Under-ascertainment of breast cancer susceptibility gene carriers in a cohort of New Zealand female breast cancer patients.

BACKGROUND: Diagnostic screening for pathogenic variants in breast cancer susceptibility genes, including BRCA1, BRCA2, PALB2, PTEN and TP53, may be offered to New Zealanders from suspected high-risk breast (and ovarian) cancer families. However, it is unknown how many high-risk pathogenic variant carriers in New Zealand are not offered genetic screening using existing triage tools and guidelines for breast (and ovarian) cancer patients. METHODS: Panel-gene sequencing of the coding and non-coding regions of the BRCA1 and BRCA2 genes, and the coding regions and splice sites of CDH1, PALB2, PTEN and TP53, was undertaken for an unselected cohort of 367 female breast cancer patients. A total of 1685 variants were evaluated using the ENIGMA and the ACMG/AMP variant classification guidelines. RESULTS: Our study identified that 13 (3.5%) breast cancer patients carried a pathogenic or likely pathogenic variant in BRCA1, BRCA2, PALB2, or PTEN. A significantly higher number of pathogenic variant carriers had grade 3 tumours (10/13) when compared to non-carriers; however, no other clinicopathological characteristics were found to be significantly different between (likely) pathogenic variant carriers and non-carriers, nor between variant of unknown significance carriers and non-carriers. Notably, 46% of the identified (likely) pathogenic variant carriers had not been referred for a genetic assessment and consideration of genetic testing. CONCLUSION: Our study shows a potential under-ascertainment of women carrying a (likely) pathogenic variant in a high-risk breast cancer susceptibility gene. These results suggest that further research into testing pathways for New Zealand breast cancer patients may be required to reduce the impact of hereditary cancer syndromes for these individuals and their families.

Novel Presenilin-1 Mutation (Ala275Ser) Associated With Clinical Features of Dementia With Lewy Bodies.

We report a case of familial dementia having some clinical features characteristic of dementia with Lewy bodies, in which a novel mutation Ala275Ser within the presenilin-1 (PSEN1) gene was identified. We review the association of PSEN1 mutation with dementia with Lewy bodies features, noting this to be an uncommonly reported observation.

Patterns of referral and uptake of BReast CAncer (BRCA) gene testing of eligible women with ovarian cancer in New Zealand.

AIMS: To determine the proportion of eligible patients with high-grade serous carcinoma of the ovary, fallopian tube or peritoneum discussed at gynaecological oncology multidisciplinary meetings (MDMs) in New Zealand and subsequently referred for genetic counselling and BRCA pathogenic variant testing. METHODS: Eligible cases were identified from Auckland, Wellington, Christchurch and Dunedin gynaecologic oncology MDM databases between 1 January 2015 to 31 December 2016. Patients who met the eligibility criteria for genetics referral were identified, and cross-referenced against genetic services databases to ascertain the rates of referrals received, the numbers attending appointments, genetic testing offered and range of results. RESULTS: During the two-year period, 205 patients were eligible for referral. Of these, 143 (70%) patients were referred for genetic counselling with 128 (90%) of this group recommended for BRCA pathogenic variant testing. Of the 126 who undertook the test, results were available for 120 (95%). Nineteen patients (16%) tested positive for a germline BRCA pathogenic variant. CONCLUSIONS: The New Zealand rate of referral to genetic counselling for women with high-grade serous cancer, (HGSC), of the ovary, fallopian tube or peritoneum diagnosed between 2015-2016 is encouraging when compared with others internationally. The rate of BRCA positive pathogenic variants is comparable to international data.

Penetrance and expressivity of the R858H CACNA1C variant in a five-generation pedigree segregating an arrhythmogenic channelopathy.

BACKGROUND: Isolated cardiac arrhythmia due to a variant in CACNA1C is of recent knowledge. Most reports have been of singleton cases or of quite small families, and estimates of penetrance and expressivity have been difficult to obtain. We here describe a large pedigree, from which such estimates have been calculated. METHODS: We studied a five-generation family, in which a CACNA1C variant c.2573G>A p.Arg858His co-segregates with syncope and cardiac arrest, documenting electrocardiographic data and cardiac symptomatology. The reported patients/families from the literature with CACNA1C gene variants were reviewed, and genotype-phenotype correlations are drawn. RESULTS: The range of phenotype in the studied family is wide, from no apparent effect, through an asymptomatic QT interval prolongation on electrocardiography, to episodes of presyncope and syncope, ventricular fibrillation, and sudden death. QT prolongation showed inconsistent correlation with functional cardiology. Based upon analysis of 28 heterozygous family members, estimates of penetrance and expressivity are derived. CONCLUSIONS: These estimates of penetrance and expressivity, for this specific variant, may be useful in clinical practice. Review of the literature indicates that individual CACNA1C variants have their own particular genotype-phenotype correlations. We suggest that, at least in respect of the particular variant reported here, "arrhythmogenic channelopathy" may be a more fitting nomenclature than long QT syndrome.

Meeting the challenges of interpreting variants of unknown clinical significance in BRCA testing.

Many BRCA1 and BRCA2 genetic mutations are known to result in an elevated breast cancer risk. Routine BRCA1/2 gene screening is offered to patients thought to have an increased risk of carrying a deleterious mutation. 5-10% of genetic tests identify a variant of unknown clinical significance (VUCS), creating significant challenges to health care providers. Recent advances in sequencing technologies allow more genes to be screened in an increasing number of individuals and at an ever decreasing cost. Significantly more VUCS will be identified, adding to the uncertainty of how to manage these patients. The addition of splicing assays to current variant classification tools may be instrumental towards understanding the disease risk of these variants and improve the reliability of these assays.

Comparison of SSCP and DHPLC for the detection of LDLR mutations in a New Zealand cohort.

Familial hypercholesterolaemia (FH) is a common inherited disorder, associated with premature vascular disease. FH may be caused by many different mutations in the low density lipoprotein receptor (LDLR) gene, about 700 mutations have been described, most of which occur rarely and often only in single families. Although particular mutations are prevalent in certain ethnic groups, countries with heterogeneous population bases (such as NZ) may carry a wide variety of mutations; making a gene screening approach the appropriate first step for a mutation detection programme. We have compared SSCP with DHPLC to assess their effectiveness as methods for LDLR mutation detection. Although five novel LDLR mutations were detected by SSCP in patients with FH, DHPLC was more sensitive, with eight novel mutations detected. Six of these mutations (T392M, R419G, Y421N, 1206-1207delCT, 1872delC, and 1943delC) were clustered in exons 9 and 13 of the EGF precursor homology domain, one (679-680delAC) in the ligand binding domain (exon 4) and the eighth (P774H) in the membrane-spanning domain (exon 16). Twenty five mutations were identified in 35 patients in total. Of these, we were able to detect only 64% of mutations by SSCP even though all variants were detected by DHPLC. All patients are heterozygous for the mutations, which is consistent with the clinical phenotypes.