Guidelines and Risk-Based Screening

Because the majority of women are not diagnosed with breast cancer in their lifetimes, they could choose to not be screened, be screened less often, or delay screening in order to reduce their higher risk of a false-positive examination compared with a lower likelihood of being diagnosed with breast cancer. It is not an entirely unreasonable recommendation, provided that women fully understand the issues and implications of their choices and the fact that third-party payers do not make these choices for them. Further, individuals vary in the degree to which they wish to make individual decisions about screening and in the degree to which various methods of information delivery and kinds of information fully communicate the issues in a manner that ensures complete understanding. In other words, we face an immense challenge in assisting those women who wish to make informed decisions about screening to do so.

Because breast cancer risk increases with increasing age, concerns about comparative risks and benefits associated with breast cancer screening have been raised. At an age when breast cancer risk is comparatively low, Gail and Rimer have proposed that a woman’s risk factor profile could be used to make decisions about whether to begin screening before age 50.

Their model, which is derived from BCDDP data, is based on the assumption that regular mammographic screening is justified for a 50-year-old woman with none of the important risk factors. Regular screening would be justified for women in their 40s if they have a prior history of breast cancer; atypical hyperplasia on a previous breast biopsy; two or more breast biopsies even with benign results; a known mutation on a breast cancer susceptibility gene; a mother, sister, or daughter previously diagnosed with breast cancer; or if they are age 45 to 49 with at least 75% breast density. For women in their 40s who do not fall into any of these categories, age at menarche, number of previous breast biopsies, and age at first live birth would be the basis for an informed decision about screening.

For example, according to the authors, in a woman in her early 40s with no history of breast biopsies and age at first live birth younger than 30 years, delay would be an option. Based on their estimates, only approximately 10% of 40-year-old women would make a decision to be screened if this model were followed, compared with 68% by age 45 and 95% by age 49. Because breast cancer risk increases with increasing age, their model may prove useful for women who wish to make an informed, risk-based decision about when to begin screening. No data are included with this model to estimate the proportion of incident cases within specific ages that would be identified if all women followed this approach. Although this kind of information is more immediately relevant for program planning, it is unknown whether it would be useful for making an informed decision at the individual level.

Another tool available to help women understand their individual risk is an interactive computer program for breast cancer risk assessment that has come to be known as the risk disk. This risk assessment tool is available from NCI and was developed to determine eligibility for participation in the Breast Cancer Prevention Trial. This program cannot estimate risk for women with a prior history of breast ancer, a history of DCIS or lobular neoplasia, or an inherited mutation on a known breast cancer susceptibility gene.

However, for women who do not fall into these higher-risk categories, absolute risk can be estimated for the next 5 years or to age 90, compared with a woman with no risk factors, based on current age, age at menarche, age at first live birth, and number of offspring; family history of breast cancer in first-degree relatives; and history of breast biopsy, including the presence of atypical hyperplasia. It is important to keep in mind that the comparison group with no risk factors does not represent an average woman. This woman’s risk to age 90 is 6.7%, whereas an average woman’s risk is closer to 9%.

These tools may have their greatest value in helping women understand individual risk against the backdrop of health education messages and articles in the popular press that emphasize risk as a basis for raising awareness about breast cancer prevention and early detection. Although well intentioned, there is concern that these messages have heightened anxiety far past the point at which they become sufficiently motivational at the individual level.

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