Diagnostic Utility of Genome-wide DNA Methylation Testing in Genetically Unsolved Individuals with Suspected Hereditary Conditions.

Conventional genetic testing of individuals with neurodevelopmental presentations and congenital anomalies (ND/CAs), i.e., the analysis of sequence and copy number variants, leaves a substantial proportion of them unexplained. Some of these cases have been shown to result from DNA methylation defects at a single locus (epi-variants), while others can exhibit syndrome-specific DNA methylation changes across multiple loci (epi-signatures). Here, we investigate the clinical diagnostic utility of genome-wide DNA methylation analysis of peripheral blood in unresolved ND/CAs. We generate a computational model enabling concurrent detection of 14 syndromes using DNA methylation data with full accuracy. We demonstrate the ability of this model in resolving 67 individuals with uncertain clinical diagnoses, some of whom had variants of unknown clinical significance (VUS) in the related genes. We show that the provisional diagnoses can be ruled out in many of the case subjects, some of whom are shown by our model to have other diseases initially not considered. By applying this model to a cohort of 965 ND/CA-affected subjects without a previous diagnostic assumption and a separate assessment of rare epi-variants in this cohort, we identify 15 case subjects with syndromic Mendelian disorders, 12 case subjects with imprinting and trinucleotide repeat expansion disorders, as well as 106 case subjects with rare epi-variants, a portion of which involved genes clinically or functionally linked to the subjects' phenotypes. This study demonstrates that genomic DNA methylation analysis can facilitate the molecular diagnosis of unresolved clinical cases and highlights the potential value of epigenomic testing in the routine clinical assessment of ND/CAs.

Comprehensive genetic sequence and copy number analysis for Charcot-Marie-Tooth disease in a Canadian cohort of 2517 patients.

Charcot-Marie-Tooth disease (CMT) is one of the most common Mendelian disorders characterised by genetic heterogeneity, progressive distal muscle weakness and atrophy, foot deformities and distal sensory loss. In this report, we describe genetic testing data including comprehensive sequencing and copy number analysis of 34 CMT-related genes in a Canadian cohort of patients with suspected CMT. We have demonstrated a notable gender testing bias, with an overall diagnostic yield of 15% in males and 21% in females. We have identified a large number of novel pathogenic variants as well as variants of unknown clinical significance in CMT-related genes. In this largest to date analysis of gene CNVs in CMT, in addition to the common PMP22 deletion/duplication, we have described a significant contribution of pathogenic CNVs in several CMT-related genes. This study significantly expand the mutational spectrum of CMT genes, while demonstrating the clinical utility of a comprehensive sequence and copy number next-generation sequencing-based clinical genetic testing in patients with suspected diagnosis of CMT.

Genomic DNA Methylation Signatures Enable Concurrent Diagnosis and Clinical Genetic Variant Classification in Neurodevelopmental Syndromes.

Pediatric developmental syndromes present with systemic, complex, and often overlapping clinical features that are not infrequently a consequence of Mendelian inheritance of mutations in genes involved in DNA methylation, establishment of histone modifications, and chromatin remodeling (the "epigenetic machinery"). The mechanistic cross-talk between histone modification and DNA methylation suggests that these syndromes might be expected to display specific DNA methylation signatures that are a reflection of those primary errors associated with chromatin dysregulation. Given the interrelated functions of these chromatin regulatory proteins, we sought to identify DNA methylation epi-signatures that could provide syndrome-specific biomarkers to complement standard clinical diagnostics. In the present study, we examined peripheral blood samples from a large cohort of individuals encompassing 14 Mendelian disorders displaying mutations in the genes encoding proteins of the epigenetic machinery. We demonstrated that specific but partially overlapping DNA methylation signatures are associated with many of these conditions. The degree of overlap among these epi-signatures is minimal, further suggesting that, consistent with the initial event, the downstream changes are unique to every syndrome. In addition, by combining these epi-signatures, we have demonstrated that a machine learning tool can be built to concurrently screen for multiple syndromes with high sensitivity and specificity, and we highlight the utility of this tool in solving ambiguous case subjects presenting with variants of unknown significance, along with its ability to generate accurate predictions for subjects presenting with the overlapping clinical and molecular features associated with the disruption of the epigenetic machinery.

