Homologous Recombination Repair Pathway Genes Research Articles

Clinical relevance of double heterozygosity revealed by next-generation sequencing of homologous recombination repair pathway genes in South African breast cancer patients

PurposeGenetically predisposed breast cancer (BC) patients represent a minor but clinically meaningful subgroup of the disease, with 25% of all cases associated with actionable variants in BRCA1/2. Diagnostic implementation of next-generation sequencing (NGS) resulted in the rare identification of BC patients with double heterozygosity for deleterious variants in genes partaking in homologous recombination repair of DNA. As clinical heterogeneity poses challenges for genetic counseling, this study focused on the occurrence and clinical relevance of double heterozygous BC in South Africa.MethodsDNA samples were diagnostically screened using the NGS-based Oncomine™ BRCA Expanded Research Assay. Data was generated on the Ion GeneStudio S5 system and analyzed using the Torrent Suite™ and reporter software. The clinical significance of the variants detected was determined using international variant classification guidelines and treatment implications.ResultsSix of 1600 BC patients (0.375%) tested were identified as being bi-allelic for two germline likely pathogenic or pathogenic variants. Most of the variants were present in BRCA1/2, including two founder-related small deletions in three cases, with family-specific variants detected in ATM, BARD1, FANCD2, NBN, and TP53. The scientific interpretation and clinical relevance were based on the clinical and tumor characteristics of each case.ConclusionThis study increased current knowledge of the risk implications associated with the co-occurrence of more than one pathogenic variant in the BC susceptibility genes, confirmed to be a rare condition in South Africa. Further molecular pathology-based studies are warranted to determine whether clinical decision-making is affected by the detection of a second pathogenic variant in BRCA1/2 and TP53 carriers.

Histologic patterns in prostatic adenocarcinoma are not predictive of mutations in the homologous recombination repair pathway

Somatic or germline homologous recombination repair (HRR) pathway gene mutations are commonly detected in prostate cancer, especially in advanced disease, and are associated with response to poly (ADP-ribose) polymerase (PARP) inhibitors. In this study, we evaluated whether histological patterns are predictive of HRR pathway gene mutations. The study population comprised 130 patients with advanced prostate carcinoma who underwent comprehensive genomic profiling (CGP) of tumor tissue at a CLIA-certified laboratory. HRR genes in the study included BRCA1, BRCA2, ATM, BARD1, BRIP, CHEK2, MRE11A, NBN, PALB2, RAD51C, RAD51D, EMSY, ATR, CHEK1, and FAM175A. Overall, 38 patients had mutations in BRCA1/2, 36 in other HRR genes, and 56 were negative for HRR mutations. All cases were re-reviewed and quantified by two genitourinary pathologists blinded to mutational status for the following histological patterns of prostate carcinoma: cribriform, ductal, intraductal carcinoma (IDC), small cell carcinoma, signet ring-like pattern, and lobular carcinoma-like pattern. Discordances were resolved by consensus review. Histologic patterns were analyzed for any correlation with mutations in HRR pathway genes (grouped as BRCA1/2 mutated or non-BRCA1/2 mutated) compared to tumors without mutations in HRR genes by Chi-square testing. Patterns with >20 % and >30 % of tumor volume were additionally evaluated for correlation with mutational status. We found no significant association between HRR pathway mutations and cribriform pattern, IDC, ductal carcinoma, small cell carcinoma, signet ring-like pattern, or lobular carcinoma-like patterns. Tumors with >20 % or >30 % histologic patterns by volume also demonstrated no significant association with mutational status. This study suggests that histopathologic examination alone is insufficient to distinguish prostate cancer with germline or somatic mutations in HRR pathway genes, highlighting the continuing importance of ancillary molecular diagnostics in guiding therapy selection for prostate cancer patients who may benefit from PARP inhibitors.

Anthracycline-related cardiotoxicity in patients with breast cancer harboring mutational signature of homologous recombination deficiency (HRD)

The BRCA proteins play a key role in the homologous recombination (HR) pathway. Beyond BRCA1/2, other genes are involved in the HR repair (HRR). Due to the prominent role in the cellular repair process, pathogenic or likely pathogenic variants (PV/LPVs) in HRR genes may cause inadequate DNA damage repair in cardiomyocytes. This was a multicenter, hospital-based, retrospective cohort study to investigate the heart toxicity from anthracycline-containing regimens (ACRs) in the adjuvant setting of breast cancer (BC) patients carrying germline BRCA PV/LPVs and no-BRCA HRR pathway genes. The left ventricular ejection fraction (LVEF) was assessed using cardiac ultrasound before starting ACR therapy and at subsequent time points according to clinical indications. Five hundred and three BC patients were included in the study. We predefined three groups: (i) BRCA cohort; (ii) no-BRCA cohort; (iii) variant of uncertain significance (VUS)/wild-type (WT) cohort. When baseline (T0) and post-ACR (T1) LVEFs between the three cohorts were compared, pre-treatment LVEF values were not different (BRCA1/2 versus HRR-no-BRCA versus VUS/WT cohort). Notably, during monitoring (T1, median 3.4 months), patients carrying BRCA or HRR no-BRCA germline pathogenic or likely pathogenic variants showed a statistically significant reduction of LVEF compared to baseline (T0). To assess the relevance of HRR on the results, we included the analysis of the subgroup of 20 BC patients carrying PV/LPVs in other genes not involved in HRR, such as mismatch repair genes (MUTYH, PMS2, MSH6). Unlike HRR genes, no significant differences in T0-T1 were found in this subgroup of patients. Our data suggest that deleterious variants in HRR genes, leading to impaired HR, could increase the sensitivity of cardiomyocytes to ACR in early BC patients. In this subgroup of patients, other measurements, such as the global longitudinal strain, and a more in-depth assessment of risk factors may be proposed in the future to optimize cardiovascular risk management and improve long-term survival.

