Definition
Colon cancer is the growth of cancer in the large intestine.
Cancer occurs when cells in the body divide without control or order. If cells keep dividing, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors. They can invade nearby tissue and spread to other parts of the body.
Risk Factors
Factors that may increase your risk of colon cancer include:
- Age: 50 or older
- Diets high in fat, low in fiber
- History of polyps , which are non-cancerous growths in the colon and rectum
- Hereditary conditions such as familial polyposis or Lynch syndrome
- Personal history of colorectal cancer
- Family history of colon or rectal cancer, especially a parent, sibling, or child
- History of ulcerative colitis or Crohn’s disease
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Other risk factors include:
- Obesity
- High body mass index (BMI)
- Physical inactivity
- Diabetes
- Smoking
- Heavy alcohol intake
- Diet high in red meats and low in fish
Symptoms
Colon cancer often does not have any symptoms. However, some symptoms associated with colon cancer include:
- A change in bowel habits such as diarrhea, constipation, or feeling that the bowel does not empty completely—Lasting for more than a few days in people aged 50 and older
- Bright red or very dark blood in the stool
- Stools that are narrower than usual
- Abdominal discomfort, such as frequent gas pains, bloating, fullness, and/or cramps
- Unexplained weight loss
- Feeling tired frequently
These may also be caused by other, less serious health conditions. Anyone experiencing these symptoms should see a doctor.
Diagnosis
The doctor will ask about your symptoms and medical history. A physical exam will be done.
Tests to screen for cancer or precancerous polyps include:
- Your rectum may need to be checked for lumps or growths. This can be done with a digital rectal exam.
- Your waste products may need to be checked. This can be done with a fecal occult blood test.
- Your rectum and colon may need to be examined. This can be done with:
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You may need to have pictures taken of your bodily structures. This may include:
- A barium enema to create a better image
- Computed tomography (CT) colonography
Additional tests may be done to confirm the presence of cancer, determine what stage the cancer is in, and/or determine if the cancer has spread:
- You may need to have your bodily fluid tested to check for anemia and markers of cancer in the blood. This can be done with blood tests.
- You may need to have tissue samples or polyps removed. This can be done with:
- Biopsy—The removal of colon or rectal tissue to be tested for cancer
- Polypectomy—The removal of a polyp during a sigmoidoscopy or colonoscopy
- You may need to have additional pictures taken of your bodily structures. This can be done with:
- CT scan
- Positron emission tomography (PET)/CT scan
- Transrectal ultrasound
Treatment
Treatment depends on the stage of the cancer but may include:
Surgery
Surgery is the main treatment. It requires removal of the cancerous tumor and nearby colon tissue. Depending on the size and location of the tumor, the surgery may be done by:
- Laparoscopy—Removal of early-stage cancer.
- Open surgery—To remove tumors, colon tissue, and sometimes nearby lymph nodes. The surgeon will also look for additional cancer in the colon during the surgery.
In some cases, the tumor and nearby healthy colon tissue will be removed. Healthy tissue is removed in case the cancer has begun to spread. The removal of a part of the colon is called a hemicolectomy. In most cases, the remaining healthy portions of the colon are reconnected. Sometimes, the end of the healthy colon is temporarily or permanently attached to an opening in the abdomen. This is called a colostomy. It allows body waste to pass out of the body if the colon cannot do so.
Radiation Therapy
Radiation therapy is the use of radiation to kill cancer cells and shrink tumors. It is directed at the site of the tumor from a source outside the body. This therapy is aimed at the immediate area of the cancer.
Chemotherapy
This therapy uses drugs to kill cancer cells. It may be given in many forms, including pill, injection, and catheter. The drugs enter the bloodstream and travel through the body killing mostly cancer cells. They can also kill some healthy cells. This therapy is systemic, meaning it affects your entire body.
If you are diagnosed with colon cancer, follow your doctor's instructions.
Prevention
Screening
The causes of most cancers are not known. However, it is possible to prevent many colon and rectal cancers by finding and removing polyps that could become cancerous. Beginning at age 50, both men and women at average risk should follow one of five screening options:
- Yearly fecal occult blood test or fecal immunochemical test
- Colonoscopy every 10 years
- Flexible sigmoidoscopy every five years
- X-rays of the colon and rectum with double-contrast barium enema every five years
- CT colonography every five years
Be sure to discuss these cancer screening tools with your doctor to see which option is best for you.
People with any of the following risk factors should begin colon and rectal cancer screening at age 40 or earlier and/or undergo screening more often:
- Strong family history of colon or rectal cancer or polyps
- Known family history of hereditary colon or rectal cancer syndromes
- Personal history of colon and rectal cancer or adenomatous polyps
- Personal history of chronic inflammatory bowel disease
Lifestyle Changes
There are also lifestyle changes that may reduce your risk of colon cancer, such as:
- Not smoking
- Being physically active, including, exercising at least 30 minutes on most days of the week
- Maintaining a healthy weight
- Eating a high-fiber diet containing fruits, vegetables, grains, and legumes
- Making other changes to your diet, like eating plenty of fruits and vegetables, not eating a lot of red meat, and not abusing alcohol
