Mutations In DNA Repair Genes Research Articles

A Prospective Phase II Single-arm Study of Niraparib Plus Dostarlimab in Patients With Advanced Non–small-cell Lung Cancer and/or Malignant Pleural Mesothelioma, Positive for PD-L1 Expression and Germline or Somatic Mutations in the DNA Repair Genes: Rationale and Study Design

Treatment with poly ADP ribose polymerase (PARP)1/2 inhibitors represents a novel opportunity to selectively kill a subset of cancer cell types by exploiting their deficiencies in DNA repair, thus leading to synthetic lethality. Treatment of homologous recombination deficient (HRD)-tumors with PARP inhibitors generates significant levels of DNA damage, which has the potential to further increasing tumor mutational burden, promoting neoantigen release, and upregulating both interferons and programmed death ligand-1 (PD-L1) expression, suggesting a potential complementary and synergistic role with immune checkpoint inhibitors in cancer treatment. Here we present the design and rationale of a prospective, phase II, single-arm study aiming to investigate the safety and antitumor activity of the combination of niraparib and dostarlimab in patients with HRD-positive and PD-L1 ≥ 1% advanced non–small-cell lung cancer (NSCLC) and/or malignant pleural mesothelioma (MPM).Considering the prevalence of pathogenetic germline mutations in DNA repair genes, reported to be around 5% to 10% in patients with MPM and NSCLC, a total of 700 to 1000 cases will be screened to identify 70 patients who are HRD-positive/PD-L1 ≥ 1% (N = 35 NSCLC; N = 35 MPM) to be included. Patients will receive the combination of niraparib orally once daily and dostarlimab intravenously. The primary endpoint is progression-free survival. Secondary endpoints are objective response, duration of response, overall survival, and safety.The results of this study will provide evidence on the safety and antitumor activity of niraparib and dostarlimab combination in patients with advanced, HRD-positive and PD-L1 ≥ 1% NSCLC and/or MPM.

Impact of DNA Damage Response and Repair (DDR) Gene Mutations on Efficacy of PD-(L)1 Immune Checkpoint Inhibition in Non-Small Cell Lung Cancer.

DNA damage response and repair (DDR) gene alterations are associated with increased tumor-infiltrating lymphocytes, higher genomic instability, and higher tumor mutational burden (TMB) in cancer. Whether DDR alterations are associated with clinical outcomes to programmed death ligand 1 [PD-(L)1] blockade in non-small cell lung cancer (NSCLC) is unknown. Tumors from patients treated with PD-(L)1 inhibitors were analyzed using targeted next-generation sequencing (NGS). Cancers were categorized on the basis of the presence or absence of deleterious mutations across a panel of 53 DDR genes. Clinical outcomes to PD-(L)1 inhibitors were evaluated according to DDR mutation status. Of 266 patients with successful NGS who received PD-(L)1 inhibitors, 132 (49.6%) were identified as having deleterious DDR mutations (DDR-positive). DDR-positive and DDR-negative groups were similar in terms of baseline clinicopathologic characteristics. The median TMB was significantly higher in the DDR-positive group compared with the DDR-negative group (12.1 vs. 7.6 mutations/megabase; P < 0.001). Compared with DDR-negative patients (N = 134), DDR-positive patients had a significantly higher objective response rate (30.3% vs. 17.2%; P = 0.01), longer median progression-free survival [PFS; 5.4 vs. 2.2 months; HR, 0.58 (95% confidence interval (CI), 0.45-0.76); P < 0.001], and longer median overall survival [OS; 18.8 vs. 9.9 months; HR, 0.57 (95% CI, 0.42-0.77); P < 0.001] with PD-(L)1 therapy. After adjusting for PD-L1, TMB, performance status, tobacco use, and line of therapy, DDR-positive status was associated with a significantly longer PFS [HR, 0.68 (95% CI, 0.51-0.92); P = 0.01] and OS [HR, 0.60 (95% CI, 0.43-0.85); P = 0.004] in multivariate analysis. Deleterious DDR mutations are frequent in NSCLC and are associated with improved clinical outcomes in patients with NSCLC treated with PD-(L)1 blockade.