Carboplatin in Patients With Metastatic Castration-Resistant Prostate Cancer Harboring Somatic or Germline Homologous Recombination Repair Gene Mutations: Phase II Single-Arm Trial.

Approximately 20%-25% of patients with metastatic castration-resistant prostate cancer (mCRPC) harbor a deleterious germline or somatic mutation in the homologous recombination repair (HRR) pathway genes, which is involved in the repair of double-stranded DNA damage. Half of these mutations are germline, while the remaining are exclusively somatic. While polyadenosine 5'diphosphoribose [poly (ADP-ribose)] polymerase inhibitors, such as olaparib and rucaparib, are effective in this subgroup, their widespread use is limited due to the associated high cost, especially in resource-constrained settings. Notably, platinum agents like carboplatin have exquisite sensitivity to cells with defective DNA repair machinery. Carboplatin, a conventional, inexpensive chemotherapeutic agent, offers a potential alternative treatment in such patients. Several retrospective small case series support this hypothesis. However, there are no prospective clinical trials of carboplatin in patients with mCRPC with HRR mutations. The primary objective is to assess the objective response rate of 3 weekly carboplatin treatments in patients with mCRPC harboring deleterious mutations in the HRR pathway genes and previously treated with a taxane or a novel antiandrogen agent. The secondary objectives include progression-free survival, health-related quality of life, and safety profile of carboplatin. Patients diagnosed with mCRPC harboring HRR pathway mutations previously treated with docetaxel or novel antiandrogen agents (abiraterone, enzalutamide, apalutamide, or darolutamide) or both will be eligible. Genes involved directly or indirectly in the HRR pathway will be tested. In this single-arm phase II study, we will screen approximately 200 patients to enroll 49 patients, and carboplatin (dosing at the area under curve=5) will be administered every 3 weeks until progression or intolerable side effects. The primary end point will be assessed as the proportion of patients with a reduction of serum prostate-specific antigen by more than 50% from enrollment. Secondary outcomes include progression-free survival-soft-tissue disease progression (by response evaluation criteria in solid tumors, version 1.1, and bone lesion progression using Prostate Cancer Clinical Trials Working Group 3 criteria), health-related quality of life during carboplatin treatment using the Functional Assessment of Cancer Therapy-Prostate questionnaire and the European Organisation for Research and Treatment of Cancer questionnaire and safety profile of carboplatin (National Cancer Institute's Common Terminology Criteria for Adverse Events version 5.0). The trial started enrollment in September 2023. This trial is ongoing, and 12 patients have been recruited to date. All 49 participants will be enrolled according to plan. This prospective phase II trial represents a critical step toward addressing the therapeutic gap in patients with mCRPC harboring HRR pathway mutations, particularly in demographic regions with limited access to poly (ADP-ribose) polymerase inhibitors. Outcomes from this study will inform clinical practice and guide future phase III randomized trials, ultimately improving patient outcomes globally. Clinical Trials Registry of India CTRI/2023/04/051507; https://ctri.nic.in/Clinicaltrials/pmaindet2.php?EncHid=Njc0NjU=&Enc=&userName=. DERR1-10.2196/54086.

Ovarian squamous cell carcinoma associated with teratoma: a report of six cases with genomic analysis

Ovarian squamous cell carcinoma (SCC), particularly the sarcomatoid variant, arising from teratoma is a rare malignant tumour with unfavourable clinical outcomes. Its molecular genetic alterations have not been well-documented to date. This study aims to characterise the molecular features and to provide potential therapeutic targets in this rare entity. We analysed the clinicopathological and immunohistochemical features of six primary ovarian SCC. These cases were subject to targeted next-generation sequencing to detect genomic features. We found that all six ovarian SCC (four conventional and two sarcomatoid SCC) were associated with mature cystic teratomas. Patient 3 (FIGO stage IIIa) and Patient 4 (stage IIb) died of disease at 10 and 11 months, respectively. The remaining patients (three with stage I and one with IIc) including the two with sarcomatoid SCC, were alive with no evidence of disease at 28-72 months. All patients showed PD-L1 expression (tumour proportion score: range 10-78%, median 41%; combined positive score: range 12-85, median 42) and a high tumour mutation burden (range 13.4-25.7 mutations/Mb, median 16.5). The most frequently recurrent mutations included PIK3CA (4/6), TP53 (4/6), TERT promoter (4/6), CDKN2A (3/6). Mutations in homologous recombination repair pathway genes (BLM, ATM, BRCA1, BRIP1 and ATM) were found in 5/6 patients. The sarcomatoid SCC shared a similar mutational profile with conventional SCC, and no recurrent genetic mutations exclusively in sarcomatoid SCC were identified. Our study suggests the potential benefits of immune checkpoint inhibitors and/or PARP inhibitors in patients with primary ovarian SCC on account of PD-L1 expression and genomic features. Ovarian sarcomatoid SCC may be clonally related to the conventional SCC. A multiple-institutional, clinical and molecular study will consolidate these findings in the future.

