Women's perceptions of breast cancer risk: how you ask matters

Some studies suggest that women dramatically overestimate the risk of having breast cancer while others conclude that they underestimate it. To understand better how women perceive the chance of getting breast cancer, the authors asked women to estimate the risk in several ways. Each woman's answer was related to her actual risk.

Women were randomly selected from a registry of female veterans in New England. A mailed questionnaire asked each woman to estimate her ten-year risk of dying from breast cancer as a number out of 1,000 ("___ in 1,000" perceived risk) and whether this risk was higher than, the same as, or lower than that of an average woman her age (comparative perceived risk). The woman was also asked to compare her risk of dying from breast cancer with her risk of dying from heart disease. Risk-factor data were collected so that each woman's actual risk of breast cancer death could be estimated (actual risk).

201 women had complete data. The median age of the respondents was 62 years (range 27-80), and 98% were high school graduates. Most women (98%) overestimated the "___ in 1,000" risk of breast cancer death-half by eightfold or more (interquartile range, 4-36-fold overestimates). In contrast, only 10% of these women thought that they were at higher risk than an average woman their age. Most correctly thought that their risk of dying from breast cancer was lower than their risk of dying from heart disease. The women's "____in 1,000" perceived risks of breast cancer death were unrelated to their actual risks and had no significant agreement with an external bench-mark of importantly "high risk" (i.e., met risk criteria for the Tamoxifen primary prevention trial). In contrast, the women's comparative perceptions of being at low, average or high risk were related to actual risks and significantly agreed with the "high risk" benchmark. Most women not at importantly "high risk" correctly classified themselves; however, almost two thirds of "high risk" women misclassified themselves as "average or lower than average risk."

The method used to elicit perceptions of risk matters. These women's responses to the comparative questions showed that they "knew more" about their actual risks than their open-ended numeric responses suggested.