Colon Cancer

Also Known as Colorectal Cancer

Colon cancer or colorectal cancer involves a cancer that originates in the large colon or in the rectum. They usually begin as polyps that form along the lining of the colon and grow on stalks. Some can be sessile and grow directly on the lining of the colon without a stalk. Most cancers of the colon are adenocarcinomas, although some can be lymphomas, sarcomas, melanomas or carcinoid tumors of the colon. These last few are very rare when compared to adenocarcinomas of the colon.

The main cause of colon cancer is an abnormally growing cell in the glands along the lining of the colon. No one knows exactly what causes this to occur; however, there are several risk factors for getting colon cancer. These include being older than age sixty years, being African American or of Eastern European descent, having other cancers in the body, eating a lot of processed meat or red meat, having multiple colonic polyps, having a family history of colon cancer, having a personal history of breast cancer and having a history of Crohn's colitis or ulcerative colitis.

There are some hereditary conditions that predispose a person to getting colorectal cancer. These include Lynch Syndrome, also known as nonpolyposis colorectal cancer and familial adenomatous polyposis, also called FAP. High fat, low fiber diets and diets high in red meat can contribute to getting colon cancer.

Symptoms of colon cancer or colorectal cancer may or may not be present. A common finding is blood in the stool or black, tarry stools that can be picked up using a fecal occult blood test of the stool. There can be pain or cramping in the abdomen, especially in the lower abdomen, and diarrhea or constipation. Stools can become thinner due to partial blockage of the stools and you can have anemia for which there is no other explanation and weight loss for no obvious reason.

Doctors can evaluate a person for colon cancer by doing fecal occult blood testing of the stool. It is a very sensitive test but not very specific. A CT scan of the colon can be done in lieu of a colonoscopy. A colonoscopy, however, remains the gold standard for colon cancer testing. It involves the insertion of a lighted flexible scope into the rectum and traveling the scope up through the large bowel until it reaches the cecum. The doctor looks for polyps or ulcerations of the colon and takes biopsies of all polyps and irregularities. Polyps and cancers can be removed in their entirety using the endoscope. A flexible sigmoidoscopy is a shorter endoscope that screens only for colon cancer in the sigmoid colon or about 60 cm into the colon.

Doctors will check for the presence of anemia using a blood test. Liver function tests can tell if the liver is involved with colon cancer. CT scanning or MRI scanning of the abdomen can look for metastatic disease, especially to lymph nodes and liver.

Colon cancer is staged in order to tell how far the tumor has progressed. Stage 0 means the cancer is just in the lining of the colon. Stage I means the inner layers of colon are affected but no other layers. Stage II means the cancer has spread through the muscular layer of the colon wall. Stage III means that lymph nodes are involved. Stage IV means that other body areas are affected with cancer and the cancer is metastatic.

Blood testing for CEA, which stands for carcinoembryonic antigen and levels of CA 19-9 are done. If they are elevated, the values can be followed for recurrences of cancer. Not every case of colon cancer shows a positive CEA or a positive CA 19-9.

Treatment of colon cancer includes surgery to remove as much of the cancer as possible. Then things like radiation are done along with chemotherapy to remove hidden pockets of cancer and to attempt to get rid of the entire cancer.