Genomic analyses of germline and somatic variation in high-grade serous ovarian cancer

BackgroundHigh-grade serous ovarian cancers (HGSCs) display a high degree of complex genetic alterations. In this study, we identified germline and somatic genetic alterations in HGSC and their association with relapse-free and overall survival. Using a targeted capture of 557 genes involved in DNA damage response and PI3K/AKT/mTOR pathways, we conducted next-generation sequencing of DNA from matched blood and tumor tissue from 71 HGSC participants. In addition, we performed the OncoScan assay on tumor DNA from 61 participants to examine somatic copy number alterations (SCNA).ResultsApproximately one-third of tumors had loss-of-function (LOF) germline (18/71, 25.4%) or somatic (7/71, 9.9%) variants in the DNA homologous recombination repair pathway genes BRCA1, BRCA2, CHEK2, MRE11A, BLM, and PALB2. LOF germline variants also were identified in other Fanconi anemia genes and in MAPK and PI3K/AKT/mTOR pathway genes. Most tumors harbored somatic TP53 variants (65/71, 91.5%). Using the OncoScan assay on tumor DNA from 61 participants, we identified focal homozygous deletions in BRCA1, BRCA2, MAP2K4, PTEN, RB1, SLX4, STK11, CREBBP, and NF1. In total, 38% (27/71) of HGSC patients harbored pathogenic variants in DNA homologous recombination repair genes. For patients with multiple tissues from the primary debulking or from multiple surgeries, the somatic mutations were maintained with few newly acquired point mutations suggesting that tumor evolution was not through somatic mutations. There was a significant association of LOF variants in homologous recombination repair pathway genes and high-amplitude somatic copy number alterations. Using GISTIC analysis, we identified NOTCH3, ZNF536, and PIK3R2 in these regions that were significantly associated with an increase in cancer recurrence and a reduction in overall survival.ConclusionsFrom 71 patients with HGCS, we performed targeted germline and tumor sequencing and provided a comprehensive analysis of these 557 genes. We identified germline and somatic genetic alterations including somatic copy number alterations and analyzed their associations with relapse-free and overall survival. This single-site long-term follow-up study provides additional information on genetic alterations related to occurrence and outcome of HGSC. Our findings suggest that targeted treatments based on both variant and SCNA profile potentially could improve relapse-free and overall survival.

Hereditary/Familial Ovarian Cancer: Testing Principles and Risk Management

Although BRCA1 and BRCA2 pathogenic or likely pathogenic variants are a well-established cause of hereditary ovarian cancer, recent studies have brought other homologous recombination repair pathway genes into the limelight. The current NCCN Guidelines reflect the most up-to-date, evidence-based data relating to the risk management of patients who are carriers of BRCA1/2 and/or other variants. Risk-reducing bilateral salpingo-oophorectomy is the current standard of care, but a recommendation for salpingectomy alone may be on the horizon.

Characteristics of homologous recombination repair pathway genes mutation in ovarian cancers.

Few studies have investigated the characteristics of non-BRCA homologous recombination repair (HRR) pathway somatic mutations, and the impact of these mutations on efficacy of treatment in ovarian cancer patients is not clear. Therefore, we conducted this study to analyze the frequency and spectrum of somatic mutations in HRR pathway genes in patients with ovarian cancer and to examine the relationships between somatic mutations in HRR pathway genes and their effects on the efficacy of platinum-based chemotherapy. We performed targeted sequencing of 688 genes related to the occurrence, development, treatment, and prognosis of solid tumors. Somatic mutations were identified by paired analysis of tumor tissue and germline DNA in blood cells. A total of 38 patients with ovarian cancer were included in the study, and 35 (92.1%) patients were diagnosed with high-grade serous carcinoma. All patients exhibited somatic mutations in the tumor tissue samples. The commonly mutated genes were TP53 (73.7%), BRCA2 (55.3%), NF1 (52.6%), BRCA1 (47.4%), and CDH1 (47.4%). Overall, 71.1% of the patients exhibited mutation in at least one HRR pathway gene. The most frequently altered HRR genes were BRCA2 (55.3%), followed by BRCA1 (47.4%), ATM (44.7%), BARD1 (42.1%), and CHEK1 (36.8%). The median progression-free survival (PFS) in patients with HRR pathway mutation was 36.0 months compared with 13.6 months in patients with no HRR pathway mutation (hazard ratio [HR], 0.25; 95% confidence interval [CI], 0.08-0.77; p = 0.016). Patients harboring BRCA1/2 and/or CDK12 mutations displayed a longer PFS (median, 36.0 months) compared with patients with no BRCA1/2 or CDK12 mutation (median, 13.6 months; HR, 0.21; 95% CI, 0.07-0.61; p = 0.004). In multivariate analysis Cox proportional hazards models, after adjustment for tumor stage at diagnosis and histology of initial diagnosis, patients with HRR pathway mutation had a longer PFS than patients with HRR wild-type genes (p = 0.006). HRR pathway somatic mutations are common in Chinese patients with ovarian cancer. HRR pathway somatic mutations were associated with improved sensitivity to platinum-based chemotherapy. Large-scale prospective studies are needed to verify our findings.

Emerging Role of PARP Inhibitors in Metastatic Prostate Cancer.

