Colorectal Cancer

The colon and rectum are part of the digestive tract. Together, they comprise the large intestine, or large bowel, which is located in the abdomen between the small intestine and the anus. Cancer that originates in the colon or rectum is called colorectal cancer.

The colon absorbs water, electrolytes, and nutrients from food and transports them into the bloodstream. It is about 6 feet in length and consists of the cecum (connects to the small intestine at the cecal valve), the ascending colon (the vertical segment located on the right side of the abdomen), the transverse colon (extends across the abdomen), the descending colon (leads vertically down the left side of the abdomen), and the sigmoid colon (extends to the rectum).

The rectum is the last segment of the large intestine. It is 8-10 inches in length and leads to the anus, which is the opening to the outside of the body. Waste material (fecal matter) is stored in the rectum until it is eliminated from the body through the anus.

Most (over 95%) colorectal cancers are adenocarcinomas that develop when a change (i.e., mutation) occurs in cells that line the wall of the colon or rectum. The disease often begins as an intestinal polyp, also called an adenoma, which is an abnormal growth of tissue, Polyps gradually can become precancerous and the cancerous. 

The incidence of colorectal cancer is highest in developed countries such as the United States and Japan, and lowest in developing countries in Africa and Asia. According to the American Cancer Society, it is the third most common type of cancer in both men and women in the United States. Incidence is slightly higher in men than women, and is highest in African American men.                                                      What Causes Colorectal Cancer?   While we do not know the exact cause of most colorectal cancer, there are certain known risk factors. A risk factor is something that increases a person's chance of getting a disease. Some risk factors, like smoking, can be controlled. Others, such as a person's age, can't be changed. Researchers have found certain risk factors that increase a person's chance of getting colorectal cancer.

Risk Factors for Colorectal Cancer

Family history of colorectal cancer: If you have close relatives (parent, brother or sister) who have had this cancer, your risk is increased. People with a family history of colorectal cancer should talk to their doctors about how often to have screening tests.

Certain family syndromes: A syndrome is a group of symptoms. For example, in some families, members tend to get a type of syndrome that involves having hundreds of polyps in their colon or rectum. Cancer often develops in one or more of these polyps.

Ethnic background: Jews of Eastern European descent (Ashkenazi Jews) have a higher rate of colon cancer.

Having had colorectal cancer before: Even if a colorectal cancer has been completely removed, new cancers may start in other areas of your colon and rectum.

Having a history of polyps: Some types of polyps increase the risk of colorectal cancer, especially if they are large or if there are many of them.

Having a history of bowel disease: A disease called Ulcerative Colitis increases the risk of colon cancer. In this disease, the colon is inflamed over a long period of time and there may be ulcers in its lining. If you have this problem you should start being screened at an earlier age.

Age: Your chance of having colorectal cancer goes up after age 50. More than 9 out of 10 people found to have colorectal cancer are older than 50.

Diet: A diet high in fat, especially fat from animal sources, can increase the risk of colorectal cancer. The American Cancer Society recommends choosing most of your foods from plant sources, eating at least 5 servings of fruits and vegetables every day, and limiting the amount of high fat foods you eat.

Lack of exercise: People who are not active have a higher risk of colorectal cancer.

Overweight: Being very overweight increases a person's colorectal cancer risk.

Smoking: Most people know that smoking causes lung cancer, but recent studies show that smokers are 30% to 40% more likely than nonsmokers to die of colorectal cancer.  

Can Colorectal Cancer Be Prevented?

Even though we don't know exactly what causes colorectal caner, there are some steps you can take to reduce your risk.

Screening tests: First, you should follow early detection test to help find colon or rectal cancer. When these cancers are found and treated early, they can often be cured. Screening can also find polyps. Removing these polyps helps prevent some cancers. Tests include yearly digital rectal examinations by your doctor, yearly fecal occult blood test to detect blood in your stools, and colonoscopy after the age of 50 to detect colon polyps.

Diet and exercise: It is important to eat plenty of fruit, vegetables, and whole grain foods and limit high-fat foods. Some studies suggest that taking a daily multivitamin containing folic acid or folate can lower colorectal cancer risk. Other studies suggest that getting more calcium with supplements or low-fat dairy products can help. Getting exercise is important as well.

Aspirin and other drugs: Aspirin appears to prevent the growth of polyps. But this medicine also has side effects and thus is not recommended simply to decrease the risk of colon polyps.

Female hormones: Hormone replacement therapy (HRT) for women after menopause may reduce the risk of colorectal cancer and osteoporosis (thinning of the bones). But those women who do get colorectal cancer may have a fast growing disease. HRT may also increase the risk of heart disease, blood clots, and breast and uterine cancer. Whether or not to use HRT is something women should discuss with their doctors.

