Clinical implications of incorporating genetic and non-genetic risk factors in CanRisk-based breast cancer risk prediction

BACKGROUND

Breast cancer (BC) risk prediction models consider cancer family history (FH) and germline pathogenic variants (PVs) in risk genes. It remains elusive to what extent complementation with polygenic risk score (PRS) and non-genetic risk factor (NGRFs) data affects individual intensified breast surveillance (IBS) recommendations according to European guidelines.

METHODS

For 425 cancer-free women with cancer FH (mean age 40·6 years, range 21-74), recruited in France, Germany and the Netherlands, germline PV status, NGRFs, and a 306 variant-based PRS (PRS306) were assessed to calculate estimated lifetime risks (eLTR) and estimated 10-year risks (e10YR) using CanRisk. The proportions of women changing country-specific European risk categories for IBS recommendations, i.e. ≥20 % and ≥30 % eLTR, or ≥5 % e10YR were determined.

FINDINGS

Of the women with non-informative PV status, including PRS306 and NGRFs changed clinical recommendations for 31·0 %, (57/184, 20 % eLTR), 15·8 % (29/184, 30 % eLTR) and 22·4 % (41/183, 5 % e10YR), respectively whereas of the women tested negative for a PV observed in their family, clinical recommendations changed for 16·7 % (25/150), 1·3 % (2/150) and 9·5 % (14/147). No change was observed for 82 women with PVs in high-risk genes (BRCA1/2, PALB2). Combined consideration of eLTRs and e10YRs identified BRCA1/2 PV carriers benefitting from IBS <30 years, and women tested non-informative/negative for whom IBS may be postponed.

INTERPRETATION

For women who tested non-informative/negative, PRS and NGRFs have a considerable impact on IBS recommendations. Combined consideration of eLTRs and e10YRs allows personalizing IBS starting age.

FUNDING

Horizon 2020, German Cancer Aid, Federal Ministry of Education and Research, Köln Fortune.

Biallelic germline BRCA1 mutations in a patient with early onset breast cancer, mild Fanconi anemia-like phenotype, and no chromosome fragility

Background

Biallelic BRCA1 mutations are regarded either embryonically lethal or to cause Fanconi anemia (FA), a genomic instability syndrome characterized by bone marrow failure, developmental abnormalities, and cancer predisposition. We report biallelic BRCA1 mutations c.181T > G (p.Cys61Gly) and c.5096G > A (p.Arg1699Gln) in a woman with breast cancer diagnosed at the age of 30 years. The common European founder mutation p.Cys61Gly confers high cancer risk, whereas the deleterious p.Arg1699Gln is hypomorphic and was suggested to confer intermediate cancer risk.

Methods and Results

Aside from significant toxicity from chemotherapy, the patient showed mild FA‐like features (e.g., short stature, microcephaly, skin hyperpigmentation). Chromosome fragility, a hallmark of FA patient cells, was not present in patient‐derived peripheral blood lymphocytes. We demonstrated that the p.Arg1699Gln mutation impairs DNA double‐strand break repair, elevates RAD51 foci levels at baseline, and compromises BRCA1 protein function in protecting from replication stress. Although the p.Arg1699Gln mutation compromises BRCA1 function, the residual activity of the p.Arg1699Gln allele likely prevents from chromosome fragility and a more severe FA phenotype.

Conclusion

Our data expand the clinical spectrum associated with biallelic BRCA1 mutations, ranging from embryonic lethality to a mild FA‐like phenotype and no chromosome fragility.