We highlight the clinical development of Poly (ADP-Ribose) polymerase (PARP) inhibitors in prostate cancer. Approximately 10 to 30% of metastatic prostate cancer patients carry germline or somatic mutations in DNA repair pathways. BRCA2 is the most commonly mutated gene in DNA damage repair pathways. Because of its critical function in homologous recombination repair (HRR) machinery, deleterious BRCA2 mutation enables synthetic lethality to a PARP inhibitor. Olaparib demonstrated clinical benefit in patients with deleterious mutations in HRR-related genes and most clearly in patients with BRCA2 mutations. Olaparib received the US FDA approval or mCRPC patients with a qualifying HRR gene mutation in May 2020. Rucaparib received an accelerated FDA approval for patients with BRCA1- or BRCA2-mutated mCRPC based on 43% objective response rate in a phase II study. To expand the application of a PARP inhibitor, several trials have evaluated various combination strategies with an androgen receptor signaling inhibitor, immunotherapy, radium-223, and others. While no PARP inhibitor combination regimen has been approved, promising data from a PARP inhibitor and an ASI combination have been reported. PARP inhibitor represents a standard treatment for patient with mCRPC with germline or somatic mutations in BRCA2 and other HRR pathway genes.

Abstract 5772: Differences in clinical actionability by comparing mutational landscape of young and old breast cancer patients

Abstract Background: Early-onset breast cancer (BC) is associated with poor prognosis, which is also characterized by high recurrence risk, distant metastases and advanced stages at the time of diagnosis. While germline mutations in BRCA1/2 are known to underlie a subset of early-onset BC cases, the clinical and genetic characteristics in other young BC patients remain to be explored. Method: We profiled primary lesions from 440 Chinese female BC patients by using a 425-cancer-gene panel. The population was sub-divided into young (≤40 years old) and old (>40 years old) BC patients according to ages at diagnosis. Young and old BC patients were compared for their associations with genomic aberrations, with focus on existing BC targetable alterations, including those in the ERBB2 gene and PI3K and homologous recombination repair (HRR) pathways. Results: 137 (31.1%) patients presented with BC at a young age (median age=35 [18-40]) and 303 (68.9%) with BC diagnosed at an older age (median age=53 [41-82]) in our study cohort. TP53 (young, 61.3%; old, 67%), PIK3CA (33.6% and 41.3%), and GATA3 (9.5% and 8.3%) were among the top frequently altered genes in both subgroups. A total of 70 patients carried pathogenic germline mutations. Of these, 57.3% were alterations in the HRR pathway genes, including BRCA1/2, WRN, BLM, and PALB2, etc, with comparable frequencies in young and old patients. Germline BRCA1/2 mutations were detected in nine (6.6%) and 23 (7.6%) of the young and old patients, respectively. Somatic BRCA1/2 mutational frequencies were also comparable between young (8.8%) and old (9.9%) patients. Overall, somatic alterations in HRR pathway genes were detected in 32.1% young and 40.6% old BC patients. While similar frequencies of ERBB2 amplification (14.6% vs. 18.2%; P= 0.41) were detected in young and old BC patients, older patients carried more ERBB2 mutations (1.5% vs. 7.3%, P= 0.01). Interestingly, the highest rate of ERBB2 amplification was observed in the 20-30 years age group. Alterations in NF1 (10.6% vs. 3.6%, P=0.02) and PKHD1 (6.9% vs. 2.2%, P=0.04) were more frequent in older patients. Alterations in the PI3K pathway genes were more enriched in the older BC patients with overall mutational frequencies of 55.5% and 68.6% (P=0.01) in young and old subgroups, respectively. Finally, we observed an age-dependent increase in tumor mutational burden. Conclusion: BC in young and old patients exhibited different genomic characteristics that could be taken into consideration for treatment recommendations. Citation Format: Jiaqi Liu, Ziqi Jia, Gang Liu, Xiang Wang, Qi Meng, Sha Wang, Yang Shao. Differences in clinical actionability by comparing mutational landscape of young and old breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5772.

Abstract 5690: The landscape of homologous recombination repair gene mutations and prognosis in Chinese patients with clear cell renal cell carcinoma

Abstract Background: Clear cell renal cell carcinoma (ccRCC) is the most common subtype of kidney cancer with poor prognosis. Mutations in homologous recombination repair (HRR) genes are associated with human tumorigenesis and response to DNA-damage-inducing therapeutics, such as platinum agents and PARP inhibitors. A better understanding of the genomic features of HRR pathway genes and its correlations with prognosis will facilitate precise personalized treatment selection. Methods: Tumor tissues and matched blood were collected from 269 ccRCC patients at the 3rd Affilated Teaching Hospital of Xinjiang Medical University(Affiliated Tumor Hospital) from 2011 to 2017. A panel targeting 450 cancer-related gene test was performed at OrigiMed (Shanghai, China). Using targeted capture genomic sequencing, we assessed patients for germline and somatic mutations in 23 HRR related genes. Survival analysis was performed using a Cox proportional hazards model and the p-value was determined with a log-rank test. Results: In total, 269 ccRCC patients, including 95 females and 174 males with a median age of 55 (range 21-87 years old), were recruited. Fifty patients developed distant metastases. The most frequently mutated genes were VHL (83%) and PBRM1 (38%). The median tumor mutational burden (TMB) of this cohort was 4 muts/Mb (0-43.9 muts/Mb), and 4.1% (11/269) of patients displayed high TMB (defined as ≥ 10 muts/Mb). HRR pathway gene mutations were detected in 90/269 patients (33.46%). The most frequently altered genes were BAP1(13.4%), ARID1A (5.2%), BRCA1 (3.72%), ATM (3.35%), and BRCA2 (1.86%). Truncation (23.05%) was the most common mutation type. 4.46% (12/269) of patients carried HRR-related germline mutations, and the most frequently mutated germline genes were RAD51C/D (33.33%,4/9) and BRCA (16.67%, 2/9). Patients with HRR pathway gene mutations were found to have a significantly higher TMB (median, 4.45 vs. 4 muts/Mb, p < 0. 05). We additionally identified that mutations in HRR pathways were significantly associated with decreased relapse-free survival (RFS)( p < 0.05). The 3-year RFS rate of the HRR-mutated group was significantly lower than the negative group (78.8% vs.90.6%, p<0.01). Conclusion: HRR gene alterations, associated with increased recurrence, occurred at a high frequency of 33.46% in Chinese ccRCC patients. Further studies regarding to therapeutic agents targeting the HRR pathway in this population should be considered in the future. Citation Format: Peng Chen, Yuan Zhang, Xing Bi, Yue Niu, Fuerhaiti Shayiti, Shuai Yuan, Ting Pan, Yan Wang. The landscape of homologous recombination repair gene mutations and prognosis in Chinese patients with clear cell renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5690.

