Characteristics of double heterozygosity for BRCA1 and BRCA2 germline mutations in Korean breast cancer patients

Characteristics of Chinese breast cancer patients with double heterozygosity for BRCA1 and BRCA2 germline pathogenic variants

PURPOSE

Despite of very rare, breast cancer patients with double heterozygosity (DH) variants in BRCA1 and BRCA2 genes have been identified in other ethnic groups and seem to be associated with distinctive phenotypes. However, little is known about the frequency and clinical characteristics of Chinese breast cancer patients with BRCA1/2 DH variants.

METHODS

Four hundred and eleven unrelated patients with BRCA1 or BRCA2 pathogenic variants (PVs) were identified in a large series of unselected breast cancer patients. Another two siblings with metachronous bilateral breast cancer were referred for genetic counseling, after which BRCA1/2 DH variants were detected.

RESULTS

Four unrelated breast cancer patients with BRCA1/2 DH were identified in the cohort of 411 patients with BRCA1 or BRCA2 PVs, the frequency of BRCA1/2 DH was 0.97%. In total, six BRCA1/2 DH patients from five families were found in this study. In two families, the hereditary pattern of DH was speculated to have originated from both sides of the family. BRCA1/2 DH patients were more likely to have a family history of breast cancer than patients with a BRCA1 (100% vs. 29.2%, P = 0.004) or BRCA2 (100% vs. 29.6%, P = 0.004) single PV. BRCA1/2 DH patients were more likely to be triple-negative breast tumors than patients with single BRCA2 PVs (66.7% vs. 14.1%, P = 0.020), which was comparable to the findings in patients with single BRCA1 PVs (66.7% vs. 56.9%, P = 1.00).

CONCLUSION

Chinese patients with BRCA1/2 DH exhibit a high percentage of family history of breast cancer. The tumor pathological features of BRCA1/2 DH carriers are similar to those of BRCA1 PV carriers.

Characterization of the HER2 status in BRCA-mutated breast cancer: a single institutional series and systematic review with pooled analysis

BACKGROUND

Pathogenic variants (PVs) in BRCA1/2 genes account for ∼6% of breast and 20% of ovarian cancers. Most breast tumors developed by BRCA1 carriers are triple negative. BRCA2 tumors have similar rates of estrogen receptor positivity as sporadic controls but are less likely to be human epidermal growth factor receptor 2 (HER2)-positive. Prevalence of HER2 positivity among breast cancers (BCs) in BRCA1/2 mutation carriers is poorly and variably described, ranging from 0% to 10% and 0% to 13% in BRCA1 and BRCA2 carriers, respectively.

PATIENTS AND METHODS

We assessed the prevalence of HER2 positivity among a single institutional cohort of 398 BCs developed in carriers of BRCA1/2 PVs (240 BRCA1, 158 BRCA2). Subsequently, a systematic review of the literature and pooled analysis was carried out.

RESULTS

In our series we found a 7% HER2 positivity rate among all first BRCA1/2 BCs overall. In BRCA1 carriers, 5.4% of BCs were HER2-positive compared with 9.5% in BRCA2-mutated patients. Among bilateral BCs, HER2-positive cases were 15.2% in the BRCA1 group and 23.1% in the BRCA2 group. Notably, six BRCA1 and eight BRCA2 carriers showed discordant HER2 status between BC and bilateral BC (23.7%, 14/59). The systematic review included 21 083 BRCA1/2 patients from 73 eligible studies. The pooled rate of BRCAmut/HER2-positive BCs is 9.1% (95% confidence interval 7.3% to 11.2%). BRCA1 and BRCA2 when reported as separate data ranged from 0% to 33.3% (mean 8.3%) and from 0% to 86% (mean 10.3%), respectively.

CONCLUSIONS

As compared with sporadic cases, BCs occurring in BRCA1 and/or BRCA2 PVs carriers are less frequently HER2-positive. Prevalence of HER2 positivity in our series was consistent with pooled analysis and did not exceed 10%. Although not common, co-existence of BRCA mutations and HER2 overexpression and/or gene amplification should be acknowledged. More research is needed to better characterize this subgroup of patients who should not be excluded a priori from clinical trials of targeted therapy for BRCA1/2-driven cancers.