Checkpoint adaptation in recombination-deficient cells drives aneuploidy and resistance to genotoxic agents

Human cancers frequently harbour mutations in DNA repair genes, rendering the use of DNA damaging agents as an effective therapeutic intervention. As therapy-resistant cells often arise, it is important to better understand the molecular pathways that drive resistance in order to facilitate the eventual targeting of such processes. We employ recombination-defective diploid yeast as a model to demonstrate that, in response to genotoxic challenges, nearly all cells eventually undergo checkpoint adaptation, resulting in the generation of aneuploid cells with whole chromosome losses that have acquired resistance to the initial genotoxic challenge. We demonstrate that adaptation inhibition, either pharmacologically, or genetically, drastically reduces the occurrence of resistant cells. Additionally, the aneuploid phenotypes of the resistant cells can be specifically targeted to induce cytotoxicity. We provide evidence that TORC1 inhibition with rapamycin, in combination with DNA damaging agents, can prevent both checkpoint adaptation and the continued growth of aneuploid resistant cells.

Yeast-based assays for the functional characterization of cancer-associated variants of human DNA repair genes.

Technological advances are continuously revealing new genetic variants that are often difficult to interpret. As one of the most genetically tractable model organisms, yeast can have a central role in determining the consequences of human genetic variation. DNA repair gene mutations are associated with many types of cancers, therefore the evaluation of the functional impact of these mutations is crucial for risk assessment and for determining therapeutic strategies. Owing to the evolutionary conservation of DNA repair pathways between human cells and the yeast Saccharomyces cerevisiae, several functional assays have been developed. Here, we describe assays for variants of human genes belonging to the major DNA repair pathways divided in functional assays for human genes with yeast orthologues and human genes lacking a yeast orthologue. Human genes with orthologues can be studied by introducing the correspondent human mutations directly in the yeast gene or expressing the human gene carrying the mutations; while the only possible approach for human genes without a yeast orthologue is the heterologous expression. The common principle of these approaches is that the mutated gene determines a phenotypic alteration that can vary according to the gene studied and the domain of the protein. Here, we show how the versatility of yeast can help in classifying cancer-associated variants.

1128 - Prognostic value of germline DNA repair gene mutations in de novo metastatic and treatment-naïve prostate cancer

1128 - Prognostic value of germline DNA repair gene mutations in de novo metastatic and treatment-naïve prostate cancer

DNA Repair and Ovarian Carcinogenesis: Impact on Risk, Prognosis and Therapy Outcome.

There is ample evidence for the essential involvement of DNA repair and DNA damage response in the onset of solid malignancies, including ovarian cancer. Indeed, high-penetrance germline mutations in DNA repair genes are important players in familial cancers: BRCA1, BRCA2 mutations or mismatch repair, and polymerase deficiency in colorectal, breast, and ovarian cancers. Recently, some molecular hallmarks (e.g., TP53, KRAS, BRAF, RAD51C/D or PTEN mutations) of ovarian carcinomas were identified. The manuscript overviews the role of DNA repair machinery in ovarian cancer, its risk, prognosis, and therapy outcome. We have attempted to expose molecular hallmarks of ovarian cancer with a focus on DNA repair system and scrutinized genetic, epigenetic, functional, and protein alterations in individual DNA repair pathways (homologous recombination, non-homologous end-joining, DNA mismatch repair, base- and nucleotide-excision repair, and direct repair). We suggest that lack of knowledge particularly in non-homologous end joining repair pathway and the interplay between DNA repair pathways needs to be confronted. The most important genes of the DNA repair system are emphasized and their targeting in ovarian cancer will deserve further attention. The function of those genes, as well as the functional status of the entire DNA repair pathways, should be investigated in detail in the near future.

Pathogenic Germline Mutations in DNA Repair Genes in Combination With Cancer Treatment Exposures and Risk of Subsequent Neoplasms Among Long-Term Survivors of Childhood Cancer.