Genetic and epigenetic profiling of BRCA1/2 in ovarian tumors reveals additive diagnostic yield and evidence of a genomic BRCA1/2 DNA methylation signature.

Poly-ADP-ribose-polymerase inhibitor (PARPi) treatment is indicated for advanced-stage ovarian tumors with BRCA1/2 deficiency. The "BRCAness" status is thought to be attributed to a tumor phenotype associated with a specific epigenomic DNA methylation profile. Here, we examined the diagnostic impact of combined BRCA1/2 sequence, copy number, and promoter DNA methylation analysis, and evaluated whether genomic DNA methylation patterns can predict the BRCAness in ovarian tumors. DNA sequencing of 172 human tissue samples of advanced-stage ovarian adenocarcinoma identified 36 samples with a clinically significant tier 1/2 sequence variants (point mutations and in/dels) and 9 samples with a CNV causing a loss of function in BRCA1/2. DNA methylation analysis of the promoter of BRCA1/2 identified promoter hypermethylation of BRCA1 in two mutation-negative samples. Computational modeling of genome-wide methylation markers, measured using Infinium EPIC arrays, resulted in a total accuracy of 0.75, sensitivity: 0.83, specificity: 0.64, positive predictive value: 0.76, negative predictive value: 0.74, and area under the receiver's operating curve (AUC): 0.77, in classifying tumors harboring a BRCA1/2 defect from the rest. These findings indicate that the assessment of CNV and promoter DNA methylation in BRCA1/2 increases the cumulative diagnostic yield by 10%, compared with the 20% yield achieved by sequence variant analysis alone. Genomic DNA methylation data can partially predict BRCAness in ovarian tumors; however, further investigation in expanded BRCA1/2 cohorts is needed, and the effect of other double strand DNA repair gene defects in these tumors warrants further investigations.

Genome-wide DNA methylation and RNA analyses enable reclassification of two variants of uncertain significance in a patient with clinical Kabuki syndrome.

Nontruncating sequence variants represent a major challenge in variant interpretation and classification. Here, we report a patient with features of Kabuki syndrome who carries two rare heterozygous variants in KMT2D: c.12935C>T, p.(Ser4312Phe) and c.15785-10T>G. The clinical significance of these variants were discordantly interpreted by different diagnostic laboratories. Parental testing showed that the missense variant was inherited from the father with a mild Kabuki phenotype and the intronic variant from the mother with mosaic status. Through genome-wide DNA methylation analysis of peripheral blood, we confirmed that the proband exhibited a previously described episignature of Kabuki syndrome. Parental samples had normal DNA methylation profiles, thus ruling out the involvement of the paternally inherited missense variant. RNA analysis revealed that the intronic change resulted in exon 49 skipping and frameshift, thereby providing a molecular diagnosis of Kabuki syndrome. This study demonstrates the utility of epigenomic and RNA analyses in resolving ambiguous clinical cases.

International trends in the uptake of cancer risk reduction strategies in women with a BRCA1 or BRCA2 mutation.

BACKGROUND: Women with a BRCA1 or BRCA2 mutation face high risks of breast and ovarian cancer. In the current study, we report on uptake of cancer screening and risk-reduction options in a cohort of BRCA mutation carriers from ten countries over two time periods (1995 to 2008 and 2009 to 2017). METHODS: Eligible subjects were identified from an international database of female BRCA mutation carriers and included women from 59 centres from ten countries. Subjects completed a questionnaire at the time of genetic testing, which included past use of cancer prevention options and screening tests. Biennial follow-up questionnaires were administered. RESULTS: Six-thousand two-hundred and twenty-three women were followed for a mean of 7.5 years. The mean age at last follow-up was 52.1 years (27-96 years) and 42.3% of the women had a prior diagnosis of breast cancer. In all, 27.8% had a prophylactic bilateral mastectomy and  64.7% had a BSO. Screening with breast MRI increased from 70% before 2009 to 81% at or after 2009. There were significant differences in uptake of all options by country. CONCLUSION: For women who received genetic testing more recently, uptake of prophylactic mastectomy and breast MRI is significantly higher than those who received genetic testing more than 10 years ago. However, uptake of both BSO and breast MRI is not optimal, and interventions to increase uptake are needed.

