Domchek, Susan M.

Purpose Massively parallel sequencing allows simultaneous testing of multiple genes associated with cancer susceptibility. Guidelines are available for variant classification; however, interpretation of these guidelines by laboratories and providers may differ and lead to conflicting reporting and, potentially, to inappropriate medical management. We describe conflicting variant interpretations between Clinical Laboratory Improvement Amendments–approved commercial clinical laboratories, as reported to the Prospective Registry of Multiplex Testing (PROMPT), an online genetic registry. Methods Clinical data and genetic testing results were gathered from 1,191 individuals tested for inherited cancer susceptibility and self-enrolled in PROMPT between September 2014 and October 2015. Overall, 518 participants (603 genetic variants) had a result interpreted by more than one laboratory, including at least one submitted to ClinVar, and these were used as the final cohort for the current analysis. Results Of the 603 variants, 221 (37%) were classified as a variant of uncertain significance (VUS), 191 (32%) as pathogenic, and 34 (6%) as benign. The interpretation differed among reporting laboratories for 155 (26%). Conflicting interpretations were most frequently reported for CHEK2 and ATM, followed by RAD51C, PALB2, BARD1, NBN, and BRIP1. Among all participants, 56 of 518 (11%) had a variant with conflicting interpretations ranging from pathogenic/likely pathogenic to VUS, a discrepancy that may alter medical management. Conclusions Conflicting interpretation of genetic findings from multiplex panel testing used in clinical practice is frequent and may have implications for medical management decisions.

Abstract Breast cancer is the most common type of cancer, and has a strong heritable component, with approximately 15 percent of new cases having family history of breast cancer. Genetic panel testing for patients with a family history of breast cancer has become a popular clinical resource. However, the risk of breast cancer associated with inactivating mutations in the predisposition genes is largely undefined, creating critical limitations in the interpretations of the results from panel testing and subsequent medical management. The Cancer Risk Estimates Related to Susceptibility Genes (CARRIERS) consortium was established to determine the risk of cancers associated with truncating mutations in the known predisposition genes and to extend these studies to the clinical classification of variants of uncertain significance (VUS) in the relevant genes. CARRIERS involves screening of approximately 30,000 population-based breast cancer cases and 30,000 study matched controls for mutations in 28 established or proposed breast cancer predisposition genes. Population-based risks for breast cancer associated with mutations in each gene will be estimated. In parallel, 10,000 breast cancer cases from moderate and high-risk breast cancer families will be similarly screened for mutations and the penetrance of the mutations in high-risk families will be estimated. Furthermore, VUS identified by mutation screening will be characterized by functional and family-based studies and models for classification of the clinical relevance of VUS in each gene will be developed. These data are expected to lead to improvements in cancer risk assessment and improved management of patients found to carry mutations or VUS in breast cancer predisposition. Citation Format: Jenna Lilyquist, Peter Kraft, Steven N. Hart, Emily J. Hallberg, Chunling Hu, Raymond Moore, Rohan Gnanaolivu, Susan M. Domchek, Jeffrey N. Weitzel, Katherine L. Nathanson, David E. Goldgar, Fergus J. Couch. The CARRIERS consortium: Establishing refined breast cancer risk estimates in known predisposition genes. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 810.

Abstract Sequencing tests assaying panels of genes or whole exomes are widely available for cancer risk evaluation. However, methods for classification of variants resulting from this testing are not well studied. We evaluated the ability of American College of Medical Genetics and Genomics (ACMG) guidelines to define the rate of mutations and variants of uncertain significance (VUS) in 180 medically relevant genes, including all ACMG designated reportable cancer and non-cancer genes, in individuals who met guidelines for hereditary cancer risk evaluation. We performed whole exome sequencing in 404 individuals in 257 families and classified 1640 variants from these genes. Potentially clinically actionable (likely-pathogenic/pathogenic, LP/P) versus nonactionable (VUS/likely-benign/benign) calls were 92% and 88% concordant with locus specific databases and Clinvar, respectively. LP/P mutations were identified in 11 of 25 breast cancer susceptibility genes in 27 BRCA1/2 negative families (11%). Evaluation of 84 additional autosomal dominant cancer susceptibility genes identified LP/P mutations in only four additional families (1.7%), suggesting they do not influence risk in this cohort. However, individuals from nine of 257 families (3.5%) had incidental LP/P mutations in 32 non-cancer disease genes, and 7% of individuals were monoallelic carriers of an LP/P mutation in 39 autosomal recessive cancer syndrome genes. Furthermore, 90% of individuals had at least one VUS. In summary, these data support the clinical utility of ACMG variant classification guidelines. In addition, evaluation of extended panels of cancer genes in breast/ovarian cancer families leads to only an incremental clinical benefit but substantially increases the complexity of the results. Citation Format: Kara N. Maxwell, Steven N. Hart, Joseph Vijai, Kasmintan A. Schrader, Tinu Thomas, Bradley Wubbenhorst, Vignesh Ravichandran, Raymond M. Moore, Chunling Hu, Lucia Guidugli, Brandon Wenz, Thomas P. Slavin, Susan M. Domchek, Mark E. Robson, Csilla Szabo, Susan L. Neuhausen, Jeffrey N. Weitzel, Kenneth Offit, Fergus J. Couch, Katherine L. Nathanson. Evaluation of ACMG guideline classified variants in 180 cancer and incidental non-cancer genes in families with breast/ovarian cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5220.