To investigate cancer treatment plus pathogenic germline mutations (PGMs) in DNA repair genes (DRGs) for identification of childhood cancer survivors at increased risk of subsequent neoplasms (SNs). Whole-genome sequencing was performed on blood-derived DNA from survivors in the St Jude Lifetime Cohort. PGMs were evaluated in 127 genes from 6 major DNA repair pathways. Cumulative doses of chemotherapy and body region-specific radiotherapy (RT) were abstracted from medical records. Relative rates (RRs) and 95% CIs of SNs by mutation status were estimated using multivariable piecewise exponential models. Of 4,402 survivors, 495 (11.2%) developed 1,269 SNs. We identified 538 PGMs in 98 DRGs (POLG, MUTYH, ERCC2, and BRCA2, among others) in 508 (11.5%) survivors. Mutations in homologous recombination (HR) genes were significantly associated with an increased rate of subsequent female breast cancer (RR, 3.7; 95% CI, 1.8 to 7.7), especially among survivors with chest RT ≥ 20 Gy (RR, 4.4; 95% CI, 1.6 to 12.4), or with a cumulative dose of anthracyclines in the second or third tertile (RR, 4.4; 95% CI, 1.7 to 11.4). Mutations in HR genes were also associated with an increased rate of subsequent sarcoma among those who received alkylating agent doses in the third tertile (RR, 14.9; 95% CI, 4.0 to 38.0). Mutations in nucleotide excision repair genes were associated with subsequent thyroid cancer for those treated with neck RT ≥ 30 Gy (RR, 12.9; 95% CI, 1.6 to 46.6) with marginal statistical significance. Our study provides novel insights regarding the contribution of genetics, in combination with known treatment-related risks, for the development of SNs. These findings have the potential to facilitate identification of high-risk survivors who may benefit from genetic counseling and/or testing of DRGs, which may further inform personalized cancer surveillance and prevention strategies.

Abstract A18: Plasma circulating tumor DNA is scarce and confounded by clonal hematopoiesis in metastatic renal cell carcinoma

Abstract Despite the recent implementation of novel targeted therapies, the 5-year survival rate for metastatic renal cell carcinoma (mRCC) remains dismal. Prognostic and predictive biomarkers are urgently required to avoid unnecessary patient morbidity and financial toxicity. Exploratory studies leveraging archival primary tumor tissue are considered suboptimal in this setting due to the considerable heterogeneity of metastatic lesions. Circulating tumor DNA (ctDNA) permits the noninvasive characterization of metastatic cancers using a simple blood draw. In this study, we sought to establish the utility of a ctDNA-based assay as a tool to profile the somatic genome of patients with mRCC. We collected whole blood from 55 progressing mRCC patients. All patients were systemic therapy naïve at the time of sample collection. Plasma cell-free DNA (cfDNA) and matched leukocyte DNA were subjected to targeted sequencing across 981 cancer-associated genes. Matched tumor tissue from 14 patients was also analyzed. The median cfDNA sequencing depth for this cohort was 938x. 33% of patients had evidence for RCC-derived ctDNA above 1% of total cfDNA; this was significantly lower than prostate or bladder cancer patients analyzed using the same approach. Among ctDNA-positive patients, ctDNA fraction averaged only 3.9% and showed no association with clinical variables or cfDNA yield. In these patients, the most commonly mutated genes were VHL, BAP1, and PBRM1, and matched tissue concordance was 77%. Evidence of somatic expansions unrelated to RCC, such as clonal hematopoiesis of indeterminate potential (CHIP), was detected in 43% of patients. Pathogenic germline mutations in DNA repair genes were detected in 11% of patients. Patients with ctDNA above 1% had shorter overall survival and progression-free survival on first-line therapy. Patients with evidence of CHIP but not ctDNA had an intermediate prognosis compared to ctDNA-positive and ctDNA-negative patients. CfDNA sequencing enables characterization of the somatic RCC genome in only a minority of metastatic RCC patients. Due to low ctDNA abundance and presence of non-RCC derived somatic clones in circulation, cfDNA sequencing may not be a simple pan-patient alternative to tissue biopsy in metastatic RCC. Citation Format: Jack V. W. Bacon, Matti Annala, Maryam Soleimani, Jean-Michel Lavoie, Alan I. So, Martin E. Gleave, Ladan Fazli, Kim N. Chi, Christian K. Kollmannsberger, Alexander W. Wyatt, Lucia Nappi. Plasma circulating tumor DNA is scarce and confounded by clonal hematopoiesis in metastatic renal cell carcinoma [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr A18.

DNA Repair Gene Mutations as Predictors of Immune Checkpoint Inhibitor Response beyond Tumor Mutation Burden

SummaryImmune checkpoint inhibitors (ICIs) have revolutionized cancer therapy, but prediction of their benefit is challenging. Neoantigens generated through impaired non-mismatch DNA repair may result in greater ICI activity. By analyzing 1,661 ICI-treated patients, we show that deletions and mutations in nucleotide excision repair (NER) and homologous repair (HR) pathways are predictors of ICI benefit independent of tumor mutation burden and tumor type. NER and HR mutations are also associated with objective response rates to ICIs in esophagogastric and non-small-cell lung cancers. In a cohort of 40,181 unique patients, NER and HR mutations are present in 3.4% and 13.9% of cancers, respectively. These results indicate that NER and HR gene mutations occur in a subpopulation of cancer patients and may aid patient selection for ICI therapy. Assessing NER and HR mutations in the context of other biomarkers may yield powerful predictors of ICI activity across different cancer types.