Breast cancer risk in BRCA1/2 mutation carriers and noncarriers under prospective intensified surveillance

Comparably little is known about breast cancer (BC) risks in women from families tested negative for BRCA1/2 mutations despite an indicative family history, as opposed to BRCA1/2 mutation carriers. We determined the age-dependent risks of first and contralateral breast cancer (FBC, CBC) both in noncarriers and carriers of BRCA1/2 mutations, who participated in an intensified breast imaging surveillance program. The study was conducted between January 1, 2005, and September 30, 2017, at 12 university centers of the German Consortium for Hereditary Breast and Ovarian Cancer. Two cohorts were prospectively followed up for incident FBC (n = 4,380; 16,398 person-years [PY], median baseline age: 39 years) and CBC (n = 2,993; 10,090 PY, median baseline age: 42 years). Cumulative FBC risk at age 60 was 61.8% (95% CI 52.8-70.9%) for BRCA1 mutation carriers, 43.2% (95% CI 32.1-56.3%) for BRCA2 mutation carriers and 15.7% (95% CI 11.9-20.4%) for noncarriers. FBC risks were significantly higher than in the general population, with incidence rate ratios of 23.9 (95% CI 18.9-29.8) for BRCA1 mutation carriers, 13.5 (95% CI 9.2-19.1) for BRCA2 mutation carriers and 4.9 (95% CI 3.8-6.3) for BRCA1/2 noncarriers. Cumulative CBC risk 10 years after FBC was 25.1% (95% CI 19.6-31.9%) for BRCA1 mutation carriers, 6.6% (95% CI 3.4-12.5%) for BRCA2 mutation carriers and 3.6% (95% CI 2.2-5.7%) for noncarriers. CBC risk in noncarriers was similar to women with unilateral BC from the general population. Further studies are needed to confirm whether less intensified surveillance is justified in women from BRCA1/2 negative families with elevated risk.

Abstract P3-09-03: Low-level gonosomal mosaicism of a de novo BRCA1 gene mutation – The origin of a constitutional mutation in a breast cancer family

Mosaicisms arise when specific cells within a developing organism mutate to result in two or more cell populations with distinct genotypes. In cases of gonosomal mosaicism a genetic variation is present in both somatic and germline cells.

Here, we describe a large Turkish breast cancer family with four affected individuals. In the Index patient (II-1; age of onset 45 years), a heterozygous deleterious frameshift mutation, c.1310dupA, p.His437Glnfs*2 in BRCA1 was identified using the TruRisk® gene panel designed by the German Consortium for Hereditary Breast and Ovarian Cancer (GC-HBOC). Predictive genetic testing showed heterozygous carrier status in the daughter (III-1).

The mutation was also analyzed in peripheral blood of the affected mother (I-1; age of onset 45 years) of the index patient by Sanger Sequencing. Interestingly, Sanger sequence did demonstrate the presence of remarkable small peaks presenting the frameshift mutation similar to a mosaic pattern. A second and third independent blood draw within a time frame of four month was tested and a mosaic signal of approximately 10 % was reproducibly detected.

In order to exclude a potential allelic drop out, independent sequencing experiments via next generation sequencing (NGS; TruRisk® gene panel) were performed. Again, the mutation was present with an allele read frequency of 12 %. No other pathogenic mutations were detected in any of the other tested breast cancer susceptibility genes.

To further examine and underscore the presence of gonosomal mosaicism different tissues should be analyzed. As no tumor material or surrounding normal breast tissue was available primary skin fibroblasts were isolated from skin biopsy. Sequencing of cultured primary fibroblasts demonstrated the absence of the familial BRCA1 mutation. With NGS-based CNV analysis as well as MLPA analysis we excluded aberrant copy numbers of BRCA1 in blood and fibroblasts.

In conclusion, our data provide striking evidence for a BRCA1 mosaicism, which is not detectable in all body cells. Due to the inheritance of the BRCA1 mutation to the next generations (II-1 and III-1), we assume the presence of a gonosomal mosaicism in the affected mother (I-1).

Additionally, the history of breast cancer onset in the family indicates that the BRCA1 mosaic mutation carrier do not necessarily have a milder phenotype compared to full heterozygotes. In this context our results implicate the importance of using highly sensitive sequencing platforms in routine diagnostics to ensure the detection of disease causing low-level mosaic mutations.Mosaicisms arise when specific cells within a developing organism mutate to result in two or more cell populations with distinct genotypes. In cases of gonosomal mosaicism a genetic variation is present in both somatic and germline cells.

