Overall this study reported a positive association between perceived lifetime risk of developing breast cancer, measured either on a numerical or verbal scale, and breast screening among women who had at least one first-degree relative diagnosed with breast and/or ovarian cancer. Women who rated their risk as 50% or greater were more likely to have a screening mammogram compared to women with a perceived risk of less than 50%, irrespective of time. In addition, women who rated their risk as above or much above average risk were significantly more likely to have a mammogram in the past 12 months and more likely to practice BSE once a month or more compared to women who rated their risk of developing breast cancer as same as or below average.
Our results that women with a greater perceived risk of developing breast cancer measured on a numerical or verbal scale were almost twice as likely to have a screening mammogram differs from other cross-sectional studies of high-risk women. Previous cross-sectional studies examining perceived risk on a numerical or verbal scale have either observed a similar utilization of screening mammography among women with a perceived risk of 50% or more compared to less than 50% [20
] or have observed no significant association between risk perception and compliance to mammography [21
]. Both a prospective study that measured mammography uptake in the following year [24
] and a retrospective study [25
] that measured mammography in the past 3 years also did not report significant associations between perceived risk estimated on a verbal Likert-type scale that asked general likelihood of getting breast cancer someday during their lifetime and mammography uptake. Differences may have occurred as most of these studies had much smaller sample sizes than ours. In addition, many of the studies recruited convenience samples of women participating in high risk clinics or genetic counseling that may have resulted in self referral bias as compared to our study that identified women from a population-based familial breast registry.
Similar to our study, other investigations did not report a significant association between higher perceived risk measured on a numerical [20
] or verbal scale [22
] and having a screening CBE. However, our study did find that women, who reported an above average perceived risk were significantly more likely to practice BSE once a month or more. One other cross-sectional study also observed slightly more frequent BSE performance in women with a perceived risk of 50% or more compared to less than 50%, although the difference was not statistically significant [20
]. However, another study observed that women who over-estimated their actual breast cancer risk on the numerical scale had significantly poorer self-reported compliance of BSE [21
]. A few studies have examined performance of excessive BSEs (weekly or daily) in women with a first-degree relative with breast cancer. One study found that women were significantly more likely to perform excessive BSE if they perceived a risk that was higher or much higher compared to other women without family histories [31
]. Another study, using a perceived risk measure that encompassed both numerical and comparative estimates, also found women who performed excessive BSE had significantly higher perceived risk [32
]. These studies suggested that high risk women might benefit from education about appropriate BSE technique to reduce their anxiety and tendencies to conduct excessive examinations.
In our study, elevated perceived risk measured on a numerical or verbal scale was not associated with having a genetic test for the BRCA1
genes. This is likely because these genetic tests require physician referral based on family history of breast and/or ovarian cancer and our study adjusted perceived risk by the woman’s familial risk of breast cancer. Although a meta-analytic review reported that women who perceive a higher breast cancer risk were more likely to pursue genetic testing [19
], the studies reviewed only examined interest in genetic testing or participation in genetic counseling. The only other study that, like our study, examined utilization of the genetic test also found a lack of significant association between perceived risk of breast cancer measured on a numerical scale and having a genetic test for the BRCA1
genes in high-risk female participants [33
A few studies have suggested that a distinction be made between whether perceived risk is measured on a numerical or verbal scale [19
]. There are indications that women tend to over-estimate their risk of developing breast cancer when asked on a numerical scale and under-estimate their risk when asked to compare themselves on a verbal-scale to their peers [19
]. A recent study examined the utility of both the numerical and verbal measures, and results supported the utilization of both under different research objectives. Specifically, for identifying women with very high or very low risk perceptions, both measures performed well with the numerical scale having the higher specificity and the verbal scale having the higher sensitivity [34
]. Generally, our results suggest that similar associations for breast cancer screening behaviors were found regardless of whether perceived risk was measured on the numerical or verbal scale.
The present study had several strengths. Firstly, this study included a large cohort of female relatives of breast cancer cases thus providing adequate power to examine associations. Secondly, participants were identified from a population-based cohort of breast cancer cases which will have minimized self-referral bias. Thirdly, since women who had undergone bilateral mastectomy might have appreciably different breast cancer screening practices, they were excluded from all analyses. This exclusion criterion was only applied in one previous study [22
]. Another unique aspect of our study was that we measured perceived risk on both a numerical and verbal scale.
Nevertheless, results from this study should be interpreted while considering the limitations. Given the cross-sectional nature of our data, we were unable to determine the direction of the relationship between perceived risk and screening behaviors. That is, perceived risk may have been influenced by previous screening or educational experiences. Misclassification may have also occurred through the use of self-reported data to measure breast screening behaviors. Although self-reported mammography data has been found to be accurate for determining whether a woman has had a mammogram, self-reported data is less accurate in determining the time since last mammogram [36
] and women tend to under-estimate the time since their last mammogram resulting in an overestimation of recent mammography use [37
]. To minimize recall inaccuracy, the PHSQ
was mailed to the participants to allow recollection of dates and events prior to the telephone interview. To estimate the magnitude of recall bias, the self-reported date of the last mammogram was validated against medical records upon informed consent. Approximately 92% of women reported their last mammogram to be within 12 months from the actual date. Finally, the findings of this study may have limited generalizability to other populations. Participants in this study were family members of breast cancer cases identified from a population-based registry in the Canadian province of Ontario where universal health care coverage and an organized breast cancer screening program for women 50 years of age or older are available.
Increased perceived risk of developing breast cancer measured on either numerical or verbal scales was significantly associated with having a screening mammogram within a large cohort of female relatives of women with breast cancer. These finding could inform educational messages and improve risk communication for women at elevated familial breast cancer risk.