The impact of HRD in patients with pancreatic adenocarcinoma undergoing surgical resection: An updated analysis.

4132 Background: Limited data is available regarding which mutations in the homologous recombination repair (HRR) pathway beyond BRCA can be targeted with platinum-based chemotherapy in the perioperative setting in patients with pancreatic ductal adenocarcinoma (PDAC). In this updated analysis, we assess the outcome of patients with homologous recombination deficiency (HRD) in response to platinum vs. non-platinum based perioperative chemotherapy in resected PDAC and have included additional variants linked to HRD. Methods: Patients with resectable PDAC, diagnosed between 1999-2020 from the participating members of the Oncology Research Information Exchange Network (ORIEN) were included in the study. Patient’s germline and somatic whole exome sequencing (WES) data were analyzed for known pathogenic and likely pathogenic variants according to ClinVar for the following HRR pathway genes: BRCA1, BRCA2, PALB2, BRIP1, BRAD1, BLM, BAP1, ATM, RAD51C, RAD51, RAD50, RAD54B, CHECK2, NBN, FANCA/B/C/D2/E/F/G, ARID1A, MRE11 and XRCC2. The Kaplan Meier method was used to compare median overall survival (mOS) between patients with and without HRR pathway mutations in response to perioperative platinum vs non-platinum-based chemotherapy. Multivariate cox proportional hazard model was used to calculate HR and 95% CIs adjusting for age, sex and pathologic stage. Results: The ORIEN cohort included 311 patients with resectable PDAC and available WES data. A total of 22 patients (7%) had an HRR pathway mutation. Of these, 8 (36%) received perioperative platinum-based chemotherapy and 9 (41%) a non-platinum based regimen, 4 patients (23%) received no perioperative systemic treatment. Frequency of HRR variants detected: BRCA2 n=8 (2.6%), BRCA1 n=3 (1%), ATM n=2 (0.6%), ARID1A n=1 (0.3%), BRIP1 n=1 (0.3%), CHECK2 n=1 (0.3%), FANCG n=1 (0.3%), PALPB2 n=1 (0.3%), RAD50 n=4 (1.3%), RAD51C n=1 (0.3%). The mOS for patients with HRR mutations exposed to perioperative platinum-based chemotherapy was 3.5 years (95% CI 3.4-NA), patients with HRR mutation but no platinum exposure had a mOS of 1.2 years (CI 0.9-NA). In patients with no HRR mutation exposed to platinum-based chemotherapy mOS was 2.7 years (CI 2.3-3.9) and in those without exposure mOS was 2.9 years, p=0.43. Comparison of risk of death between the 4 groups is demonstrated in the table. Conclusions: There was a trend towards improved survival in patients with PDAC who harbored a HRR pathway mutation and were treated with perioperative platinum-based chemotherapy compared to those with no platinum exposure. Our results highlight the importance of identifying patients with HRD beyond BRCA and the need for large prospective studies in the perioperative setting to further assess their predictive role. [Table: see text]

2. Analytical tools to support detection of homologous recombination deficiency (HRD) using cytogenomic scar markers

Homologous Recombination Deficiency (HRD) has been shown to be an effective pharmacogenetic biomarker for determining the efficacy of PARP inhibitor therapy across various tumor types. There is continued research on the best approach to measure HRD status including assessments of sequence variants of homologous recombination repair pathway genes and consequential patterns of genomic instability. Recent technological advancements have enabled for more robust measurement of the cytogenomic aberrations associated with genomic instability emphasizing the importance of its analysis for HRD.

Heart toxicity effects (HTE) of anthracyclines-containing regimens (ACRs) in patients with breast cancer (BC) carrying mutational signature of homologous recombination deficiency (HRD).