Oophorectomy and risk of contralateral breast cancer among BRCA1 and BRCA2 mutation carriers.

PURPOSE: Following a diagnosis of breast cancer, BRCA mutation carriers face an increased risk of developing a second (contralateral) cancer in the unaffected breast. It is important to identify predictors of contralateral cancer in order to make informed decisions about bilateral mastectomy. The impact of bilateral salpingo-oophorectomy (i.e., oophorectomy) on the risk of developing contralateral breast cancer is unclear. Thus, we conducted a prospective study of the relationship between oophorectomy and the risk of contralateral breast cancer in 1781 BRCA1 and 503 BRCA2 mutation carriers with breast cancer. METHODS: Women were followed from the date of diagnosis of their first breast cancer until the date of diagnosis of a contralateral breast cancer, bilateral mastectomy, date of death, or date of last follow-up. Cox proportional hazards regression was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) of contralateral breast cancer associated with oophorectomy. Oophorectomy was included as a time-dependent covariate. We performed a left-censored analysis for those women who reported a primary breast cancer prior to study entry (i.e., from completion of baseline questionnaire). RESULTS: After an average of 9.8 years of follow-up, there were 179 (7.8%) contralateral breast cancers diagnosed. Oophorectomy was not associated with the risk of developing a second breast cancer (HR 0.92; 95% CI 0.68-1.25). The relationship did not vary by BRCA mutation type or by age at diagnosis of the first breast cancer. There was some evidence for a decreased risk of contralateral breast cancer among women with an ER-positive primary breast cancer, but this was based on a small number of events (n = 240). CONCLUSION: Overall, our findings suggest that oophorectomy has little impact on the risk of contralateral breast cancer.

Implementation of an NGS-based sequencing and gene fusion panel for clinical screening of patients with suspected hematologic malignancies.

OBJECTIVES: The diagnosis of hematologic malignancies integrates multiple diagnostic and clinical disciplines. Historically, targeted (single-analyte) genetic testing has been used as reflex to initial prescreening by other diagnostic modalities including flow cytometry, anatomic pathology, and clinical cytogenetics. Given the wide range of mutations associated with hematologic malignancies a DNA/RNA-based NGS panel can provide a more effective and economical approach to comprehensive testing of patients as an initial, tier-1 screen. METHODS: Using a cohort of 380 patients, we performed clinical validation of a gene panel designed to assess 40 genes (DNA), and 29 fusion driver genes with over 600 gene fusion partners (RNA), including sample exchange data across three clinical laboratories, and correlation with cytogenetic testing results. RESULTS: The clinical validation of this technology demonstrated that its accuracy, sensitivity, and specificity are comparable to the majority of targeted single-gene approaches, while assessment of the initial patient cohort data demonstrated a high diagnostic yield of 50.5%. CONCLUSIONS: Implementation of a tier-1 NGS-based protocol for gene panel screening provides a comprehensive alternative to targeted molecular testing in patients with suspected hematologic malignancies, with increased diagnostic yield, scalability, reproducibility, and cost effectiveness, making it ideally suited for implementation in clinical laboratories.

Age at first full-term birth and breast cancer risk in BRCA1 and BRCA2 mutation carriers.

PURPOSE: In the general population, an early age at first full-term birth confers protection against the risk of developing breast cancer. The relationship between age at first birth and breast cancer risk is not clear for women with a mutation in the BRCA1 or BRCA2 gene. Thus, we undertook a case-control study of women with a BRCA1 or BRCA2 mutation to study the effects of age at first full-term birth matched for other reproductive factors. METHODS: Information about reproductive factors, including age at first birth as well as medical history, was collected from a routinely administered research questionnaire. There were 2,295 matched pairs of women with a BRCA1 or BRCA2 mutation included in the final analysis. RESULTS: There was no significant difference in the mean age at first full-term birth among the BRCA1 (24.9 vs. 25.2; P = 0.10) or BRCA2 mutation carriers (26.5 vs. 26.6 years; P = 0.80). Findings were similar in the analysis limited to cases who were diagnosed with breast cancer prior to age 45. CONCLUSION: This matched analysis of a large number of BRCA mutation carriers suggests that age at first birth has little influence on BRCA1 or BRCA2 breast cancer risk.

