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School of Nursing [J. L. B., P. A. R., L. G. B.] and Department of Health Care and Epidemiology [C. G. R., J. B.], University of British Columbia, Vancouver, British Columbia, V6T 2B5; British Columbia Cancer Agency, Vancouver, British Columbia Y5Z 4E6 [M. M.]; and Faculty of Nursing, University of Manitoba, Winnipeg, Manitoba [T. H., K. C.], R3T 2N2 Canada
| Abstract |
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50 years of age, had a positive family history, and had more years of education. Women with a family history of breast cancer, well-educated women with breast cancer, and younger women, particularly those with knowledge of genetic testing, are important target audiences for community-based education on genetic testing for breast cancer risk. | Introduction |
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An emerging body of literature describes demographic factors that influence womens interest in genetic testing for breast cancer risk. The percentage of women interested in genetic testing is estimated to range from 43 to 89%, with interest being higher in younger women (2 , 8 , 9) and in those with a diagnosis of breast cancer (10) . Studies of the association between family history of breast cancer and interest in genetic testing are equivocal. Some researchers have reported that interest in genetic testing is higher among those with a family history of breast cancer (11) , others have reported lower levels of interest in individuals with a family history (12) , and yet others have found no association between interest in genetic testing and a family history of breast or ovarian cancer (13) .
There is also a lack of consensus on the relationship between educational attainment and interest in genetic testing, with some researchers reporting greater interest among those with more than high school education (12 , 14) and others describing higher levels of interest among those whose years of education were less than or equal to high school completion (11 , 13) . In one study, no demographic variables, including age, educational level, marital status, presence of children, religion, or family income, were associated with interest in genetic testing (10) .
Women with and without a diagnosis of breast cancer are reported to have poor or limited knowledge of the availability of genetic testing for breast cancer risk (15) , the information provided by testing, and the implications of testing (16) . Although in clinical settings it has been observed that knowledge of genetic testing for breast cancer risk and its limitations may reduce interest in testing in high-risk individuals, a similar association has not been observed among women in the general public (8 , 10 , 13) .
Although previous research provides important insights, the predominant use of relatively small, nonprobability samples and the variety of approaches used to assess interest in and knowledge of genetic testing make it difficult to draw conclusions. Researchers have tended to survey women with breast cancer or those with family histories of breast cancer. Few have studied probability samples of women from the general population, including those without breast cancer or positive family histories. Furthermore, limited research has been conducted to examine the combined effects of sociodemographic factors, family history of breast cancer, and womens knowledge of genetic testing for breast cancer risk on their interest in testing using multivariate techniques. These limitations have restricted the development of targeted community educational strategies related to genetic testing for breast cancer risk.
The purpose of the present study was to examine womens interest in genetic testing for breast cancer risk to provide a basis for the development of community educational programs. Specifically, we explored the following questions: (a) What proportion of women are interested in genetic testing for breast cancer risk? (b) Are there significant differences between women who have been diagnosed with breast cancer and those who have not with regard to interest in genetic testing for breast cancer risk? (c) Are knowledge of genetic testing and sociodemographic factors associated with womens interest in genetic testing for breast cancer risk? (d) What are the important gaps in womens knowledge of hereditary breast cancer risk and genetic testing?
| Materials and Methods |
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The target population of the other sample was all living women who had been diagnosed with invasive breast cancer between September 1, 1994 and September 1, 1998, treated for breast cancer by the provincial cancer agency, who were 20 years of age or older at the time of diagnosis, and remain residents of the province. Of the total population (n = 5888) meeting these criteria, a probability sample stratified on the basis of four age groups (2039 years; 4059 years; 6079 years; and 80+ years) was selected from the provincial breast cancer registry. To obtain a sample of each age group using predicted response rates of 70% for the three youngest age groups and of 40% for women 80+ years and a maximum margin of error of ± 4.8% for estimated proportions, a sample of 653 women was randomly selected. Of these, 128 were excluded because physicians advised against contacting the women for the study or because these women were too ill to participate, were not English speaking, or had moved. A total of 260 of the remaining eligible women participated, resulting in a response rate of 49.5%. Respondents were significantly younger [mean, 57.8 years ± 1.9% (95% CI)3
] at age of first breast cancer diagnosis than nonrespondents [mean, 65.3 years ± 2.2% (95% CI)]. A significant relationship between participation status and breast cancer stage (
2 = 8.4; P = 0.038) was found with women in stages 1, 2, and 3 having similar participation rates and women with stage 4 breast cancer tending not to participate. It should be noted that women with stages 3 and 4 breast cancer represented <5% of the eligible sample.
Procedures.
The survey instrument was developed using items from well-established questionnaires and standardized measures. The survey was pretested with 20 women (15 from the general public and 5 from the breast cancer registry) to ensure ease of question flow and overall comprehensibility. All respondents were interviewed over the telephone by trained female interviewers using computer-assisted telephone interviewing.
