PROREPAIR-B: A Prospective Cohort Study of the Impact of Germline DNA Repair Mutations on the Outcomes of Patients With Metastatic Castration-Resistant Prostate Cancer

Urinary DNA as a Tool for Germline and Somatic Mutation Detection in Castration-Resistant Prostate Cancer Patients

(1) Background: DNA damage response (DDR) pathway gene mutations are detectable in a significant number of patients with metastatic castration-resistant prostate cancer (mCRPC). The study aimed at identification of germline and/or somatic DDR mutations in blood and urine samples from patients with mCRPC for correlation with responses to entire sequence of systemic treatment and survival outcomes. (2) Methods: DDR gene mutations were assessed prospectively in DNA samples from leukocytes and urine sediments from 149 mCRPC patients using five-gene panel targeted sequencing. The impact of DDR status on progression-free survival, as well as treatment-specific and overall survival, was evaluated using Kaplan–Meier curves and Cox regression. (3) Results: DDR mutations were detected in 16.6% of urine and 15.4% of blood samples. BRCA1, BRCA2, CHEK2, ATM and NBN mutations were associated with significantly shorter PFS in response to conventional androgen deprivation therapy and first-line mCRPC therapy with abiraterone acetate. Additionally, BRCA1 and BRCA2 mutation-bearing patients had a significantly worse response to radium-223. However, DDR mutation status was predictive for the favourable effect of second-line abiraterone acetate after previous taxane-based chemotherapy. (4) Conclusions: Our data confirm the benefit of non-invasive urine-based genetic testing for timely identification of high-risk prostate cancer cases for treatment personalization.

Impact of concurrent tumor events on the prostate cancer outcomes of germline BRCA2 mutation carriers

BACKGROUND

Several studies have reported the association of germline BRCA2 (gBRCA2) mutations with poor clinical outcomes in prostate cancer (PCa), but the impact of concurrent somatic events on gBRCA2 carriers survival and disease progression is unknown.

PATIENTS AND METHODS

To ascertain the role of frequent somatic genomic alterations and histology subtypes in the outcomes of gBRCA2 mutation carriers and non-carriers, we correlated the tumour characteristics and clinical outcomes of 73 gBRCA2 and 127 non-carriers. Fluorescent in-situ hybridisation and next-generation sequencing were used to detect copy number variations in BRCA2, RB1, MYC and PTEN. Presence of intraductal and cribriform subtypes was also assessed. The independent impact of these events on cause-specific survival (CSS), metastasis-free survival and time to castration-resistant disease was assessed using cox-regression models.

RESULTS

Somatic BRCA2-RB1 co-deletion (41% versus 12%, p < 0.001) and MYC amplification (53.4% versus 18.8%, p < 0.001) were enriched in gBRCA2 compared to sporadic tumours. Median CSS from diagnosis of PCa was 9.1 versus 17.6 years in gBRCA2 carriers and non-carriers, respectively (HR 2.12; p = 0.002), Median CSS in gBRCA2 carriers increased to 11.3 and 13.4 years in the absence of BRCA2-RB1 deletion or MYC amplification, respectively. Median CSS of non-carriers decreased to 8 and 2.6 years if BRCA2-RB1 deletion or MYC amplification were detected.

CONCLUSIONS

gBRCA2-related prostate tumours are enriched for aggressive genomic features, such as BRCA2-RB1 co-deletion and MYC amplification. The presence or absence of these events modify the outcomes of gBRCA2 carriers.

Tumor testing and treatment patterns in veterans with metastatic castration-resistant prostate cancer

INTRODUCTION

In 2016, the Department of Veterans Affairs (VA) and Prostate Cancer Foundation (PCF) began a partnership to improve access to testing. The primary objective of this analysis was to describe the use of tumor testing and treatment patterns in Veterans who progressed to metastatic castration-resistant prostate cancer (mCRPC) from 2016 to 2021. Secondary objectives including identifying factors associated with receipt of tumor testing, and reporting HRR mutation results among a subset who were tested.

METHODS AND MATERIALS

Natural language processing algorithms were applied to VA electronic health record data to identify a nationwide cohort of veterans with mCRPC. Tumor testing over time and by region were reported, alongside first-, second-, and third-line treatment patterns. Factors associated with receipt of tumor testing were identified using generalized linear mixed models with binomial distributions and logit links to account for clustering by VA facility.