Age-specific ovarian cancer risks among women with a BRCA1 or BRCA2 mutation.

OBJECTIVES: For women at high risk of developing ovarian cancer, it is important to provide an accurate recommendation for the optimal age for preventive surgery in order to maximize the preventative effect while delaying symptoms associated with early surgical menopause. The goal of the current study was to estimate age-specific incidence rates of ovarian cancer among women with a BRCA1 or BRCA2 mutation. METHODS: From our international registry, we identified 5689 women with no previous diagnosis of ovarian or fallopian tube cancer or preventive oophorectomy. Women were followed from the date of completion of the baseline questionnaire until either a diagnosis of ovarian or fallopian tube cancer, prophylactic oophorectomy, death or last follow-up. The annual and cumulative incidence rates of ovarian cancer were estimated. RESULTS: Over a mean follow-up period of 4.7 years (ranges 0-22.6), 195 incident ovarian or fallopian tube cancers were diagnosed (169 [86%] ovarian cancers, 22 [11%] fallopian tube cancers and four [2%] cancers that involved both the ovaries and fallopian tubes). Of these, 45 (23%) cancers were diagnosed at preventive surgery (occult cancers). The cumulative risk of ovarian cancer to age 80 was 49% for BRCA1 and 21% for BRCA2 mutation carriers. The mean age at diagnosis was 51.3 years (ranges 33-84) among women with a BRCA1 mutation and 61.4 years (ranges 44-80) among women with a BRCA2 mutation. CONCLUSION: Based on a cumulative risk of 0.55% to age 35 for BRCA1 mutation carriers and of 0.56% to age 45 for BRCA2 mutation carriers, we recommend bilateral salpingo-oophorectomy before age 40, but ideally by age 35, for women with a BRCA1 mutation and by age 45 for those with a BRCA2 mutation to maximize prevention and to minimize adverse effects.

Genetics Consultation Rates Following a Diagnosis of High-Grade Serous Ovarian Carcinoma in the Canadian Province of Ontario.

OBJECTIVE: In 2001, the province of Ontario expanded cancer genetic testing eligibility to include all women with high-grade serous ovarian carcinoma (HGSC) of the ovary, fallopian tube, and peritoneum. The aim of this study was to determine the proportion of women who attended genetics counseling for consideration of BRCA1/2 gene analysis. We also sought to examine if regional differences in consultation rate exist across administrative health regions in the province of Ontario. METHODS: We identified all women with a pathological diagnosis of HGSC in the province of Ontario between 1997 until 2011. Our primary outcome was the 2-year rate of genetics consultation following a diagnosis of HGSC. We compared consultation rates over time and geographical regions and applied multiple logistic regression to identify predictors of genetics consultation. RESULTS: Of the 5412 women with a diagnosis of HGSC over the study period, 6.6% were seen for genetics consultation within 2 years of diagnosis. Factors predictive of genetics consultation included history of breast cancer (odds ratio [OR], 3.56; 95% confidence interval [CI], 1.87-6.78), era of diagnosis (2009-2011 vs 1997-2000; OR, 10.59; 95% CI, 5.02-22.33), and younger age at diagnosis (OR, 0.95; 95% CI, 0.94-0.97 for each additional year). No regional differences in consultation rate were seen. CONCLUSIONS: Despite an increasing rate across eras, a small proportion of women with HGSC undergo genetics consultation. Efforts are required to increase cancer genetics consultation in patients with HGSC in the province of Ontario.

DNA methylation analysis in constitutional disorders: Clinical implications of the epigenome.

