bims-lifras 2019-09-22 papers

Issue of 2019‒09‒22
six papers selected by
Joanna Zawacka-Pankau

Breast Cancer Res. 2019 Sep 18. 21(1): 107

Li-Fraumeni syndrome: not a straightforward diagnosis anymore-the interpretation of pathogenic variants of low allele frequency and the differences between germline PVs, mosaicism, and clonal hematopoiesis.

Batalini F, Peacock EG, Stobie L, Robertson A, Garber J, Weitzel JN, Tung NM.

The introduction of next-generation sequencing has resulted in testing multiple genes simultaneously to identify inherited pathogenic variants (PVs) in cancer susceptibility genes. PVs with low minor allele frequencies (MAFs) (< 25-35%) are highlighted on germline genetic test reports. In this review, we focus on the challenges of interpreting PVs with low MAF in breast cancer patients undergoing germline testing and the implications for management.The clinical implications of a germline PV are substantial. For PV carriers in high-penetrance genes like BRCA1, BRCA2, and TP53, prophylactic mastectomy is often recommended and radiation therapy avoided when possible for those with Li-Fraumeni syndrome (LFS). For germline PV carriers in more moderate-risk genes such as PALB2, ATM, and CHEK2, annual breast MRI is recommended and prophylactic mastectomies considered for those with significant family histories. Detection of PVs in cancer susceptibility genes can also lead to recommendations for other prophylactic surgeries (e.g., salpingo-oophorectomy) and increased surveillance for other cancers. Therefore, recognizing when a PV is somatic rather than germline and distinguishing somatic mosaicism from clonal hematopoiesis (CH) is essential. Mutational events that occur at a post-zygotic stage are somatic and will only be present in tissues derived from the mutated cell, characterizing classic mosaicism. Clonal hematopoiesis is a form of mosaicism restricted to the hematopoietic compartment.Among the genes in multi-gene panels used for germline testing of breast cancer patients, the detection of a PV with low MAF occurs most often in TP53, though has been reported in other breast cancer susceptibility genes. Distinguishing a germline TP53 PV (LFS) from a somatic PV (TP53 mosaicism or CH) has enormous implications for breast cancer patients and their relatives.We review how to evaluate a PV with low MAF. The identification of the PV in another tissue confirms mosaicism. Older age, exposure to chemotherapy, radiation, and tobacco are known risk factors for CH, as is the absence of a LFS-related cancer in the setting of a TP53 PV with low MAF. The ability to recognize and understand the implications of somatic PVs, including somatic mosaicism and CH, enables optimal personalized care of breast cancer patients.

Keywords: Clonal hematopoiesis; Hereditary breast cancer; Li-Fraumeni syndrome; Low allele frequency; Mosaicism; Mutation; Pathogenic variant; TP53

DOI: https://doi.org/10.1186/s13058-019-1193-1

Mod Pathol. 2019 Sep 19.

Expanding the spectrum of dicer1-associated sarcomas.

Warren M, Hiemenz MC, Schmidt R, Shows J, Cotter J, Toll S, Parham DM, Biegel JA, Mascarenhas L, Shah R.

DICER1 syndrome is a hereditary cancer predisposition syndrome caused by deleterious germline DICER1 mutations. Characteristic "hotspot" somatic mutations of DICER1 have been identified in DICER1-associated tumors. With the exception of genitourinary embryonal rhabdomyosarcoma and anaplastic sarcoma of the kidney, sarcomas are rarely reported in DICER1 syndrome. Herein, we report the clinical, histopathologic, and molecular findings of a germline DICER1-associated ovarian sarcoma in a 5-year-old female, a somatic DICER1-associated metastatic peritoneal sarcoma in a 16-year-old female, and a somatic DICER1-associated primary intracranial sarcoma in a 4-year-old male. A comprehensive review of the literature, including 83 DICER1-associated sarcomas, illustrates an unequivocal histologic pattern mimicking pleuropulmonary blastoma, regardless of the site of origin. The features include undifferentiated small round blue cells, poorly differentiated spindle cells, and large bizarre pleomorphic cells (anaplasia), often with rhabdomyoblastic and/or chondroid differentiation, and rare bone/osteoid formation. This unique heterogeneous histologic pattern should raise suspicion for pathogenic DICER1 mutation(s) warranting a detailed review of the family history and DICER1 mutation analysis. In addition to expanding the phenotypic spectrum of DICER1-associated conditions, identification of pathogenic DICER1 variants facilitates optimized genetic counseling, caregiver education and judicious imaging-based surveillance.

DOI: https://doi.org/10.1038/s41379-019-0366-x

Fam Cancer. 2019 Sep 17.

Inequities in multi-gene hereditary cancer testing: lower diagnostic yield and higher VUS rate in individuals who identify as Hispanic, African or Asian and Pacific Islander as compared to European.

Ndugga-Kabuye MK, Issaka RB.

