Colorectal cancer

Colorectal cancer is an uncontrolled development of malignant cells in the rectum or colon.


Anatomy
The small and large intestines form the bowel.
The large intestine extends from the small intestine to the anus (the opening at the far end of the digestive tract through which waste leaves the body).

The large intestine is divided into segments: the ascending (right) colon, the transverse colon, the descending (left) colon and the sigmoid colon, which is connected to the rectum. Together, the segments of the colon extract water from undigested food and temporarily store bodily waste, which eventually leaves the body through the anus.


Causes/associated factors
Colorectal cancer is one of the most common forms of cancer in the United States. The exact cause of colorectal cancer remains unknown. However, a variety of factors may increase the risk of developing colorectal cancer, including:
Age: The risk of developing colorectal cancer increases with age. Although younger people can develop the condition, more than 90 percent of people who have colorectal cancer are older than age 50.

Lifestyle: Colorectal cancer may be linked to diets high in calories and fat (especially animal fat) and low in fiber. Lack of exercise, obesity, smoking and alcohol use may be other contributing factors.

Family history: If you have a first-degree relative (a parent, sibling or child) who's had colorectal cancer, you're two to four times more likely to develop the condition yourself.

Cancer: Women who have a history of ovarian, uterine or breast cancer are at increased risk for developing colorectal cancer. Also, anyone who's had a previous bout with colorectal cancer may have a recurrence.

Polyps: Certain types of polyps (abnormal tissue growths, typically benign) can increase the risk of developing colorectal cancer. Familial polyposis, for example, is a rare inherited condition in which numerous polyps develop on the inside walls of the colon and rectum. If the diseased area isn't surgically removed, the condition is likely to become cancerous.

Inflammatory bowel disease: The presence of an inflammatory bowel disease, such as ulcerative colitis or Crohn's disease, may increase the risk of developing colorectal cancer. Ulcerative colitis is a chronic disease characterized by diarrhea, inflammation and open sores of the inner lining of the colon. Crohn's disease is a chronic inflammatory condition of the gastrointestinal tract.

Signs/symptoms
Colorectal cancer may have no symptoms. If symptoms appear, they may include:
blood in bowel movements
constipation
diarrhea
weight loss
anemia (a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron)
abdominal pain, discomfort or fullness

Diagnosis
Your doctor will do a physical exam and ask questions about your medical history. Certain diagnostic tests may be recommended, such as:
blood tests
standard X-ray
barium enema (an X-ray of the bowel after the doctor inserts barium, a contrast dye, into the rectum)
flexible sigmoidoscopy (examination of the rectum and lower part of the colon)
colonoscopy (another procedure that helps doctors see the inside of the entire colon)
polypectomy (surgical removal of a polyp during a colonoscopy or sigmoidoscopy)
biopsy (taking a tissue sample for microscopic examination)
computed tomography (CT scan -- a computer-generated, cross-sectional picture of internal body parts)
ultrasound (using sound waves to create an image of internal body parts)
If cancer cells are detected, the doctor will determine how far the cancer has spread through a process called staging. This process helps your doctor determine the most appropriate treatment options, as well as your prognosis.

Staging is based on the TNM system -- tumor, node and metastasis (the spread of the primary tumor to other unrelated sites in the body). The stages range from stage 0 (lowest) to stage IV (most advanced). Staging may involve more biopsies, X-rays, scans and other diagnostic tests.


Treatment
Treatment of colorectal cancer depends largely on how far the cancer has spread or the cancer stage. Treatment options may include surgery, chemotherapy and radiation.
Surgery
Surgical removal of the tumor, nearby tissue and lymph nodes is the primary treatment for colorectal cancer.

In most cases, the healthy portions of the colon or rectum are able to be reconnected. If this isn't possible, a colostomy is needed. A colostomy is a surgical procedure that diverts the colon to the outside of the abdomen. The opening serves as a temporary or permanent exit for feces to leave the body.

