Although the benefits of cancer screening in elderly people are often less certain than the risks, many silver-haired Americans are still getting the routine tests, researchers said Monday.
More than half of women ages 75 to 79 in a nationwide survey said they were being screened for breast cancer and had had recent Pap smears to look for signs of cervical cancer.
Similarly, most men in that age group had been screened for prostate cancer recently. The numbers dropped some for people over 80, but were still high.
That's despite the fact that there is still substantial uncertainty over the potential benefits of screening tests in the elderly.
"Historically older adults have been excluded from screening trials, so the screening efficacy data in this population are really limited," said Keith M. Bellizzi, a public health researcher at the University of Connecticut, who lead the new work.
While some screening tests -- say, mammography or colonoscopy -- have been shown to save lives in middle-aged adults, all have downsides.
There is the cost of looking for disease in people who feel fine, for instance, and the potential complications of procedures such as colonoscopies. The tests may also sound a false alarm that can lead to unnecessary biopsies, and in some cases doctors diagnose and treat cancers that would never have caused any harm if left alone -- a phenomenon known as overdiagnosis.
The benefits may outweigh the risks in younger adults, but as people get older and sicker, the balance tips.
"At a minimum, in order to see any benefit of screening, you would want your patient to have a life expectancy of more than five years," Bellizzi told Reuters Health.
And screening people who have other health problems may also require extra thought, he added.
"If you are going to screen in older adults for a cancer, you wouldn't want to do that unless you're sure that individual would be able to tolerate that treatment," Bellizzi said.
He and his colleagues used data on more than 4,000 Americans 75 and older, who had been interviewed in 2005 and 2008 as part of the National Health Interview Survey. Their findings appear in the Archives of Internal Medicine.
The researchers found that 57 percent of seniors aged 75 to 79 had been screened for colon cancer, and 56 percent of men had been screened for prostate cancer in the past year.
Sixty-two percent of similarly aged women had been screened for breast cancer within the past two years, and 53 percent had been screened for cervical cancer sometime during the past three years.
Medical groups differ somewhat in their screening advice, especially for older adults in whom the benefits are less certain.
The government-backed U.S. Preventive Services Task Force, for instance, either recommends against routine screening of people 75 and older, or says the evidence is insufficient to balance the benefits and harms, depending on the type of cancer.
The American Cancer Society, on the other hand, has no upper age limit for its colon cancer recommendations, but notes that men whose life expectancy is less than 10 years should not be offered prostate cancer screening.
Bellizzi warned that his data didn't show why people were being screened, and so couldn't tell whether or not the tests were being used appropriately.
While some screened seniors may be healthy and have a long life ahead of them, others may be very unlikely to get anything but harm from screening.
How to separate those two groups is a question that hasn't received attention, he said.
"Over 50 percent of physicians are continuing to recommend screening tests in older men and women," Bellizzi said. "I'm hopeful that these findings will serve as a catalyst for an important dialogue that needs to take place."
For graying citizens who face the choice of whether or not to get screened, he said they should weigh their options with their physicians based on their personal values and preferences.
"I would recommend for patients to have a real thoughtful conversation with their provider to talk about the potential harms and benefits of screening," Bellizzi said.