Colorectal Cancer:
What is Colorectal cancer?
Tumors of the colon and rectum are growths that arise from the inner wall of the large intestine. While benign tumors of the large intestine are called polyps, malignant tumors of the large intestine known as cancers. Most of the cancers of the large intestine are believed to have developed from polyps. Cancer of the colon and rectum (also referred to as colorectal cancer) can invade and damage adjacent tissues and organs. Cancer cells can also break away and spread to other parts of the body (such as liver and lung) where new tumors form. The spread of colon cancer to distant organs is called metastasis of the colon cancer. Once metastasis has occurred in colorectal cancer, a complete cure of the cancer is unlikely
Throughout the world, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. The frequency of colorectal cancer varies around the world. It is common in the Western world, and is very rare in both Asia and Africa. In countries where the people have adopted western diets, the incidence of colorectal cancer is quickly rising.
Causes of Colorectal Cancer:
Colorectal cancer is not contagious. Some people are more likely to develop colorectal cancer than others based on family and lifestyle dynamics. Factors that increase a person's risk of colorectal cancer include high fat intake, a family history of colorectal cancer and polyps, the presence of polyps in the large intestine, and chronic ulcerative colitis.
Diet and colorectal cancer:
Diets that are high in fat are believed to predispose humans to colorectal cancer. In countries with high colorectal cancer rates, the fat intake by the population is much higher than in countries with low cancer rates. It is believed that the breakdown products of fat lead to the formation of cancer-causing chemicals, known as carcinogens. Diets high in vegetables and high-fiber foods such as whole-grain breads and cereals may rid the bowel of these carcinogens and help reduce the risk of cancer.
Colon polyps and colorectal cancer:
Doctors believe that most colon cancers develop in colon as polyps. Therefore, removing benign colon polyps can prevent colorectal cancer. Colon polyps develop when chromosome damage occurs in cells of the inner lining of the colon. When chromosomes are damaged, cell growth becomes uncontrolled, resulting in masses of extra tissue, known as polyps. Colon polyps are initially benign; however, over years, benign colon polyps can acquire additional chromosome damage and may become cancerous.
Ulcerative colitis and colorectal cancer:
Chronic ulcerative colitis causes inflammation of the inner lining of the colon. The risk of colon cancer is much higher than average for patients with chronic ulcerative colitis of long duration. The risk of colon cancer increases significantly after a person has been diagnosed with ulcerative colitis for 10 years.
Genetics and colorectal cancer:
A person's genetic background is an important factor in colon cancer risk. Among first-degree relatives of colon cancer patients, the lifetime risk of developing colon cancer is eighteen percent. Even though family history of colon cancer is an important risk factor, the majority (approximately 80%) of colon cancers occur in patients with no family history of colon cancer. Approximately 20% of cancers are associated with a family history of colon cancer, and 5 % of colon cancers are due to hereditary colon cancer syndromes. Hereditary colon caner syndromes are disorders where affected family members have inherited cancer causing genetic defects from one or both of the parents.
Symptoms:
Symptoms of colorectal cancer differ greatly depending on the person and the extent of the cancer. Common symptoms may include:
- Fatigue
- Weakness
- Shortness of breath
- Change in bowel habits
- Narrow stools
- Diarrhea or constipation
- Red or dark blood in stool
- Weight loss
- Abdominal pain
- Cramps
- Bloating
Colorectal cancer can be present for several years before symptoms develop, and therefore, prevention and early detection are extremely important.
Prevention and Early Detection:
When colon cancer is suspected, either a lower GI series (barium enema x-ray) or colonoscopy is performed to confirm the diagnosis and to localize the tumor. A colonoscopy is generally considered more accurate than barium enema x-rays, especially in detecting small polyps. If colon polyps are found, they are usually removed through the colonoscope and sent to the pathologist where they will be examined to check for cancer. While the majority of the polyps removed through the colonoscopes are benign, many are precancerous. Removal of precancerous polyps prevents the future development of colon cancer from these polyps.
Unfortunately, colorectal cancers can be present long before they are detected. The most effective prevention of colon cancer is early detection and removal of precancerous colon polyps before they turn cancerous. Even in cases where cancer has already developed, early detection still significantly improves the chances of a cure by surgically removing the cancer before the disease spreads to other organs. Multiple world health organizations have suggested that beginning at age 50, colonoscopies are recommended every 10 years. If a person has an increased chance of polyps or has symptoms of colorectal cancer, a physician will recommend they have screenings more frequently.
If cancerous growths are found during colonoscopy, small tissue samples can be obtained and examined under the microscope to confirm the diagnosis. If colon cancer is confirmed by a biopsy, staging examinations are performed to determine whether the cancer has already spread to other organs. Since colorectal cancer tends to spread to the lungs and the liver, staging tests usually include chest x-rays, ultrasonography, or a CAT scan of the lungs, liver, and abdomen.
* Print a copy of a Colorectal Cancer screening guide.
Treatment options:
Surgery is the most common treatment for colorectal cancer. During surgery, the tumor, a small margin of the surrounding healthy bowel, and adjacent lymph nodes are removed. The surgeon then reconnects the healthy sections of the bowel. In patients with rectal cancer, the rectum is permanently removed. The surgeon then creates an opening (colostomy) on the abdomen wall through which solid waste in the colon is excreted. Specially trained nurses can help patients adjust to colostomies, and most patients with colostomies return to a normal lifestyle.
The long term prognosis after surgery depends on whether the cancer has spread to other organs. The risk of metastasis is proportional to the depth of penetration of the cancer into the bowel wall. In patients with early colon cancer which is limited to the superficial layer of the bowel wall, surgery is often the only treatment needed. These patients can experience long term survival in excess of eighty percent. In patients with advanced colon cancer, wherein the tumor has penetrated beyond the bowel wall and there is evidence of metastasis to distant organs, the five year survival rate is less than ten percent.
In some patients, there is no evidence of distant metastasis at the time of surgery, but the cancer has penetrated deeply into the colon wall, or reached adjacent lymph nodes. These patients are at risk of tumor recurrence either locally or in distant organs. Chemotherapy in these patients may delay tumor recurrence and improve survival. Chemotherapy is the use of medications to kill cancer cells. It is a systemic therapy, meaning that the medication travels throughout the body to destroy cancer cells. After colon cancer surgery, some patients may harbor microscopic metastasis. Chemotherapy is given shortly after surgery to destroy these microscopic cells.
Radiation therapy in colorectal cancer has been limited to treating cancer of the rectum. There is a decreased local recurrence of rectal cancer in patients receiving radiation either prior to or after surgery. Without radiation, the risk of rectal cancer recurrence is close to fifty percent. With radiation, the risk is lowered to approximately seven percent. Side effects of radiation treatment include fatigue, temporary or permanent pelvic hair loss, and skin irritation in the treated areas.
** Additional treatment options and prevention methods at the Cancer Society Home Page
Related information:
- Functions of the bowel
- What is a Colonoscopy?
- The Susan Cohan Kasdas Colon Cancer Foundation
- National Cancer Institute
- Colorectal Cancer Network
- More patient resources
| University of Missouri Health Care | This information is not intended to replace the advice of a doctor. |