Genomic, chromosomal, and gene-specific changes in the DNA sequence underpin both phenotypic variations in populations as well as disease associations, and the application of genomic technologies for the identification of constitutional (inherited) or somatic (acquired) alterations in DNA sequence forms a cornerstone of clinical and molecular genetics. In addition to the disruption of primary DNA sequence, the modulation of DNA function by epigenetic phenomena, in particular by DNA methylation, has long been known to play a role in the regulation of gene expression and consequent pathogenesis. However, these epigenetic factors have been identified only in a handful of pediatric conditions, including imprinting disorders. Technological advances in the past decade that have revolutionized clinical genomics are now rapidly being applied to the emerging discipline of clinical epigenomics. Here, we present an overview of epigenetic mechanisms with a focus on DNA modifications, including the molecular mechanisms of DNA methylation and subtypes of DNA modifications, and we describe the classic and emerging genomic technologies that are being applied to this study. This review focuses primarily on constitutional epigenomic conditions associated with a spectrum of developmental and intellectual disabilities. Epigenomic disorders are discussed in the context of global genomic disorders, imprinting disorders, and single gene disorders. We include a section focused on integration of genetic and epigenetic mechanisms together with their effect on clinical phenotypes. Finally, we summarize emerging epigenomic technologies and their impact on diagnostic aspects of constitutional genetic and epigenetic disorders.

Gender and BCR-ABL transcript type are correlated with molecular response to imatinib treatment in patients with chronic myeloid leukemia.

OBJECTIVES: Achieving a major molecular response (MMR) is the goal of imatinib therapy for chronic myeloid leukemia. However, the association between gender, BCR-ABL transcript type, and age with MMR is not well understood and often controversial. METHODS: We retrospectively analyzed 166 patients who have been treated with imatinib for up to 10 yr. RESULTS: Men had a lower MMR rate than women (63.3% vs. 81.6%, P = 0.006) and a shorter time to relapse (median 354 vs. 675 d, P = 0.049), while patients with b3a2 or with both b3a2 and b2a2 break point transcripts had higher MMR rate than those with b2a2 (81.8%, 77.1% vs. 60.7%, P = 0.023 for b3a2 vs. b2a2, P = 0.043 for both vs. b2a2). A striking difference was found between men with b2a2 and women with both b2a2 and b3a2 in terms of MMR rate (43.8% vs. 88.9%), MMR rate within 6 months (7.1% vs. 62.5%) and the time to MMR (median d 493 vs. 159, P = 0.036). CONCLUSIONS: Both gender and BCR-ABL transcript, but not age, were significantly associated with the molecular response. Men with b2a2 represent a less favorable group in their response to imatinib treatment and may need alternative therapy regimen and closer monitoring.

Prospective evaluation of alcohol consumption and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers.

Given the adverse effect of alcohol in the development of breast cancer among women in the general population, we evaluated whether a similar association exists among women with a BRCA1 or BRCA2 mutation. Information regarding baseline daily alcohol consumption was abstracted from a research questionnaire for 3067 BRCA mutation carriers enrolled in a prospective cohort study. Women were followed biennially until the date of the last follow-up questionnaire, date of breast cancer diagnosis, date of prophylactic bilateral mastectomy, or date of death. Cox proportional hazards models were used to estimate relative risks (RRs) and 95 % confidence intervals (CIs) for invasive breast cancer associated with alcohol consumed at or prior to completion of the baseline questionnaire. After a mean of 5.4 years of follow-up, we observed 259 incident cases of primary invasive breast cancer. Compared with non-users, the adjusted RRs were 1.06 (95 % CI 0.78-1.44) for ever use and 1.08 (0.79-1.47) for current alcohol use. For women in the highest versus lowest quintile of cumulative alcohol consumption, the RR was 0.94 (95 % CI 0.63-1.40; P trend = 0.65). Our findings suggest that alcohol consumption is not a risk factor for breast cancer among women with a BRCA1 or BRCA2 mutation.

Duration of tamoxifen use and the risk of contralateral breast cancer in BRCA1 and BRCA2 mutation carriers.

Women with a mutation in BRCA1 or BRCA2 face a lifetime risk of breast cancer of approximately 80 %. Tamoxifen treatment of the first cancer has been associated with a reduction in the risk of a subsequent contralateral cancer. We studied 1,504 women with a known BRCA1 or BRCA2 mutation, 411 women with bilateral breast cancer (cases) and 1,093 women with unilateral breast cancer (controls) in a matched case-control study. Control women were of similar age and had a similar age of diagnosis of first breast cancer as the cases. For each woman who used tamoxifen, the starting and stopping dates were abstracted and the duration of tamoxifen use was calculated. Three hundred and thirty-one women had used tamoxifen (22 %); of these 84 (25 %) had completed four or more years of tamoxifen, the remainder stopped prematurely or were current users. For women with up to 1 year of tamoxifen use, the odds ratio for contralateral breast cancer was 0.37 (95 % CI 0.20-0.69; p = 0.001) compared to women with no tamoxifen use. Among women with 1-4 years of tamoxifen use the odds ratio was 0.53 (95 % CI 0.32-0.87; p = 0.01). Among women with four or more years of tamoxifen use the odds ratio was 0.83 (95 % CI 0.44-1.55; p = 0.55). Short-term use of tamoxifen for chemoprevention in BRCA1 and BRCA2 mutation carriers may be as effective as a conventional 5-year course of treatment.

