Colorectal cancer, also called colon cancer or large bowel cancer, includes cancerous growths in the colon, rectum and appendix. It is a silent killer that develops slowly over a long period of time and affects thedigestive system. Colorectal cancer is the third most common form of cancer and the second leading cause of cancer-related death in the Western world. Colorectal cancer causes 655,000 deaths worldwide per year. Many colorectal cancers are thought to arise from adenomatous polyps in the colon. These mushroom-like growths are usually benign, but some may develop into cancer over time. The majority of the time, the diagnosis of localised colon cancer is through colonoscopy. Therapy is usually through surgery, which in many cases is followed by chemotherapy.

Causes

Doctors are certain that colorectal cancer is not contagious (a person cannot catch the disease from a cancer patient). Some people are more likely to develop colorectal cancer than others. Factors that increase a person's risk of colorectal cancer include high fat intake, overdependence on junk food, a family history of colorectal cancer and polyps, the presence of polyps in the large intestine, and chronic ulcerative colitis.

Treatment options

"The treatment depends on several factors, including the size, the location, and the extent of the tumour. Surgery to remove polyps or the tumour and the surrounding tissue is really the most common type of treatment. Chemotherapy and radiation treatment are also used for cancer. Chemotherapy and radiation therapy may also be combined with surgery. Again, it's important to discuss definitions. Chemotherapy uses drugs to kill cancer cells, control tumour growth, and also to relieve symptoms. Radiation therapy uses X-rays to kill cancer cells, shrink tumours, or destroy remaining cancer cells in the body after surgery,” says Dr Atul Sharma (All India Institute of Medical Sciences , New Delhi).

Risk factors

Certain factors increase a person's risk of developing the disease. These include:

Age:  The risk of developing colorectal cancer increases with age. Colorectal cancer is most common in adults over the age of 50, with more than 90 per cent of cancers occurring in this age group

History of cancer:  Individuals who have previously been diagnosed and treated for colon cancer are at risk for developing colon cancer in the future. Women who have had cancer of the ovary, uterus, or breast are at higher risk of developing colorectal cancer.

Heredity:  Family history of colon cancer, especially in a close relative before the age of 55 or multiple relatives 
Long-standing ulcerative colitis or Crohn's disease of the colon

Smoking: Smokers are more likely to die of colorectal cancer than non-smokers. An American Cancer Society study found that women who smoked were more than 40 per cent more likely to die from colorectal cancer than women who never had smoked. Male smokers had more than a 30 per cent increase in risk of dying from the disease compared to men who never had smoked.

Diet : In June 2005, a study by the European Prospective Investigation into Cancer and Nutrition suggested that diets high in red and processed meat, as well as those low in fibre, are associated with an increased risk of colorectal cancer. Changes in the lifestyle cause the killer cancer with higher pre-disposition in women.

Physical inactivity: People who are physically active are at lower risk of developing colorectal cancer.
Virus: Exposure to some viruses (such as particular strains of human papilloma virus) may be associated with colorectal cancer.

Alcohol: Drinking may be a cause of earlier onset of colorectal cancer. People who drank more than eight servings of beer or spirits per week had at least a one in five chance of having significant colorectal neoplasia detected by screening colonoscopy.

Environmental factors: Industrialised countries are at a relatively increased risk compared to less developed countries or countries that traditionally had high-fibre/low-fat diets.

It's important to note that because symptoms are not always present, regular screenings and early detection of polyps are very important for people at average risk and those at higher risk of colon cancer, such as people with ulcerative colitis and Crohn's.

What's really important to emphasise is that when the cancer is symptomatic, typically it is at an advanced stage and it's not a good idea to wait to have symptoms in order to say that at that moment one wants to have a colonoscopy. It would be significant to note that amongst patients who are diagnosed of colorectal cancer women outnumber men drastically.
Prevention
According to Dr R Ranga Rao (Rajiv Gandhi Cancer Institute, New Delhi), "A diet rich in fibre actually prevents colorectal cancer. Many years ago the researchers found that Africans who ate high fibre diets had a low incidence of colon cancer. Since then dozens of studies have supported the protective role of fibre. There are plenty of reasons fibre might lower colon cancer risk: fibre increases faecal bulk and may dilute potential cancer-causing substances; fibre reduces the time the stool spends in the intestine, which might limit the colon's exposure to carcinogens.

Even if cancer is found, it's important to realise that cancer is treatable when found early.  The survival rate for colon cancer is 93% when treated at the earliest stages.

Screening: It is a test performed before symptoms of cancer develop. Screening is extremely important. Its goals are to prevent cancer by identifying and removing precancerous polyps.