RESULTS

Of the 9,852 veterans analyzed, 1,972 (20%) received tumor testing, with 73% of testing occurring in 2020-2021. Factors associated with tumor testing included younger age, later diagnosis year, being treated in the Midwest, or Puerto Rico or other compared to the South, and being treated at a PCF-VA Center of Excellence. Fifteen percent of tests were positive for a pathogenic HRR mutation. Seventy-six percent of the study cohort received first-line treatment, and among those, a subsequent 52% received second-line treatment. A subsequent 46% received third-line treatment.

CONCLUSION

After the VA-PCF partnership, one-fifth of veterans with mCRPC received tumor testing, with most tests occurring in 2020-2021.

The prevalence of gene mutations in homologous recombination repair pathways in Japanese patients with metastatic castration-resistant prostate cancer in real-world clinical practice: The multi-institutional observational ZENSHIN study

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) is a genetically heterogeneous disease with a poor prognosis. The prevalence of mutations in homologous recombination repair (HRR) pathway genes, including BRCA1/2, as well as treatment patterns and clinical outcomes, are not well characterized among Japanese men with mCRPC.

METHODS

This multicenter, noninterventional cohort study enrolled Japanese men with mCRPC from 24 institutions between 2014 and 2018. Mutations in the 15 HRR-related genes were assessed using archival primary or metastatic tumor samples. Patterns of sequential therapies for mCRPC were investigated. Patients were followed up for survival evaluation including prostate-specific antigen progression-free survival (PSA-PFS) and overall survival (OS).

RESULTS

Of the 143 patients analyzed, HRR-related mutations were detected in 51 patients (35.7%). The most frequently mutated genes were CDK12 (N = 19, 13.3%), followed by BRCA2 (N = 18, 12.6%), ATM (N = 8, 5.6%), and CHEK2 (N = 3, 2.1%). The most common type of first-line therapy for mCRPC was next-generation hormonal agents (NHA, 44.4%), followed by first-generation antiandrogens (FGA, 30.3%), and taxanes (22.5%). Commonly prescribed first-/second-line sequential regimens included FGA/NHA (17.6%), NHA/NHA (15.5%), and NHA/taxanes (14.1%). The median PSA-PFS and OS for the entire cohort were 5.6 and 26.1 months, respectively. Patients carrying BRCA1/2 mutations had numerically shorter PSA-PFS (median 3.3 vs. 5.9 months) and OS (median 20.7 vs. 27.3 months) than those without mutations.

CONCLUSIONS

In conclusion, approximately one-third of Japanese patients with mCRPC carried mutations in HRR-related genes in this study. The real-world outcomes of mCRPC are poor with conventional therapy, warranting an expansion of treatment options based on genetic abnormalities of the disease.

A real-world retrospective analysis of the management of metastatic castrate-resistant prostate cancer in Ontario, Canada from 2010 - 2018

PURPOSE

We sought to quantify mCRPC patient treatment patterns and survival across multiple lines of therapy after prior androgen-receptor-axis-targeted therapy (ARAT) failure.

METHODS

Individuals diagnosed with prostate cancer between 2010 and 2018 were identified in the Ontario Cancer Registry (OCR). An algorithm was created to identify patients with mCRPC that was aligned to Prostate Cancer Clinical Trials Working Group 3 criteria (PCWG3) and validated with Canadian clinical experts. In the mCRPC setting, treatment patterns were assessed by line of therapy, and survival was calculated from treatment initiation until death or lost to follow-up.

RESULTS

64,484 men were diagnosed withprostate cancer in Ontario between 2010 and 2018with 5,588 men assessed to have mCRPC and 2,970 (53%) of those received first-line systemic treatment. Across the first-, second- and third-line of therapy, ARATs (abiraterone and enzalutamide) were the most used therapies. Survival for mCRPC patients treated with ARATs in first-, second- and third-line were 13.0 (95% CI, 11.6 - 14.5), 11.5 (95% CI, 10.1 - 13.4) and 8.9 (95% CI, 7.4 - 10.2) months, respectively. Survival for mCRPC patients treated with taxanes in first, second- and third-line were 16.7 (95% CI, 14.8 - 18.0), 11.3 (95% CI, 10.1 - 12.5) and 7.8 (95% CI, 6.5 - 10.6) months, respectively. No statistical difference in overall survival was found between taxanes and ARATs.

CONCLUSION

In this analysis of a large retrospective cohort of Canadian men with mCRPC, we found that survival in patients treated with ARATs and taxanes was fairly similar across all lines of therapy. Importantly, this trend was maintained in ARAT-exposed patients, where sequential ARAT and taxanes offered similar survival. These data may help inform optimal sequencing of therapies in mCRPC.

