Amidst gloomy reports about the rates of cancer, there is a ray of good news. Over the past several decades, the incidence of colon and rectal cancers (colorectal, or CRC) has declined significantly.

CRC is the fourth most common type of cancer in the world, and the leading cause of cancer deaths in North America. In the mid 1970s, physicians diagnosed about 60 cases of CRC for every 100,000 people; about half of them survived at least five years. In 2004, the latest year for which we have data, the rate dropped to 48 cases per 100,000, and 65 percent survived five or more years. Other data demonstrates that between 1984 and 2004, CRC rates fell almost 26 percent.

What's Behind the Decline?

There are several factors at play, but the most significant reason is the increase in colon cancer screenings. Screening for breast cancer and prostate cancer is widespread. However, mammography and PSA tests catch cancers after they've already developed. In contrast, colonoscopy, the best available CRC screening tool, also plays an important role in preventing colon and rectal cancers. During a colonoscopy, physicians can remove pre-cancerous polyps from the wall of the colon at the same time they are checking for signs of cancer. Polyps are usually benign, but can potentially develop into cancer.

Despite the effectiveness of colonoscopy, fewer than half the people who should be screened are. The American College of Gastroenterology recommends that adults who don't have risk factors, such as a family history, begin screening at 50 and repeat colonoscopies every 10 years. Colon cancer is more prevalent in African Americans so they should have a baseline colonoscopy at 45.

CRC Prevention

In addition to getting colonoscopies, you can take other steps to reduce your risk for colon cancer.

Eat a balanced diet that contains a variety of fruits, vegetables and whole grains. They are chock full of fiber, which is important for digestive health.

Maintain a healthy weight. Obesity is a major risk factor for CRC. Obese individuals are two-to-three times more likely to develop colon or rectal cancer. Exercise is great for cancer prevention and helps you control your weight.

Don't smoke. People who have smoked for 20 years or more increase their risk for CRC by 50 percent, and have a higher risk of dying from the disease.

Researchers are also looking for drugs that can block or reverse CRC so there may be more good news on the horizon.