Other factors: People with a family history of colorectal cancer may benefit from getting screening tests when they are younger and having them done more often than people without this risk factor. 

Signs and Symptoms Colorectal cancer can be asymptomatic (i.e., it may not cause symptoms). Blood in the stools is a common sign of the disease. Blood may be bright red or dark in color, and may not be noticeable. Chronic bleeding may result in iron deficiency anemia, which may cause fatigue and pale skin.Other symptoms include the following:

-       Abdominal discomfort (i.e., pain, bloating, cramping, fullness).

-       Change in bowel habits

-       Constipation or diarrhea

-       Narrow stools

-       Nausea and vomiting

-       Unexplained weight loss

Diagnosis of Colorectal Cancer

Diagnosis involves screening to detect colorectal cancer in asymptomatic patients (i.e., those without symptoms) with no family history of the disease. Screening is recommended beginning at age 50 and includes the following:

-       Digital rectal examination annually

-       Fecal occult blood tests annually

-       Total colonoscopy every 10 years

Diagnosis of colorectal cancer in symptomatic patients and high-risk patients includes laboratory test and colonoscopy. Biopsy (i.e., removal of a tissue sample for examination under a microscope) using colonoscopy is necessary to confirm the diagnosis.  

Office Test

Digital rectal examination: The physician inserts a lubricated, gloved finger into the patient's rectum to feel for tumors. Approximately 5-10% of colorectal cancers are palpable (i.e., able to be felt).

Fecal occult blood test: This test is used to detect microscopic blood in stool, which may indicate early colorectal cancer. When results of this test are positive, the diagnosis is confirmed using additional procedures (e.g., barium enema or colonoscopy).  

Imaging Tests

Chest x-ray: Used to detect cancer that has metastasized (spread) to the lungs.

CT scan: Used to detect metastasis to lymph nodes, liver, or lung.

Double contrast barium enema: With this examination air and a contrast solution (barium) are introduced into the large intestine and x-rays are taken to evaluate the colon.

Flexible sigmoidoscopy: This test allows the physician to look for early signs of colorectal cancer in the lining of the sigmoid colon and rectum. In this test, a flexible tube containing a light and a camera is inserted through the anus into the rectum and sigmoid colon. If suspicious tissue is found, the physician inserts special instruments through the scope and biopsies and abnormal tissue.

Total colonoscopy: This test is the same as the flexible sigmoidoscopy examination except the tube is longer so the entire colon can be examined. Biopsies of abnormal tissue can also be taken.  

Stages of Colon Cancer

After colon cancer has been diagnosed, tests are done to find out in cancer cells have spread within the colon or to other parts of the body. The process used to find out if cancer has spread is called staging. The information gathered from the staging process determines the stage of the disease. It is important to stage in order to plan treatment. The following tests and procedures may be used in the staging process. 

-       CT scan (CAT scan): Procedure that makes a series of detailed pictures of areas inside the body taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly.

-       Complete blood work including liver tests: This can help determine if there is any anemia or elevations in the liver enzymes.

-       CEA (carcinoembryonic antigen assay): A test that measures the level of CEA in the blood. CEA is released into the bloodstream from both cancer cells and normal cells. When found in higher than normal amounts, it can be a sign of colon cancer or other conditions.

-       Chest x-ray: An x-ray to see if there is any spread of tumor to the lung.

-       Surgery: This procedure will remove the tumor and examine if the tumor has spread outside the bowl to the lymph nodes.  

The Following Stages are used for Colon Cancer    

 Stage 0 (Carcinoma in Situ): In Stage 0, the cancer is found only in the innermost lining of the colon. Stage 0 cancer is also call carcinoma in situ.

Stage I: In stage I, the cancer has spread beyond the innermost tissue layer of the colon wall to the middle layersStage I colon cancer is sometimes called Dukes' A colon cancer

Stage II: Stage II colon cancer is divided into stage IIA and IIB.

-       Stage IIA: Cancer has spread beyond the middle tissue layers of the colon wall or has spread to nearby tissues around the colon or rectum.

-       Stage IIB: Cancer has spread beyond the colon wall into nearby organs and/or through the peritoneum.

Stage II colon cancer is sometimes called Dukes' B colon cancer.

Sage III: Stage III colon cancer is divided into stage IIIA, stage IIIB, and Stage IIIC.

- Stage IIIA: Cancer has spread from the innermost tissue layer of the colon wall to the middle layers and has spread to as many as 3 lymph nodes.

- Stage IIIB: Cancer has spread to as many as 3 nearby lymph nodes and has spread: o      Beyond the middle tissue layers of the colon wall; or o      To nearby tissues around the colon or rectum; or o      Beyond the colon wall into nearby organs and/or through the peritoneum.

