Simple Summary Genetic variants explaining approximately 40% of familial breast cancer risk have been identified, thus leaving a significant fraction of the heritability of this disease still... Show moreSimple Summary Genetic variants explaining approximately 40% of familial breast cancer risk have been identified, thus leaving a significant fraction of the heritability of this disease still unexplained. The exact nature of this missing fraction is unknown; more extensive sequencing efforts could potentially identify new moderate-penetrance breast cancer risk alleles. The aim of this study was to perform a large-scale whole-exome sequencing study, followed by a targeted validation, in breast cancer patients and healthy women of European descent. We identified 20 novel genes with modest evidence of association (p-value < 0.05) for either overall or subtype-specific breast cancer; however, much larger studies are needed to confirm the exact role of these genes in susceptibility to breast cancer. Rare variants in at least 10 genes, including BRCA1, BRCA2, PALB2, ATM, and CHEK2, are associated with increased risk of breast cancer; however, these variants, in combination with common variants identified through genome-wide association studies, explain only a fraction of the familial aggregation of the disease. To identify further susceptibility genes, we performed a two-stage whole-exome sequencing study. In the discovery stage, samples from 1528 breast cancer cases enriched for breast cancer susceptibility and 3733 geographically matched unaffected controls were sequenced. Using five different filtering and gene prioritization strategies, 198 genes were selected for further validation. These genes, and a panel of 32 known or suspected breast cancer susceptibility genes, were assessed in a validation set of 6211 cases and 6019 controls for their association with risk of breast cancer overall, and by estrogen receptor (ER) disease subtypes, using gene burden tests applied to loss-of-function and rare missense variants. Twenty genes showed nominal evidence of association (p-value < 0.05) with either overall or subtype-specific breast cancer. Our study had the statistical power to detect susceptibility genes with effect sizes similar to ATM, CHEK2, and PALB2, however, it was underpowered to identify genes in which susceptibility variants are rarer or confer smaller effect sizes. Larger sample sizes would be required in order to identify such genes. Show less
Breast cancer risk is approximately twice as high in first-degree relatives of female breast cancer cases than in women in the general population. Less than half of this risk can be attributed to... Show moreBreast cancer risk is approximately twice as high in first-degree relatives of female breast cancer cases than in women in the general population. Less than half of this risk can be attributed to the currently known genetic risk factors. Recessive risk alleles represent a relatively underexplored explanation for the remainder of familial risk. To address this, we selected 19 non-BRCA1/2 breast cancer families in which at least three siblings were affected, while no first-degree relatives of the previous or following generation had breast cancer. Germline DNA from one of the siblings was subjected to exome sequencing, while all affected siblings were genotyped using SNP arrays to assess haplotype sharing and to calculate a polygenic risk score (PRS) based on 160 low-risk variants. We found no convincing candidate recessive alleles among exome sequencing variants in genomic regions for which all three siblings shared two haplotypes. However, we found two families in which all affected siblings carried the CHEK2*1100delC. In addition, the average normalized PRS of the "recessive" family probands (0.81) was significantly higher than that in both general population cases (0.35, P = .026) and controls (P = .0004). These findings suggest that the familial aggregation is, at least in part, explained by a polygenic effect of common low-risk variants and rarer intermediate-risk variants, while we did not find evidence of a role for novel recessive risk alleles. Show less
Purpose: Counselees' preferences are considered important for the choice of risk communication format and for improving patient-centered care. We here report on counselees' preferences for how... Show morePurpose: Counselees' preferences are considered important for the choice of risk communication format and for improving patient-centered care. We here report on counselees' preferences for how risks are presented in familial breast cancer counseling and the impact of this preferred format on their understanding of risk.Patients and Methods: As part of a practice-based randomized controlled trial, 326 unaffected women with a family history of breast cancer received their lifetime risk in one of five presentation formats after standard genetic counseling in three Dutch familial cancer clinics: 1) in percentages, 2) in frequencies ("X out of 100"), 3) in frequencies plus graphical format (10x10 human icons), 4) in frequencies and 10-year age-related risk and 5) in frequencies and 10-year age-related risk plus graphical format. Format preferences and risk understanding (accuracy) were assessed at 2-week follow-up by a questionnaire, completed by 279/326 women.Results: The most preferred risk communication formats were numbers combined with verbal descriptions (37%) and numbers only (26%). Of the numerical formats, most (55%) women preferred percentages. The majority (73%) preferred to be informed about both lifetime and 10-year age-related risk. Women who had received a graphical display were more likely to choose a graphical display as their preferred format. There was no significant effect between the intervention groups with regard to risk accuracy. Overall, women given risk estimates in their preferred format had a slightly better understanding of risk.Conclusion: The results suggest that the accuracy of breast cancer risk estimation is slightly better for women who had received this information in their preferred format, but the risk format used had no effect on women's risk accuracy. To meet the most frequent preference, counselors should consider providing a time frame of reference (eg, risk in the next 10 years) in a numerical format, in addition to lifetime risk. Show less
