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Colorectal cancer is a major health concern and public health problem in
most of the Western countries despite widespread use of screening technique
to detect early stages of this disease. In the United States alone more than
148,000 people are diagnosed with colorectal cancer each year. Over 55,000
deaths occur in the United States due to colorectal cancer. Colon cancer is
a very common disease and it is the third most common type of cancer in both
sexes. In men it ranks third after prostate and lung cancer and in women
after lung and breast cancer. Colorectal cancer ranks second after lung
cancer in terms of number of deaths from cancer.

Majority of colorectal cancers (72%) start in the colon and smaller fraction
(28%) arises in the rectum. The lifetime risk of being diagnosed with
colorectal cancer in the United States is 5.9% for men and 5.5% for women.

There are several known risk factors for colorectal cancer. Being a male
poses higher risk of colorectal cancer compared to being female. Increasing
age is associated with an increase in the risk of colorectal cancer.
Incidence of colorectal cancer is higher among African Americans compared to
Caucasians. Risk of developing colorectal cancer is much higher for people
living in the industrialized nations compared to less industrialized
nations.

Diet, rich in fat and cholesterol, is linked to higher risk of developing
colorectal cancer. Lack of proper exercise, presence of inflammatory bowel
disease, some types of polyps and history of family members with diagnosis
of colorectal cancer have been associated with higher risk of development of
colorectal cancer.

Early stages of colorectal cancer may not cause any symptoms. Some people
might experience vague symptoms like mild abdominal pain, flatulence or
diarrhea. Occasionally there might be microscopic bleeding and the diagnosis
of colorectal cancer would be suspected because of presence of anemia from
chronic bleeding. Some people might develop frank bleeding or symptoms of
bowel obstruction.

Screening for colorectal cancer can detect the disease at an early stage. A
rectal examination and examination of the stool specimen for the presence of
microscopic quantity of blood are very common screening tools. Sigmoidocopy
and colonoscopy are more invasive investigations, which can detect and
remove some polyps that might be precursors of cancer. Less invasive
techniques like barium enema, virtual colonoscopy using a CT scan machine
are also often used in screening and diagnosis of colorectal cancer. Adults
having an average risk of colorectal cancer should start colorectal cancer
screening beginning at age 50.

Treatment of colorectal cancer depends upon the stage of the disease. Early
stages of colorectal cancers are treated with surgery alone, later stages of
colorectal cancer are treated with surgery followed by chemotherapy with or
without radiation treatment. Rectal cancers are more often treated with
radiation therapy compared to colon cancer. Advanced stages of colorectal
cancer, where the disease has spread to other organs, are usually treated
with chemotherapy alone. There are several new chemotherapeutic agents and
biological drugs available for the treatment of colorectal cancer. Treatment
of colorectal cancer has undergone marked changes in the last 10 years. The
newer drugs are showing much improved efficacy and prolonging life
expectancy in patients with advanced stage colorectal cancer.