MutSα deficiency increases tolerance to DNA damage in yeast lacking postreplication repair

By combining mutations in DNA repair genes, important and unexpected interactions between different repair pathways can be discovered. In this study, we identified a novel link between mismatch repair (MMR) genes and postreplication repair (PRR) in Saccharomyces cerevisiae. Strains lacking Rad5 (HLTF in mammals), a protein important for restarting stalled replication forks in the error-free PRR pathway, were supersensitive to the DNA methylating agent methyl methanesulfonate (MMS). Deletion of the mismatch repair genes, MSH2 or MSH6, which together constitutes the MutSα complex, partially suppressed the MMS super-sensitivity of the rad5Δ strain. Deletion of MSH2 also suppressed the MMS sensitivity of mms2Δ, which acts together with Rad5 in error-free PRR. However, inactivating the mismatch repair genes MSH3 and MLH1 did not suppress rad5Δ, showing that the suppression was specific for disabling MutSα. The partial suppression did not require translesion DNA synthesis (REV1, REV3 or RAD30), base excision repair (MAG1) or homologous recombination (RAD51). Instead, the underlying mechanism was dependent on RAD52 while independent of established pathways involving RAD52, like single-strand annealing and break-induced replication. We propose a Rad5- and Rad51-independent template switch pathway, capable of compensating for the loss of the error-free template-switch subpathway of postreplication repair, triggered by the loss of MutSα.

Germline mutations in DNA repair genes in a large series of unselected Chinese prostate cancer patients.

e17523 Background: Germline DNA repair gene (DRG) mutations has emerged as a potential determinant of cancer risk and therapeutic response in PCa. Despite substantial advances in delineating the germline mutation in DRGs among Caucasian population, the prevalence of mutations in DRGs are largely unknown among a large series of unselected prostate cancer patients in Chinese population. Methods: We enrolled 1003 prostate cancer patients from three different hospitals in China, unselected for family history of cancer or age at diagnosis. All patients received germline genetic testing using a clinician-selected multi-gene panel. The 18 DNA repair genes and HOXB13, which has established or emerging potential clinical actionability in PCa, were analyzed in our study. Results: A total of 94 (9.7%) deleterious germline mutations were identified among the 1003 unselected prostate cancer patients. Of these, 5.6% patients carried a BRCA1 or BRCA2 mutations (5.2% in BRCA2 and 0.4% in BRCA1), 3.6% patients carried other DRG mutations (including 10 genes) and 0.5% patients carried HOXB13 mutations. Besides, variants with uncertain significance (VUS) were found in approximately 45% patients. We also divided 633 metastatic PCa patients into 542 de novo metastastic PCa and 91 recurrent metastastic PCa and found mutation frequencies did not differ between these two groups (9.0% vs 11.6%, p = 0.6). Patients with younger age of onset or family history of cancers were more likely to harbour germline mutations in DRGs. However, the rate of germline mutations were still at a high level for patients more than 70 years old (6.7%) and patients without family history of cancers (7.5%). There is no statistically significant difference in the mutation frequencies between patients with metastasis and without metastasis (7.5% vs 9.2%, p = 0.4), which may be because 85% patients without metastasis in our cohort were in high to very high risk group or have lymph node metastasis. Conclusions: To our knowledge, our study reported the largested series of Chinese PCa patients who received germline genetic testing. Our study provided a rationality for germline genetic testing criteria from high risk to metastastic PCa regardless of family history considering the high proportion. In addition, we recommended a multigene panel covering 13 genes ( ATM, BRCA1, BRCA2, CHEK2, FANCA, HOXB13, MSH2, MSH6, NBN, PALB2, RAD51C, RAD51D, TP53) in China. Nevertheless, the high prevalence of VUS (45%) in Chinese PCa patients warrant further efforts.

Phase II study of olaparib in malignant mesothelioma (MM) to correlate efficacy with germline and somatic mutations in DNA repair genes.