Genetic Aspects and Molecular Testing in Prostate Cancer: A Report from a Dutch Multidisciplinary Consensus Meeting

Background

Germline and tumour genetic testing in prostate cancer (PCa) is becoming more broadly accepted, but testing indications and clinical consequences for carriers in each disease stage are not yet well defined.

Objective

To determine the consensus of a Dutch multidisciplinary expert panel on the indication and application of germline and tumour genetic testing in PCa.

Design setting and participants

The panel consisted of 39 specialists involved in PCa management. We used a modified Delphi method consisting of two voting rounds and a virtual consensus meeting.

Outcome measurements and statistical analysis

Consensus was reached if ≥75% of the panellists chose the same option. Appropriateness was assessed by the RAND/UCLA appropriateness method.

Results and limitations

Of the multiple-choice questions, 44% reached consensus. For men without PCa having a relevant family history (familial PCa/BRCA-related hereditary cancer), follow-up by prostate-specific antigen was considered appropriate. For patients with low-risk localised PCa and a family history of PCa, active surveillance was considered appropriate, except in case of the patient being a BRCA2 germline pathogenic variant carrier. Germline and tumour genetic testing should not be done for nonmetastatic hormone-sensitive PCa in the absence of a relevant family history of cancer. Tumour genetic testing was deemed most appropriate for the identification of actionable variants, with uncertainty for germline testing. For tumour genetic testing in metastatic castration-resistant PCa, consensus was not reached for the timing and panel composition. The principal limitations are as follows: (1) a number of topics discussed lack scientific evidence, and therefore the recommendations are partly opinion based, and (2) there was a small number of experts per discipline.

Conclusions

The outcomes of this Dutch consensus meeting may provide further guidance on genetic counselling and molecular testing related to PCa.

Patient summary

A group of Dutch specialists discussed the use of germline and tumour genetic testing in prostate cancer (PCa) patients, indication of these tests (which patients and when), and impact of these tests on the management and treatment of PCa.

Prognostic value of genomic mutations in metastatic prostate cancer

Metastatic prostate cancer (mPC) has a poor prognosis, and new treatment strategies are currently being offered for patients in clinical practice, but mPC is still incurable. A considerable proportion of patients with mPC harbor homologous recombination repair (HRR) mutations, which may be more sensitive to poly (ADP-ribose) polymerase inhibitors (PARPis). We retrospectively included genomic and clinical data from 147 patients with mPC from a single clinical center, with a total of 102 circulating tumor DNA (ctDNA) samples and 60 tissue samples. The frequency of genomic mutations was analyzed and compared with that in Western cohorts. Cox analysis was used to assess progression-free survival (PFS) and prognostic factors related to prostate-specific antigen (PSA) after standard systemic therapy for mPC. The most frequently mutated gene in the HRR pathway was CDK12 (18.3%), followed by ATM (13.7%) and BRCA2 (13.0%). The remaining common ones were TP53 (31.3%), PTEN (12.2%), and PIK3CA (11.5%). The frequency of BRCA2 mutation was close to that of the SU2C-PCF cohort (13.3%), but the frequency of CDK12, ATM, and PIK3CA mutations was significantly higher than that in the SU2C-PCF cohort: 4.7%, 7.3%, and 5.3%, respectively. CDK12 mutation were less responsive to androgen receptor signaling inhibitors (ARSIs), docetaxel, and PARPi. BRCA2 mutation helps predict PARPi efficacy. Additionally, androgen receptor (AR)-amplified patients do not respond well to ARSIs, and PTEN mutation are associated with poorer docetaxel response. These findings support the genetic profiling of patients with mPC after diagnosis to guide treatment stratification to customize personalized treatment.

Differential responses to taxanes and PARP inhibitors in ATM- versus BRCA2-mutated metastatic castrate-resistant prostate cancer

BACKGROUND

PARP (poly(ADP-ribose) polymerase) inhibitors (PARPi) are now standard of care in metastatic castrate-resistant prostate cancer (mCRPC) patients with select mutations in DNA damage repair (DDR) pathways, but patients with ATM- and BRCA2 mutations may respond differently to PARPi. We hypothesized that differences may also exist in response to taxanes, which may inform treatment sequencing decisions.

METHODS

mCRPC patients (N = 158) with deleterious ATM or BRCA2 mutations who received taxanes, PARPi, or both were retrospectively identified from 11 US academic centers. Demographic, treatment, and survival data were collected. Kaplan-Meier analyses were performed and Cox hazard ratios (HR) were calculated for progression-free survival (PFS) as well as overall survival (OS), from time of first taxane or PARPi therapy.