10519 Background: BRCA1/2 genes ( BRCA) play a prominent role in the Homologous Recombination Repair (HRR) pathway. Following the technological progress and deeper knowledge on BRCA-related cancers, the demand for genetic testing is rapidly increasing. Beyond BRCA1/2, other genes are involved in the HRR, including ATM, PALB2, RAD51, and BARD1. Due to the important role in the cellular repair process, deleterious variants in HRR genes may cause inadequate DNA damage repair in cardiomyocytes. The role of BRCA1/2 as predisposing condition to cardiac dysfunction is debated, and the contribution by no- BRCA genes is still unknown. Methods: This is a multicenter, retrospective, study to investigate the risk of heart-insults from anthracyclines on adjuvant setting in BC patients carrying germline pathogenic or likely pathogenic variant (PV) (classes IV and V) in BRCA and no- BRCA HRR pathway genes. We collected genetic and clinical data, and evaluated the left ventricular ejection fraction (LVEF) at cardiac ultrasound, before starting ACR therapy, and at subsequent time points, according to clinical indications. Results: Three hundred and sixty (360) BC patients, aging 22 to 80, were included in this study; 131 patients were carriers of germline PVs in HRR pathway genes: 52 in BRCA1 gene (39.7%), 48 in BRCA2 gene (36.6%), and 31 harbored PVs in no- BRCA HRR pathway genes (23.7%), including PVs in PALB2, CHEK2, ATM, RAD51C, RAD50 and BARD1 genes. In the cohort of 229 patients without PVs, 47 showed variant of uncertain significance (VUS, class III), and 173 had genetic testing not informative. When LVEF between the groups was compared, the difference was not significant for the pre-treatment values. Notably, individuals carrying BRCA or other HRR gene deleterious variants, showed a statistically significant reduction of LVEF > 5% at the second time-point (3 month), compared to the LVEF pre-treatment values (p = 0.001). A marked LVEF reduction was in mutated patients treated with risk-reducing bilateral salpingo-oophorectomy prior to age 40, body mass index > 25, and type-II diabetes mellitus. The latter risk factor was probably related to increased risk developing insulin-resistance reported for BRCA-mutated patients. Conclusions: Our data suggest that PVs in BRCA or other genes involved in HRR pathway, can lead to impaired homologous recombination, thus increasing sensitivity of cardiac cells to DNA damaging chemotherapy in BC patients. In this subgroup of patients, other measurements such as the global longitudinal strain (GLS), and a more in-depth assessment of risk factors, could be proposed to optimize cardiovascular risk-management and to improve long-term survival.

Application of next-generation sequencing in detection of BRCA1/2 and homologous recombination repair pathway multi-genes germline mutation and correlation analysis

Objective: To investigate the germline mutation status of related genes in breast cancer patients and high-risk individuals by next-generation sequencing. To analyze the correlations between homologous recombination repair (HR) pathway gene mutation status and clinicopathological characteristics of breast cancer patients. To supplement the database of breast cancer related gene mutations in Chinese population. Methods: This study is a cross-sectional study. From October 2020 to September 2021, whole blood samples were collected from 350 breast cancer patients and 49 high-risk individuals, admitted to Peking University People's Hospital and accepted genetic testing voluntarily. Germline mutations in 32 breast cancer related genes were detected by NGS. The clinicopathological characteristics, including age at the onset, family history, unilateral/bilateral tumor, Luminal typing (Luminal A subtype, Luminal B subtype, HER2-enriched subtype and triple negative breast cancer), tumor size and metastasis, were analyzed, and the correlations between HR pathway gene mutation status and clinicopathological characteristics were analyzed by Chi-squared test and Fisher's exact probability test. Results: Among 350 breast cancer patients, 64 (18.3%) cases carried gene pathogenic mutations (including pathogenic and likely pathogenic mutations), including 47 (13.4%) in BRCA1/2, 16 (4.6%) in non-BRCA1/2 genes, 1 (0.3%) in BRCA2 and FANCL. Among 49 high-risk individuals, 7 (14.3%) cases carried gene pathogenic mutations, including 6 (12.3%) in BRCA1/2 and 1 (2%) in ATM genes. BRCA1/2 pathogenic mutations were associated with age at the onset (18%, 8.7%, χ²=6.346, P=0.012), and the BRCA1/2 pathogenic mutation frequency was higher in patients diagnosed at age ≤45 years. HR pathway gene mutations (including pathogenic, likely pathogenic and uncertain significance mutations) were correlated with unilateral/bilateral tumor (49.5%, 68.4%, χ²=4.841, P=0.028) and Luminal typing (45.7%, 62.2%, 32%, 60%, χ²=12.004, P=0.007), and the HR mutation frequencies were higher in patients with bilateral tumor, Luminal B breast cancer and triple negative breast cancer (TNBC). Conclusion: The BRCA1/2 pathogenic mutation frequency in high-risk individuals is similar to that in breast cancer patients, and BRCA1/2 testing is helpful to guide breast cancer screening and prevention in high-risk individuals. Patients with early onset breast cancer, bilateral breast cancer, Luminal B breast cancer and TNBC have higher mutation frequencies of HR pathway genes, and HR pathway genes testing should be conducted as soon as possible to provide laboratory evidence for diagnosis, treatment, prognosis and risk evaluation of breast cancer.

Interrelation of functional homologous recombination deficiency and hrr pathway alterations in prostate cancer.

