colo-rectal cancerAlternative Names
Colo-rectal cancer affects the lining of the large intestine and rectum.
What is going on in the body?
The colon is also called the large intestine. The colon begins near the junction of the small intestine and extends to the rectum. The colon has four parts:
Colo-rectal cancer starts in the lining, or mucosa, of the bowel. It usually develops in one area of the bowel over a long period of time. It occurs on the left side in the descending colon 40% to 50% of the time. The cancer grows along the opening in the colon. It also can grow further into the lining and muscle tissue.
- the caecum, which lies on the right side of the body
- the ascending colon, which rises slightly as it crosses from the right to the left side
- the transverse colon, which runs across the abdomen
- the descending colon, which drops down from the left side of the body
- the sigmoid colon, a U-shaped bend of bowel that leads toward the rectum
Like other tumours, colo-rectal cancer can spread to lymph nodes and other parts of the body.
What are the signs and symptoms of the disease?
The colo-rectal tumour can bleed into the inside of the bowel. Symptoms may include:
A tumour can narrow or block the bowel. It can also perforate the bowel, causing infection or bleeding into the abdominal cavity. When colo-rectal cancer spreads to other sites in the body, it can cause:
- rectal bleeding
- dark stools called melena, caused by blood in the stools
- anaemia, which is a low blood cell count, from blood or iron loss
- changes in bowel habits, such as the frequency of bowel movements
- smaller stools
- mucous discharge from the rectum
- vague abdominal distress
- wind pain
- haemorrhoids, which are dilated blood vessels in the rectal area
Rarely, swollen lymph nodes are a sign of colo-rectal cancer. Unusual health problems sometimes associated with colo-rectal cancer include:
- liver cancer
- pain in the liver
- loss of appetite and weight loss
- lung cancer
What are the causes and risks of the disease?
- thrombophlebitis, an inflammation in the veins of the lower leg
- unusual syndromes that change skin coloring
- muscle problems
Colo-rectal cancer is the third most common cancer. People have an increasing risk for it starting at the age of 40. People over the age of 50 account for 93% of colo-rectal cancer cases.
Experts believe that this slow-growing cancer begins when normal cells in the mucosa become overactive. These overactive cells form a small benign tumour called an adenoma. Abnormal cell changes continue, ultimately turning into cancer. Several genes play a role in colo-rectal cancer, too.
Some risk factors for the disease are:
Certain foods increase the risk for getting this disease, such as:
- small growths in the colon called colo-rectal polyps
- polyp syndromes, which means that colo-rectal polyps form frequently
- a family history of colo-rectal cancer
- ulcerative colitis, a chronic inflammatory disease of the bowel mucous, or inflammation of the bowel that results in ulcers
- environmental factors
What can be done to prevent the disease?
- eating a lot of meat
- eating a diet high in fat and low in fibre
Research findings show that eating a diet high in fibre and getting enough calcium can help prevent colo-rectal cancer. Use of aspirin and vitamin E are also associated with a lower risk of colo-rectal cancer.
Early diagnosis is key to preventing death from this disease. Starting at the age of 40, people should have yearly digital rectal examinations and faecal occult blood tests. This screening may help in the early detection of colo-rectal polyps. These precancerous lesions can be removed before they turn into colo-rectal cancer.
Beginning at the age of 50, a person should have a colonoscopy every 3 to 5 years. A colonoscopy is a procedure that allows a doctor to look into the rectum and bowel through a flexible scope.
More frequent or earlier screening may be needed for people who:
People who are at high risk for colo-rectal cancer because of family polyp syndrome or ulcerative colitis often choose to have the colonb removed. This is called a colectomy.
- have a family history of colo-rectal cancer
- have developed colo-rectal polyps. Polyps are removed during colonoscopy to keep the polyps from becoming cancerous or to assess a person's future risk for cancer.
How is the disease diagnosed?
Colo-rectal cancer may be diagnosed in several ways, including:
Colo-rectal cancer is divided into stages, and the likelihood of cure and long-term disease-free survival is determined by the stage.