The genetics of hereditary cancer risk syndromes in Brazil: a comprehensive analysis of 1682 patients

Hereditary cancer risk syndromes are caused by germline variants, commonly in tumor suppressor genes. Most studies on hereditary cancer have been conducted in white populations. We report the largest study in Brazilian individuals with multiple ethnicities. We genotyped 1682 individuals from all country regions with Next-generation sequencing (NGS) panels. Most were women with a personal/family history of cancer, mostly breast and ovarian. We identified 321 pathogenic/likely pathogenic (P/LP) variants in 305 people (18.1%) distributed among 32 genes. Most were on BRCA1 and BRCA2 (129 patients, 26.2% and 14.3% of all P/LP, respectively), MUTYH (42 monoallelic patients, 13.1%), PALB2 (25, 7.8%), Lynch syndrome genes (17, 5.3%), and TP53 (17, 5.3%). Transheterozygosity prevalence in our sample was 0.89% (15/1682). BRCA1/BRCA2 double heterozygosity rate was 0.78% (1/129) for BRCA variants carriers and 0.06% (1/1682) overall. We evaluated the performance of the genetic testing criteria by NCCN and the Brazilian National Health Agency (ANS). The inclusion criteria currently used in Brazil fail to identify 17%-25% of carriers of P/LP variants in hereditary cancer genes. Our results add knowledge on the Brazilian spectrum of cancer risk germline variants, demonstrate that large multigene panels have high positivity rates, and indicate that Brazilian inclusion criteria for genetic testing should be improved.

Concurrent pathogenic variations in patients with hereditary cancer syndromes

Cancer is a multifactorial disorder; however, 5-10% of all cancers show hereditary background. In recent years many targeted next generation sequencing panels comprising cancer predisposition genes have been developed and used for diagnostic purposes in patients with increased cancer risk. Screening multiple genes at a time allows multiple variants in different genes to be detected as well. This study aims to determine the cases with concurrent mutations in different hereditary cancer predisposition genes and how they are clinically affected. Here, we screened 1090 index cases by next generation sequencing based hereditary cancer panels and evaluated the reflection of multiple variations on the phenotype. We detected 11 (1%) cases with pathogenic variants in more than one gene. These concurrent variations occurred mostly in BRCA1/2 (7/11) accompanied with MUTYH, ATM, CHECK2, NBN, and RAD50. In addition, MUTYH&ATM, NBN&MSH6, MUTYH&CHEK2 double heterozygous cases were detected. Moreover, we identified a case with three heterozygous variations in CDH1, MUTYH, and CHEK2. These patients presented malignancies that were mostly related to pathogenic variations they carried. Although they are rare, defining double heterozygous cases is important for managing appropriate therapy and accurate genetic consulting for the patients and family members.

Clinicopathological Characterization of Double Heterozygosity for BRCA1 and BRCA2 Variants in Korean Breast Cancer Patients

Purpose

Double heterozygosity (DH) for BRCA1 and BRCA2 variant is very rare with only a few cases reported, and most those in Caucasians. In this article, we present seven unrelated cases of DH for BRCA1/2 identified from a single institution in Korea, and describe the characteristics and phenotype of DH individuals compared to those with a single BRCA variant.

Materials and Methods

This study included 27,678 patients diagnosed with breast cancer and surgically treated at Samsung Medical Center (SMC) between January 2008 and June 2020. In total, 4,215 high-risk breast cancer patients were tested for the BRCA1/2 genes, and electronic medical records from 456 cases with pathogenic/likely pathogenic variants were reviewed.

Results

A younger mean age at diagnosis was associated with DH than a single variant of BRCA1/2. More triple-negative breast cancer and higher nuclear and histologic grade cancer occurred with DH than BRCA2 variant. All seven cases of DH were unrelated, and their mutation combinations were different. There were no Ashkenazi founder variants detected.

Conclusion

We suggest that patients with DH for BRCA1/2 variants develop breast cancer at a younger age, but the histopathologic features are similar to those of BRCA1.