Abstract Background: Despite the recent progress made with front-line treatment for advanced pancreatic cancer (PC), most patients (pts) will either relapse or be refractory to treatment. Others may not even be eligible due to the toxicity profile of the available options or due to clinical deterioration. Once the disease progresses following front-line treatment, there is no accepted standard of care. Treatment options are clearly needed for patients with refractory disease. Approximately 5% of unselected PC pts, 10% of PC patients of Ashkenazi Jewish descent, and up to 19% of familial PC cases, harbor a germline BRCA mutation. Though less well characterized to date, somatic BRCA mutations also appear to play a significant role in PC. Clinical data have shown that pts with BRCA-mutant (BRCAmut) tumors, including those with PC, respond to treatment with a PARP inhibitor (PARPi). Early data suggest that other genomic characteristics may be surrogate biomarkers of homologous recombination deficiency (HRD) and define a larger group of responders than just BRCA mutation(s) alone. Rucaparib, an oral PARPi, is being developed for treatment of cancers associated with HRD due to a BRCA mutation or other homologous recombination pathway defect. Rucaparib has a desirable PK profile, is well tolerated, and has demonstrated clinical activity (RECIST and/or CA-125 responses) in patients with BRCAmut pancreatic, ovarian, or breast cancer in an ongoing Phase 1/2 study (NCT01482715). Three studies are currently ongoing in ovarian cancer and a trial in BRCAmut pancreatic cancer is now planned. The clinical activity of PARPi, including rucaparib, in BRCAmut PC, combined with the paucity of active 2nd-line therapies, support evaluation of rucaparib in PC pts with a BRCA mutation. Methods: Study CO-338-023 (NCT02042378) is a single-arm, open-label Phase 2 trial of continuous monotherapy rucaparib in up to 100 pts with pancreatic ductal adenocarcinoma (or related subtype) who are known to harbor a deleterious BRCA mutation (germline or somatic). Pts must have received at least 1, but no more than 2, prior regimens for locally advanced or metastatic disease and have relapsed / progressive disease confirmed by radiologic assessment, or are no longer able to tolerate chemotherapy due to toxicity, and radiologic assessment confirms stable or progressive disease. Other key inclusion criteria include measurable disease, ECOG Performance Status 0 or 1, and adequate organ function. Pts with endocrine tumors or who received prior PARPi treatment are excluded. Pts will take 600 mg BID rucaparib continuously and be evaluated for safety every 2–4 wks, disease status (CT scans, CA19–9) every 4–8 wks until disease progression, and then for survival every 4 wks. Blood and archival tumor tissue (if available) will be collected from all pts. The primary endpoint is ORR by RECIST v1.1. Key secondary endpoints include duration of response, PFS, OS, and safety. Exploratory analyses include gene sequence and structural rearrangements of tumor DNA and evaluation of circulating tumor DNA. A group sequential interim monitoring plan will be implemented to stop the study early for either superior efficacy or futility. Interim analyses will occur after every 10th patient enrolled has sufficient disease assessment data available. If robust activity is observed in the BRCAmut PC population, the trial may be broadened to include PC pts with HRD due to other than a BRCA mutation. The trial will be open to enrollment at clinical sites in the US and Israel in 2Q 2014. Citation Format: Susan M. Domchek, Robert McWilliams, Andrew Hendifar, Rachna T. Shroff, Lawrence Leichman, Ron Epelbaum, Ravit Geva, George Kim, Steven R. Alberts, Robert A. Wolff, Andrew Allen, Heidi Giordano, Mitch Raponi, Jeff Isaacson, Lindsey Rolfe, Andrew Biankin, Robert H. Vonderheide. A phase 2, open-label study of the PARP inhibitor rucaparib in patients with pancreatic cancer and a known deleterious BRCA mutation. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B102.

