[Identification and management of hereditary breast-ovarian cancers (2004 update)]

Classification of 101 BRCA1 and BRCA2 variants of uncertain significance by cosegregation study: A powerful approach

Up to 80% of BRCA1 and BRCA2 genetic variants remain of uncertain clinical significance (VUSs). Only variants classified as pathogenic or likely pathogenic can guide breast and ovarian cancer prevention measures and treatment by PARP inhibitors. We report the first results of the ongoing French national COVAR (cosegregation variant) study, the aim of which is to classify BRCA1/2 VUSs. The classification method was a multifactorial model combining different associations between VUSs and cancer, including cosegregation data. At this time, among the 653 variants selected, 101 (15%) distinct variants shared by 1,624 families were classified as pathogenic/likely pathogenic or benign/likely benign by the COVAR study. Sixty-six of the 101 (65%) variants classified by COVAR would have remained VUSs without cosegregation data. Of note, among the 34 variants classified as pathogenic by COVAR, 16 remained VUSs or likely pathogenic when following the ACMG/AMP variant classification guidelines. Although the initiation and organization of cosegregation analyses require a considerable effort, the growing number of available genetic tests results in an increasing number of families sharing a particular variant, and thereby increases the power of such analyses. Here we demonstrate that variant cosegregation analyses are a powerful tool for the classification of variants in the BRCA1/2 breast-ovarian cancer predisposition genes.

[Prophylactic mastectomy and occult cancer: a ten-year experience at a cancer center]

INTRODUCTION

Women identified as high-risk for breast cancer may choose between close follow-up and radical mastectomy. Prophylactic mastectomy, as any other surgery, is associated with benefits and harms. The aim of this study was to assess the morbidity associated with prophylactic mastectomy and to evaluate the prevalence of occult cancers.

METHODS

All patients who underwent unilateral or bilateral prophylactic mastectomy between 2007 and 2017 in our institution were eligible for inclusion in this retrospective study. Medical history, type of surgery, occurrence of complication or reoperation and pathological reports were examined in medical charts.

RESULTS

79 women underwent prophylactic mastectomy over the studied period of which 58.2% were contralateral after breast cancer. A genetic mutation was present in 86.1% of cases. Postoperative complications occurred in 43.0% of cases. An additional surgery for medical or esthetic purpose was needed in 72.1% of cases. Occult cancer was found in 11.4% of the pathological reports. Triple negative invasive ductal carcinoma was discovered in two cases (2.5%).

DISCUSSION

Prophylactic mastectomy is the only effective preventive action against breast cancer. Women must be clearly informed of possible complications, high reoperation rate and potential pathological findings. Identifying women most at risk for breast cancer would help to better target those who will benefit most from surgery.

[The French Genetic and Cancer Consortium guidelines for multigene panel analysis in hereditary breast and ovarian cancer predisposition]

INTRODUCTION

Next generation sequencing allows the simultaneous analysis of large panel of genes for families or individuals with a strong suspicion of hereditary breast and/or ovarian cancer (HBOC). Because of lack of guidelines, several panels of genes potentially involved in HBOC were designed, with large disparities not only in their composition but also in medical care offered to mutation carriers. Then, homogenization in practices is needed.

METHODS

The French Genetic and Cancer Group (GGC) - Unicancer conducted an exhaustive bibliographic work on 18 genes of interest. Only publications with unbiased risk estimates were retained.

RESULTS

The expertise of each 18 genes was based on clinical utility criteria, i.e. a relative risk of cancer of 4 and more, available medical tools for screening and prevention of mutation carriers, and pre-symptomatic genetic tests for relatives. Finally, 13 genes were selected to be included in a HBOC diagnosis gene panel: BRCA1, BRCA2, PALB2, TP53, CDH1, PTEN, RAD51C, RAD51D, MLH1, MSH2, MSH6, PMS2, EPCAM. The reasons for excluding NBN, RAD51B, CHEK2, STK11, ATM, BARD1, BRIP1 from the HBOC diagnosis panel are presented. Screening, prevention and genetic counselling guidelines were detailed for each of the 18 genes.

DISCUSSION

Due to the rapid increase in knowledge, the GGC has planned a yearly update of the bibliography to take into account new findings. Furthermore, genetic-epidemiological studies are being initiated to better estimate the cancer risk associated with genes which are not yet included in the HBOC diagnosis panel.

Assessment of the functional impact of germline BRCA1/2 variants located in non-coding regions in families with breast and/or ovarian cancer predisposition

PURPOSE

The molecular mechanism of breast and/or ovarian cancer susceptibility remains unclear in the majority of patients. While germline mutations in the regulatory non-coding regions of BRCA1 and BRCA2 genes have been described, screening has generally been limited to coding regions. The aim of this study was to evaluate the contribution of BRCA1/2 non-coding variants.

METHODS

Four BRCA1/2 non-coding regions were screened using high-resolution melting analysis/Sanger sequencing or next-generation sequencing on DNA extracted from index cases with breast and ovarian cancer predisposition (3926 for BRCA1 and 3910 for BRCA2). The impact of a set of variants on BRCA1/2 gene regulation was evaluated by site-directed mutagenesis, transfection, followed by Luciferase gene reporter assay.

RESULTS

We identified a total of 117 variants and tested twelve BRCA1 and 8 BRCA2 variants mapping to promoter and intronic regions. We highlighted two neighboring BRCA1 promoter variants (c.-130del; c.-125C > T) and one BRCA2 promoter variants (c.-296C > T) inhibiting significantly the promoter activity. In the functional assays, a regulating region within the intron 12 was found with the same enhancing impact as within the intron 2. Furthermore, the variants c.81-3980A > G and c.4186-2022C > T suppress the positive effect of the introns 2 and 12, respectively, on the BRCA1 promoter activity. We also found some variants inducing the promoter activities.

