Colon cancer incidence rates decreasing steeply in older Americans

Colon cancer incidence rates have dropped 30 percent in the U.S. in the last 10 years among adults 50 and older due to the widespread uptake of colonoscopy, with the largest decrease in people over age 65. Colonoscopy use has almost tripled among adults ages 50 to 75, from 19 percent in 2000 to 55 percent in 2010.

The findings come from Colorectal Cancer Statistics, 2014, published in the March/April issue of CA: A Cancer Journal for Clinicians. The article and its companion report, Colorectal Cancer Facts & Figures, were released today by American Cancer Society researchers as part of a new initiative by the National Colorectal Cancer Roundtable to increase screening rates to 80 percent by 2018.

Colorectal cancer, commonly called colon cancer, is the third most common cancer and the third leading cause of cancer death in men and women in the United States. Its slow growth from precancerous polyp to invasive cancer provides a rare opportunity to prevent cancer through the detection and removal of precancerous growths. Screening also allows early detection of cancer, when treatment is more successful. As a result, screening reduces colorectal cancer mortality both by decreasing the incidence of disease and by increasing the likelihood of survival.

Using incidence data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program and the Centers for Disease Control and Prevention's National Program of Cancer Registries, as provided by the North American Association of Central Cancer Registries (NAACCR), researchers led by Rebecca Siegel, MPH found that during the most recent decade of data (2001 to 2010), overall incidence rates decreased by an average of 3.4 percent per year.

However, trends vary substantially by age. Rates declined by 3.9 percent per year among adults aged 50 years and older, but increased by 1.1 percent per year among men and women younger than 50. That increase was confined to tumors in the distal colon and rectum, patterns for which a rise in obesity and emergence of unfavorable dietary patterns has been implicated.

Most strikingly, the rate of decline has surged among those 65 and older, with the decline accelerating from 3.6 percent per year during 2001-2008 to 7.2 percent per year during 2008-2010. The "larger declines among Medicare-eligible seniors likely reflect higher rates of screening because of universal insurance coverage," the authors write. "In 2010, 55 percent of adults aged 50 to 64 years reported having undergone a recent colorectal cancer screening test, compared with 64 percent of those aged 65 years and older."

Like incidence, mortality rates have also declined most rapidly within the past decade. From 2001 to 2010, rates decreased by approximately 3 percent per year in both men and women, compared with declines of approximately 2 percent per year during the 1990s.

Colon cancer is the third most commonly diagnosed cancer and the second leading cause of cancer death in men and women combined in the US. The American Cancer Society estimates 136,830 people will be diagnosed in 2014 and 50,310 will die from colon cancer in the United States.