Abstract BRCA1 and BRCA2 (BRCA) testing is uninformative in approximately 80% of families with clinical features of inherited susceptibility to breast cancer. Early identification of the individuals at risk in BRCAx families may lead to enhanced screening and prevention strategies, and potentially improved overall survival as has been seen for carriers of BRCA1/2 mutations. A proportion of these families are likely explained by mutations in other high penetrance and moderate penetrance breast cancer susceptibility genes. Although multi-gene panels are now commercially available for clinical testing, only limited information is available on the spectrum of mutations in breast cancer susceptibility genes in specific subgroups of high-risk breast cancer patients. We performed whole exome sequencing in 278 BRCA1/2 negative individuals with high-risk familial breast cancer, defined as a proband and at least two first or second degree relatives with breast cancer. Samples included 232 individuals from 97 families and 49 unrelated individuals, for a total of 146 independent cases. Data were analyzed for identification of all variants in 18 known high and moderate penetrance breast cancer susceptibility genes, in addition to BRCA1 and BRCA2. Two of the 97 families and one of the 49 singletons (2% of independent cases) were found to have deleterious mutations in high penetrance genes, namely TP53 (2) and CDH1 (1). In addition, nine of 146 independent cases (6%) were found to have deleterious mutations in the other predisposition genes. Mutations in ATM and CHEK2 accounted for seven of the ten moderate penetrance mutations identified; additionally one family had a mutation in BLM, one in MRE11A, and one in PALB2. Furthermore, 15 of 146 independent cases (10%) were found to have variants of unknown significance (VUS) in one of eight genes. There were no deleterious mutations or VUS in eight of the 18 genes. Our data show that significant genetic heterogeneity exists in BRCAx families. Large-scale collaborative efforts will be required to attain sufficient power to understand how to appropriately apply these results clinically in cancer risk evaluation. Citation Format: Kara N. Maxwell, Lucia Guidugli, Kasmintan Schrader, Steven Hart, Vijai Joseph, Tinu Thomas, Xianshu Wang, Bradley Wubbenhorst, Robert Klein, Susan M. Domchek, Csilla Szabo, Susan Neuhausen, Jeffrey Weitzel, Katherine L. Nathanson, Kenneth Offit, Fergus Couch. High and moderate penetrance germline mutations in a number of genes are responsible for a small proportion of familial breast cancer risk in BRCAx families. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1291. doi:10.1158/1538-7445.AM2014-1291

Abstract Background:BRCA1 and BRCA2 mutation carriers are at substantially increased risk for developing breast and ovarian cancer. The incomplete penetrance coupled with the variable age at diagnosis in carriers of the same mutation suggests the existence of genetic and nongenetic modifying factors. In this study, we evaluated the putative role of variants in many candidate modifier genes. Methods: Genotyping data from 15,252 BRCA1 and 8,211 BRCA2 mutation carriers, for known variants (n = 3,248) located within or around 445 candidate genes, were available through the iCOGS custom-designed array. Breast and ovarian cancer association analysis was performed within a retrospective cohort approach. Results: The observed P values of association ranged between 0.005 and 1.000. None of the variants was significantly associated with breast or ovarian cancer risk in either BRCA1 or BRCA2 mutation carriers, after multiple testing adjustments. Conclusion: There is little evidence that any of the evaluated candidate variants act as modifiers of breast and/or ovarian cancer risk in BRCA1 or BRCA2 mutation carriers. Impact: Genome-wide association studies have been more successful at identifying genetic modifiers of BRCA1/2 penetrance than candidate gene studies. Cancer Epidemiol Biomarkers Prev; 24(1); 308–16. ©2014 AACR.