9054 Background: BRCA1 associated protein 1 ( BAP1), a nuclear deubiquitinase involved in DNA double-strand break repair is frequently mutated in MM. Because poly(ADP-ribose) polymerase inhibitors (PARPIs) induce synthetic lethality in BRCA1/2 mutant cancers, we sought to evaluate efficacy of olaparib in patients with MM and correlate it with pathogenic germline and somatic mutations in DNA repair genes. Methods: Phase II single-center study (NCT03531840) enrolled patients with advanced pleural or peritoneal mesothelioma who had progressed on prior therapies, age &gt;18 years, ECOG performance status &lt;1, adequate organ and bone marrow function. Olaparib 300mg was given twice daily orally in 3 week cycles until disease progression or toxicity. Efficacy was assessed by CT scan every 6 weeks using RECIST criteria. Whole exome sequencing (WES) was performed on blood and tumor samples to identify pathogenic germline and somatic mutations in DNA repair genes. Primary objective was to determine response rate based on germline or somatic mutation status of DNA repair genes. Results: Between July 2018 to May 2019, 23 patients were enrolled, 15 pleural and 8 peritoneal MM [14 male; median age 63 (range 41-75 years); median number of prior treatments 3 (range 1-5)]. Median olaparib cycles received was 4 (2-21). WES to identify pathogenic mutations in the germline and tumor was performed in 23 and 17 patients respectively. Four patients had germline BAP1, 1 germline MRE11A, and 5 had somatic BAP1 mutations. Of 22 evaluable patients, 1(4%) had partial response (PR), 17 (77%) had stable disease at 6 weeks and 4 (18%) had progressive disease. Patient with PR had a germline mutation in MRE11A. Median progression free survival (PFS) and overall survival (OS) for all patients was 3.4 months (95% CI: 2.7 – 4.8 months) and 8.1 months (95% CI: 4.5 months – not estimable) respectively. Median PFS of germline BAP1 mutant patients (n = 4) was 2.3 months (95% CI: 1.3 – 3.6 months) compared to 4.1 months (95% CI: 2.7 – 5.5 months) for BAP1wild type patients (n = 18;P = 0.026). Median OS was 4.6 months (95% CI: 3.1 – 4.9 months) for patients with germline BAP1 mutation versus not reached for those without germline BAP1 mutation (P = 0.0058). The most common side effects of olaparib were anemia (16%), lymphopenia (24%), nausea (14%), and increased creatinine (9%). Conclusions: Olaparib has limited anti-tumor activity in previously treated MM patients including those with germline or somatic BAP1 mutations. Presence of germline BAP1 mutations was associated with decreased PFS and OS. Clinical trial information: NCT03531840.

Durvalumab following multimodality therapy for locally advanced esophageal and GEJ adenocarcinoma: Updated survival and early translational results from Big Ten Cancer Research Consortium Study.

4572 Background: Concurrent chemoradiation(CRT) followed by esophagectomy is a standard of care for locally advanced esophageal(LA-EAC) and GEJ adenocarcinoma. Approximately 50% of patients(pts) experience disease relapse within the 1st yr after treatment(tx) completion. Immune checkpoint inhibitors have activity in metastatic PD-L1 positive EAC. Preclinical studies have shown radiation +/- chemotherapy upregulates PD-1/PD-L1 pathway. Methods: We conducted a phase II trial evaluating safety and efficacy of PD-L1 inhibitor durvalumab(durva) in pts with LA-EAC and GEJ adenocarcinoma who had residual disease in surgical specimen after neoadjuvant CRT and R0 resection. Pts received durva 1500mg IV every 4 weeks for up to 1yr. Results: Initially 24 pts were enrolled, study was expanded to enroll additional 13 pts. Median age: 61yrs (range, 43-73). 31 received carbo/paclitaxel and 6 received cis/5-FU concurrently with RT. 24(64.9%) pts had positive lymph nodes(LN) at the time of surgery following CRT: N3(n = 3,8.1%), N2(n = 10, 27%), N1(n = 11,29.7%).17 pts relapsed: 11 on tx, 6 had late relapses. 3/5 late relapses were locoregional and were re-treated with chemo-RT. Remaining relapses were systemic with lung and LN being the most common sites. 2 of 3 pts who developed grade 3 irAEs are alive and disease free at 17 and 23 mo. RFS/OS:1 yr- 79.2%/95.5%, 2yr-55.5%/67.4%. 20/37 pts have HER-2 status available: 5/6 HER2 positive pts had disease relapse, 1 is undergoing tx. Molecular profiling is available on 8 relapsed pts: all were microsatellite stable with low TMB and PD-L1 &lt; 10% CPS. Mutations in DNA repair genes ( ARID1A, ATM, ATR, CHEK2), and PIK3CA E542K were more prevalent among late relapsing pts. Circulating tumor cells (CTCs) analysis is available for 10/37 pts. 4/5 pts where CTCs increased from C1 to C4 had disease relapse. Molecular profiling of the remaining pts and correlation of PD-L1 expression, TMB, specific genes mutations, CTCs, and Immunoscore with outcomes with durva is being evaluated will be presented at the meeting. Conclusions: Adjuvant durva following trimodality therapy for LA-EAC and GEJ adenocarcinoma improved 1-yr RFS to 79.2% compared to historical rate of 50%.2-yr RFS and OS data are encouraging in this high risk pt population. HER-2 positivity may be associated with lack of benefit from durva. Mutations in DNA repair genes are prevalent in pts with delayed relapse. Rise in CTCs during durva tx may be an early marker of disease relapse. Clinical trial information: NCT02639065 .