Laparoscopic colon surgery is being investigated as an alternative to traditional surgery. During laparoscopic surgery, the doctor uses special instruments and a thin tube (laparoscope) equipped with a camera lens and light. This type of surgery may offer advantages such as smaller incisions, less pain after surgery and more rapid recovery. Further study is needed, however.

Benefits: Surgery is the preferred method of treatment simply because the tumor and the surrounding tissue is removed from the body. Doctors can then examine the tumor to determine how advanced the cancer is and what additional treatment may be needed.

Risks: There's a chance that the healthy portions of the colon or rectum can never be reattached, resulting in a permanent colostomy. Surgical complications may include infections, such as a wound infection, pneumonia or abscess (collection of pus). Other complications may include bleeding, blood clots and, rarely, anastomotic leaks (a leak where the two ends of the colon are reattached). An anastomotic leak may require additional surgery.
Chemotherapy
Medication therapy is often used to treat colorectal cancer, typically along with another treatment option (such as surgery). Chemotherapy is intended to shrink the tumor and prevent it from growing and spreading.

Benefits: Chemotherapy is systemic therapy, which means the drugs enter the bloodstream and travel through the body. It can destroy any cancer cells that remain after surgery.

Risks: Chemotherapy can have side effects, including nausea, vomiting, a weakened immune system and hair loss.
Radiation therapy
Radiation therapy (also called radiotherapy) uses high-energy rays to destroy cancer cells and prevent new cells from growing. It may be done before or after surgery. Radiation therapy is most often used for people who have rectal cancer.

Benefits: Radiation therapy used prior to surgery can help shrink the tumor, making removal easier.

Risks: Radiation may cause fatigue, nausea, diarrhea, and changes to your skin where treatment is given.

Complications
Colorectal cancer can also recur or spread to the lymph nodes, lungs or other parts of the body.
Careful monitoring and treatment can help prevent complications. See your doctor for regular follow-up visits, and notify your doctor of any changes in your health status.


Pregnancy-specific information
Pregnancy doesn't increase the risk of developing colorectal cancer. If you have colorectal cancer, treatment measures may differ from those recommended for other adults.

Senior-specific information
The risk for developing colorectal cancer increases with age, especially after age 50.

Prevention
Although evidence about the link between lifestyle changes and colorectal cancer isn't yet conclusive, it's wise to limit your alcohol consumption and intake of animal fat. Exercise regularly, maintain a healthy body weight, and eat plenty of fiber, fruits and vegetables.
To detect colorectal cancer in the early stages, the U.S. Preventive Services Task Force (USPSTF) and the American Cancer Society (ACS) recommend one of the following five options beginning at age 50:

routine at-home fecal occult blood testing (The USPSTF recommends at-home testing every one to two years. The ACS recommends yearly testing.)
flexible sigmoidoscopy every three to five years
a combination of at-home fecal occult blood testing and flexible sigmoidoscopy
colonoscopy every 10 years
double-contrast barium enema every five years
The ACS recommends the combination of at-home fecal occult blood testing and flexible sigmoidoscopy as the most effective. The USPSTF hasn't recommended one method over the others.

If you're younger than age 50 but have any of the risk factors listed above, consult your doctor about the need for earlier or more frequent screenings.


Research
Gene therapy trials that may help scientists develop new medications and treatments for colorectal cancer are in the early phases.
Clinical trials are underway to test immunotherapy (using the body's immune system to counteract the side effects of certain treatments) as a way to boost a person's ability to fight colorectal cancer.

Virtual colonoscopy is being evaluated as a tool to detect colorectal cancer early, but thus far it's unproven. This procedure would allow the doctor to examine the colon with detailed computed tomography scans (computer-generated, cross-sectional pictures of internal body parts), rather than using a scope inside the colon.

Another tool that's being evaluated is DNA stool testing, during which cells shed into the stool from the walls of the colon and rectum are tested for genetic abnormalities that typically occur in colorectal cancer.