Awareness of breast cancer genes was assessed in the first question of the survey by asking respondents, "How much have you heard or read about breast cancer genes, that is, genes that put some women at a higher risk for breast cancer?" Response categories included "almost nothing, a little bit, a fair amount, and a lot."
Interest in genetic testing for breast cancer risk was measured near the beginning of the interview by asking respondents which statement described them best: "You are . . . not considering or havent thought about genetic testing; are considering genetic testing; probably will have genetic testing; definitely will have genetic testing; or already have had genetic testing." (14 , 17 , 18) . Responses were dichotomized into expressions of no interest versus expressions of all other levels of interest. An open-ended question was also included to determine womens reasons for being interested in genetic testing, and responses were subjected to content analysis.
To assess womens knowledge about hereditary breast cancer and genetic testing for breast cancer risk, a seven-item true-false scale was used. The scale included six breast cancer-related items based on the knowledge scale develop by the United States NIH Cancer Genetic Studies Consortium (19) and one item to assess womens knowledge of the availability of tests to detect breast cancer genes. Modifications were made to the phrasing of questions to minimize confusion associated with scientific terms (e.g., mutations or alterations in genes) and to enhance comprehension of the questions by a lay audience. Although we acknowledge the phrasing may not reflect current scientific understanding in all instances, the wording reflects the way women in the general population commonly talk about BCRA1 and BRCA2 gene mutations or alterations (5) . One point was given for each correct answer. The survey also included questions concerning demographics and family history of breast cancer.
Statistical Analysis.
Descriptive statistics were used to characterize the study samples and to describe the study variables. Weighting factors for women from the general public were calculated based on 1996 age-stratified population distributions of women living in the study region (1996 Canadian Census Profile Tables) to accommodate over- and undersampling. For the sample of women with breast cancer, the study regions 1996 cancer registry statistics for age at breast cancer diagnosis were used to determine the weighting factors. The weighting factors were standardized such that the weighted number of cases equaled the sample size; consequently, the tests of statistical significance were neither inflated nor deflated. Ninety-five % confidence intervals were calculated for each samples point estimates. We highlight instances where the confidence intervals do not overlap.
The two samples were combined to evaluate the influence of knowledge, family history, and sociodemographic factors on interest in genetic testing for breast cancer risk using multiple logistic regression analysis. Personal history of breast cancer (only those from the cancer registry had a diagnosis of breast cancer), age (deciles), years of education, family history of breast cancer (at least one primary or secondary relative with breast cancer), knowledge of genetic testing (continuous variable), and all theoretically plausible two-way interactions were entered as predictor variables in one block. Using backwards deletion, interaction variables that did not contribute significantly to the regression model were removed one at a time. Model fit was assessed with the Hosmer-Lemeshow goodness-of-fit statistic (20) . Adjusted odds ratios and 95% CIs were estimated for each predictor.
| Results |
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Knowledge Related to Genetic Testing.
The percentage of participants responding correctly to each knowledge question ranged from 13.5% [±2.4% (95% CI)] to 89.8% [±2.2% (95% CI); Table 2
]. No significant differences were found in summated knowledge scores between women with and without breast cancer. The average summated knowledge scores were 4.2 [±0.2 (95% CI)] and 4.1 [± 0.1 (95% CI)] for women with and without breast cancer, respectively. Regardless of their breast cancer status, almost two-thirds of the women did not know that ones paternal family history of breast cancer is important. More than two-thirds lacked knowledge about the prevalence of inherited genetic mutations and their role in breast cancer. For the most part, women with breast cancer did not express superior knowledge of breast cancer genetic testing.
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| Discussion |
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Despite media attention and increasing availability of information about genetic testing, the level of awareness about breast cancer genes observed in the study samples was relatively low. The proportion of women who reported some awareness of breast cancer genes is similar to that found by others (12 , 21) . Consistent with moderately low levels of awareness, women demonstrated limited knowledge of genetic testing, regardless of their breast cancer status. Although most women appeared to understand that not all breast cancer is caused by inherited gene mutations, that breast cancer gene mutations are not 100% penetrant, and that a womans chance of carrying the breast cancer gene is 50% if her sister is a carrier, their lack of knowledge of the prevalence of breast cancer genes and the incidence of hereditary breast cancer is striking. Researchers have reported similar results from surveys of women seeking medical services (13) and women at high risk for breast or ovarian cancer (19 , 21) . Knowledge of the importance of paternal family history of breast cancer was particularly low in our study samples. In comparison, 4875% correct response rates to this item have been reported in United States studies (13 , 19 , 21) .
The reasons women gave for being interested in genetic testing for breast cancer risk indicate a lack of understanding about the limitations and implications of genetic testing. The primary reasons given for wanting genetic testing by women in this study are similar to those reported in other studies (2 , 11 , 17) , with one exception. Unlike other studies, wanting to know their status or simple curiosity was the most frequently cited reason for being interested in genetic testing for both women with and without breast cancer. This finding reflects womens interest in obtaining categorical (will get the disease or not) rather than probabilistic information about their risk for breast cancer and their unrealistic expectations of what genetic testing for breast cancer risk can provide (5) . Womens desire for categorical information may also be a function of the difficulty the general public has in understanding probabilistic risk information.