Burden of genetic testing in an academic biobank by pathological and family history-based criteria in prostate cancer (PCa).

1576 Background: Approximately 5% of localized PCa and 12% of metastatic PCa are associated with germline mutations in DNA repair genes. The National Comprehensive Cancer Network (NCCN) issued genetic testing guidelines to identify PCa patients (pts) likely to harbor a germline DNA repair mutation. The overall burden of this guideline-based, resource-intensive genetic testing is unknown. Using supervised phenotype-genotype information extraction algorithms, we determined the projected genetic testing burden at a single institution adhering to NCCN PCa genetic testing guidelines. Methods: A PCa cohort of 2127 pts was identified from the Penn Medicine BioBank via ICD 9/10 codes. Phenotypic data were extracted from the Penn Medicine Cancer Registry and electronic health record systems via natural language processing and manual chart review. Pts were classified based on 9 germline genetic testing criteria outlined in the NCCN PCa guidelines (Version 4.2019). Results: 895/2127 pts met at least 1 of the 9 NCCN genetic testing criteria, corresponding to a 42.1% overall genetic testing burden. 35.2% qualified for testing via high-risk localized PCa and 6.4% qualified via metastatic disease. Of the pts with localized PCa (n=2014), 15.1% qualified for genetic testing via high Gleason score, 5.1% via high-risk family history, 3.7% via PSA&gt;20ng/mL, 8.7% via Ashkenazi Jewish descent, and 0.8% via intraductal/ductal histology. Conclusions: In this single-center PCa cohort, germline genetic testing was NCCN-guideline recommended for a larger proportion of pts than would otherwise be expected based on previously published reports. Future studies are needed to validate the sensitivity and specificity of these criteria for identifying germline mutations. Our study also highlights a need for novel methods to improve the efficiency of genetic testing for a large cohort. [Table: see text]

Insights into Chinese prostate cancer germline gene mutation profile: HOXB13 G84E mutation is unsuitable for genetic testing.

e17515 Background: Philadelphia Prostate Cancer Consensus Conference 2017 developed an expert consensus-driven working framework for comprehensive genetic evaluation of inherited PCA. However, the consensus was mainly based on data from Caucasian populations. Genetic differences in the PC molecular landscape between Asian and Caucasian men have been established. Whether Caucasian-based genetic information can be used to guide clinical practice in Chinese population needs further evidence. Methods: 1123 patients with confirmed prostate cancer admitted from March 2018 to August 2019 from 18 Chinese centers were included in this retrospective study. We sequenced the association of 50 gene with prostate cancer risk, clinical treatment implications and predisposition, focusing on DNA repair gene and genetic susceptibility genes pathogenic mutations in Philadelphia Prostate Cancer Consensus Conference. Only protein-truncating alterations (nonsense/stop-gains, frameshift insertions and deletions, and donor and acceptor splice-site mutations) were coded as pathogenic or likely pathogenic protein-truncating alterations. Results: Among all cases, DNA repair gene pathogenic mutations were found in 133 men (11.84%), including BRCA2 (62 [5.5%]), ATM (15 [1.3%]), PALB2 (11 [0.97%]), GEN1 (7 [0.62%]), BRCA1 (6 [0.53%]), MLH3 (4 [0.35%]), MUTYH (4 [0.35%]), PMS1 (4 [0.35%]), RAD50 (4 [0.35%]), ATR (3 [0.27%]), CHEK2 (3 [0.27%]), FANCD2 (3 [0.27%]) etc. Similar germline DRG mutation frequencies were observed between our cohort and Caucasian men. Noticeably, G84E mutation in HOXB13, a rare but recurrent missense mutation associated with a significantly increased risk of hereditary prostate cancer was not found in our cohort of patients. Furthermore, the frequency of HSD3B1 (1245C) allele in the Chinese patients is much lower than that in the Caucasian populations (11.7% vs 63%). Conclusions: Our study retrospectively analyzed germline mutation profile of prostate cancer in Chinese population. The frequency of HSD3B1 (1245C) allele varies across ethnic populations in spite of the similar DNA repair gene mutations rates. Considering the gene list should be tested based on clinical/familial scenarios from the Philadelphia Prostate Cancer Consensus Conference, a prevalence of certain mutations, G84E mutation in HOXB13 was unnecessary for genetic testing in Chinese population.