Abstract BRCA1 and BRCA2 are the most important breast and ovarian cancer susceptibility genes. Biallelic mutations in BRCA2 can lead to Fanconi anemia and predisposition to cancers, whereas biallelic BRCA1 mutations have not been confirmed, presumably because one wild-type BRCA1 allele is required during embryogenesis. This study describes an individual who was diagnosed with ovarian carcinoma at age 28 and found to have one allele with a deleterious mutation in BRCA1, c.2457delC (p.Asp821Ilefs*25), and a second allele with a variant of unknown significance in BRCA1, c.5207T>C (p.Val1736Ala). Medical records revealed short stature, microcephaly, developmental delay, and significant toxicity from chemotherapy. BRCA1 p.Val1736Ala cosegregated with cancer in multiple families, associated tumors showed loss of wild-type BRCA1, and BRCA1 p.Val1736Ala showed reduced DNA damage localization. These findings represent the first validated example of biallelic deleterious human BRCA1 mutations and have implications for the interpretation of genetic test results. Significance: Accurate assessment of genetic testing data for BRCA1 mutations is essential for clinical monitoring and treatment strategies. Here, we report the first validated example of an individual with biallelic BRCA1 mutations, early-onset ovarian cancer, and clinically significant hypersensitivity to chemotherapy. Cancer Discov; 3(4); 399–405. ©2012 AACR. See related commentary by D'Andrea, p. 376 This article is highlighted in the In This Issue feature, p. 363

Abstract The relevance of many BRCA2 variants of uncertain significance (VUS) to breast cancer has not been determined due to limited genetic information from families carrying these alterations. Here, we classified six new variants as pathogenic or nonpathogenic by analysis of genetic information from families carrying 64 individual BRCA2 DNA binding domain (DBD) missense mutations using a multifactorial likelihood model of cancer causality. Next, we evaluated the use of a homology-directed DNA break repair (HDR) functional assay as a method for inferring the clinical relevance of VUS in the DBD of BRCA2 using 18 established nonpathogenic missense variants and all 13 established pathogenic missense mutations from the BRCA2 DBD. Compared with the known status of these variants based on the multifactorial likelihood model, the sensitivity of the HDR assay for pathogenic mutations was estimated at 100% [95% confidence interval (CI): 75.3%–100%] and specificity was estimated at 100% (95% CI: 81.5%–100%). A statistical classifier for predicting the probability of pathogenicity of BRCA2 DBD variants was developed using these functional results. When applied to 33 additional VUS, the classifier identified eight with 99% or more probability of nonpathogenicity and 18 with 99% or more probability of pathogenicity. Thus, in the absence of genetic evidence, a cell-based HDR assay can provide a probability of pathogenicity for all VUS in the BRCA2 DBD, suggesting that the assay can be used in combination with other information to determine the cancer relevance of BRCA2 VUS. Cancer Res; 73(1); 265–75. ©2012 AACR.

Background Clinical classification of rare sequence changes identified in the breast cancer susceptibility genes BRCA1 and BRCA2 is essential for appropriate genetic counselling of individuals carrying these variants. We previously showed that variant BRCA1 c.5096G>A p.Arg1699Gln in the BRCA1 transcriptional transactivation domain demonstrated equivocal results from a series of functional assays, and proposed that this variant may confer low to moderate risk of cancer. Methods Measures of genetic risk (report of family history, segregation) were assessed for 68 BRCA1 c.5096G>A p.Arg1699Gln (R1699Q) families recruited through family cancer clinics, comparing results with 34 families carrying the previously classified pathogenic BRCA1 c.5095C>T p.Arg1699Trp (R1699W) mutation at the same residue, and to 243 breast cancer families with no BRCA1 pathogenic mutation (BRCA-X). Results Comparison of BRCA1 carrier prediction scores of probands using the BOADICEA risk prediction tool revealed that BRCA1 c.5096G>A p.Arg1699Gln variant carriers had family histories that were less ‘ BRCA1 -like’ than BRCA1 c.5095C>T p.Arg1699Trp mutation carriers (p<0.00001), but more ‘ BRCA1 -like’ than BRCA-X families (p=0.0004). Further, modified segregation analysis of the subset of 30 families with additional genotyping showed that BRCA1 c.5096G >A p.Arg1699Gln had reduced penetrance compared with the average truncating BRCA1 mutation penetrance (p=0.0002), with estimated cumulative risks to age 70 of breast or ovarian cancer of 24%. Conclusions Our results provide substantial evidence that the BRCA1 c.5096G>A p.Arg1699Gln (R1699Q) variant, demonstrating ambiguous functional deficiency across multiple assays, is associated with intermediate risk of breast and ovarian cancer, highlighting challenges for risk modelling and clinical management of patients of this and other potential moderate-risk variants.