The colon is a part of the digestive tract that connects the stomach and small intestine to the anus. Colon cancer is a growth that occurs in the lining of this colon. It is an extremely common problem worldwide, with over 1 million new cases of this illness diagnosed annually. It is thought that both environmental factors such as diet and smoking, as well as genetic factors play important role in its development.
The diagnosis of colon cancer often involves colonoscopy, an examination of the colon using an instrument called colonoscope that enables an evaluation of the inner lining of the colon as well as to take a biopsy or sampling of cancer tissue. Once the diagnosis of colon cancer is made, the extent of the disease is often determined using a radiologic examination called CT scan. It allows an initial assessment of the extent of spread of cancer. Often routine blood tests including complete blood count (CBC), liver function tests, and a tumor marker called CEA are obtained during the initial evaluation.
There are 4 stages of colon cancer. It is defined as Stage 1, if the cancer tissue is confined to the lining of the colon or polyp. In Stage 2 colon cancer, the cancer tissue has invaded the layers of colonic wall, but has not yet spread beyond the wall. In Stage 3 colon cancer, the cancer tissue has penetrated the entire thickness of the colonic wall and spread to nearby lymph nodes. In Stage 4 disease, the cancer has spread to other organs such as liver.
The staging of colon cancer is important since the prognosis of affected individual is highly dependent on the staging of cancer. For example, patients diagnosed with Stage 1 colon cancer have overall 5-year survival rate of 93%. On the other hand, those diagnosed with stage 4 cancer can only expect 7% survival rate at 5 year.
For cancer that has not spread, the surgery is the treatment of choice. In fact, surgery may be the only treatment necessary for patients with Stage 1 or 2 disease. However, some with Stage 2 disease may elect to receive chemotherapy. Following surgery, Stage 3 cancer requires chemotherapy, usually for about 6 months. The most commonly used chemotherapy is called FOLFOX regimen consisting of 5-FU, leucovorin, and oxaliplatin. Some may also elect to receive additional treatment with a new class of thearpy such as Erbitux or Avastin. Treatment for Stage 4 disease has to be individualized as a complete cure is unlikely, although many often also receive surgery and chemotherapy.
Following these treatment, careful follow-up is recommended even when the cancer is believed to be in complete remission. Thus, periodic evaluations including routine blood tests including CEA, CT scan and colonoscopy are advised.