It has not spread to distant sites.
Stage 4: Cancer has reached other tissues beyond the wall of the colon. As stage 4 progresses, colon cancer reaches distant parts of the body.

Symptoms and Causes

You might not experience colon cancer symptoms at all, especially in the early stages.
 
If you do experience symptoms of colon cancer, they may include:
 
-constipation
-diarrhea
-blood in the stool
-changes in stool color
-changes in stool shape, such as narrowed stool
-bleeding from the rectum
-unintentional weight loss
-abdominal pain
-excessive fatigue
-the feeling that your bowel won’t completely empty (tenesmus)
 
It’s important to note that many of these symptoms may also be caused by other, less serious, conditions.
 
As such, it’s a good idea to see a doctor if you’ve had any of these symptoms for 3 weeks or more. You and the doctor can discuss your symptoms and decide if colon cancer screening is appropriate.
 
What causes colon cancer?
 
Like all types of cancer, colon cancer happens when cells grow and divide uncontrollably. All cells in your body are constantly growing, dividing and dying. That’s how your body remains healthy and working as it should. In colon cancer, cells lining your colon and rectum keep growing and dividing even when they’re supposed to die. These cancerous cells may come from polyps in your colon.

When to see a doctor

If you notice lasting symptoms that worry you, make an appointment with a health care professional.

Risk factors

Some factors that increase your risk of developing colon cancer can’t be changed. For instance, your age, ethnicity, and family health history can all impact your risk of colon cancer.
 
Risk factors you can’t control include:
 
-being over age 50 years
-a prior history of colon polyps
-a prior history of bowel diseases
-a family history of colorectal cancer
-having certain genetic syndromes, such as familial adenomatous polyposis (FAP)
-having certain health conditions, such as inflammatory bowel disease (IBD)
-having previously had certain medical procedures, such as abdominal radiation and gallbladder removal
-being of African or Ashkenazi Jewish descent

Prevention

Avoiding the risk factors that you have control over may help prevent some cancers. That includes:
 
-Not smoking
-Limiting alcohol to under three drinks per day
-Managing your weight
 
There are also other steps you can take to try to prevent colorectal cancer. They include:
 
-Getting regular colorectal cancer screenings
-Having polyps removed before they can become cancerous
-Getting regular exercise

Diagnosis

Laboratory studies that may be helpful include the following:
 
-Complete blood count
-Chemistries and liver function tests
-Serum carcinoembryonic antigen
 
Imaging studies that may facilitate staging include the following:
 
-Chest radiography
-Chest computed tomography
-Abdominal barium study
-Abdominal/pelvic CT
-Contrast ultrasonography of the abdomen and liver
-Abdominal/pelvic MRI
-Positron emission tomography, including fusion PET-CT scan
 
Other procedures that may be warranted include the following:
 
-Colonoscopy
-Sigmoidoscopy
-Biopsy of suspicious lesions
-Double-contrast barium enema

How colorectal cancer spreads

If cancer forms in a polyp, it can grow into the wall of the colon or rectum over time. The wall of the colon and rectum is made up of many layers. Colorectal cancer starts in the innermost layer (the mucosa) and can grow outward through some or all of the other layers (see picture below).
 
When cancer cells are in the wall, they can then grow into blood vessels or lymph vessels (tiny channels that carry away waste and fluid). From there, they can travel to nearby lymph nodes or to distant parts of the body.
 
The stage (extent of spread) of a colorectal cancer depends on how deeply it grows into the wall and if it has spread outside the colon or rectum.

Management and Treatment

Surgery is the most common colon cancer treatment. There are different colon cancer surgeries and procedures:

 

*Polypectomy: This surgery removes cancerous polyps.

 

*Partial colectomy: This is also called colon resection surgery. Surgeons remove the section of your colon that contains a tumor and some surrounding healthy tissue. They’ll reconnect healthy colon sections in a procedure called anastomosis.

 

*Surgical resection with colostomy: Like a colectomy, surgeons remove the section of your colon that contains a tumor. In this surgery, however, they can’t connect healthy colon sections. Instead, they do a colostomy. In a colostomy, your bowel is moved to an opening in your abdominal wall so your poop is collected in a bag.

 

*Radiofrequency ablation: This procedure uses heat to destroy cancer cells.

 
Healthcare providers may combine surgery with adjuvant therapy. This is cancer treatment done before or after surgery. They may also use these treatments for colon cancer that has spread or come back. Treatments may include:
 

*Chemotherapy: Healthcare providers may use chemotherapy drugs to shrink tumors and ease colon cancer symptoms.

 

*Targeted therapy: This treatment targets the genes, proteins and tissues that help colon cancer cells grow and multiply. Healthcare providers often use a type of targeted therapy called monoclonal antibody therapy. This therapy uses lab-created antibodies that attach to specific targets on cancer cells or cells that help cancer cells grow. The antibodies kill the cancer cells.

Living With

Self-care is an important part of living with colon cancer, but everyone’s situation is different. People treated for early-stage colon cancer may become cancer-free. They’re cancer survivors, but they may worry that their colon cancer will come back.
 
People who have advanced colon cancer have different concerns. They’re also cancer survivors. But for them, living with colon cancer may mean treatment that eases symptoms but doesn’t cure colon cancer. They may benefit from having palliative care. Palliative care helps people manage cancer symptoms and treatment side effects.
Sources and references
 
https://my.clevelandclinic.org/health/diseases/14501-colorectal-colon-cancer
https://www.cancer.org/cancer/types/colon-rectal-cancer/about/what-is-colorectal-cancer.html
https://www.medicalnewstoday.com/articles/150496#treatment-options
https://www.cancer.gov/types/colorectal
https://medlineplus.gov/colorectalcancer.html
https://www.healthline.com/health/colon-cancer#prevention
https://www.mountsinai.org/health-library/diseases-conditions/colon-cancer
https://emedicine.medscape.com/article/277496-overview
https://medlineplus.gov/colorectalcancer.html
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