The impact of pregnancy on breast cancer survival in women who carry a BRCA1 or BRCA2 mutation.

Physicians are often approached by young women with a BRCA mutation and a recent history of breast cancer who wish to have a baby. They wish to know if pregnancy impacts upon their future risks of cancer recurrence and survival. To date, there is little information on the survival experience of women who carry a mutation in one of the BRCA genes and who become pregnant. From an international multi-center cohort study of 12,084 women with a BRCA1 or BRCA2 mutation, we identified 128 case subjects who were diagnosed with breast cancer while pregnant or who became pregnant after a diagnosis of breast cancer. These women were age-matched to 269 mutation carriers with breast cancer who did not become pregnant (controls). Subjects were followed from the date of breast cancer diagnosis until the date of last follow-up or death from breast cancer. The Kaplan-Meier method was used to estimate 15-year survival rates. The hazard ratio for survival associated with pregnancy was calculated using a left-truncated Cox proportional hazard model, adjusting for other prognostic factors. Among women who were diagnosed with breast cancer when pregnant or who became pregnant thereafter, the 15-year survival rate was 91.5 %, compared to a survival of 88.6 % for women who did not become pregnant (adjusted hazard ratio = 0.76; 95 % CI 0.31-1.91; p = 0.56). Pregnancy concurrent with or after a diagnosis of breast cancer does not appear to adversely affect survival among BRCA1/2 mutation carriers.

International rates of breast reconstruction after prophylactic mastectomy in BRCA1 and BRCA2 mutation carriers.

BACKGROUND: Breast reconstruction is an option for women with BRCA1 or BRCA2 mutations who elect to undergo prophylactic mastectomy to prevent breast cancer. We report on the uptake of breast reconstruction after prophylactic mastectomy in women with BRCA mutations from eight countries. METHODS: Women with a BRCA1 or BRCA2 mutation were questioned regarding their cancer preventive practices. Information was recorded on prophylactic mastectomy and breast reconstruction. RESULTS: A total of 1,635 women with a BRCA1 or BRCA2 mutation who elected to undergo prophylactic mastectomy from eight countries were included. A total of 1,137 women (69.5%) had breast reconstruction after prophylactic mastectomy. A total of 58.7% of women over the age of 45 years at the time of prophylactic mastectomy had breast reconstruction compared to 77.6% of women 35 years of age or younger [odds ratio (OR) 0.36, 95% confidence interval (CI) 0.26-0.50, p < 0.001]. In addition, 62.9% of women with a breast cancer diagnosis (contralateral prophylactic mastectomy) had breast reconstruction after prophylactic mastectomy compared to 79.7% of women without a previous breast cancer diagnosis (OR 0.48, 95% CI 0.38-0.61, p < 0.001). A total of 66.9% of women from Canada had breast reconstruction after mastectomy compared to 71.9% of American women (OR 0.75, 95% CI 0.59-0.96, p = 0.02). CONCLUSIONS: The majority of women elect for breast reconstruction after prophylactic mastectomy. However, younger women and those without a previous diagnosis of breast cancer are more likely to have breast reconstruction than older women or those with a previous diagnosis of cancer.

Breastfeeding and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers.

