Colorectal Cancer

Cancer affecting the colon and the rectum are collectively known as colorectal cancer.

  • Bleeding from the rectum and fatigue are the common symptoms of colorectal cancer
  • Colorectal cancer in the early stage is curable
  • Diagnosis is confirmed by a colonoscopy.
  • People above the age of 50 should regularly undergo screening tests
  • Hereditary factors and certain dietary habits predispose some people to this disease
  • The main treatment is the surgical removal of cancer

Adenocarcinomas are the usual type of cancer found to affect the rectum and the large intestine. They originate either directly from the lining of the rectum and colon or from pre-existing colorectal polyps. The cancerous growths initially start as tiny mushroom-like outgrowths on the lining, but they soon grow into the wall of the colon and rectum. The cancer may spread to lymph nodes too. Colorectal cancer has a high probability of metastasizing to the liver as the blood flow from the intestinal wall continues to the liver.

Colorectal cancer is more prevalent in industrialized countries. For example, in Europe and the US, colon cancer and rectal cancer are among the most common cancers. They are also a leading cause of fatalities due to cancer. The incidence of colorectal cancer is found to vary according to age and gender. People above the age of 40 may start developing the disease but it is most prevalent in those above 60 years of age. Women are found to be more prone to it than men. Among the people who have colon cancer, a few may have it in more than one location independent of one another. Every year, around one hundred and fifty thousand people are diagnosed with bowel cancer in the United States alone and about one third of them succumb to the disease.

Risk Factors

Colorectal cancer seems to run in families. So, people who have one or more family members with the disease are at greater risk of this disease. Since colorectal polyps have a tendency to become malignant, people who already have familial adenomatous polyposis risk, also have a higher chance of colorectal cancer.

Crohn’s disease or ulcerative colitis is another risk factor that predisposes people to colon cancer. The longer a person has had the above conditions, the greater the risk.

Diet also is considered to play a role in the development of colorectal cancer. Diet high in fat and low in fiber content is a risk factor. The presence of carcinogens in the air and water, due to industrial pollution, also could be a reason for the greater incidence of colorectal cancer in the industrialized countries.

Some people have a mutated gene which predisposes them to early onset of colorectal cancer.70 to 80% of those who have inherited this mutated gene develop the disease even before they reach 50 years. This condition is known as HNPCC or Hereditary Non polyposis Colorectal Carcinoma. People with this gene have a higher risk of developing various other cancers of the digestive tract such as stomach cancer and cancer of the small intestine. They have a higher incidence of ovarian and endometrial cancers too.

Symptoms

Colorectal cancer remains asymptomatic for years as it is a slow growing cancer. Slight bleeding from the cancer results in occult blood in the stool, but it cannot be seen except in a lab test. Over a period, this continuous bleeding may result in fatigue and anemia. Some Patients may notice blood on toilet paper. Depending on the type of cancer, the stage it is in, and also the area affected, other symptoms start to appear.

When a tumor develops in the ascending colon on the right side, there may not be any symptoms as there is no chance of obstructions here. This part of the bowel is quite large in size and the stool passing through it is in liquid state. Usually, the cancer is not detected till the growth becomes large enough to be felt by the doctor during a routine abdominal examination.

 On the other hand, if a tumor is present in the descending colon on the left side, obstructions usually occur. This part of the colon is smaller, and the stool is in a semisolid state as it passes here. Symptoms display an alternating pattern in bowel movements; high frequency of bowel movements for a period followed by a period of constipation. Abdominal cramps and pain are other symptoms which may be present along with severe constipation. They usually prompt people to get medical help, which often leads to the diagnosis of cancer.

Slow and steady bleeding from colon and rectal cancers are common, but sometimes, the blood may not be visible to people. A stool test for occult blood may detect the bleeding, but if the stool is blood stained, it may prompt people to see a doctor. It may result in early detection of the cancer as bleeding from rectum is the characteristic symptom of colorectal cancer. There are other abnormal conditions such as diverticulitis and hemorrhoids which have the same symptom of blood in the stool or blood on toilet paper. But when a person comes to the doctor with the complaint of bleeding from the rectum, it is mandatory to check for cancer. When a person feels incomplete emptying of the rectum immediately after a good bowel movement, it may be an indication of rectal cancer and has to be investigated without delay. People with cancer of the rectum may have pain during defecation, or when they sit, but the absence of such symptoms cannot rule out the presence of cancer.

Diagnosis

Screening Tests: Routine tests and screening for cancer is the best way to diagnose colorectal cancer. People who are at high risk of developing the disease should have periodic scanning. Occult blood test is done usually on a sample of stool collected after the patient is put on a meat-free diet for 3 days. Diet high in fiber is also recommended on these days to get an accurate result. Physical examination of the rectum with a gloved finger may help detect bleeding. If the doctor finds evidence of rectal bleeding, more tests are conducted to confirm the diagnosis.

For regular screening for colorectal cancer, a viewing test called sigmoidoscopy is employed. If abnormalities are detected, colonoscopy is done. Sometimes colonoscopy itself is used as a standard screening procedure, especially for people in the high risk category. The advantage of colonoscopy is that, in addition to the detection of cancer, some treatment procedures such as cauterization, or surgical removal of polyps and small tumors, also can be done during the procedure.