Five Italian Families with Two Mutations in BRCA Genes

Double heterozygosity (DH) in BRCA1 and BRCA2 genes and double mutation (DM) in BRCA1 or BRCA2 are extremely rare events in the general population, and few cases have been reported worldwide so far. Here, we describe five probands, all women, with breast and/or ovarian cancer and their families. Particularly, we identified two probands with DH in the BRCA1/2 genes with a frequency of 0.3% and three probands with DM in the BRCA2 gene with a frequency of 0.5%. The DH BRCA1 c.547+2T>A (IVS8+2T>A)/BRCA2 c.2830A>T (p.Lys944Ter) and BRCA1 c.3752_3755GTCT (p.Ser1253fs)/BRCA2 c.425+2T>C (IVS4+2T>C) have not been described together so far. The DM in BRCA2, c.631G>A (p.Val211Ile) and c.7008-2A>T (IVS13-2A>T), found in three unrelated probands, was previously reported in further unrelated patients. Due to its peculiarity, it is likely that both pathogenic variants descend from a common ancestor and, therefore, are founder mutations. Interestingly, analyzing the tumor types occurring in DH and DM families, we observed ovarian cancer only in DH families, probably due to the presence in DH patients of BRCA1 pathogenic variants, which predispose one more to ovarian cancer onset. Furthermore, male breast cancer and pancreatic cancer ensued in families with DM but not with DH. These data confirm that BRCA2 pathogenic variants have greater penetrance to develop breast cancer in men and are associated with an increased risk of pancreatic cancer.

Clinical Characteristics of Korean Breast Cancer Patients Who Carry Pathogenic Germline Mutations in Both BRCA1 and BRCA2: A Single-Center Experience

There are few reports of breast cancer patients who carry germline mutations in both germline breast cancer susceptibility genes 1 (gBRCA1) and 2 (gBRCA2). In this study, we analyzed the clinical, pathological, and genomic characteristics of Korean breast cancer patients with both gBRCA1 and gBRCA2 mutations. Medical records of patients who received gBRCA1 and gBRCA2 testing at Samsung Medical Center between January 2007 to October 2018 were retrospectively reviewed. Genomic DNA was isolated from peripheral blood leukocytes. Among a total of 2720 patients, four patients with both gBRCA1 and gBRCA2 mutations were identified (4/2720; 0.14%). Seven patients who had a gBRCA1 mutation and gBRCA2 variants of uncertain significance (VUS) were also identified. In those patients with both gBRCA1 and gBRCA2 mutations, the mean age at diagnosis for breast cancer was 36 years (range, 31–43 years). All four tumors were infiltrating ductal carcinomas and three of the tumors were estrogen receptor-negative, progesterone receptor-negative, and human epidermal growth factor receptor 2-negative (triple-negative). All four patients who carried germline mutations in both BRCA1 and BRCA2 had a family history of breast/ovarian cancer. Pathologic stage was II in three patients and I in one patient. Breast cancer patients with both gBRCA1 and gBRCA2 mutations were rare, young at diagnosis, and all but one tumor was triple-negative based on our single-center experience.

Allele-specific expression mediates primary resistance to poly (ADP-ribose) polymerase inhibitor therapy in a case of BRCA1/2 double-germline mutant gastric cancer

Breast cancer gene 1 and 2 (BRCA1 and BRCA2) are human tumor suppressor genes. BRCA mutations increase the risk for breast, ovarian, and gastric cancer. However, double heterozygosity for BRCA1 and BRCA2 mutations in gastric cancer have not been reported and their clinical significance is unclear. In this study, a 52-year-old Chinese male patient with gastric cancer was chosen for analysis. A tumor tissue biopsy and blood sample were collected, and next-generation sequencing-based deep panel sequencing was performed on the IlluminaNextSeq-500 platform. Comprehensive genomic alterations of 450 cancer-related genes and 47 tumor susceptibility genes were analyzed. Here, we report for the first time a case of gastric cancer that carried both BRCA1 S1841Vfs*2 and BRCA2 Q1886* heterozygous mutations. Unfortunately, the patient was resistant to olaparib treatment. Further RNA analysis revealed that only the wild-type alleles of BRCA1 and BRCA2 were expressed, although genetic BRCA1 and BRCA2 mutations were present in the patient. This genetic finding may explain the mechanism for primary resistance to olaparib observed in the BRCA1/2-mutated patient.

The association between non-breast and ovary cancers and BRCA mutation in first- and second-degree relatives of high-risk breast cancer patients: a large-scale study of Koreans

Background

As a large-scale study of Koreans, we evaluated the association between BRCA mutation and the prevalence of non-breast and ovary cancers in first- and second-degree relatives of high-risk breast cancer patients.

