Vanquishing colon cancer: Screening credited for decline in incidence, mortality

A colonoscopy may be one of the more dreaded rituals of turning 50, but a new report reinforces its role in bringing about a dramatic drop in one of the country’s most common—and deadly—cancers.

The percentage of Americans aged 50 to 75 who have had at least one colonoscopy almost tripled in a decade, from 19 percent in 2000 to 55 percent in 2010, according to an American Cancer Society report published this week in the March/April issue of CA: A Cancer Journal for Clinicians. The rate of new colorectal cancer diagnoses in Americans aged 50 and over fell 30 percent during that same period, the report said.  

Mortality rates, which have been declining for 20 years, also fell more in that decade than the previous one, about 30 percent over 10 years, compared with 20 percent in the 1990s, according to the report, an analysis of government data. Researchers credited colonoscopies and other screening tests—along with improvements in treatment—for the drop.

Dr. Polly Newcomb, head of the Cancer Prevention Program in Fred Hutchinson Cancer Research Center’s Public Health Division, agreed that the declines in incidence and mortality—which she called terrific news—are consistent with the use of screening.

 “Colorectal cancer is the second leading cause of cancer death in men and women but is very preventable,” she said. “Screening for colorectal cancer, unlike breast cancer, actually prevents disease from occurring through the identification and removal of precursor polyps. It also prevents serious disease by identifying cancer at its early stage when it is most effectively treated.”

The continuing decline in colon cancer rates gives rise to the hope that perhaps one day it could be eradicated.

Dr. Robert W. Day, a former director and president of Fred Hutch and an expert in disease prevention and screening, likened the effort to screen for colon cancer to the successful campaign to eradicate polio. “We could almost do the same thing with colon cancer,” he said.

When to get screened
Experts recommend that beginning at age 50, most people should undergo one of several types of screening: a colonoscopy every 10 years, a test for blood in the stool every year, or a sigmoidoscopy (which examines only the lower third of the colon and the rectum) every five years along with a stool test every three to five years. People with higher risk factors, including African Americans, whose incidence rates are 25 percent higher than whites, and those with relatives with the disease, should talk with their doctors about whether they should begin screening earlier and how often they should be tested.

A colonoscopy has the potential to prevent cancer by detecting polyps, or abnormal growths, before they might develop into cancer. A doctor inserts a flexible lighted tube with a small camera on the end to examine the entire length of the colon and rectum—a muscular tube about 3 feet long—then snips off any polyps found.

It is considered by many the gold standard of screening tests, and most people choose it over the other tests.  But it also requires a day or two of laxatives and liquids to “prep,” or empty out the colon, for examination, leading some people to delay doing the test or refusing outright. Studies have shown that people are far more likely to be screened for colon cancer if their doctors offer them a range of screening options.

In addition to recommended screenings, other steps can decrease the risk of colon cancer. Regular moderate-to-vigorous aerobic exercise significantly reduces a risk factor associated with the formation of colon polyps and colon cancer in men, according to a study led by Fred Hutch researchers.  

“In addition to receiving screening at regular intervals, there are many lifestyle factors that can reduce risk, stopping smoking, maintaining a normal body weight, being physically active, and limiting the consumption of red meat,” said the Hutch’s Newcomb.

Even with the gains announced this week, colorectal cancer remains the third most commonly diagnosed and the second leading cancer killer in the U.S. for both men and women. The report estimates that 136,830 people will be diagnosed with colon cancer in 2014 and 50,130 people will die from it.

At a news conference releasing the 2014 colorectal cancer statistics, a coalition of more than 70 public, private, and voluntary organizations, led by the American Cancer Society and the U.S. Centers for Disease Control and Prevention, announced a joint effort to increase colon screening rates in the United States to 80 percent by 2018. 

Solid tumors, such as those of the colon, are the focus of Solid Tumor Translational Research, a network comprised of Fred Hutchinson Cancer Research Center, UW Medicine and Seattle Cancer Care Alliance. STTR is bridging laboratory sciences and patient care to provide the most precise treatment options for patients with solid tumor cancers. 

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