Prevention strategies and screening tests could help cut the number of deaths in the United States from colorectal cancer — if people took full advantage of them.

As it is, only 65 percent of the adults who should be screened actually are, a government survey found. And even with many screening and prevention strategies, colorectal cancer remains the country’s second-leading cause of cancer-related deaths for both men and women. (Lung cancer is the first.)

A survey of 3,357 men and women published in 2010 in the American Journal of Preventive Medicine found that the top three reasons for not getting screened for colorectal cancer were the failure of a health-care professional to suggest testing, a lack of awareness by patients about whether they should be screened and a belief that testing is too costly. (Under the 2010 health-care overhaul law, Medicare and new private insurance plans are required to cover most types of colorectal cancer screening with no co-payments or deductibles.)

In 2011, an estimated 141,000 Americans received a diagnosis of colorectal cancer, and the disease caused 49,000 deaths. Although better screening and treatment have resulted in a drop of almost 3 percent in mortality rates each year since the late 1990s, nearly half of the cases are diagnosed at a late stage, when treatment is less likely to be lifesaving.

Highly preventable

Colorectal cancer usually develops over 10 to 15 years without causing symptoms. Most cases start as noncancerous polyps in the lining of the large intestine or its final segment, the rectum. Detecting and removing polyps prevents them from developing into cancer. Screening tests, such as colonoscopy, can reveal not only cancer but also precancerous growths, which can be removed early.

The five-year survival rate for early-stage colorectal cancer is 90 percent if the disease is detected while still localized. Survival drops to 10 percent in cases discovered after the cancer has spread to other organs. Researchers estimate that 1,900 deaths could be prevented for every 10 percent increase in the number of people being screened.

Several screening tests are available, but a positive result doesn’t necessarily mean you have cancer. Stool tests can return false positives because of bleeding from noncancerous conditions such as hemorrhoids, ulcers, infections or inflammatory bowel disease. Questionable findings revealed by stool testing, sigmoidoscopy or CT colonography should be confirmed by a colonoscopy.

An anti-cancer lifestyle

Various studies suggest that the following diet and lifestyle changes could eliminate up to 40 percent of colorectal cancer:

Eat less red meat. During digestion, red and processed meats form carcinogenic chemicals. The colorectal cancer risk was 22 percent greater among people who ate five ounces of red and processed meat a day compared with those who ate less than an ounce a day, according to a 2011 meta-analysis combining results of 21 studies.

Eat more vegetables, fruit and fiber. A recent study looked at the impact of diet on 1,900 people with a history of precancerous polyps. Those who met goals for cutting fat and consumed at least 18 grams of fiber and 3.5 servings of fruit and vegetables per 1,000 calories each day were 35 percent less likely to develop new polyps during the study.

Exercise. Sedentary people are about twice as likely to develop colorectal cancer as highly active exercisers. Aim for at least 30 minutes a day of moderately intense exercise.

Maintain a healthy weight. Being overweight increases the risk of colorectal cancer no matter how active you are. Excess abdominal fat (indicated by a waist size that exceeds 35 inches for women and 40 inches for men) could be a more important risk factor than overall body weight.

Don’t rely too much on drugs or supplements. Some, such as aspirin and related nonsteroidal anti-inflammatory drugs, calcium supplements and, for women, post-menopausal hormone therapy, might lower risk, evidence shows. But all pose additional health risks, and there’s not enough proof of their effectiveness and safety to recommend routine use to prevent colon cancer.

Limit alcohol. People who average two to four drinks a day have a 23 percent higher risk than those averaging less than one drink a day.

Don’t smoke. Researchers have enough evidence to conclude definitively that smoking tobacco contributes to colorectal cancer.

Copyright 2011. Consumers Union of United States Inc.