151 Background: The use of PARP inhibitors (PARPi) may trigger synthetic lethality of tumor cells in the context of deficient homologous recombination repair (HRR). Approximately 10-20% of patients with prostate cancer harbor mutations in the HRR pathway, but HRR-associated mutations do not consistently predict the response to PARPi. Considering alternative methods to define Homologous Recombination Deficiency (HRD)—the inability to repair double strand breaks—may aid in identifying additional tumors that are sensitive to PARPi. Here, we evaluate the relationship between HRD status and HRR mutations amongst a large cohort of patients with prostate cancer. Methods: Retrospective analysis of 1,022 de-identified patients with prostate cancer that underwent next generation sequencing (NGS) with the Tempus|xT assay (DNA-seq of 648 genes at 500x coverage, whole-exome capture RNA-seq) was performed. Comparison groups were defined based on HRR alterations—either mono- or bi-allelic alterations of BRCA1 or BRCA2 ( BRCA1/2), ATM, or other HRR pathway genes. HRD status was determined via the Tempus RNA-based HRD algorithm. Results: Among this cohort, mono (-/+) or biallelic (-/-) alterations of HRR genes were found in 432 patients: BRCA1/2 -/- (n = 31), BRCA1/2 -/+ (n = 87), ATM-/- (n = 24), ATM-/+ (n = 67), other HRR-/- (n = 54), other HRR-/+ (n = 169) or no HRR alterations (n = 590). The BRCA1/2-/- group had a higher frequency of Asians (17% vs. < 7% in all other groups) and were diagnosed at younger ages (median 62 years vs. > 65 for all other groups). We identified 130/1022 (13%) patients with prostate cancer to be HRD-positive (HRD+) and observed significant differences in HRD positivity according to the type of HRR alteration observed (Table). Notably, 54% (70/130) of HRD+ patients had no mutations in any genes associated with the HRR pathway. Conversely, 89% (278/314) of patients with non- BRCA1/2 HRR mutations were HRD negative. Amongst all individuals with biallelic loss of any HRR gene, HRD positivity was most enriched for BRCA2-/- (16/29, p < 0.001) and PALB2-/- (3/4, p = 0.082). Conclusions: By using an RNA-based HRD algorithm, we found 13% of patients with prostate cancer are HRD+. This RNA-based HRD signature not only captures patients with HRR mutations but also identifies a substantial population of HRD+ patients who are currently undetectable by methods based solely on sequencing HRR genes. Further research is needed to assess the clinical response to PARPi in this HRD+ population, as well as the response to PARPi in the HRD negative population who harbor HRR gene alterations.[Table: see text]

Homologous recombination repair pathway alterations and their relationship to homologous recombination deficiency in advanced pancreatic cancer patients.

609 Background: Homologous recombination repair (HRR) is critical for limiting DNA damage arising from double strand breaks. Disrupting HRR has emerged as a therapeutic strategy in pancreatic cancer given the development of PARP inhibitors that can specifically target tumors with homologous recombination deficiency (HRD). While HRD is strongly associated with loss-of-function mutations in BRCA1/2, a broad range of pathogenic alterations have been identified in other HRR genes. Identification of pathogenic alterations that predict response to PARP inhibition remains a critical knowledge gap in the field. Methods: We retrospectively analyzed de-identified records from 895 patients with advanced pancreatic cancer that underwent next generation sequencing (NGS) with the Tempus|xT assay (DNA-seq of 648 genes at 500x coverage, matched normal, full transcriptome RNA-seq). HRD-positivity and genome-wide loss of heterozygosity (LOH) were compared across groups, which were defined based on alterations to BRCA1/2 or other HRR pathway genes. Results: We identified 293/895 (33%) pancreatic cancer patients to be HRD-positive. Among HRD positive patients, 23/895 (2.6%) tumors harbored two alterations in BRCA1/2 (BRCA++), 179/895 (20%) harbored a single alteration in BRCA1/2 (BRCA+), 25/895 (2.8%) harbored two alterations in at least one other non-BRCA HRR gene (other HRR++), 367/895 (41%) harbored a single alteration in one other HRR gene (other HRR+), and 143/895 (16%) had pathogenic alterations in neither BRCA1/2 nor other HRR genes. In terms of HRD status, 23/23 (100%) of BRCA++ cases, 179/337 (53%) of BRCA+ cases, 4/25 (16%) of other HRR++ cases, and 87/367 (24%) of other HRR+ cases were HRD-positive. We observed no cases that were HRD-positive without an alteration in either BRCA1/2 or other HRR gene. Within the other HRR+ group, we found that single alterations in CHEK1/2, FANCA/L, MRE11, PALB2, and RAD51B were all significantly associated with HRD-positivity whereas CDK12, for instance, was not (Table). Conclusions: Comprehensive genomic profiling demonstrates that approximately 1 in 4 patients without BRCA alterations may potentially benefit from PARP inhibition due to alterations in other HRR genes. Future studies may examine the role of PARP inhibition in this population of HRR+ pancreatic cancer patients.[Table: see text]

The impact of germline and somatic mutations in the homologous recombination repair pathway in pancreatic cancer patients who undergo perioperative chemotherapy.

602 Background: Limited data is available regarding the effects of germline and somatic mutations in the homologous recombination repair (HRR) pathway in patients with resectable pancreatic cancer and exactly which mutations can be targeted with platinum-based chemotherapy. We aimed to assess the impact of HRR pathway mutations in a large cohort of pancreatic patients who underwent curative intent surgical resection. Methods: Patients with resectable pancreatic cancer who underwent perioperative chemotherapy, diagnosed from 1999-2020 from the participating members of the Oncology Research Information Exchange Network (ORIEN) were included in the study. Patients with germline and somatic whole exome sequencing data were analyzed for known pathogenic and likely pathogenic variants according to ClinVar in the following HRR pathway genes: BRCA1, BRCA2, PALB2, BRIP1, BRAD1, ATM, RAD51C, RAD51, RAD50, CHECK2, FANCC, FANCA, MRE11 and XRCC2. The Kaplan Meier method was used to compare median overall survival (OS) between patients with adenocarcinoma, with and without HRR pathway mutations. Multivariate cox proportional hazard model was used to calculate HR and 95% CI adjusting for age at diagnosis, sex and pathologic stage. Results: During the study period, the ORIEN cohort included 417 patients with resectable pancreatic cancer and whole exome sequencing. Of these 313 (75%) patients had adenocarcinoma and 104 (25%) neuroendocrine tumor. A total of 19 patients (5%) had an HRR pathway mutation - 15 (5%) in the adenocarcinoma group and 4 (4%) in the neuroendocrine group. In the adenocarcinoma group, 97 (31%) patients underwent platinum-based perioperative chemotherapy. Median OS was 2.8 years (IQR 2.5-3.3) in the adenocarcinoma group without HRR pathway mutation and 3.8 years (IQR 3.4-NA) in the group with HRR pathway mutation (HR 0.6: 95% CI 0.3-1.4, p = 0.76). Conclusions: There was a trend towards improved survival in patients with adenocarcinoma receiving perioperative platinum-based chemotherapy with HRR pathway mutations compared to those without a mutation. This finding supports previous data in the literature regarding the prognostic role of HRR pathway alterations in pancreatic cancer. Larger prospective studies are needed to assess the predictive role of these mutations in the perioperative setting in response to platinum-based chemotherapy.

