Breast Cancer Screening in Older Women
Concerns and Controversy
Current guideline recommendations regarding screening mammography are based primarily on research that involved only women 75 or younger. What other factors should the clinician take into account when helping an older patient decide for or against breast cancer screening?
At age 82, Helen was healthy and active and living independently. A mother, grandmother, and great-grandmother, she enjoyed aerobics, tai chi, and walking, painting (which she also taught), writing poetry, and stimulating conversation. She took pride in looking much younger than her age and watched out for her older neighbors.
An active participant in her health care, Helen had been happy when, at 75, she was told by her primary care provider that she no longer needed regular mammograms. But one morning, seven years later, she felt a sharp pain in her right breast. Self-examination revealed a grape-sized lesion under her nipple. Helen sought immediate health care and was diagnosed with a stage IIb tumor.
Given an option of lumpectomy followed by radiation, Helen decided that a double mastectomy would better allow her to return to the life she had been living. After her surgery, however, Helen experienced a steady decline, with increasing pain, debilitating skin lesions, fractures, and edema. Against her will, she was moved to an assisted living facility, where she was too debilitated to participate in activities. Helen died six months later—three years after she discovered her breast lump.
The lack of clear breast cancer screening guidelines has left many providers confused about how to advise their patients, particularly women older than 75. Screening recommendations based on patient age alone are of insufficient value, as health status and life expectancy—which vary widely in this patient population—are also, along with patient preferences, important considerations. The purpose of this article is to present the reported benefits and risks of breast cancer screening among older women, in order to help primary care providers more effectively advise their elderly female patients in the decision-making process.
The Breast Cancer Screening Debate
There is strong consensus among expert advisory groups (the US Preventive Services Task Force,1 the American Cancer Society,2 the American College of Obstetricians and Gynecologists,3 the American Academy of Family Physicians,4 and the American Geriatrics Society5) that mammography is to be recommended to screen for the early detection of breast cancer in women between ages 50 and 75. However, a recent review of the randomized controlled studies on which these recommendations were based suggests that the benefits of mammography may be relatively minimal, and that the risks for overdiagnosis and overtreatment may be significant.6 None of these trials enrolled women older than 74, so further information is needed to make evidence-based decisions regarding breast cancer screening for the older woman. Currently available evidence for such decision making is limited to observational or retrospective analyses.6
Women 75 or older have a greater risk than younger women for breast cancer, but older women are also at greater risk for dying of another disease—even those who have breast cancer.7,8 Thus, as with any health screening, it is advisable that a woman’s health status be carefully considered before screening decisions are made.
Breast Cancer in Older Women
Breast cancer incidence increases with age. Almost half of all invasive breast cancers and breast cancer deaths occur among women 65 and older, and almost one-quarter of all invasive breast cancers occur in women age 80 and older.9 Approximately one in six women diagnosed with breast cancer dies of the disease within 10 years.10 Once the cancer has metastasized, median survival time is two to four years. Older women have about a 1% chance of dying of breast cancer in a 10-year period.11
At the same time, older women are more likely than their younger counterparts to have comorbid illnesses—conditions that can compete with breast cancer as a cause of death and increase treatment-related morbidity. Older women with breast cancer and two or more other comorbid diseases are 20 times more likely to die of one of these diseases than of breast cancer.8
Use of Mammography in Older Women
Regular mammography has been shown to help detect tumors that are smaller and at an earlier stage of development than would be identified without this screening.8 Women who undergo regular mammograms have been shown to outlive those who do not, provided they live for at least five years after starting screening.12
Life expectancy for older women is often underestimated. The average 75-year-old woman has 12 more years of life expectancy, and the healthiest 25% of 80-year-old women will live an additional 13 years.13 Most of these women do not receive regular mammographic screening for breast cancer. However, if health status and life expectancy were considered as screening criteria in addition to age, many of these women would qualify for mammographic screening.
Using the Surveillance, Epidemiology, and End Results (SEER) Medicare database to evaluate 12,358 women age 80 and older who had been diagnosed with breast cancer, Badgwell et al14 found that only 51% had had one or more mammograms within the previous five years. Biennial screening rates were 24% to 27% among women ages 80 to 84 and 14% to 23% among those 85 to 89. In this cohort of elderly women, the researchers found that regular mammographic screening was associated with detection of breast cancer at earlier stages and suggest that the low rates of screening in this age-group may represent a missed opportunity for early detection of disease.