Here, we describe a large Turkish breast cancer family with four affected individuals. In the Index patient (II-1; age of onset 45 years), a heterozygous deleterious frameshift mutation, c.1310dupA, p.His437Glnfs*2 in BRCA1 was identified using the TruRisk® gene panel designed by the German Consortium for Hereditary Breast and Ovarian Cancer (GC-HBOC). Predictive genetic testing showed heterozygous carrier status in the daughter (III-1).

The mutation was also analyzed in peripheral blood of the affected mother (I-1; age of onset 45 years) of the index patient by Sanger Sequencing. Interestingly, Sanger sequence did demonstrate the presence of remarkable small peaks presenting the frameshift mutation similar to a mosaic pattern. A second and third independent blood draw within a time frame of four month was tested and a mosaic signal of approximately 10 % was reproducibly detected.

In order to exclude a potential allelic drop out, independent sequencing experiments via next generation sequencing (NGS; TruRisk® gene panel) were performed. Again, the mutation was present with an allele read frequency of 12 %. No other pathogenic mutations were detected in any of the other tested breast cancer susceptibility genes.

To further examine and underscore the presence of gonosomal mosaicism different tissues should be analyzed. As no tumor material or surrounding normal breast tissue was available primary skin fibroblasts were isolated from skin biopsy. Sequencing of cultured primary fibroblasts demonstrated the absence of the familial BRCA1 mutation. With NGS-based CNV analysis as well as MLPA analysis we excluded aberrant copy numbers of BRCA1 in blood and fibroblasts.

In conclusion, our data provide striking evidence for a BRCA1 mosaicism, which is not detectable in all body cells. Due to the inheritance of the BRCA1 mutation to the next generations (II-1 and III-1), we assume the presence of a gonosomal mosaicism in the affected mother (I-1).

Additionally, the history of breast cancer onset in the family indicates that the BRCA1 mosaic mutation carrier do not necessarily have a milder phenotype compared to full heterozygotes. In this context our results implicate the importance of using highly sensitive sequencing platforms in routine diagnostics to ensure the detection of disease causing low-level mosaic mutations.

Citation Format: Bülow L, Keupp K, Richters L, Pohl E, Wappenschmidt B, Zarghooni V, Reichstein-Gnielinski S, Maringa M, Giesecke J, Rhiem K, Hahnen E, Schmutzler R. Low-level gonosomal mosaicism of a de novo BRCA1 gene mutation – The origin of a constitutional mutation in a breast cancer family [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-09-03.

[Clinical parameters for molecular testing of Maturity Onset Diabetes of the Young (MODY)]

BACKGROUND

Monogenic forms of diabetes are often diagnosed by chance, due to the variety of clinical presentation and limited experience of the diabetologists with this kind of diabetes. Aim of this study was to evaluate clinical parameters for an efficient screening.

METHODS

Clinical parameters were: negative diabetes-specific antibodies at onset of diabetes, positive family history of diabetes, and low to moderate insulin requirements after one year of diabetes treatment. Molecular testing was performed through sequencing of the programming regions of HNF-4alpha (MODY 1), glucokinase (MODY 2) and HNF-1alpha/TCF1 (MODY 3) and in one patient the HNF-1beta/TCF2 region (MODY 5). 39 of 292 patients treated with insulin were negative for GADA and IA2A, and 8 (20.5%) patients fulfilled both other criteria.

RESULTS

Positive molecular results were found in five (63%) patients (two with MODY 2, two with MODY 3, one with MODY 5). At diabetes onset, the mean age of the 5 patients with MODY was 10.6 ± 5.3 yrs (range 2.6-15 yrs), HbA(1c) was 8.4 ± 3.1 % (6.5-13.9%), mean diabetes duration until diagnosis of MODY was 3.3 ± 3.6 yrs (0.8-9.6 yrs) with insulin requirements of 0.44 ± 0.17 U/kg/d (0.2-0.6 U/kg/d). Patients with MODY 3 were changed from insulin to repaglinide, those with MODY 2 were recommended discontinuing insulin treatment.

CONCLUSION

In patients with negative diabetes-specific antibodies at onset of diabetes, with a positive family history, and low to moderate insulin needs a genetic screening for MODY is indicated. Watchful consideration of these clinical parameters may lead to an early genetic testing, and to an adequate treatment.