Methods

We organized familial pedigrees of 2555 patients with breast cancer who underwent genetic screening for BRCA1/2 in Samsung Medical Center between January 2002 and May 2018. Families with a member that had a history of cancer other than of the breast or ovary were regarded positive for other primary cancer.

Results

The median age of the population was 40 years (range, 19 to 82 years). BRCA mutation was detected in 377 (14.8%) of the patients. The BRCA-positive group had a higher frequency of family history of breast or ovarian cancer (p <  0.001), bilateral breast cancer (p = 0.021), and the male gender (p = 0.038). There were 103 (27.3%) patients who had multiple risk factors in the BRCA-positive group, while there were 165 (7.6%) patients who had multiple risk factors in the BRCA-negative group (p <  0.001). BRCA mutation was detected in 215 (11.7%) of the 1841 families without history of other primary cancers. Among the 714 families with histories of other primary cancers, 162 (22.7%) had BRCA mutation, and this was significantly more frequent (p < 0.001) than in those without a history. The occurrence of other primary cancers in families of high-risk patients was associated with a younger age at diagnosis (p = 0.044), bilateral breast cancer (p = 0.006), and BRCA mutations (p < 0.001). The most common site for the occurrence of another type of primary cancer was the stomach. In the BRCA-positive group, the proportional incidences of stomach, pancreas, colorectal, lung, and uterine cancer were 13.8, 4.0, 7.7, 8.8, and 5.0%, respectively; these were all relatively higher than those in the BRCA-negative group.

Conclusions

We confirmed that BRCA mutation was associated with having multiple risk factors and an increased prevalence of non-breast and ovary cancers in first- and second-degree relatives of high-risk breast cancer patients. Due to the possibility of inherited cancer risk, genetic counseling with options for risk assessment and management should be provided to both patients and families of BRCA mutation carriers.

Double Heterozygosity for BRCA1 Pathogenic Variant and BRCA2 Polymorphic Stop Codon K3326X: A Case Report in a Southern Italian Family

Here, we describe a patient with bilateral breast cancer and melanoma, and with a concomitant double variant, namely p.Gln563Ter in BRCA1 and p.Lys3326Ter in BRCA2. The BRCA2 p.Lys3326Ter (K3326X) (rs11571833) mutation identified in our patient is a debated substitution of thymidine for adenine which is currently regarded as benign polymorphism in main gene databases. Recent studies, however, describe this variant as associated with breast and ovarian tumors. Based on the observation of the cancer’s earliest age of onset in this subject, our purpose was to reevaluate this variant according to recent papers indicating a role of powerful modifier of the genetic penetrance. Genetic testing was performed in all consenting patient’s relatives, and in the collection of the clinical data particular attention was paid to the age of onset of the neoplasia. Following our observation that the our patient with double heterozygosis had an early age of onset for cancer similar to a few rare cases of double mutation for BRCA1 and BRCA2, we also performed an extensive review of the literature relative to patients carrying a double heterozygosity for both genes. In line with previous studies relative to the rare double heterozygosity in both BRCA1/2 genes, we found the earlier onset of breast cancer in our patient with both BRCA1/2 mutations with respect to other relatives carrying the single BRCA1 mutation. The presence of the second K3326X variant in our case induces a phenotype characterized by early onset of the neoplasia in a manner similar to the other cases of double heterozygosity previously described. Therefore, we suggest that during the genetic counseling, it should be recommendable to evaluate the presence of the K3326X variant in association with other pathogenic mutations.

Concurrent DNA Copy-Number Alterations and Mutations in Genes Related to Maintenance of Genome Stability in Uninvolved Mammary Glandular Tissue from Breast Cancer Patients

Somatic mosaicism for DNA copy-number alterations (SMC-CNAs) is defined as gain or loss of chromosomal segments in somatic cells within a single organism. As cells harboring SMC-CNAs can undergo clonal expansion, it has been proposed that SMC-CNAs may contribute to the predisposition of these cells to genetic disease including cancer. Herein, the gross genomic alterations (>500 kbp) were characterized in uninvolved mammary glandular tissue from 59 breast cancer patients and matched samples of primary tumors and lymph node metastases. Array-based comparative genomic hybridization showed 10% (6/59) of patients harbored one to 359 large SMC-CNAs (mean: 1,328 kbp; median: 961 kbp) in a substantial portion of glandular tissue cells, distal from the primary tumor site. SMC-CNAs were partially recurrent in tumors, albeit with considerable contribution of stochastic SMC-CNAs indicating genomic destabilization. Targeted resequencing of 301 known predisposition and somatic driver loci revealed mutations and rare variants in genes related to maintenance of genomic integrity: BRCA1 (p.Gln1756Profs*74, p.Arg504Cys), BRCA2 (p.Asn3124Ile), NCOR1 (p.Pro1570Glnfs*45), PALB2 (p.Ser500Pro), and TP53 (p.Arg306*). Co-occurrence of gross SMC-CNAs along with point mutations or rare variants in genes responsible for safeguarding genomic integrity highlights the temporal and spatial neoplastic potential of uninvolved glandular tissue in breast cancer patients.

