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Colon Rectal Cancer

Colorectal cancer is cancer of either the colon or the rectum. This cancer is characterized by the development of malignant cells in the lining or epithelium of the first and longest portion of the large intestine, down into the lowest part, the rectum. Malignant cells are those have lost normal control mechanisms governing their growth. These cells often invade surrounding local tissue and they may spread throughout the body and invade other organ systems.

The colon is also known as the large bowel or the large intestine. The rectum is the continuation of the large intestine into the pelvis that terminates in the anus. Physiologically, the colon is responsible for the preservation of fluid and electrolytes as it propels the increasingly solid waste towards the rectum and anus for excretion.

If the cells lining the colon or rectum become malignant, they grow first locally and can invade partially or totally through the wall of the bowel and even into adjacent structures and organs. In this way, a tumor penetrates and invades the lymphatic system and the capillaries; thereby it gains access to the circulation system. Then the malignant cells invade other areas of the body, and start a new cancer in a different area. These tumor deposits, originating from the colon or rectum primary tumor, are the metastases.

The causes of colorectal cancer are now believed to be mostly environmental (about 80% of all cases), and about 20% genetic in the other casese. As malignant cells have a damaged genetic configuration, this means that in 80% of all cases, the environment spontaneously casued that change, whereas in those born with a genetic predisposition, they are either destined to get the cancer or environmental stimulii can easily cause the cancer. Exposure to cancerous agents known as carcinogens (cancer-causing agents in the environment may cause the genetic mutation. This is called carcinogenesis. Although carcinogens have been difficult to identify; however, in colorectal cancer, dietary factors seem to be involved.

It has been found that diets high in fat, red meat, high calories, and alcohol seem to predispose to colorectal cancer. Age plays a definite role in the predisposition to colorectal cancer, as it is uncommon before age 40. This incidence increases substantially after age 50 and doubles with each succeeding decade. There is also an increased risk for colorectal cancer for people who smoke. It has also been found that people who suffer from inflammatory diseases of the colon known as ulcerative colitis and Crohn's colitis are also at increased risk.

As for genetic predisposition, where a family has family of colorectal cancer, the offsprings are at substantial risk.
The cancer usually begins with the presence of polyps. In fact, the development of polyps of the colon can precede the development of colorectal cancer by 5 or more years. Polyps are benign growths on the colon and rectum lining. They can be totally unrelated to cancer. Polyps, when identified, should be removed for diagnosis. If the polyps are benign, the patient should undergo careful surveillance for the development of more polyps or the development of colorectal cancer. It they are malignant, an operation will be required to remove them in totality.

Colorectal cancer causes very recognizable symptoms related to its local presence in the large bowel or by its effect on other organs if it has spread. These symptoms may occur alone or in combination (but the same symptoms can relate to a number of other non-cancerous diseases)

• blood in the stool
  
• unexplained weight loss
  
• a change in bowel habit
  
• bloating, persistent abdominal distention
  
• constipation
  
• a feeling of fullness even after having a bowel movement
  
• narrowing of the stool-so-called ribbon stools
  
• persistent, chronic fatigue
  
• abdominal discomfort
  
• sometimes, nausea and vomiting
  

Once colorectal cancer has been detected, its exact stage (see below) must be established, and a team of surgeon, chemotherapist and radio (and/or radium) therapist have to be assembled.

The doctors will be most interested in the characteristics of the primary tumor, its depth of penetration through the bowel, and the presence or absence of regional or distant metastases, stage is derived. Unfortunately, the depth of penetration through the bowel or the presence of regional lymph nodes can't be understood before surgery.

Colon cancer is assigned stages I through IV, based on the following general criteria:

• Stage I: the tumor is limited to the epithelium or has not penetrated through the first layer of muscle in the colorectal wall.
  
• Stage II: the tumor will have penetrated through to the outer wall of the colon or has gone through it, possibly invading other local tissue.
  
• Stage III: Where the depth or size of tumor associated with regional lymph node involvement.
  
• Stage IV: any of previous criteria associated with metastasis.
  

As with all cancers, staging plays an important pre-treatment role to best determine treatment options. With colorectal cancer, almost all cancers are treated with surgery first, regardless of stage. Colon cancers through Stage III, and even some Stage IV colon cancers, are treated with surgery first, before any other treatments are considered.

Thereafter radio and/or radium therapy is used as an adjunct to surgery if there is concern about potential for local recurrence post-operatively and the area of concern will tolerate the radiation. Unfortunately, radiation has significant dose limits when residual bowel (what is left after the surgery) is exposed to it because the small and large intestine do not tolerate radiation well.

Radiation is also used in the treatment of patients who have advanced to metastatic stage. Radiation is particularly useful in shrinking metastatic colon cancer to the brain.

Chemotherapy is used for patients who have had all established tumors removed but are at risk for recurrence (adjuvant chemotherapy). Chemotherapy may also be used when the cancer is stage IV and is beyond the scope of regional therapy.
Prognosis is the long-term outlook or survival after therapy. Statisically, about 50% of patients treated for colorectal cancer survive. The survival rates are really dependent upon the stage of the cancer at the time of diagnosis, making early detection a very worthwhile endeavor.

Therefore, approximately 15% of patients are found with stage I, and 85-90% survive. 20-30% of cases are Stage II and 65-75% survive. Stage III comprises 30% to 40% of which 55% survive. The remaining 20-25% found with stage IV and survival is rare.
At present, many alternative therapies exist, but have not been studied in a large-scale, scientific way. These include, but are not limited to large doses of vitamins, high-fiber diets, and green tea are among therapies employed. It is generally considered that smoking and drinking alcohol should be avoided completely. However, it is established that a low-fat, vegetable and fruit diet rich also in fiber combined with a regular exercise program can perhaps avoid many of the environmental factor that can cause gene mutation and the onset of colorectal cancer.