CONCLUSION

In this study, we highlighted some variants among many, modulating negatively the promoter activity of BRCA1 or 2 and thus having a potential impact on the risk of developing cancer. This selection makes it possible to conduct future validation studies on a limited number of variants.

[Personalized medicine and breast cancer: anticipatory medicine, prognostic evaluation and therapeutic targeting]

Breast cancer is now considered as a large collection of distinct biological entities, the management of which is increasingly personalized. Personalized medicine - defined as a medicine, which uses molecular profiles, notably genetic profiles, from patients and/or tumors to tailor therapeutic decisions - is now introduced in the management of breast cancer at any stages: screening and prevention of hereditary forms, prognostic and predictive evaluation of early breast cancer, and, more recently, novel clinical trials in advanced breast cancer, where genetic characterization of tumor tissue based on genomics, including next-generation sequencing tools, is used to drive specific therapeutic targeting.

Prophylactic Mastectomy: An Appraisal

The main indication of prophylactic mastectomy pertains to BRCA1 or BRCA2 mutation carriers. Prophylactic mastectomy includes the simple method and the subcutaneous method. Both methods can be followed by breast plastic reconstruction either at the same time or later. This review examines key issues regarding prophylactic mastectomy: the selection of patients, its effectiveness, its limitations, convergence/divergence in existing guidelines, and future perspectives.

An entire exon 3 germ-line rearrangement in the BRCA2 gene: pathogenic relevance of exon 3 deletion in breast cancer predisposition

Background

Germ-line mutations in the BRCA1 and BRCA2 genes are major contributors to hereditary breast/ovarian cancer. Large rearrangements are less frequent in the BRCA2 gene than in BRCA1. We report, here, the first total deletion of exon 3 in the BRCA2 gene that was detected during screening of 2058 index cases from breast/ovarian cancer families for BRCA2 large rearrangements. Deletion of exon 3, which is in phase, does not alter the reading frame. Low levels of alternative transcripts lacking exon 3 (Δ3 delta3 transcript) have been reported in normal tissues, which raises the question whether deletion of exon 3 is pathogenic.

Methods

Large BRCA2 rearrangements were analysed by QMPSF (Quantitative Multiplex PCR of Short Fluorescent Fragments) or MLPA (Multiplex Ligation-Dependent Probe Amplification). The exon 3 deletion was characterized with a "zoom-in" dedicated CGH array to the BRCA2 gene and sequencing. To determine the effect of exon 3 deletion and assess its pathogenic effect, three methods of transcript quantification were used: fragment analysis of FAM-labelled PCR products, specific allelic expression using an intron 2 polymorphism and competitive quantitative RT-PCR.

Results

Large rearrangements of BRCA2 were detected in six index cases out of 2058 tested (3% of all deleterious BRCA2 mutations). This study reports the first large rearrangement of the BRCA2 gene that includes all of exon 3 and leads to an in frame deletion of exon 3 at the transcriptional level. Thirty five variants in exon 3 and junction regions of BRCA2 are also reported, that contribute to the interpretation of the pathogenicity of the deletion. The quantitative approaches showed that there are three classes of delta3 BRCA2 transcripts (low, moderate and exclusive). Exclusive expression of the delta3 transcript by the mutant allele and segregation data provide evidence for a causal effect of the exon 3 deletion.

Conclusion

This paper highlights that large rearrangements and total deletion of exon 3 in the BRCA2 gene could contribute to hereditary breast and/or ovarian cancer. In addition, our findings suggest that, to interpret the pathogenic effect of any variants of exon 3, both accurate transcript quantification and co-segregation analysis are required.

[Management of families at high risk for hereditary breast-ovarian cancers: the endocrinologist's point of view]

Most cancers have a sporadic physiopathology, but approximately 5 to 10% of breast cancers and 10% of ovarian cancers involve a genetic predisposition. Sometimes, the gene involved in these hereditary cancers can be identified (usually BRCA1 or 2), but most of the time it remains unknown. However, all women considered at high risk, because of their familial history, must be identified so they can be provided with the most adequate care, since the probability is very high that they develop such a cancer in the future. Fortunately, effective strategies have been developed to reduce this risk. Early detection of breast cancer is possible and prophylactic treatments (chemoprevention and prophylactic surgery) exist for both breast and ovarian cancers. Another reason why it is essential that these high risk women are identified is that treatment for hereditary cancers differs in some ways from that of sporadic cancers. It is best that counseling be given in an interdisciplinary cancer genetic clinic, where all practionners are aware of the latest data and guidelines.

Screening for hereditary breast cancer

Most women at risk for hereditary breast cancer opt for intensive breast screening rather than risk-reducing mastectomy. For this to be a rational choice, the vast majority of tumors must be detected either while still in situ or at a very early stage of invasion. Annual screening mammography has low sensitivity in this population, in part due to the greater breast density of younger women, resulting in cancers being detected at a suboptimal stage. In six prospective comparative studies, the addition of annual contrast-enhanced magnetic resonance imaging (MRI) of the breast to mammography demonstrated greater than 90% sensitivity, more than twice that of mammography alone. In those studies that included ultrasound and clinical breast examination, additional cancers were rarely detected by these modalities. False positive rates were higher with the addition of MRI, but specificity improved on successive rounds of screening. Although long-term survival data are still lacking, there is mounting evidence that the addition of screening MRI to mammography detects hereditary breast cancers at an earlier stage and is thus estimated to be cost-effective, at least for women with BRCA mutations. This review will examine the literature and current screening recommendations.