This week I want to talk about screening for colorectal cancer (CRC). Fortunately, screening for this type of cancer has become more common due to increased public awareness aided by campaigns such as CDC's Screen for Life

The most recent statistics for CRC are from 2010. That year, 125,968 people were diagnosed with CRC. The disease killed 51,848 in 2009, making it the third deadliest cancer in men and women over 50 years of age. If caught when the disease is localized to the colon, 90 percent of patients are alive at 5 years after diagnosis. However, only 39 percent of people are diagnosed at an early stage.

The good news is that the number of new cases and deaths has continued to drop over the last decade or so. The incidence of new cases dropped 4.1 percent per year from 2005 to 2009 and the death rate dropped 2.4 percent per year for men and 3.1% per year for women over that time span. The decreases are likely due to more people undergoing recommended screening.

Warning signs that may indicate CRC include blood in the stool, persistent abdominal pain, change in bowel movements (especially smaller diameter stools), unexplained weight loss and iron-deficiency anemia.

An advertisement that ran in the New York Times a few years ago listed three frightening early warning signs of colon cancer: You feel great; You have a healthy appetite; You're only 50. This ad was designed to let people know they can have CRC without any warning signs.

The risk of developing CRC increases with age (93 percent of cancers occur after age 50). A family history of a sibling or parent with CRC or colon polyps also increases one's risk for CRC, though 75 percent of CRC occurs in patients with no family history.

Inflammatory bowel disease (Crohn's disease & ulcerative colitis) also increases the risk of CRC. Others who may be increasing their risk include those who don't exercise regularly, have a diet high in fat and low in fruits, vegetables and fiber, smoke cigarettes, are obese, or who drink too much alcohol.

Colorectal cancer usually begins its life as a small nest of abnormal gland cells in the wall of the colon (large intestine). The cells eventually grow into structures called polyps. These polyps are not cancerous, but they have the potential to transform into full-blown cancer. There are two types of polyps - adenomatous and hyperplastic. Adenomatous polyps have the potential to become cancerous.

The goal of any cancer screening program is to either find abnormal cells before they have turned into cancer or when the cancer is very small. There are a number of different ways to screen for CRC and different professional groups have produced various screening recommendations. I prefer the one recommended by the U.S. Preventive Services Task Force that can be found at

CRC screening tests can be divided into those that detect adenomatous polyps and cancer and those that detect only cancer. The former group includes flexible sigmoidoscopy (a scope that visualizes the lower part of the colon), colonoscopy (a scope that looks at the entire colon), double-contrast barium enema (an X-ray procedure where dye and air are inserted in the colon), and "virtual colonoscopy" (an X-ray study using a CT scan to construct a three dimensional image of the colon). Flexible sigmoidoscopy and colonoscopy offer the added benefit of allowing the physician to remove polyps or biopsy suspicious lesions at the time of screening.

Tests that primarily detect cancer include high-sensitivity fecal occult blood testing (FOBT) and fecal immunochemical testing (FIT). FOBT involves following a specific diet and submitting multiple stool samples to a doctor or lab where they are tested for microscopic blood.

The FIT test is supplanting the FOBT in most doctors' offices. It has the advantage of not requiring dietary restrictions prior to doing the test and can be performed on a single stool specimen. It is also specific for human blood proteins whereas the FOBT may detect animal blood protein that a patient consumed and give a false positive test. If any of these tests are positive, patients usually need to have a colonoscopy to locate the source of the blood.

All of these tests have pros and cons that are too detailed to explore in this article, but a good summary can be found at: If you are over 50 or have other risk factors, you should speak to your doctor about what test or combination of tests may be right for you. The key to preventing or catching CRC early is to get screened and to stick to the recommended intervals for repeat screening.