Overview, Causes, & Risk Factors
Colorectal 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:
Colorectal 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.
Like other tumors, colorectal cancer can spread to lymph nodes and other parts of the body.
What are the causes and risks of the disease?
Colorectal 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 colorectal 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 tumor called an adenoma. Abnormal cell changes continue, ultimately turning into cancer. Several genes play a role in colorectal cancer, too.
Some risk factors for the disease are:
Certain foods increase the risk for getting this disease, such as:
Symptoms & Signs
What are the signs and symptoms of the disease?
The colorectal tumor can bleed into the inside of the bowel. Symptoms may include:
A tumor can narrow or block the bowel. It can also perforate the bowel, causing infection or bleeding into the abdominal cavity. When colorectal cancer spreads to other sites in the body, it can cause:
Rarely, swollen lymph nodes are a sign of colorectal cancer. Unusual health problems sometimes associated with colorectal cancer include:
Diagnosis & Tests
How is the disease diagnosed?
Colorectal cancer may be diagnosed in several ways, including:
Colorectal cancer is divided into stages, and the likelihood of cure and long-term disease-free survival is determined by the stage.
To determine the stage of the cancer, a surgeon removes the primary tumor 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 colorectal cancer are:
Sometimes, the primary tumor or the sites where the cancer has spread cannot be removed entirely. In these cases, other tests can help in diagnosis, such as:
Prevention & Expectations
What can be done to prevent the disease?
Research findings show that eating a diet high in fiber and getting enough calcium can help prevent colorectal cancer. Use of aspirin and vitamin E are also associated with a lower risk of colorectal cancer.
Early diagnosis is key to preventing death from this disease. Starting at the age of 40, people should have yearly digital rectal exams and fecal occult blood tests. This screening allows early detection of colorectal polyps. These precancerous lesions can be removed before they turn into colorectal cancer.
Beginning at the age of 50, a person should have asigmoidoscopy every 3 to 5 years. A sigmoidoscopy is a procedure that allows a healthcare professional to look into the rectum and the sigmoid colon through a flexible scope.
More frequent or earlier screening may be needed for people who:
People who are at high risk for colorectal cancer because of family polyp syndrome or ulcerative colitis often choose to have the colon removed. This is called a colectomy.
What are the long-term effects of the disease?
People with Stage D cancer generally cannot be cured. They can survive for several weeks to a few years depending on the tumor’s location and behavior. Home healthcare or hospice care may be helpful.
What are the risks to others?
Colorectal cancer is not contagious and poses no risk to others. However, it does tend to run in families.
Treatment & Monitoring
What are the treatments for the disease?
Several healthcare providers often work together to help manage colorectal cancer. Among them might be a general surgeon or cancer surgeon, radiation therapist, cancer doctor called an oncologist, and a primary care physician.
Colorectal cancer is treated with surgery. The surgeon removes the entire tumor, if possible. Often, this means part of the colon must be removed. This is called a hemicolectomy. The colon 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 colon 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 tumor, 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:
When chemotherapy is given, it is usually tolerated well. However, side effects can include:
Side effects of treatment for late-stage colorectal cancer vary depending on the medications used but may include those mentioned above. The drawbacks may outweigh the benefits.
Sometimes, chemotherapy medications are directed at an artery that supplies the liver. This can cause:
What happens after treatment for the disease?
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 colorectal cancer can involve:
Colorectal cancer usually does not grow rapidly. Recurrences can happen several years later. Also, a second primary tumor can develop in the rest of the bowel.
Article type: xmedgeneral