Association between BRCA Mutation Status, Pathological Findings, and Magnetic Resonance Imaging Features in Patients with Breast Cancer at Risk for the Mutation

PURPOSE

We investigated the relationship between BRCA mutations, pathological findings, and magnetic resonance imaging (MRI) features in patients with breast cancer at risk for the mutation.

METHODS

Genetic testing for BRCA mutations was performed in 275 breast cancer patients with at least one risk factor for the mutation. Using the breast imaging reporting and data system MR lexicon, morphological and kinetic features were reviewed on MRI scans of 230 tumors in 209 patients. The relationship between BRCA mutations, pathologic findings, and MRI data was examined, and disease recurrence was estimated.

RESULTS

BRCA mutations were detected in 48 patients (23.0%), of which 21 (10.0%) were in BRCA1, and 25 (12.0%) in BRCA2. Additionally, two patients (1.0%) had mutations in both genes. Cancers in patients with BRCA1 mutations more frequently showed a higher nuclear grade (p=0.0041), and triple-negative (TN) phenotype (p<0.0001). On MRI scans, the cancers were seen as mass-type in 182 out of 230 lesions (79.1%), and nonmass type in 48 cases (20.9%). Among the features indentified by MRI, rim enhancement was significantly associated with molecular subtypes based on immunohistochemistry (p<0.0001), and nuclear grade (p=0.0387) in multiple logistic regression analysis. Rim enhancement on MRI, along with advanced pathologic N stage, was associated with increased disease recurrence (p=0.0023) based on multivariate analysis. However, the proportion of mass and nonmass tumors, and the distribution of morphological shape, margin, internal enhancement, and kinetic features assessed by MRI were not different according to BRCA mutation status.

CONCLUSION

BRCA1 mutations were associated with aggressive pathological characteristics, and the TN phenotype. Rim enhancement was frequently seen on MRI scans of high-grade cancers and in the TN phenotype. And it was a significant predictor of disease recurrence. However, a direct association with BRCA mutations was not observed.

Associations between BRCA Mutations in High-Risk Breast Cancer Patients and Familial Cancers Other than Breast or Ovary

PURPOSE

We investigated the relationship between BRCA mutations and the distribution of familial cancers other than breast or ovary in high-risk breast cancer patients.

METHODS

PATIENTS WITH BREAST CANCER WHO HAD AT LEAST ONE OF THE FOLLOWING RISK FACTORS WERE ENROLLED: reported family history of breast or ovarian cancer; 40 years of age or younger age at diagnosis; bilateral breast cancer; or male gender. Genetic testing for BRCA mutation and questionnaires about personal and family histories of malignancies were performed.

RESULTS

Among the 238 eligible patients, 49 (20.6%) patients had BRCA1/2 mutations, which were more frequent in patients with multiple risk factors (p<0.0001). There were 271 members of 156 (65.5%) families who had histories of other primary cancer. The distribution of the families was 119 (63.0%) and 37 (75.5%) in the BRCA-negative and positive group, respectively (p=0.0996). Multiple familial cancers occurred in 70 families, which were significantly more frequent in BRCA-positive families (p=0.0034). By ordinal logistic regression, the occurrence of multiple familial cancers was associated with BRCA mutations (p=0.0045), not with other risk factors. The most common site of disease was the stomach, which is the most common in nationwide. And the proportional incidence of pancreatic cancer (6.8%) was significantly higher than that of nationwide cancer statistics (2.4%, p=0.0137).

CONCLUSION

BRCA mutations in high-risk breast cancer patients were associated with multiple risk factors and multiple family members with other primary cancers. Genetic counseling based on accurate information should be provided to families with BRCA mutation carriers.