Germline DNA repair gene mutations in Taiwan prostate cancer patients.

e13640 Background: Genetic testing for inherited mutations in DNA-repair genes such as BRCA1, BRCA2, ATM, PALP2, FANCA has been proposed for high-risk and metastatic prostate cancer patients for personalized therapy and management. Although the prevalence of germline DNA-repair gene mutations among Caucasian populations are known, the frequency of such mutations in Taiwan prostate cancer patients has not been established. In this study, we performed next-generation sequencing (NGS) analysis of BRCA1, BRCA2, ATM, PALP2, and FANCA in 49 prostate cancer patients stratified according to the NCCN risk criteria using blood sample collected from a single hospital center. Methods: 4ml whole blood samples are collected in EDTA tube from prostate cancer patients of low-intermediate, high to very high, regional, and metastatic risks. The samples are subjected to buffy coat fractionation, genomic DNA extraction, library preparation, full-exon NGS, and comparative analysis with all known germline variants. We identified and correlated the frequency of germline DNA-repair gene mutations with patient’s age at diagnosis, Gleason grades, initial PSA, family history of prostate cancer, and NCCN risk. Results: A total of 49 blood samples were tested and analyzed for BRCA1, BRCA2, ATM, PALP2, and FANCA mutations. Among all cases, 6.1% (3/49, 95% confidence interval [CI]: - 0.6%-12.8%) carried pathogenic mutations: 2.0% (1/49) in BRCA1, 2.0% (1/49) in BRCA2, and 2.0% (1/49) in ATM. They were compatible with previously reported mutations and no new germline variants were detected. These mutations were associated with initial PSA and NCCN risk; all identified mutations belonged to Gleason grade 5 and high to very high risk subgroups. No clinical association was observed with patient’s age of diagnosis and family history. Conclusions: In this single hospital center study, we observed a modest incidence of DNA-repair gene mutations in the Taiwan prostate cancer cohort. Germline DNA-repair gene mutations were observed in high risk prostate cancer patients with the highest Gleason grade. Frequencies of the mutations did not differ significantly according to age at diagnosis or family history of prostate cancer. These results were similar to the reported findings in the Caucasian populations. Our findings confirmed the necessity of genetic testing in Taiwan prostate cancer patients. [Table: see text]

Germline genetic mutational landscape and characteristics of men with prostate cancer (PCa): A single institution experience.

e13679 Background: The role of germline genetic testing (GGT) is rapidly changing for men with PCa. We describe the characteristics of men with PCa diagnosed with pathogenic (P) and likely pathogenic (LP) mutations on GGT. Methods: We conducted a retrospective single-institution study for all men with PCa who received single gene or multi-gene GGT from 1997-2019, unselected for disease stage, Gleason score, or age at diagnosis, and while most had a family history of cancer, some did not. All participants were from the Risk Assessment Program (RAP) database at FCCC and consented for research purposes at the time of GGT. Results: 160 men with PCa had GGT. 72/160 (45%) patients had no mutations. 41/160 (26%) patients had a variant of undetermined significance (VUS) (13 with 2 VUS, 1 with 3 VUS). 47/160 (29%) men were found to have a P or LP germline mutation. 26/47 (55%) with recurrent disease, and 1/47 (2%) unknown. 46 were Caucasian, and 1 was African American ( PALB2). 28/47 (60%) had Gleason Scores (GS) ≤7. 6/47 (13%) had a Prostate Specific Antigen (PSA) at diagnosis &lt; 4.0 ng/mL. 23/47 (49%) were diagnosed &lt; 60 years of age, and 8/47 (17%) at ≤ 50. 19/23 (83%) PCa cases with P/LP diagnosed below age 60 had DNA repair genes: BRCA2 (8), BRCA1 (4), CHEK2 (4), ATM (2), and PALB2 (1). 74/160 (46%) were tested after PCa NCCN genetics guidelines changed (October 2017), of which 19/74 (25%) had P/LP, and of those positive for P/LP, 6/19 (32%) had non-metastatic disease. Two patients had small cell neuroendocrine PCa ( CHEK2 and BRCA2), the remaining had adenocarcinoma PCa. Please see Table for full results. Conclusions: To our knowledge, this is the largest single-institution study reporting PCa characteristics and incidence of P/LP germline mutations. Rates of DNA-repair gene mutations were higher than previously reported, possibly reflecting our specialized cancer center’s population. While BRCA1/2 mutations were the most represented (55%), we describe PCa patients with mutations in ATM, CHEK2, NBN, PALB2, CFTR, and MUTYH, recognizing a few are not known to be linked to PCa. More than half of P/LP mutation carriers had GS ≤7. Additionally, 13% of the men with P/LP germline mutations had low PSA ( &lt; 4.0 ng/mL) at diagnosis. Our findings highlight the importance of the new guidelines and GGT importance in some men with PCa, particularly if they could benefit from a different therapeutic approach, or be influenced into cascade GGT. [Table: see text]

