During my training to become a primary care physician, the importance of preventive cancer screening was ingrained in me. The idea of catching cancer at an early stage so we can better treat it made intuitive sense. But as I’ve learned over the years, the simplicity of this concept can obscure its limitations and make it difficult to persuade older or sick individuals that screening can do them more harm than good.

Early in my career, I dutifully kept track of what cancer screening tests my patients needed and made sure to remind them about these tests. But after poring over the details of the evidence behind various screening tests, working with thousands of patients, and conducting formal interviews of patients and doctors about screening, I’ve developed a more nuanced approach.

The catch-cancer-early-save-a-life trope is a bit misleading: the benefit of some tests is smaller than I had initially thought. Say 1,000 women have biennial mammograms between the ages of 50 and 74. Those 12,000 mammograms would prevent seven deaths from breast cancer. Yearly PSA testing among 1,000 men between the ages of 55 and 69 would lead to one to two fewer deaths from prostate cancer.

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Another often-overlooked aspect of screening is that the benefit isn’t immediate but lags by about 10 to 15 years for breast, colon, and prostate cancer. This means that if you look at one group of patients who got screened for these cancers and another group that did not, there would be no difference in deaths for 10 to 15 years.

If cancer screening had no side effects, then the small number of lives saved or the lag time wouldn’t matter. But there are downsides to cancer screening that can, at times, outweigh the small and delayed benefit.

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The hazards of cancer screening became more relevant as I became a geriatrician and devoted myself to caring for older adults. Although some of my patients are still working full time or traveling the world in their 70s and 80s, I usually see patients who have accumulated a number of serious illnesses, need to take multiple medications, and can no longer manage their daily activities without help. These patients, whose life expectancies tend to be less than 10 years, are unlikely to reap a benefit from cancer screening and are at increased risk of experiencing short-term harms and burdens, including complications from screening and follow-up tests, over-diagnosis and over-treatment of clinically unimportant cancers, diverted attention from other health priorities, and psychological stress from false positive results.

Yet many of these patients are wary when I broach the idea of stopping screening.

To explore what older patients and their doctors think about stopping cancer screening, several colleagues and I interviewed 40 older adults and 28 primary care clinicians. As we wrote in the journal The Gerontologist, one theme that emerged among clinicians was that patients might interpret a recommendation to stop cancer screening as “giving up on them.” Patients, however, didn’t share that concern. As one older adult said, “I would think that [the clinician] would base saying something like that to me [on] facts that she studied.”

To counter any potential negative perceptions, both clinicians and patients suggested focusing on other health concerns. As one clinician said, “Let’s shift the focus to things that are more relevant right now.”

One area of difference between clinicians and patients is whether life expectancy should be part of the discussion about stopping cancer screening. Clinicians said they generally didn’t mention limited life expectancy as one of the reasons for stopping screening because they found it difficult to discuss the issue with patients, were concerned how they would react, and weren’t certain which patients would be open to having such a conversation.

Their concerns were somewhat justified. Although the older adults we interviewed thought that their clinicians should know what to say about life expectancy and how to say it, some wanted to hear about their life expectancies, some thought it was okay not discuss it, and others just didn’t want to hear about it.

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There are several take-home messages from this work. One is that many older adults are willing to stop routine cancer screening when it makes sense to do so, especially when they trust their doctors. Another is that not all older adults may want to hear about life expectancy when thinking about cancer screening, and framing the decision as a shift in health priorities may be a better approach.

I still believe that cancer screening is a helpful intervention for many people — we just have to be better at recognizing when it stops being helpful.

Nancy L. Schoenborn, M.D., is a geriatrician and associate professor of medicine at Johns Hopkins University School of Medicine.