The identification of germline pathogenic/likely pathogenic (P/LP) variants in cancer predisposition genes can guide treatment and management decisions for the individual being tested and potentially at-risk relatives. Prior studies have raised concerns of racial/ethnic disparities in the detection rates of P/LP variants and variants of uncertain significance (VUSs). In 2018, Color Genomics™, a commercial laboratory, made de-identified, aggregate genetic and clinical information from 50,000 individuals who completed testing for 30 cancer predisposition genes publicly available. It is the largest publicly available database of its kind from a single laboratory. An analysis of individuals from this database with a negative personal history of cancer that identify as European (n = 31,920), Hispanic (n = 1700), African (n = 462) or Asian and Pacific Islander (n = 2602), demonstrated that the VUS rate in the hereditary breast and ovarian cancer syndrome and Lynch syndrome genes was higher for all non-European groups as compared to the European group; Hispanic (7.1% vs. 5.8%; p = 0.029), African (12.3% vs. 5.8%; p < 0.001), Asian and Pacific Islander (13.1% vs. 5.8%; p < 0.001). In the other cancer genes (OCGs), the P/LP rate was lower; Hispanic (5.1% vs. 7.6%; p < 0.001), African (2.4% vs. 7.6%; p < 0.001), and Asian and Pacific Islander (4.3% vs. 7.6%; p < 0.001). The VUS rate was also higher in the OCGs; Hispanic (16.2% vs. 12.2%; p < 0.001), African (21.6% vs. 12.2%; p < 0.001), Asian and Pacific Islander (24.4% vs. 12.2%; p < 0.001). Our study emphasizes the reality of disparities in the results of cancer genetic testing and highlights factors that propagate these inequities.

Keywords: BRCA1/2; Cancer genetic testing; Health disparities; Hereditary cancer

DOI: https://doi.org/10.1007/s10689-019-00144-6

Hered Cancer Clin Pract. 2019 ;17 27

Spectrum and prevalence of BRCA1/2 germline mutations in Pakistani breast cancer patients: results from a large comprehensive study.

Rashid MU, Muhammad N, Naeemi H, Khan FA, Hassan M, Faisal S, Gull S, Amin A, Loya A, Hamann U.

Background: Pathogenic germline mutations in BRCA1 and BRCA2 (BRCA1/2) account for the majority of hereditary breast and/or ovarian cancers worldwide. To refine the spectrum of BRCA1/2 mutations and to accurately estimate the prevalence of mutation in the Pakistani population, we studied 539 breast cancer patients selected for family history and age of diagnosis.Methods: Comprehensive screening for BRCA1/2 germline mutations was performed using state-of-the-art technologies.
Results: A total of 133 deleterious mutations were identified in 539 families (24.7%), comprising 110 in BRCA1 and 23 in BRCA2. The prevalence of BRCA1/2 small-range mutations and large genomic rearrangements was 55.4% (36/65) for families with breast and ovarian cancer, 27.4% (67/244) for families with two or more cases of breast cancer, 18.5% (5/27) for families with male breast cancer, and 12.3% (25/203) for families with a single case of early-onset breast cancer. Nine mutations were specific to the Pakistani population. Eighteen mutations in BRCA1 and three in BRCA2 were recurrent and accounted for 68.2% (75/110) and 34.8% (8/23) of all identified mutations in BRCA1 and BRCA2, respectively. Most of these mutations were exclusive to a specific ethnic group and may result from founder effects.
Conclusions: Our findings show that BRCA1/2 mutations account for one in four cases of hereditary breast/ovarian cancer, one in five cases of male breast cancer, and one in eight cases of early-onset breast cancer in Pakistan. Our study suggests genetic testing of an extended panel of 21 recurrent BRCA1/2 mutations for appropriately selected patients and their families in Pakistan.

Keywords: BRCA1/2; Pakistan; breast cancer; germline mutations

DOI: https://doi.org/10.1186/s13053-019-0125-5

Cancer Med. 2019 Sep 18.

Population prevalence of individuals meeting criteria for hereditary breast and ovarian cancer testing.

Greenberg S, Buys SS, Edwards SL, Espinel W, Fraser A, Gammon A, Hafen B, Herget KA, Kohlmann W, Roundy C, Sweeney C.

BACKGROUND: Personal cancer diagnosis and family cancer history factor into which individuals should undergo genetic testing for hereditary breast and ovarian cancer (HBOC) syndrome. Family history is often determined in the research setting through kindreds with disease clusters, or clinically from self-report. The population prevalence of individuals with diagnostic characteristics and/or family cancer history meeting criteria for HBOC testing is unknown.METHODS: Utilizing Surveillance, Epidemiology, and End Results (SEER) cancer registry data and a research resource linking registry records to genealogies, the Utah Population Database, the population-based prevalence of diagnostic and family history characteristics meeting National Comprehensive Cancer Network (NCCN) criteria for HBOC testing was objectively assessed.
RESULTS: Among Utah residents with an incident breast cancer diagnosis 2010-2015 and evaluable for family history, 21.6% met criteria for testing based on diagnostic characteristics, but the proportion increased to 62.9% when family history was evaluated. The proportion of cases meeting testing criteria at diagnosis was 94% for ovarian cancer, 23% for prostate cancer, and 51.1% for pancreatic cancer. Among an unaffected Utah population of approximately 1.7 million evaluable for family history, 197,601 or 11.6% met testing criteria based on family history.
CONCLUSIONS: This study quantifies the population-based prevalence of HBOC criteria using objectively determined genealogy and cancer incidence data. Sporadic breast cancer likely represents a portion of the high prevalence of family cancer history seen in this study. These results underline the importance of establishing presence of a deleterious mutation in an affected family member, per NCCN guidelines, before testing unaffected relatives.

Keywords: BRCA1/2; cancer registry; epidemiology; genetic counseling; hereditary cancer

DOI: https://doi.org/10.1002/cam4.2534