Expanded clinical spectrum in hepatocyte nuclear factor 1b-maturity-onset diabetes of the young

AIMS

HNF1B-maturity-onset diabetes of the young is caused by abnormalities in the HNF1B gene encoding the transcription factor HNF-1beta. We aimed to investigate detailed clinical features and the type of HNF1B gene anomaly in five pediatric cases with HNF1B-MODY.

METHODS

From a cohort of 995 children and adolescents with diabetes, we analyzed the most frequent maturity-onset diabetes of the young genes (GCK, HNF1A, HNF4A) including HNF1B sequencing and deletion analysis by quantitative Multiplex-PCR of Short Fluorescent Fragments (QMPSF) if patients were islet autoantibody-negative and had one parent with diabetes or associated extrapancreatic features or detectable C-peptide outside honeymoon phase. Presence and size of disease-causing chromosomal rearrangements detected by QMPSF were further analyzed by array comparative genomic hybridization.

RESULTS

Overall, five patients had a heterozygous HNF1B deletion, presenting renal disease, elevated liver enzymes, and diabetes. Diabetes was characterized by insulin resistance and adolescent onset of hyperglycemia. Additionally, clinical features in some patients were pancreas dysplasia and exocrine insufficiency (two of five patients), genital defects (three of five), mental retardation (two of five), and eye abnormalities (coloboma, cataract in two of five). One case also had severe growth deficit combined with congenital cholestasis, and another case had common variable immune deficiency. All patients reported here had monoallelic loss of the entire HNF1B gene. Whole genome array comparative genomic hybridization confirmed a precurrent genomic deletion of approximately 1.3-1.7 Mb in size.

CONCLUSION

The clinical data of our cases enlarge the wide spectrum of patients with HNF1B anomaly. The underlying molecular defect in all cases was a 1.3- to 1.7-Mb deletion, and paired, segmental duplications along with breakpoints were most likely involved in this recurrent chromosomal microdeletion.

Diagnostic difficulties in glucokinase hyperinsulinism

Glucokinase hyperinsulinism is a rare variant of congenital hyperinsulinism caused by activating mutations in the glucokinase gene and has been reported so far to be a result of overactivity of glucokinase within the pancreatic beta-cell. Here we report on a new patient with difficulties to diagnose persistent hyperinsulinism and discuss diagnostic procedures of this as well as the other reported individuals. After neonatal hypoglycemia, the patient was reevaluated at the age of 3 years for developmental delay. Morning glucose after overnight fast was 2.5-3.6 mmol/l. Fasting tests revealed supressed insulin secretion at the end of fasting (1.4-14.5 pmol/l). In addition, diagnostic data of the patients reported so far were reviewed. A novel heterozygous missense mutation in exon 10 c.1354G>C (p.Val452Leu) was found and functional studies confirmed the activating mutation. There was no single consistent diagnostic criterion found for our patient and glucokinase hyperinsulinism individuals in general. Often at the time of hypoglycemia low insulin levels were found. Therefore insulin concentrations at hypoglycemia, or during fasting test as well as reactive hypoglycemia after an oral glucose tolerance test were not conclusive for all patients. A glucose lowering effect in extra-pancreatic tissues independent from hyperinsulinism that results in diagnostic difficulties may contribute to underestimation of glucokinase hyperinsulinism. Mutational analysis of the GCK-gene should be performed in all individuals with unclear episodes of hypoglycemia even without documented hyperinsulinism during hypoglycemia. Delay of diagnosis might result in mental handicap of the affected individuals.

Weight estimation by three-dimensional ultrasound imaging in the small fetus

OBJECTIVES

To improve birth weight estimation in fetuses weighing <or= 1600 g at birth by deriving a new formula including measurements obtained using three-dimensional (3D) sonography.

METHODS

In a prospective cohort study, biometric data of 150 singleton fetuses weighing <or= 1600 g at birth were obtained by sonographic examination within 1 week before delivery. Exclusion criteria were multiple pregnancy, intrauterine death as well as major structural or chromosomal anomalies. A new formula was derived using our data, and was then compared with currently available equations for estimating weight in the preterm fetus.