In the US, 57% of breast cancers are detected by mammography; in the remaining cases, patients present with a palpable mass or in response to other breast symptoms. Cancers detected by mammography are found at an earlier stage.15
When statisticians used several models to assess the role of screening mammography in reducing breast cancer mortality, they found that mammography has contributed to about 46% of the overall reduction in breast cancer deaths in the US during the past 20 years.16 Mammography is more effective in detecting breast cancers in older than younger women, and the number of false-positive results decreases among women of advancing age. The sensitivity and specificity of mammography for detection of breast cancer is 85% and 94%, respectively, for women ages 75 to 89.17
Although this strong specificity would seem to suggest that older women are at low risk for overdiagnosis, this is not the case. Many benign and clinically insignificant lesions are also detected through mammography, resulting in unnecessary breast biopsies. In one group of 23,000 women age 65 or older who underwent a one-time screening mammogram, 8% had an abnormal result that required additional evaluation. Among these women, only about 10% actually had cancer.18 Rates of false-positive mammographic findings vary by radiologist but are generally higher among women who are younger than 65.19
Schonberg20 followed 2,011 community-dwelling women 80 and older who underwent mammography screening and found an 11% rate of false-positive results. Ductal carcinoma in situ (DCIS) is a common mammographic finding in older women. Since only one-third of these cases will convert to invasive breast cancer over 10 to 15 years, DCIS likely exemplifies overdiagnosis in older women.20
Clinical Breast Exams and Self-Examination
There is insufficient evidence to determine whether clinical breast exams improve early detection and treatment outcomes in women with breast cancer. Additionally, results from two large randomized controlled trials of breast self-examination suggest that the practice is not of benefit in reducing breast cancer mortality and morbidity.1,21,22
Age, Breast Cancer Types, and Outcomes
It has been suggested that older women may be subject to less aggressive cancers and thus be more vulnerable to overdiagnosis.23 Schonberg et al24 evaluated SEER data to determine the tumor characteristics, treatments, and outcomes in women 80 and older, compared with women ages 67 to 79. They found no difference in tumor grade or hormone receptivity between these groups. It is important to note that women older than 80 were significantly more likely than younger women to die of breast cancer, perhaps in part because the older patients were less likely to receive aggressive treatment (see “Breast Cancer Treatment in Older Women”24-26).
Women between ages 74 and 85 who undergo regular mammographic screenings have been shown to have half the risk for breast cancer–related death, compared with those who are not screened.25 However, risks have been shown to outweigh benefits when mammography is continued into old age without regard to life expectancy.
Walter et al27 studied a group of 216 frail, nursing home–eligible older women who had had at least one mammogram. Seventeen percent had abnormal results, and most opted for further evaluation with breast biopsy. Of these biopsies, 23% yielded positive results, and of these, 75% revealed invasive breast cancer; the remaining 25% of women had DCIS.
All of the women with abnormal biopsy results underwent surgical treatment, but half died of other causes or experienced surgical complications. The investigators found that 1% of the women may have received some benefit from screening, but more women experienced harm as a result of the mammogram and subsequent procedures. The study authors, along with almost all clinicians who have written on this topic, agree that mammography is inappropriate for frail, elderly women with less than five years’ life expectancy.27
Expert Guideline Recommendations
Provider recommendation has been found to be the most important factor in older women’s decisions to have or forego a mammogram.8 Unfortunately, there is little clear, decisive support for providers to help women make this decision. The summary of breast cancer screening recommendations for older women shown in the table reveals that no consensus exists among the expert panels regarding the best approach. In part, these discrepancies can be explained by the low numbers of women older than 75 who have been included in clinical trials evaluating the risks and benefits of mammography screening.
Helpful Criteria for Breast Cancer Screening Decisions
In 2003, the American Geriatrics Society Ethics Committee published a set of basic rules to guide decision making regarding screening tests.5 These include the following:
• In patients with a limited life expectancy, focus should be on treatments that are likely to offer immediate benefit
• Patients with dementia or multiple comorbidities may find routine screening tests burdensome
• Screening decisions should be individualized rather than based on age alone
• Health care systems and insurance plans should not restrict coverage for screening tests in older adults based solely on age.5
Walter and Covinsky13 created a model to facilitate decisions about mammography for older women. They suggest first estimating life expectancy according to age and health status (see Arias28 at www.cdc.gov/nchs/data/nvsr/nvsr58/nvsr58_21.pdf). Factors considered in this decision model include a woman’s risk for dying of breast cancer, the effect of screening on this death rate, the potential risks involved with screening, and the woman’s preferences.
According to this model, Helen, at 82, would have had a life expectancy of 11.5 years. The annual breast cancer mortality rate for a woman of her age is 157/100,000.29 Based on these data, Helen’s risk for dying of breast cancer is calculated to be 1.8%. The number of patients Helen’s age who would have to be screened to prevent one case of breast cancer is 240.
In Helen’s case, the risks involved with screening mammography would include a roughly 8% chance of her needing a subsequent diagnostic mammogram and/or breast biopsy. If Helen underwent biopsy, there would be a 75% chance that the suspicious mammogram would prove to be a false-negative result, possibly causing the patient undue anxiety. In Walter and Covinski’s model,13 these possibilities would be discussed with Helen in advance to help her clarify her own values and reach a screening decision.
By comparison, consider a hypothetical 70-year-old woman who is in the lowest quadrant of health status for her age; based on her age alone, the expert panels would agree that screening mammography is indicated. This patient has a life expectancy of 9.5 years and a 1.2% lifetime risk for dying of breast cancer. To prevent one case of breast cancer, 642 women of this age and health status would have to be screened. Thus, Helen would derive far more benefit from screening than would this hypothetical woman.
Life Expectancy, Health Status
In order to help an older woman make well-reasoned decisions about mammography screening, it is important for the clinician to evaluate her overall health status and life expectancy, as well as her risk for breast cancer and her long-term goals.