-  Stage IIIC: Cancer has spread to 4 or more nearby lymph nodes and has spread:

• To or beyond the middle tissue layers of the
  colon wall; or
• To nearby tissues around the colon or rectum; or
• To nearby organs and/or through the peritoneum.

Stage III colon cancer is sometimes called Dukes' C colon cancer.

Stage IV: In stage IV, cancer may have spread to nearby lymph nodes and has spread to other parts of the body such as the liver or lungs. Stage IV colon cancer is sometimes called Dukes' D colon cancer

Treatment Options

Three types of standard treatment are used. These included the following:

Surgery: Surgery (removing the cancer in an operation) is the most common treatment for all stages of colon cancer. A surgeon may remove the cancer using one of the following types of surgery:

Local excision: If the cancer is found at a very early stage, the doctor may remove it without cutting the abdominal wall. Instead, the doctor may put a tube (a colonoscope) through the rectum into the colon and cut the cancer out. This is called a polypectomy.

Resection: If the cancer is larger, the doctor will perform; a partial colectomy (removing the cancer and a small amount of healthy tissue around it). The doctor may then perform an anastomosis (sewing the healthy parts of the colon together). The doctor will also usually remove lymph nodes near the colon and examine them under a microscope to see whether they contain cancer. Colon cancer surgery with anastomosis. Part of the colon containing the cancer and nearby health tissue is removed, and then the cut ends of the colon are joined.

Resection and colostomy: If the doctor is not able to sew the two ends of the colon back together, a stoma (an opening) is made on the outside of the body for waste to pass through. This procedure is called a colostomy. A bag is placed around the stoma to collect the waste. Sometimes the colostomy is needed until the lower colon has healed, and then it can be reversed. If the doctor needs to remove the lower colon and rectum, however, the colostomy may be permanent. Colon cancer surgery with colostomy. Part of the colon containing the cancer and nearby healthy tissue is removed, a stoma is created, and a colostomy bag is attached to the stoma. The surgical resection of the tumor is usually done through and midline open abdominal incision but in some cases may be done through smaller incisions and a laparoscope. Even if the doctor removes all the cancer that can be seen at the time of the operation, some patients may be given chemotherapy or radiation therapy after surgery to kill any cancer cells that are left. Treatment given after the surgery, to increase the chances of a cure, is called adjuvant therapy.

Chemotherapy: Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. Usually patients with tumor spreading to the lymph nodes at the time of surgery receive chemotherapy. When chemotherapy is taken by mouth or injected into a vein the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy) This is the most common form of chemotherapy. When the drug is placed directly into an organ or body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas only (regional chemotherapy).The doctor giving the chemotherapy is called an oncologist and will consult with the surgeon on the case. The chemotherapy if given is usually started several weeks after the surgery and can be given in the oncologist office. Occasionally with large rectal cancers this may be started with radiation prior to surgery to shrink the size of the tumor.  

Radiation: Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells. There are two types of radiation therapy. The most common type is external radiation therapy which uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way radiation is given depends on the type and stage of the cancer being treated. Radiation is most commonly given for cancers low in the rectum. It is often given with chemotherapy for these large rectal cancers.

Summary of Treatment Options for Colon Cancer Stage 0 Colon Cancer (Carcinoma in Situ)

-       Local excision or simple polypectomy

-       Resection/anastomosis. This is done when the cancerous tissue is too large to remove with local excision

Stage I Colon Cancer

-       Resection/anastomosis.

Stage II Colon Cancer
-       Resection/anastomosis

Stage III Colon Cancer

-       Resection/anastomosis with chemotherapy. Radiation is often added for low rectal cancers

Stage IV and Recurrent Colon Cancer             Treatment may include any of the following

-       Resection/anastomosis (surgery to remove the cancer so it will not bleed or obstruct in the future. Also bypass surgery if an obstruction is present).

-       Surgery to remove parts of other organs, such as the liver, lungs or ovaries, where the tumor has recurred or spread to.

-       Radiation therapy or chemotherapy may be offered to some patients as palliative therapy for symptoms and to improve the quality of life.

-       Cryosurgery or Radiofrequency ablation for live metastasis if they can not be resected surgically.

Follow-up After Colon and Rectum Cancer Treatment

For years after treatment ends, regular follow-up exams will be very important for you. These exams, which will include a physical and rectal exam, colonoscopy, and blood tests, can tell if the cancer has come back. Other tests such as chest x-ray, CT and MRI scans may also be done if anything suggests that the cancer has returned. If the cancer returns, it is often within the first 2 to 3 years after surgery.