RESULTS

Different statistical estimation strategies were pursued. Gradient boosting with component- wise smoothing splines achieved the best results. The resulting new formula (estimated fetal weight = 656.41 + 1.8321 x volABDO + 31.1981 x HC + 5.7787 x volFEM + 73.5214 x FL + 8.3009 x AC - 449.8863 x BPD + 32.5340 x BPD(2), where volABDO is abdominal volume determined by 3D volumetry, HC is head circumference, volFEM is thigh volume determined by 3D volumetry, FL is femur length and BPD is biparietal diameter) proved to be superior to established equations in terms of mean squared prediction errors, signed percentage errors and absolute percentage errors.

CONCLUSIONS

Our new formula is relatively easy to use and needs no adjustment to weight percentiles or to fetal lie. In fetuses weighing <or= 1600 g at birth it is superior to weight estimation by traditional formulae using two-dimensional measurements.

A case of new mutation in maturity-onset diabetes of the young type 3 (MODY 3) responsive to a low dose of sulphonylurea

We describe a girl aged 10.5 years with hyperglycemia, whose mother and maternal father had insulin treated diabetes since adolescence. Using genetic analysis in mother and child, we identified identical new mutation of the HNF-1alpha sequence. Treatment with small doses of sulphonylurea was initiated and that therapy gave good results.

Breast MR imaging screening in 192 women proved or suspected to be carriers of a breast cancer susceptibility gene: preliminary results

PURPOSE

To compare magnetic resonance (MR) imaging with conventional imaging in screening high-risk women.

MATERIALS AND METHODS

This prospective trial included 192 asymptomatic and six symptomatic women who, on the basis of personal or family history or genetic analysis, were suspected or proved to carry a breast cancer susceptibility gene.

RESULTS

Fifteen breast cancers were identified: nine in the 192 asymptomatic women (six in the first and three in the second screening round) and six in the symptomatic patients. Concerning the asymptomatic women, four of the nine breast cancers were detected and correctly classified with mammography and ultrasonography (US) combined; another two cancers were visible as well-circumscribed masses and were diagnosed as fibroadenomas. MR imaging allowed the correct classification and local staging of all nine cancers. In 105 asymptomatic women with validation of the 1st-year screening results, the sensitivities of mammography, US, and MR imaging were 33%, 33% (mammography and US combined, 44%), and 100%, respectively; the positive predictive values were 30%, 12%, and 64%, respectively.

CONCLUSION

The accuracy of MR imaging is significantly higher than that of conventional imaging in screening high-risk women. Difficulties can be caused by an atypical manifestation of hereditary breast cancers at both conventional and MR imaging and by contrast material enhancement associated with hormonal stimulation.

Dominant mutations in ROR2, encoding an orphan receptor tyrosine kinase, cause brachydactyly type B

Inherited limb malformations provide a valuable resource for the identification of genes involved in limb development. Brachydactyly type B (BDB), an autosomal dominant disorder, is the most severe of the brachydactylies and characterized by terminal deficiency of the fingers and toes. In the typical form of BDB, the thumbs and big toes are spared, sometimes with broadening or partial duplication. The BDB1 locus was previously mapped to chromosome 9q22 within an interval of 7.5 cM (refs 9,10). Here we describe mutations in ROR2, which encodes the orphan receptor tyrosine kinase ROR2 (ref. 11), in three unrelated families with BDB1. We identified distinct heterozygous mutations (2 nonsense, 1 frameshift) within a 7-amino-acid segment of the 943-amino-acid protein, all of which predict truncation of the intracellular portion of the protein immediately after the tyrosine kinase domain. The localized nature of these mutations suggests that they confer a specific gain of function. We obtained further evidence for this by demonstrating that two patients heterozygous for 9q22 deletions including ROR2 do not exhibit BDB. Expression of the mouse mouse orthologue, Ror2, early in limb development indicates that BDB arises as a primary defect of skeletal patterning.