The often-cited statistic that American women have “a 1 in 8 chance” of developing breast cancer, while it has served to heighten awareness of the importance of self-examinations and screening mammography, has also led many women to greatly overestimate their risk and to overlook their far greater likelihood of dying from heart disease. The “1 in 8” statistic defines lifetime risk, with the assumption that a woman will live to be 90 and with the highest risk greatly concentrated in the later decades of life. Authorities are now attempting to provide more comprehensible information about individual risk, so that breast cancer risk can be seen in the larger context of long-term health.

One assessment tool now available was developed by the NCI and the NSABP - a 3 1/2-inch floppy “risk disk” - that can assist obstetrician-gynecologists in determining a woman’s likelihood of developing breast cancer during two time periods: within the next 5 years and during her lifetime. Based on a risk-benefit algorithm developed by Mitchell H. Gail, MD, Chief of the Biostatistics Branch in the Division of Cancer Epidemiology and Genetics at the NCI, the risk disk is a useful tool for providing women with a realistic concept of their likelihood of developing breast cancer.

With the assessment tool, the obstetrician-gynecologist asks a series of questions about the patient’s medical history and the program calculates the risk, comparing it to the cancer risk of a woman of the same age but with no other identifiable risk factors. Among the risk factors included in the calculation are:

  * age;
  * age at menarche;
  * age at first live birth;
  * number of first-degree relatives (mother, sisters, daughters) with breast cancer;
  * number of previous breast biopsies (whether results were positive or negative); and
  * at least one biopsy showing atypical hyperplasia.

The program then calculates the patient’s risk compared with that of a woman her age with no identifiable risk factors, and the resulting number can then be compared with that considered sufficiently high as to qualify for eligibility in the BCPT. That number, approximately 1.7, reflects the 5-year risk for invasive breast cancer for a “normal” 60-year-old woman.

The tool also presents the risk evaluation in another way - one which many women may find more useful for putting the numbers in perspective - by explaining the likelihood of not developing breast cancer during the next 5 years or at any time in life (see “The risk disk: putting the numbers into perspective,” below). While some women may interpret this information as cause to be careless or unconcerned, many will be encouraged by their excellent chances of avoiding the disease and be motivated to pay closer attention to other potential, but as yet unquantifiable, risk factors (see Patient Information, question 2, below). The kit containing the disk and accompanying literature is available without cost from the NCI.

Not all authorities believe that the Gail model is the most useful tool for risk assessment, however - particularly with regard to decisions about tamoxifen - because it does not factor in the probability of a tumor being estrogen-receptor-positive and therefore suitable for hormonal intervention. Other techniques for evaluating risk are now being considered, and more specific alternative tools developed, based on factors such as estrogen level, bone density level, and tissue density on mammogram.

By Trudy L. Bush, PhD, Steven R. Cummings, MD, and Clifford A. Hudis, MD

References

1. Struewing JP, Hartge P, Wacholder S, et al. The risk of cancer associated with specific mutations of BRCA1 and BRCA2 among Ashkenazi Jews. N Engl J Med. 1997;336:1401-1408.

2. Peto J, Collins N, Barfoot R, et al. Prevalence of BRCA1 and BRCA2 mutations in patients with early-onset breast cancer. J Natl Cancer Inst. 1999;91:943-949.

3. Hartmann LC, Schaid DJ, Woods JE, et al. Efficacy of bilateral prophylactic mastectomy in women with a family history of breast cancer. N Engl J Med. 1999;340:77-84.

4. Wisen A, Weber BL. Prophylactic mastectomy - the price of fear. N Engl J Med. 1999;320:137-138.