What are the guidelines for screening in postmenopausal women? Are mammograms passe’? Who should be given chemopreventive agents? Does ERT/HRT increase breast cancer risk? Find answers to these and other important questions in this latest update.
The diagnosis, treatment, and follow-up of breast cancer in postmenopausal women is changing rapidly - cancers are being diagnosed earlier and prognoses are improving; hormone replacement therapy (HRT) is being considered for breast cancer survivors with debilitating menopausal symptoms; and new pharmacologic choices for cancer prevention are becoming available. One of these, tamoxifen, has been reported to reduce the risk of invasive breast cancer by 50%. In subgroups with atypical hyperplasia or lobular carcinoma in situ breast lesions, the relative risk reduction was even greater. Raloxifene, another selective estrogen receptor modulator (SERM), also reduces the risk of breast cancer to a similar degree in women taking it for treatment of osteoporosis. Increasingly, breast cancer risk assessment and chemoprevention counseling are becoming standard components of breast cancer screening and overall health maintenance.
Screening postmenopausal women
Appropriate screening reduces breast cancer-related mortality among women aged 50 to 75 by 25% to 30%. The American Cancer Society currently recommends that women begin monthly breast self-examination at age 20. Between ages 20 and 39, women should have a clinical breast examination every 3 years.
Guidelines on the appropriate interval between screening mammograms in asymptomatic low-risk women older than 40 differ among various organizations; some recommend yearly, others, every other year. Nearly everyone agrees that women over 50 should have yearly mammography. Vigilant screening remains important in women older than 65, as nearly 50% of new cases and nearly two thirds of the deaths from breast cancer occur among the 13% of the female population that is 65 years or older. Note that older black women experience higher rates of breast cancer mortality that are not explained by risk factor analysis nor by changes in breast cancer incidence rates. The unexplained increase of breast cancer mortality appears to occur in the postmenopausal period.
- Appropriate screening reduces breast cancer-related mortality among women aged 50 to 75 by 25% to 30%.
- Mammography remains the most effective screening tool for finding early breast lesions. Vigilantly screen women older than 65, as nearly 50% of new cases - and nearly two thirds of deaths from breast cancer - occur among this population.
- The evidence fails to show that ERT/HRT users have an increased risk of breast cancer. The reported slight increase in numbers of diagnosed cancers after 10 to 15 years of use is a complex and unresolved issue.
- NCI recommends that only women at increased risk for breast cancer based on the Gail Model should consider taking tamoxifen.
- Tamoxifen has been shown to reduce the risk of new breast cancers in either breast; how tamoxifen and raloxifene do so is still under investigation.
There is presently some controversy regarding the lifetime value of mammography as a screening tool. But the argument is so esoteric that it should not concern women at this time. No one is questioning the ability of mammograms to detect breast cancers; rather, the two reports of concern fault mammography since it finds early cancers for which treatment has not yet been defined. These reports are based on selective reviews of epidemiologic studies (meta-analyses) of all cause mortality in breast cancer patients who received screening mammograms, compared with those who did not. Since there were no data on the causes of death, most of these deaths were likely due to diseases other than breast cancer.
The first, a meta-analysis by Gotzsche and Olsen, has itself been controversial for its methods and possible bias. The authors do not actually address the value of mammography, just whether it affects all cause mortality among breast cancer subjects. Moreover, there is important internal inconsistency in their meta-analysis approach. When they used all studies that they deemed adequate, they showed a 20% protective effect; but their two “best” studies alone did not show protection against mortality. The authors’ conclusions are driven by concern that early detection has led to overly aggressive treatment of early lesions. This justifies neither their methods or conclusions.
A second meta-analysis was done by a private consulting group, Physician Data Query (PDQ), a body affiliated with but independent of the NCI. Using similar data, that group also concluded that the use of all cause mortality was not sufficient to distinguish mammography as a screening tool. Since breast cancers are responsible for less than 5% of all deaths, the rise of all cause mortality as a measure of the value of mammography as a screening tool is clinically not relevant for individual women. The controversy over the value of screening mammography is not likely to be resolved in the near future and does not directly relate to diagnosis, just to outcomes of diagnosis. We prefer to continue to use mammography as a screening tool and await further information.
Mammography use by older women remains relatively low, however - fewer than 50% of women older than 65 have ever undergone mammography, and an even smaller proportion undergo mammography regularly. Scheduling a mammogram may become more difficult than it has been in many areas as several hospitals have scaled back their mammography programs. We suggest that a mammogram should be a “ticket” for the annual exam, and that patient pressure should be applied to any log jams and under reimbursement by insurers.