Doctors and medical organizations often advise that past a certain age, older adults can forgo various screening tests for cancer. But many patients, no matter how old or sick they may be, are reluctant to abandon tests they’ve long been told can be lifesaving.

To be sure, among my close circle of septuagenarian friends, none of us have stopped getting annual mammograms, even though I, having previously had breast cancer, am likely to be the only one among them for whom the potential benefit might conceivably outweigh the risks.

I’ve met people with no known risk for colorectal cancer who continue to get colonoscopies well past the age of established recommendations. Not to mention the countless men at low risk for prostate cancer who continue to get PSA tests, often at the suggestion of their doctors, when the best evidence says that for such men the test can result in more harm than good.

Few may realize that ill-advised screening tests come at a price, and not just a monetary one that adds many billions to the nation’s health care bill. Every screening test has a rate of false positive results – misleading indications of a possible cancer that requires additional, usually invasive, testing with its own rate of complications.

A new online survey of randomly selected participants clearly showed that women are more aware of the benefits of mammography screening than its harms. If, for example, a mammogram falsely detects a lesion — a not infrequent occurrence — the false-positive result may cause not only serious emotional distress but also lead to a surgical biopsy, which carries its own risks. And by the time they’ve had 10 mammograms, nearly half of women will experience a false-positive finding.

Likewise for men with a suspicious rise in the PSA test that results in multiple biopsies of the prostate. And colonoscopy itself can be hazardous, particularly for older people whose intestinal walls have become fragile and susceptible to perforation.

Why, you may wonder, do people continue to get tests they don’t need and that may exact costs to their health, time and pocketbook?

A primary reason: The widespread belief that it’s better to be safe than sorry. Why take a chance that a potentially lethal cancer will go undetected until it’s too late for a cure? Doing something is often more appealing than doing nothing. Many who think this way consider only the beneficial “what if’s” and not the possible downsides of cancer screening tests.

Another likely reason: Insurance often pays for the test, so why not take advantage? Indeed, Medicare covers the cost of annual mammograms, including the digital version, which is likely to be more accurate in discriminating between a real lesion and an artifact. Medicare also pays for the PSA, and many states mandate that private insurers also must cover it.

The Affordable Care Act (Obamacare) requires health plans that started on or after Sept. 23, 2010, to cover colonoscopy as a screening test (although older plans may not), and Medicare covers the cost of this test every two years for people 50 and older at high risk and every 10 years for people at average risk. (Colonoscopy can actually prevent cancer, not just detect it; if a polyp is found in which cancer could develop, it can be removed during the screening.)

Doctors themselves often directly or indirectly encourage ill-advised screening tests. As two California doctors, Dr. Deborah Grady and Dr. Rita F. Redberg, who are concerned about overuse of screening mammography, recently noted, “Payment systems in the United States typically reward ordering tests and procedures over taking the time to talk to patients about risks and benefits.”

They also pointed out that doctors often fear litigation if they fail to perform or order a test and the patient later turns out to have a cancer that might have been cured had it been detected sooner.

And doctors often believe at least as strongly as their patients do in the benefits of screening tests. For example, although both the American Cancer Society and the guidelines issued by the United States Preventive Services Task Force recommend mammogram screening every two years for women 55 and older, most doctors who endorse screening think it should be done annually, even for women aged 75 and older.

Although among young and midlife adults, the main challenge for doctors can be convincing them of the benefits of screening, among people in my age group and beyond, the difficult task more often involves advising patients that it’s time to forgo screening.

“Clinicians are frequently uncomfortable stopping cancer screening,” a medical team at Johns Hopkins University School of Medicine and School of Public Health reported in June. As a result, “Older adults with limited life expectancy are frequently screened for cancer even though it exposes them to risks of screening with minimal benefits,” they reported in JAMA Internal Medicine.

Practice guidelines for physicians called Choosing Wisely advise not recommending cancer screening to patients with a limited life expectancy. However, as the Hopkins team found in interviewing 40 older adults, many people believe that doctors cannot accurately predict a person’s life expectancy and don’t want to consider how long they may live when making screening decisions.

Rather than being told: “You may not live long enough to benefit from this test,” patients are likely to prefer a more positive message like: “This test would not help you live longer,” the team concluded. The team suggested that poor health status is a better reason than age for suggesting an end to screening.

Screening Guidelines

What the United States Preventive Services Task Force recommends.

Breast Cancer: Screening mammography every two years is recommended for women ages 50 to 74. For women 40 to 49 at average risk of cancer, regular screening can result in diagnosis and treatment of cancers that would not ever have become a health threat. For women 75 and older, current evidence is not adequate to balance benefits and harms of screening mammography.

Prostate Cancer: According to a draft recommendation, for men ages 55 to 69, doctors should inform them that screening “offers a small potential benefit of reducing the chance of dying of prostate cancer,” as well as the potential for harm from testing of overdiagnosis, overtreatment and ensuing complications. Screening is not recommended for men 70 and older.

Colorectal Cancer: For people of average risk, screening should start at 50 and continue until age 75. Screening adults aged 76 to 85 should be individualized depending on the patient’s overall health and prior screening history; they should have a reasonable life expectancy and be healthy enough to withstand treatment if cancer is found.