CT colonography, also called virtual colonoscopy is a CT scan procedure in which instead of the actual viewing of the colon, a small tube inserted into the colon to take very clear 3-d pictures of the intestine and the rectum. Prior to the test, a contrast agent is swallowed, and the colon is filled with gas to expand it for a clearer view. Anesthesia can be avoided in this procedure but the gas may cause considerable distress to the patient. Another drawback is that, repair of lesions or collection of tissue for lab tests is not possible in virtual colonoscopy. If abnormalities are detected, the patient may still have to undergo colonoscopy.

The patient is made to swallow a tiny capsule containing a tiny camera in a diagnostic procedure named capsule endoscopy. It is a procedure which has great diagnostic potential but there are several limitations which have to be addressed before it can become a popular test.

 Diagnostic Tests: If abnormalities in the rectum are discovered while viewing it with a sigmoidoscope, or if blood is found in the stool, a more comprehensive diagnostic test called colonoscopy is conducted. It has the advantage that, if any lesions are found in the colon or the rectum during the test, they can be repaired. Also, biopsy of a tissue sample becomes possible.

When cancer of the colon and the rectum are detected, x-rays of the chest and abdomen are taken to check for metastases. CT scan of the abdomen also may be done. Routine blood tests are also done to assess the general condition of the patient and to check for anemia.

Colorectal cancer is not detected by blood tests. However, after the surgical removal of the cancerous growth, blood tests for certain markers help in assessing the chance of recurrence. Carcinoembryonic antigen or CEA, CA 125 and CA19-9 are cancer markers which are found in high levels when colorectal cancer starts developing again.

Prognosis and Treatment

Prognosis for people with colorectal cancer is good when the disease is detected in early stages and appropriate treatment is given. When the cancer is confined to the lining of the colon and the rectum, it can be cured by surgery in nearly 90% of the cases. If it has spread a little into the wall of the bowel, surgical removal of the affected part cures the disease in 70% of instances. The rate of survival significantly reduces to less than 50% when the cancer has invaded nearby lymph nodes. Once it has grown deep into the walls of the bowel, it may have crossed the stage for successful treatment. Even before metastases become apparent, the cancer cells may have taken root in other tissues and organs such as the liver.

After the cancer has spread, the chances of a complete cure are slim and the treatment is mainly aimed at the management of the disease. The treatment of cancer varies according to its spread. Surgical removal of the cancerous growth and the surrounding tissue is the first line of treatment, and the most effective, in curing cancer in the early stages. Often, the affected part of the colon or rectum is completely removed and the remaining pieces are stitched back together. Doctors may prefer to remove the lymph nodes also, to prevent the recurrence of cancer. In case the cancer has spread deep into the wall of the bowel, or to the lymph nodes, chemotherapy is given after the surgery. It may help prolong life by retarding the growth of cancer cells which may be remaining in the body. Radiotherapy also may be given to prevent the development of new tumors and to suppress the growth of existing ones. It is not a cure for the disease, but it may help prolong life to some extent.

For cancer of the rectum, in addition to the extent of its growth, its location is also taken into consideration while deciding on the surgical treatment. If the cancer is widespread, the rectum and the anus are completely removed. Another route is created for the excretion of feces. By a procedure called colostomy, the colon is directly attached to a specially created opening in the abdominal wall. The stool gets collected in a plastic bag attached to this opening, via a tube. The bag is emptied out periodically. Whenever possible, doctors try to save at least the lower part of the rectum and the anus so that the colon can be connected to the rectal stump. This avoids the hassle of colostomy and carrying around of the bag of stool.

The liver is usually the first organ to be affected by the metastasizing colorectal cancer because the portal vein collecting the nutrient rich blood from the intestines goes to the liver directly. When the colorectal cancer has metastasized into the liver, a small pump is used to deliver chemotherapy drugs into the hepatic artery for more effective treatment. An implantable pump can be fixed under the skin, or a pump can be worn externally, in this procedure called arterial hepatic chemotherapy. This treatment is beneficial only if the cancer has not spread to anywhere other than the liver.

Desiccation is a procedure for shrinking the tumors using either an electric current applied directly to them, or Argon gas which is electrified into plasma state. It will cauterize the cancerous growths and cause them to shrink and shrivel. The probes and devices used for these procedures are introduced into the colon and rectum with the help of a colonoscope. These minimally invasive procedures are generally used in people who are too old or too weak to undergo surgical removal of the colorectal cancer. However, desiccation is not a cure for the cancer. It is a temporary measure to provide relief from the symptoms of cancer and to prolong life by slowing down its growth.

If the cancer has metastasized widely, and if many lymph nodes and other organs are affected, surgery may not help, and the effect of chemotherapy or radiation therapy also may be limited. Chemotherapy using fluorouracil or another chemotherapy drug may be given but it may not help much in prolonging life. Sometimes, surgery may become necessary to remove obstruction in the colon or the rectum. When the cancer has reached this stage, the expected survival time is less than a year and death may occur in 6 to7 months. The main focus is in keeping the patient as comfortable as possible and in ensuring quality of life to the extent possible. At this stage, the doctor and the patient may have to discuss various options for palliative treatment, and end-of –life care, involving the patient’s family and caregivers in the discussion.

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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One Response to Colorectal Cancer

  1. Shantae Fishburne says:

    Most colorectal cancer occurs due to lifestyle and increasing age with only a minority of cases associated with underlying genetic disorders. It typically starts in the lining of the bowel and if left untreated, can grow into the muscle layers underneath, and then through the bowel wall.

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