The fact that mammography is generally less sensitive in younger women and that younger women are more sensitive to radiation alters the balance of risk and benefit. Detection technologies that do not involve radiation would thus be likely to offer a relatively greater advantage to younger women.
Women fear breast cancer more than any other disease,51,52 but their perception of risk is often distorted. In general, women in the United States and Canada tend to overestimate their risk of breast cancer, whereas women in the United Kingdom are more likely to underestimate their risk (reviewed by Hopwood in 2000).39 Many women are also unclear about risk factors. More than three-quarters of women in one large survey recognized family history as a major determining factor for developing breast cancer, but only 13 percent correctly identified old age as a risk factor.51 As a result, older women are more likely to underestimate their risk than younger women,20,36 who tend to overestimate their risk. One study reported that women in their forties overestimated their probability of dying of breast cancer within 10 years by more than 20-fold.6 The women in that study also overestimated the effectiveness of mammography. Considering the extreme bias in the media toward telling personal breast cancer stories of women in their thirties and the rarity of such stories of older women, these distorted perceptions are perhaps not surprising.11
The likelihood that a woman will adhere to screening recommendations depends, in part, on her perceived risk of developing breast cancer.3,14 Despite the general validity of the Gail model in predicting risk, it does not predict risk perception or the inclination of a woman to follow mammography guidelines. A 1996 study in which more than 900 women were inter-viewed found a striking disparity between Gail model objective risk factors and the accuracy of women’s beliefs about their own risk and adherence to mammography screening guidelines.20 The observation that participation in screening mammography programs declines with age reflects this discordance between belief and behavior (Figure 4-2).
Reports of risk factors in the media as well as the scientific literature typically highlight relative risk rather than absolute risk which makes sense in the attempt to identify risk factors (see Box 4-1 for definitions), but it encourages exaggerated perceptions of personal risk. Most women whose mother had breast cancer are acutely aware that they are “at risk” for breast cancer, but few of them appreciate the moderate extent of their added risk. For example, the relative risk of developing breast cancer for a woman whose mother had breast cancer after age 50 is estimated to be 1.8 (see Table 4-2). If that woman is 40 years old, her underlying risk of