Emerging Subtypes and New Treatments for Castration-Resistant Prostate Cancer.

Genomic characterization of metastatic castration-resistant prostate cancer (mCRPC) has been remodeling the treatment landscape of this disease in the past decade. The emergence of molecularly defined subsets of mCRPC is altering the treatment paradigm from therapeutics with nonspecific activity across the spectrum, including androgen receptor (AR)-directed treatments, docetaxel, and cabazitaxel, to targeted approaches directed at molecular subsets of disease. The meaningful benefit of PARP inhibitors in mCRPC carrying mutations in DNA repair genes demonstrated in a phase III trial epitomizes this transition in the treatment paradigm of mCRPC and brings new challenges related to how to sequence and integrate the targeted therapies on top of the treatments with broad activity in all mCRPC. To enable and sustain the advance of precision oncology in the management of mCRPC, genomic characterization is required, including somatic and germline testing, for all patients with the ultimate goal of longitudinal molecular profiling guiding treatment decisions and sequential treatments of this lethal disease. This article reviews the emerging molecular subtypes of mCRPC that are driving the evolution of mCRPC treatment.

Therapeutic targeting of the DNA damage response in prostate cancer.

The present article highlights the most common DNA repair gene mutations, using specific examples of individual genes or gene classes, and reviews the epidemiology and treatment implications for each one [with particular emphasis on poly-ADP-ribose polymerase (PARP) inhibition and PD-1 blockade]. Genetic and genomic testing have an increasingly important role in the oncology clinic. For patients with prostate cancer, germline genetic testing is now recommended for all men with high-risk and metastatic disease, and somatic multigene tumor testing is recommended for men with metastatic castration-resistant disease. The most common mutations that are present in men with advanced prostate cancer are in genes coordinating DNA repair and the DNA damage response. Although much of what is discussed currently remains investigational, it is clear that genomically-targeted treatments will become increasingly important for patients with prostate cancer in the near future and beyond.

Germline and somatic DNA repair gene alterations in prostate cancer.

Emerging evidence has suggested that DNA repair gene alterations may be important in prostate cancer pathogenesis. In the current study, the authors sought to characterize alterations in DNA repair pathway genes in both primary and metastatic prostate tumors with attention to tissue distribution as well as specific genomic alterations. The authors studied the distribution and type of alterations in 24 genes that are considered important for DNA repair in 944 prostate cancers harvested from localized and metastatic tumors. Tumor DNA underwent hybrid capture for all coding exons of 287 or 395 cancer-related genes plus select introns from 19 or 31 genes frequently rearranged in cancer. Captured libraries were sequenced to a median exon coverage depth of >×500. Specific genomic alterations were characterized and the frequencies of mutations by tissue site (prostate vs metastases) were compared using logistic regression. A total of 152 patients from the cohort of 944 men (16%) harbored a germline or somatic mutation in ≥1 DNA repair genes. The most frequently mutated genes were BRCA2 (11.4%) and ATM (5.8%), followed by MSH6 (2.5%) and MSH2 (2.1%). Mutations were identified in approximately 20.1% of primary prostate tumors compared with 18.8% of bone metastases. When stratified by tissue site, the highest rates of DNA repair mutations were found in solid organ metastases, including brain and visceral metastases, compared with prostate. DNA repair gene mutations are more common in metastatic than localized prostate tumors. Visceral and other solid organ metastases appear enriched for these mutations compared with localized tumors or bone and lymph node metastases.