Precision Oncology of High-Grade Ovarian Cancer Defined through Targeted Sequencing.

Simple SummaryOvarian cancer is a rare and deadly gynaecologic cancer, with a relatively large hereditary component. Genomic analysis of tumour material can potentially provide information regarding therapy and identify hereditary carriers and their families. The aim of our prospective study was to apply genomic characterization to tumour material from women with ovarian cancer to identify women that might benefit from PARP inhibitor therapy, as well as to detect and triage women to genetic counselling. We used next generation sequencing using a targeted panel to prospectively analyse 274 tumours and identified 50 with a BRCA1/2 pathogenic variant. Twenty patients received olaparib based on these results, and 16 previously unknown hereditary carriers were identified. In addition, in a subset examined by an extended sequencing panel, actionable mutations were found in 84/88 tumours. This study demonstrates that personalized medicine approaches can be useful for women with ovarian cancer and can help with therapy selection and identification of at risk families. Background: We examined whether molecular characterization of high-grade epithelial ovarian cancer can inform the diagnosis and/or identify potential actionable targets. Methods: All of the consecutively sequenced high-grade ovarian tumours with consent between 2014 until 2019 were included. A total of 274 tumours underwent next generation sequencing using a targeted panel. Results: Patients with high-grade ovarian epithelial cancer were consented to prospective molecular characterization. Clinical information was extracted from their medical record. Tumour DNA was subjected to sequencing, and selected patients received PARP inhibitor therapy. Conclusions: Tumours from 274 women were sequenced, including high-grade serous carcinoma (n = 252), clear cell carcinoma (n = 4), carcinosarcoma (n = 9), endometrioid carcinoma (n = 3), undifferentiated carcinoma (n = 1), and mixed tumours (n = 5). Genomic profiling did not influence histologic diagnosis. Mutations were identified in TP53, BRCA1, BRCA2, as well as additional homologous recombination repair pathway genes BARD1, ATR, CHEK2, PALB2, RAD51D, RAD50, SLX4, FANCA, RAD51C, and RAD54L. In addition, mutations in PTEN and CDKN2A were identified. Several somatic mutations with implications for germline testing were identified, including RMI1, STK11, and CDH1. Germline testing identified 16 previously unknown BRCA1/2 carriers. Finally, 20 patients were treated with the PARP inhibitor olaparib based on the sequencing results.

Pilot experience using tumor-based next generation sequencing increases compliance and reduces barriers for ovarian cancer genetic testing

<h3>Objectives:</h3> Although hereditary risk assessment is advised for all ovarian/tubal/peritoneal (OTP) cancer patients, a variety of barriers limit universal compliance. A workflow using tumor-based next generation sequencing (NGS) germline testing implemented by the pathologist at the time of primary or interval debulking surgery. The objective of this study is to report compliance and turnaround time of a pilot workflow of germline testing via tumor-based NGS in OTP cancer. may reduce some of these barriers. <h3>Methods:</h3> We identified all patients with a new diagnosis of epithelial OTP carcinoma who underwent primary or interval debulking surgery from January to August 2020. All patients were recommended to undergo tumor and germline sequencing, either through our institutional NGS platform or through commercial sequencing. We compared time to results as well as influence of results on maintenance/second-line therapy. <h3>Results:</h3> We identified 35 patients with a median age of 61 (range 29-78) and a median follow-up time of 5 months (range 0-13). Our stage breakdown included 8 Stage I, 4 Stage II, 20 Stage III, and 3 Stage IV patients. A total of 24 patients had high grade serous carcinoma, with 5 endometrioid, 3 clear cell, 2 mucinous, and one high grade NOS tumor. A total of 11 patients underwent interval debulking surgery after neoadjuvant chemotherapy. All but 2 (94.2%) of patients received a genetic counseling referral. A total of 2 patients did not have sequencing performed, while 1 patient did not have enough tumor for sequencing at the time of interval debulking surgery. A total of 10 patients had both tumor and germline sequencing performed at the time of tumor testing, while 20 others had tumor only sequencing. For those patients who did not have a known hereditary germline mutation prior to surgery, the mean turnaround time for germline genetic testing results was 26.5 days (range 19-51) in the NGS + germline group whereas the median turnaround time after commercial testing was 75 days (regardless of primary or interval debulking, range 19-202), p=0.006. A total of 5 patients were identified as germline carriers of the <i>BRCA1</i> or <i>BRCA2</i> mutation, with 1 addition germline finding of a pathogenic variant in ATM. An additional 5 patients had somatic pathogenic mutations in homologous recombination repair pathway genes, all of whom are receiving or being considered for PARP inhibitor maintenance after primary treatment. <h3>Conclusions:</h3> Combining somatic and germline tumor testing at the time of staging/debulking surgery requires upfront coordination with pathology and patient consent, but streamlines the genetic testing process to improve testing rates allow timely results for treatment planning. This approach may also identify additional patients with homologous recombination deficient tumors through simultaneous somatic mutation assessment.