INTRODUCTION: Breastfeeding has been inversely related to breast cancer risk in the general population. Clarifying the role of breastfeeding among women with a BRCA1 or BRCA2 mutation may be helpful for risk assessment and for recommendations regarding prevention. We present an updated analysis of breastfeeding and risk of breast cancer using a large matched sample of BRCA mutation carriers. METHODS: We conducted a case-control study of 1,665 pairs of women with a deleterious mutation in either BRCA1 (n = 1,243 pairs) or BRCA2 (n = 422 pairs). Breast cancer cases and unaffected controls were matched on year of birth, mutation status, country of residence and parity. Information about reproductive factors, including breastfeeding for each live birth, was collected from a routinely administered questionnaire. Conditional logistic regression was used to estimate the association between ever having breastfed, as well as total duration of breastfeeding, and the risk of breast cancer. RESULTS: Among BRCA1 mutation carriers, breastfeeding for at least one year was associated with a 32% reduction in risk (OR = 0.68; 95% CI 0.52 to 0.91; P = 0.008); breastfeeding for two or more years conferred a greater reduction in risk (OR = 0.51; 95% CI 0.35 to 0.74). Among BRCA2 mutation carriers, there was no significant association between breastfeeding for at least one year and breast cancer risk (OR = 0.83; 95% CI 0.53 to 1.31; P = 0.43). CONCLUSIONS: These data extend our previous findings that breastfeeding protects against BRCA1-, but not BRCA2-associated breast cancer. BRCA mutation carriers should be advised of the benefit of breastfeeding in terms of reducing breast cancer risk.

The impact of population-based screening studies on hemochromatosis screening practices.

OBJECTIVES: To determine if community population screening studies for hemochromatosis affected HFE genetic screening practices in non-study populations. METHODS: An audit of all genetic testing for HFE mutations at London Health Sciences Center, London, Ontario, Canada from 1997 to 2010 was performed. The frequency of genetic testing and the frequency of C282Y homozygous cases identified during the years of the London Red Cross (1998-1999) and HEIRS (2000-2005) screening studies were compared with the corresponding frequencies in the specified years outside this range (1997-1998 and 2006-2010). RESULTS: An increase in HFE gene mutation testing is seen during the London Red Cross study, and the frequency of testing rose further during the HEIRS study. Genetic screening activity continued to increase in the years after publication of the HEIRS study. The proportion of patients with homozygosity for C282Y mutation remained relatively constant despite fluctuations in numbers of persons screened per annum. CONCLUSIONS: The rise in HFE gene testing among non-study populations during the HH studies could be explained by the Hawthorne effect, a phenomenon referring to the improvement or modification of behavior by a population as a consequence of it being studied. In this case, we postulate that primary care physicians at our center performed more HFE gene tests for their patients as a consequence of being affected by knowledge of the screening studies. Despite a general increase in testing during and after completion of the studies, the total number of hemochromatosis cases (C282Y homozygotes) diagnosed per annum remained relatively constant.

Recognizing BRCA gene mutation risk subsequent to breast cancer diagnosis in southwestern Ontario.

OBJECTIVE: To describe the population of women in southwestern Ontario who were diagnosed with potentially preventable BRCA mutation-related breast cancer. DESIGN: Retrospective chart review. SETTING: The Cancer Genetics Clinic of the London Regional Cancer Program in London, Ont. PARTICIPANTS: Patients younger than 52 years of age who were referred to the London Regional Cancer Program Cancer Genetics Clinic between 1997 and 2007 for BRCA testing after being diagnosed with breast cancer (N = 1017). MAIN OUTCOME MEASURES: The proportion of women with BRCA1 or BRCA2 gene mutations and the proportion of women who would have qualified, based on family cancer history, for referral for genetic counseling and testing before their breast cancer diagnoses. RESULTS: Among the 1017 women referred for BRCA testing, 63 women younger than 52 years of age who had been diagnosed with breast cancer were found, subsequent to this diagnosis, to have BRCA1 or BRCA2 gene mutations. Of these, 41 (65%) had family cancer histories that would have qualified them for genetic counseling and testing, according to provincial criteria, before their own breast cancer diagnoses. Of the 63 women, most (81%) had been referred for BRCA gene mutation testing by their oncologists or surgeons. CONCLUSION: Our results suggest that the diagnosis of breast cancer could have been anticipated, and perhaps in some cases prevented, in up to two-thirds of high-risk women younger than 52 years of age in southwestern Ontario. If the high-risk status of these women had been recognized, they might have had the opportunity to choose genetic counseling, testing, more effective cancer surveillance, and potentially preventive options. The results of this study call for increased public and care provider awareness about hereditary breast cancer risk to promote women's ability to choose to access genetic counseling.