Colorectal cancer affects the lining of the large intestine and rectum.
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: the cecum and ascending colon, which are in the right side of the abdomen the transverse colon, which runs across the abdomen and rises slightly as it crosses from the right to the left sidethe descending colon, which drops down along the left side of the abdomen the sigmoid colon, a U-shaped bend of bowel that leads from the descending colon toward the rectum
The rectum is below the sigmoid colon, and lies below the level of the peritoneum (the lining of the inside walls of the abdomen).
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 generally begins along the interior lining in the colon, then, if not detected, also grows further into the lining and muscle tissue. Like other tumors, colorectal cancer can spread to lymph nodes and other parts of the body.
The colorectal tumor can bleed into the inside of the bowel. Symptoms may include: rectal bleedingdark stools called melena, caused by blood in the stoolsanemia, which is a low blood cell count, from blood or iron losschanges in bowel habits, such as the frequency of bowel movementssmaller stoolsmucus discharge from the rectumvague abdominal distressgas painHemorrhoids, which are dilated blood vessels in the low rectal or anal area, can also bleed and are not usually related to cancer.
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 the liver, it can cause pain, jaundice, and abnormal liver function. It can also spread to the lungs, bones, and other sites, causing pain and other symptoms specific to the site of spread. Loss of appetite and weight loss are common.
Unusual health problems sometimes associated with colorectal cancer include: thrombophlebitis, an inflammation in the veins of the lower legunusual syndromes that change skin coloringmuscle problems
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: small growths in the colon called colorectal polypspolyp syndromes, which means that colorectal polyps form frequentlya family history of colorectal cancerulcerative colitis, a chronic inflammatory disease of the bowel mucus, or inflammation of the colon that results in ulcersenvironmental factorssmoking
Certain foods increase the risk for getting this disease, such as: eating a lot of meateating a diet high in fat and low in fiber
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: have a family history of colorectal cancerhave developed colorectal polyps. Polyps are removed during sigmoidoscopy to keep the polyps from becoming cancerous or to assess a person's future risk for cancer.
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.
Barium enema x-rays are also used for early diagnosis of colorectal polyps.
Colorectal cancer may be diagnosed in several ways, including: colonoscopy, a procedure in which a healthcare professional can look into the entire colon and collect tissue samples through the scopecolon surgeryendoscopy, a procedure in which a small tube is used to take a sample of tissue
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: Stage A, which is very limited and highly curableStages B1 and B2, in which the cancer has invaded the bowel wall but hasn't spread to any of the lymph nodesStages C1 and C2, in which cancer has invaded the bowel wall and has spread to some of the nearby lymph nodesStage D, in which the cancer has spread to distant sites such as the lung, liver, and lymph nodes
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: CEA tumor marker, a blood test to determine whether the cancer cells have spread to another siteCT scans of the liver and abdomenchest X-ray
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.
Colorectal cancer is not contagious and poses no risk to others. However, it does tend to run in families.
Several healthcare professionals often work together to help manage colorectal cancer. Among them might be a general surgeon or cancer surgeon, radiation oncologist, medical oncologist, and a primary care physician.
Colorectal cancer is primarily 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. In this case, the rectal-anal sphincter may be preserved and the person will have normal bowel movements.
In other cases, a colostomy may be needed. 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 radiation and chemotherapy.
A person with rectal cancer may be given radiation before, during, or after surgery. The purpose of the radiation is to decrease the risk of tumor recurrence. Often, one or more chemotherapy medications, such as fluorouracil (5-FU), capecitabine (oral 5-FU), leucovorin, oxaliplatin and irinotecan, are given over several months. This significantly reduces the likelihood that cancer will recur several years later.
Sometimes the cancer has spread 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. Research into treatment options for colon cancer continues, in the hope of producing better response rates than are seen currently.
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: bladder inflammation resulting from radiationprostatitis, or inflammation of the prostate erectile dysfunctionpelvic burns
Occasionally, there are other problems, such as: poor healing of the colostomy or a portion of the bowelpoor absorption of food after part or all of the colon is removed
When chemotherapy is given, it is usually tolerated well. However, side effects can include: mouth irritationdiarrhealow red and white blood cell countspainful, reddened, swollen hands or feethair loss
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 given directly into an artery that supplies the liver, in order to target tumors that have spread there.
Side effects from this approach include: hepatitisinflammation of the pancreas, called pancreatitisblood clotsinfectionspain
After treatment, a person must be watched to make sure that the reconnected bowel or the colostomy is working.
Monitoring for recurrence of colorectal cancer can involve: physical examsfecal occult blood testlab tests, including tests of the CEA tumor markercolonoscopychest X-rayCT scans of the abdomen and pelvis
Colorectal cancer usually does not grow rapidly. Recurrences can happen several years later. Also, a second primary tumor can develop in the remaining bowel.