Critical gaps in knowledge essential to understanding hereditary breast cancer and genetic testing appear to persist and point to the need for better educational strategies. Understanding the role of hereditary breast cancer in relation to other risk factors and the limitations of genetic testing (e.g., the potential for inconclusive results) are important not only to those most likely to be eligible for genetic testing but also for those at low or moderate risk for hereditary breast cancer who express an interest in testing. This information may help women of low or moderate risk understand why they do not need genetic testing.
Levels of interest in genetic testing for breast cancer risk observed in this study are considerably lower than those reported in the United States and in other regions in Canada. Only one United States study conducted in 1998 reported rates of interest in genetic testing for breast cancer <50%, and this was limited to women who were >60 years of age (2) . The only published Canadian study examining interest in genetic testing for breast cancer risk reported that 72% of women diagnosed with breast cancer before the age of 50 years were interested in genetic testing as were 46% of women without breast cancer (1850 years of age; Ref. 10 ). Compared with these studies, the rates of interest in genetic testing in this study come closer to reflecting the actual demand for genetic testing (23) . These comparably low rates of interest in genetic testing for breast cancer risk may be a reflection of the relatively low levels of awareness of this testing, demonstrated in our samples, that could be linked with the minimal use of direct advertising of genetic services in Canada and the limited availability of testing in the study region.
An important but not surprising finding is that after controlling for the effects of age, education, breast cancer status, and knowledge of genetic testing, women with at least one first- or second-degree relative with breast cancer are more likely to express an interest in genetic testing than women without a positive history. This may in part be a reflection of the profound influence of family experiences with breast cancer on risk perceptions and the level of anxiety this generates (24 , 25) . That interest in genetic testing among women who have breast cancer steadily increases with educational attainment has not been reported previously. Given that increasing levels of educational attainment are likely to positively influence womens ability to comprehend factors associated with hereditary breast cancer and assess the relevance of genetic testing for themselves or their families, it is possible that interest levels in this group may translate into higher levels of actual requests for genetic counseling and testing. Although this study did not consider psychosocial factors that may influence interest in genetic testing (e.g., psychological distress, perceptions of risk), our examination of demographic variables demonstrates the usefulness of this readily available information to direct the development of community education strategies related to genetic testing for breast cancer risk.
The findings revealed that interest in genetic testing among those with more knowledge of genetic testing declines steadily with advancing age, whereas more modest declines are demonstrated among those with low levels of knowledge. Younger womens interest in testing may reflect the perceived implications of a breast cancer diagnosis during mid-life as well as better understanding of genetics because of exposure to developments in science and genetics during their formal education. The combined effect of knowledge of genetic testing and age, however, suggests that women with more knowledge of genetic testing have a better understanding of hereditary breast cancer and its association with premenopausal cancer.
The results of this study provide important directions for the development of educational strategies that should accompany increases in public awareness and the availability of genetic testing. Broad-based community education strategies are required to address interest in genetic testing for breast cancer risk among women in the general public as well as among those with breast cancer to facilitate informed decision-making. Critical gaps in knowledge of genetic testing and hereditary breast cancer risk identified in this study can provide a focus for these educational strategies. The broader implications of genetic testing (e.g., potential for discrimination and barriers to reasonable life insurance) should also be addressed. Educational strategies should be targeted toward those who appear to be most interested in genetic testing for breast cancer risk, including women with a family history of breast cancer, well-educated women with breast cancer, and younger women, particularly those with some knowledge of genetic testing. Developing understandable and practical educational materials will ensure their accessibility to a broad range of audiences, including those women who may be candidates for genetic testing for hereditary breast cancer risk but who are not yet aware of its availability.
| Footnotes |
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1 This research was supported by a grant from the Medical Research Council of Canada and through a Canadian Institutes for Health Research (CIHR) scholar award (to P. A. R.), a CIHR investigator award (to J. L. B.), the Dorothy J. Lamont Scientist Award (CIHR/National Cancer Institute of Canada; to T. H.), a National Health Research and Development Program Ph.D. Fellowship (to L. G. B.), and a Social Science and Humanities Ph.D. Fellowship (to C. G. R.). ![]()
2 To whom requests for reprints should be addressed, University of British Columbia, T2012211 Wesbrook Mall, Vancouver, British Columbia, V6T 2B5 Canada. Phone: (604) 822-7438; Fax: (604) 822-7600; E-mail: bottorff{at}nursing.ubc.ca ![]()
3 The abbreviation used is: CI, confidence interval. ![]()
Received 4/13/01; revised 10/ 5/01; accepted 10/23/01.
| References |
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