Tip Sheets

When is it time to stop cancer screening in older people?


Alan Cassels

by Alan Cassels

In the U.S. there are frequent appeals for people to submit to regular cancer screening—whether it’s for colon, cervical, prostate, lung or breast cancer screening—but when is it too much of a good thing? When should older people, perhaps those with limited life expectancy, stop getting periodic screening?

At study published in JAMA Medicine in 2014 found that “large numbers of elderly U.S. people with limited life expectancy continue to be screened for cancer even though such tests are of little benefit and can pose substantial harms.” Specifically that study found:

  • 31-55 percent of those people who were a ‘very high’ risk of mortality (a more than 75 percent risk of dying in the next nine years) received recent cancer screening, with prostate cancer screening being most common (55 percent).

  • 34-56 percent of women who had had a hysterectomy for benign reasons, had a Pap test within the past 3 years.

  • 38 percent of women with a very high mortality risk reported having undergone mammography in the past two years, and 31 percent had been screened for cervical cancer within the past three years.

  • Screening was also common in individuals with less than 5-year life expectancy.

  • 41 percent of both men and women with a very high mortality risk had been screened for colorectal cancer in the past five years, either with colonoscopy, sigmoidoscopy, or the fecal occult blood test.

There are some key facts that journalists need to know about medical screening:

All screening involves harm due to overdiagnosis (finding lesions which will never go on to hurt you, and the biopsies, chemotheraphy and surgery for such lesions). In a May 11, 2015, article in the New Yorker magazine, author and physician Atul Gawande provides several great examples of the U.S. health care system’s tendency to “Overkill” (the title of his article) and wrote that “an avalanche of unnecessary medical care is harming patients physically and financially.”

Both physicians and patients need to know the limitations of cancer screening, especially the harm for those who have limited life expectancy.

There are often variations in existing screening guidelines, especially concerning screening in individuals with limited life expectancy. Some groups (with closer ties to the pharmaceutical and medical screening industries) have much more liberal “screen everyone all the time” recommendations compared to other groups without ties to the private screening industry (such as the USPSTF). Journalistic treatment of screening has been getting better, such as this May 18, 2015, piece in the Los Angeles Times, “Cancer screening: An example of when less can be more, experts say.”

Questions for journalists to pursue:

  • Medicare pays for services that are “reasonable and necessary,” but is it “‘reasonable” or “necessary” to perform a screening test on an older person if the risks are likely to outweigh the benefits? This article from Medscape indicates that “A substantial proportion of older people in the United States continue to undergo cancer screening, even though they are unlikely to benefit from it.”

  • Find out, what are the numerical (in Numbers needed to screen) in order to save one life?

  • What is the likelihood that older people are overscreened (or underscreened).

  • How has life expectancies changed (or not) due to screening?

  • What are the trends in screening and how have recent USPSTF recommendations on PSA testing for prostate cancer changed what physicians routinely offer?

  • Some physicians may refuse to send their older patients for screening, but how do they explain this decision to patients?

On mammography: Should we be screening older women for breast cancer?

Many women are told they need to be proactive when it comes to cancer screening. Many of them have been getting regular Pap screens and mammograms most of their adult lives.

After all, people are routinely told that early detection is important to help you live a long and healthy life breast cancer free. But at 75 years (or older) women may start wondering if a periodic mammogram is still necessary or appropriate. What kinds of information do they need to help them make an informed decision? Some basic facts:

  1. The benefits of annual mammography screening change as a person gets older. High quality independent evaluations of mammography, such as produced by the United States Preventive Services Task Force (USPSTF), a team of independent scientists who assess the value of screening, recommend that women 50 to 74 have biennial mammograms (every two years) and that the decision to be screened should take a woman’s individual values into account, especially concerning the specific benefits and harms.
    But what happens after a woman turns 75? The USPSTF says that there is “insufficient evidence to assess the additional benefits and harms of screening mammography in women 75 years or older.” These recommendations are controversial because other groups recommend breast cancer screening start at a younger age. For example, the American Cancer Society recommends that “women age 40 and older should have a mammogram every year and should continue to do so for as long as they are in good health.”

  2. Women should be informed of harms in screening for breast cancer (at any age) and these include the extra tests and worry that might happen because of a false positive (something abnormal found on a mammogram that causes extra testing), or the opposite where a mammogram may find no abnormalities even though breast cancer is present.

  3. Considerations around continuing to have mammograms at 75 or older should reflect on life expectancy and health status. On average, a 75-year-old woman has about 12 more years of life, but individual life expectancy depends on what other health problems she might have. Therefore it is her health status, rather than her age, that should determine whether she should continue having mammograms. An individual must also consider the treatment she would face if a tumor were found, including radiation and chemotherapy.

Show me the numbers

Researchers have been able to quantify the benefits of mammography screening in women aged 70 to 79. If 1,000 women aged 70 years have a mammogram every two years for a period of 10 years this is what they will find:

  • 961 women will not have breast cancer

  • 756 women will have normal results.

  • 244 women will have abnormal results at some point during 10 years.

  • 213 of the abnormal results are false alarms, which will be normal after further testing.

  • 31 women will have breast cancer detected by the mammogram.

  • 8 women will develop breast cancer in between screening visits.

Essentially what these numbers mean is that the vast majority of women who are screened won’t have breast cancer, and even among those who do have abnormal results, the vast majority of won’t have breast cancer.

How many lives will be saved?

Since the ultimate goal is not to find cancer, but to save lives, if we screen 1,000 women aged 70-79 years once every two years for a period of 10 years:

  • 208 women will die from some cause other than breast cancer.

  • 7 women will die of breast cancer despite the mammograms

  • 3 deaths from breast cancer will be prevented.

Essentially what these numbers mean is that most women this age die of things other than breast cancer, and only very few (3 in 1,000) deaths could be prevented from screening mammography.

Further reading

There are a number of high quality sources of information that journalists can consult if writing about cancer screening (particularly mammography) in older people.

  • When to start breast cancer screening is as controversial as when to stop, but there is a growing recognition that the problem of overdiagnosis remains; which is to say many women screened for cancer will never benefit from the screening and likely will only be harmed. This is as true for younger women as for older women. An article from National Public Radio discusses the degree to which breast cancers are overtreated. Dr. Gilbert Welch says that "seventy thousand women a year are overdiagnosed and treated unnecessarily for breast cancer.” Read more here.

  • The Daily Mail, a major newspaper in the U.K., reports on controversies in mammography screening and says in this article that the benefits of mammography are much less than we think and the harms are likely worse. According to one of the world’s major breast screening researchers, the Danish physician, Peter Gotzsche, “healthy women are getting unnecessary diagnoses of pre-cancerous conditions that are unlikely to develop during their lifetime.” The USPSTF provides an evidence-based assessment of mammography recommendations.

  • The Public Health Agency of Canada produces a high quality, easy to read Decision Aid for Breast Cancer Screening.  The following graph comes from that decision aid which shows the difference in death rates among women who get screened and those who don’t.

Comparison of deaths among 1000 women aged 70-79 years who screen and who do not screen

Excellent resources on medical screening:

 

Alan Cassels (@AKECassels) is a writer and drug policy researcher affiliated with the School of Health Information Sciences at the University of Victoria. The author of “Seeking Sickness: Medical Screening and the Misguided Hunt for Disease” (Greystone, 2012), Cassels welcomes questions from journalists. Contact him at cassels@uvic.ca or 240-361-3120.