By Truls Østbye, MD, PhD

The laudable goal of mammography screening and Pap tests in women is the early discovery of asymptomatic and treatable cancers.

And the current guidelines from national organizations, including the American Cancer Society (ACS) and the U.S. Preventive Services Task Force (USPSTF), generally agree about the appropriate age to begin these tests and the optimal screening interval for women up to age 70.

After age 70, however, the lack of conclusive evidence muddies the water, especially concerning mammograms.

The fact that the incidence of breast cancer continues to increase throughout life argues in favor of continuing mammograms past the age of 70. On the other hand, life expectancy obviously decreases with age, while the competing risk of dying from other causes increases rapidly, thereby reducing the number of years that can be saved through screening.

Furthermore, there are no rigorous clinical studies demonstrating that screening women over 70 with mammography has a clear benefit. Self-selection also plays a role in previous observational and retrospective studies, since the healthiest elderly with lower risk of disease are more likely to undergo screening.

A group of researchers at Duke, including myself, set out to determine the frequency with which elderly patients reported receiving screening mammograms and Pap tests and look for predictors of utilization of these services.¹

We examined data from two national longitudinal surveys: the Health and Retirement Study (HRS), which contains information about health behavior, disease, disability, and medical care usage for a cohort born in 1931-1941, and the Asset and Health Dynamics Among the Oldest Old (AHEAD), a companion study that surveyed an older age group, people who were 70 years and older during the initial survey in 1993.

Along with examining the reported breast and cervical cancer screening at two follow-up interviews, we also looked at explanatory variables, such as race, education, household income, smoking, exercise levels, and self-reported health.

Expensive Preventives

Our data analysis revealed a consistent age-related pattern of decline for both screening tests in both surveys and at both survey question periods (1995/96 and 2000).

However, we also found that elderly women are receiving a large and increasing number of screening mammograms and Pap tests, despite the lack of evidence supporting their beneficial effect in older women.

Based on United States population data and the proportion of each age group in the AHEAD survey who had undergone a screening test, at a cost per mammogram of $100 and per Pap test of $14.60, we estimate that in 2000 women age 70 and older underwent 4.6 million screening mammograms at an annual cost of $460 million and 3.7 million Pap tests at an annual cost of $47 million. These amounts do not include the cost of follow-up visits or subsequent clinical management of any problem.

Even though both tests are covered by Medicare and therefore not paid for directly by the seniors, the societal costs of continuing such testing are substantial.

This is especially notable for Pap tests, since the relative rates of mortality from cervical cancer in elderly women are low, and there is a lack of evidence in randomized controlled trials to support its use.

In addition, current ACS recommendations state that women over age 70 who have had three consecutive negative Pap tests during the prior 10 years may discontinue screening. The USPSTF recommends discontinuing screening at age 65 provided women have had adequate recent screening with normal Pap results (although "adequate recent screening" is not defined).

Questioning Benefits of Mammography

Although we did not address this issue in our study, the benefits of screening mammography continue to be controversial even in younger women.

Some experts believe that mammography has not had an effect on breast cancer survival, citing randomized controlled trials from as far back as the 1960s to support their claim. Others point out the flaws of those trials and note that technology has significantly improved the quality of mammograms while greatly reducing the associated radiation exposure.

Because of conflicting results in clinical trials and uncertainty about the risk-to-benefit ratio of screening, the Canadian Task Force on Preventive Health Care does not support nor discourage screening mammography for women ages 40 to 49 at average risk of breast cancer.

United States guidelines for women are clearer: the ACS states that women age 40 and older should have a screening mammogram every year and should continue to do so for as long as they are in good health, whereas the USPSTF recommends mammography every one to two years starting at age 40.

The most recent USPSTF guidelines recommend that women stop being screened at age 74 because there is insufficient evidence to determine the benefits and harms of screening mammograph in women older than 75 years.

Better Investments

A significant problem of screening -- one not confined to the elderly -- is access to care. The healthiest people with the lowest risk of disease are those most often screened. In other words, those who need screening the most are the least likely to receive it.

Fortunately, there is an alternative for these women. The National Breast and Cervical Cancer Early Detection Program, administered by the Centers for Disease Control and Prevention, helps low-income, uninsured, and underserved women gain access to screening programs for early detection of breast and cervical cancers.

Since its establishment in 1991, the program has screened 1.9 million women and diagnosed approximately 17,000 breast cancers, 61,000 precancerous cervical lesions, and 1,200 cervical cancers. Perhaps our limited health care dollars are better spent on programs such as this one instead of using Medicare dollars to screen older women.

It is clear that mammography and Pap tests continue to be performed in the elderly, at a substantial societal cost, despite limited scientific evidence supporting it.

We need to focus research efforts on documenting screening efforts in the oldest population group, examining the benefits of and the rationale behind those screening practices.

Furthermore, screening among the elderly should be better and more specifically addressed in national clinical guidelines. Without guidelines, doctors must err on the side of caution because of the social and legal consequences of discontinuing screening, even in the most fragile elderly.

Dr. Østbye is a professor in the Department of Community and Family Medicine at Duke.

Originally published in Duke Med Magazine, fall/winter 2005.

¹ Source: Østbye T, Greenberg GN, Taylor DH, and Lee AM. Screening mammography and Pap tests among older American women 1996-2000: Results from the Health and Retirement Study (HRS) and Asset and Health Dynamics Among the Oldest Old (AHEAD). Ann Fam Med 2003:1;209-217.