Melbourne School of Population and Global Health - Research Publications
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ItemNo Preview AvailablePerceived Versus Predicted Risks of Colorectal Cancer and Self-Reported Colonoscopies by Members of Mismatch Repair Gene Mutation-Carrying Families Who Have Declined Genetic Testing(WILEY, 2014-02)People carrying germline mutations in mismatch repair genes are at high risk of colorectal cancer (CRC), yet about half of people from mutation-carrying families decline genetic counselling and/or testing to identify mutation status. We studied the association of quantitative measures of risk perception, risk prediction and self-reported screening colonoscopy in this elusive yet high-risk group. The sample of 26 participants (mean age 43.1 years, 14 women) in the Australasian Colorectal Cancer Family Registry were relatives of mutation carriers; had not been diagnosed with any cancer at the time of recruitment and had declined an invitation to attend genetic counselling and/or testing. A structured elicitation protocol captured perceived CRC risk over the next 10 years. Self-reported colonoscopy screening was elicited during a 45-minute semi-structured interview. Predicted 10-year CRC risk based on age, gender, known mutation status and family history was calculated using "MMRpro." Mean perceived 10-year risk of CRC was 31 % [95 % CI 21, 40], compared with mean predicted risk of 4 % [2, 7] (p < 0.001); this was independent of age and sex (p = 0.9). Among those reporting any medical advice and any screening colonoscopy (n = 18), those with higher risk perception had less frequent colonoscopy (Pearson's r = 0.49 [0.02, 0.79]). People who decline genetic testing for CRC susceptibility mutations perceive themselves to be at substantially higher risk than they really are. Those with high perceived risk do not undertake screening colonoscopy more often than those who perceive themselves to be at average risk.
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ItemUptake of offer to receive genetic information about BRCA1 and BRCA2 mutations in an Australian population-based study(American Association for Cancer Research, 2004)Research on the utilization of genetic testing services for mutations in BRCA1 and BRCA2 has focused on women with a strong family history of breast and ovarian cancer. We conducted a population-based case-control-family study of Australian women diagnosed with invasive breast cancer before age 40 years, unselected for family history, and tested for germ line mutations in BRCA1 and BRCA2. Case subjects found to carry a deleterious mutation and their relatives who had given a research blood sample were informed by mail that the study had identified “genetic information” and were offered the opportunity to learn more. Those interested were referred to a government-funded family cancer clinic. Of 94 subjects who received the letter, 3 (3%) did not respond and 38 (40%) declined to learn their result (16 declined the referral, 10 accepted but did not attend a clinic, and 12 attended a clinic but declined testing), and 12 (13%) remain “on hold”. The remaining 41 (44%) chose to learn their result (3 of whom already knew their mutation status). There was no evidence that the decision to learn of mutation status depended on age, gender, family history, or having been diagnosed with breast cancer. Of 19 families with more than one participant, in 11 (58%) there was discordance between relatives in receiving genetic results.