Colon cancer is a disease in which malignant (cancer) cells form in the tissues of the colon.
The colon is part of the body’s digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).
Signs and symptoms
A doctor should be consulted if any of the following problems occur:
> A change in bowel habits.
> Blood (either bright red or very dark) in the stool.
> Diarrhea, constipation, or feeling that the bowel does not empty completely.
> Stools that are narrower than usual.
> Frequent gas pains, bloating, fullness, or cramps.
> Weight loss for no known reason.
> Feeling very tired.
Risk factors include the following:
> Age 50 or older.
> A family history of cancer of the colon or rectum.
> A personal history of cancer of the colon, rectum, ovary, endometrium, or breast.
> A history of polyps (small pieces of bulging tissue) in the colon.
> A history of ulcerative colitis (ulcers in the lining of the large intestine) or Crohn disease.
- Stage 0 (Carcinoma in Situ): In stage 0, abnormal cells are found in the innermost lining of the colon. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.
- Stage I: In stage I, cancer has formed and spread beyond the innermost tissue layer of the colon wall to the middle layers. Stage I colon cancer is sometimes called Dukes A colon cancer.
Stage II colon cancer is divided into stage IIA and stage 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 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:
– 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 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.
- Recurrent Colon Cancer: Recurrent colon cancer is cancer that has recurred (come back) after it has been treated. The cancer may come back in the colon or in other parts of the body, such as the liver, lungs, or both.
Transurethral resection (TUR) with fulguration: Surgery in which a cystoscope (a thin lighted tube) is inserted into the bladder through the urethra. A tool with a small wire loop on the end is then used to remove the cancer or to burn the tumor away with high-energy electricity. This is known as fulguration.
Surgery (removing the cancer in an operation) is the most common treatment for all stages of colon cancer. A doctor 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 through the abdominal wall. Instead, the doctor may put a tube through the rectum into the colon and cut the cancer out. This is called a local excision. If the cancer is found in a polyp (a small bulging piece of tissue), the operation 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.
> Resection and colostomy: If the doctor is not able to sew the 2 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 only until the lower colon has healed, and then it can be reversed. If the doctor needs to remove the entire lower colon, however, the colostomy may be permanent.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the spinal column, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy).
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy. External radiation therapy 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 the radiation therapy is given depends on the type and stage of the cancer being treated.
Targeted therapy is a type of treatment that uses drugs or other substances to identify and attack specific cancer cells without harming normal cells. Monoclonal antibody therapy is a type of targeted therapy being studied in the treatment of colon cancer.
Monoclonal antibody therapy uses antibodies made in the laboratory from a single type of immune system cell. These antibodies can identify substances on cancer cells or normal substances that may help cancer cells grow. The antibodies attach to the substances and kill the cancer cells, block their growth, or keep them from spreading. Monoclonal antibodies are given by infusion. They may be used alone or to carry drugs, toxins, or radioactive material directly to cancer cells.