- colonoscopy, a procedure in which a doctor can look into the entire colon and collect tissue samples through the scope
- bowel surgery
- endoscopy, a procedure in which a small tube is used to take a sample of tissue
To determine the stage of the cancer, a surgeon removes the primary tumour and surrounding colon. Local lymph nodes are also removed and the abdomen is explored. The tissue is then examined under a microscope.
The stages of colo-rectal cancer are:
Sometimes, the primary tumour or the sites where the cancer has spread cannot be removed entirely. In these cases, other tests can help in diagnosis, such as:
- Stage A, which is very limited and highly curable
- Stages B1 and B2, in which the cancer has invaded the bowel wall but hasn't spread to any of the lymph nodes
- Stages C1 and C2, in which cancer has invaded the bowel wall and has spread to some of the nearby lymph nodes
- Stage D, in which the cancer has spread to distant sites such as the lung, liver, and lymph nodes
What are the long-term effects of the disease?
- CEA tumour marker, a blood test to determine whether the cancer cells have spread to another site
- CT scans of the liver and abdomen
- chest X-ray
People with Stage D cancer generally cannot be cured. They can survive for several weeks to a few years depending on the tumour's location and behaviour. Home care or hospice care may be helpful.
What are the risks to others?
Colo-rectal cancer is not contagious and poses no risk to others. However, it does tend to run in families.
What are the treatments for the disease?
Several doctors often work together to help manage colo-rectal cancer. Among them might be a general surgeon or cancer surgeon, radiation therapist, cancer doctor called an oncologist, and GP.
Colorectal cancer is treated with surgery. The surgeon removes the entire tumour, if possible. Often, this means part of the bowel must be removed. This is called a hemicolectomy. The bowel may be reconnected internally or a colostomy may be done. A colostomy allows the stool to drain into a bag on the outside of the body.
If cancer has spread to the lymph nodes, the risk of a recurrence is higher. Usually, surgery is combined with other types of treatment in these cases. Radiation and chemotherapy are other treatments. A person with rectal cancer may be given radiation before, during, or after surgery. Often, chemotherapy is used, too.
Cancer in part of the bowel may be treated with chemotherapy. Often, a number of medications, such as fluorouracil (5-FU) and levamisole, are given over several months. This significantly reduces the likelihood that cancer will recur several years later.
Sometimes the cancer spreads too far to be removed surgically. While a number of chemotherapy medications are used at this point, none offer a cure. Treatment mostly relieves symptoms, such as swelling and jaundice.
Colorectal cancer responds to chemotherapy in less than 50% of cases. Treatment of this type of cancer continues to evolve. Experimental approaches are very important.
What are the side effects of the treatments?
Depending on the site and size of the tumour, colostomy can be a side effect of surgery for colorectal cancer.
Rectal cancer is treated aggressively with surgery, radiation, and sometimes chemotherapy. Side effects can include:
Occasionally, there are other problems, such as:
- bladder inflammation resulting from radiation
- prostatitis, or inflammation of the prostate
- erectile dysfunction
- pelvic burns
When chemotherapy is given, it is usually tolerated well. However, side effects can include:
- poor healing of the colostomy or a portion of the bowel
- poor absorption of food after part or all of the bowel is removed
Side effects of treatment for late-stage colo-rectal cancer vary depending on the medications used but may include those mentioned above. The drawbacks may outweigh the benefits.
- mouth irritation
- low red and white blood cell counts
- painful, reddened, swollen hands or feet
- hair loss
Sometimes, chemotherapy medications are directed at an artery that supplies the liver. This can cause:
What happens after treatment for the disease?
- inflammation of the pancreas, called pancreatitis
- blood clots
After treatment, a person must be watched to make sure that the reconnected bowel or the colostomy is working.
How is the disease monitored?
Monitoring for recurrence of colo-rectal cancer can involve:
Colo-rectal cancer usually does not grow rapidly. Recurrences can happen several years later. Also, a second primary tumour can develop in the rest of the bowel.
- physical examinations
- faecal occult blood test
- laboratory tests, including tests of the CEA tumour marker
- chest X-ray
- CT scans of the abdomen and pelvis
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 5/02/2005
Potential conflict of interest information for reviewers available on request