RESULTS

Fifty-eight patients with ATM mutations and 100 with BRCA2 mutations were identified. Fourty-four (76%) patients with ATM mutations received taxane only or taxane before PARPi, while 14 (24%) received PARPi only or PARPi before taxane. Patients with ATM mutations had longer PFS when taxane was given first versus PARPi given first (HR: 0.74 [95% confidence interval [CI]: 0.37-1.50]; p = 0.40). Similarly, OS was longer in patients with ATM mutations who received taxane first (HR: 0.56 [CI: 0.20-1.54]; p = 0.26). Among patients with BRCA2 mutations, 51 (51%) received taxane first and 49 (49%) received PARPi first. In contrast, patients with BRCA2 mutations had longer PFS when PARPi was given first versus taxane given first (HR: 0.85 [CI: 0.54-1.35]; p = 0.49). Similarly, OS was longer in patients with BRCA2 mutations who received PARPi first (HR: 0.75 [CI: 0.41-1.37]; p = 0.35).

CONCLUSIONS

Our retrospective data suggest differential response between ATM and BRCA2 mutated prostate cancers in terms of response to PARPi and to taxane chemotherapy. When considering the sequence of PARPi versus taxane chemotherapy for mCRPC with DDR mutations, ATM, and BRCA2 mutation status may be helpful in guiding choice of initial therapy.

Estimating copy number to determine BRCA2 deletion status and to expect prognosis in localized prostate cancer

BACKGROUND

The significance of BRCA alterations has been implicated in the development of metastatic castration-resistant prostate cancer (PC). The details of the frequency and significance of BRCA alterations in localized PC remain unknown. In this study, we investigated the frequency and clinical significance of BRCA alterations in localized PCs using an in-house next-generation sequencer (NGS) system.

METHODS

DNA was extracted from formalin-fixed paraffin-embedded tissues of surgical specimens from 126 patients with clinically localized PC who underwent radical prostatectomy. The mutation information of 164 cancer genes was analyzed using the PleSSision-Rapid test. Both copy number (CN) variation and loss of heterozygosity of various genes, such as BRCA1 and BRCA2, were estimated and reported.

RESULTS

Next-generation sequencer analyses revealed that the BRCA2 CN was decreased in 17 patients (13.5%) and the BRCA1 CN in six (4.8%) patients. NGS-based CN values were shown to be highly correlated with droplet digital PCR-based CN values. Tissue-specific BRCA expression investigated using the Human Protein Atlas showed that the decreased CN of BRCA2, but not BRCA1, is responsible for the decreased BRCA activity in PC. Ten of the 22 patients with decreased BRCA2 CN were presumed to have somatic heterozygous deletion. There were no observed associations between the heterozygous deletion of BRCA2 and various clinicopathological parameters. Furthermore, three of 10 patients developed biochemical recurrence within 3 months after surgery. Multivariate analyses revealed that the initial prostate-specific antigen levels and BRCA2 CN were independent factors for biochemical recurrence.

CONCLUSION

Our results suggest that a decrease in BRCA2 CN may be used as a biomarker for predicting recurrence after surgery in localized PC. Early screening for somatic alterations in BRCA2 using NGS may help to broadly predict the risk of PC progression.

Internet-Based Germline Genetic Testing for Men With Metastatic Prostate Cancer

PURPOSE

Germline mutations in DNA repair genes are present in approximately 10% of men with metastatic prostate cancer (mPC), and guidelines recommend genetic germline testing. Notable barriers exist, including access to genetic counseling, insurance coverage, and out-of-pocket costs. The GENTleMEN study was designed to determine the feasibility of an Internet-based, patient-driven germline genetic testing approach for men with mPC.

PATIENTS AND METHODS

In this prospective cohort study, men with mPC provided informed consent via an Internet-based platform and completed a questionnaire including demographics and family cancer history. Supporting medical data were also collected. Genetic testing was performed using the Color Genomics 30-gene targeted panel of cancer predisposition genes on a mailed saliva sample. Men whose test results identified a germline pathogenic or likely pathogenic variant received results by phone or telehealth genetic counseling; other participants received results by email with an option for phone-based or telehealth genetic counseling.

RESULTS

As of August 18, 2021, 816 eligible men were consented, of whom 68% (551) completed genetic testing, and 8.7% (48 of 551) were found to carry a pathogenic or likely pathogenic variant in a germline DNA repair gene: CHEK2 (17), BRCA2 (15), ATM (6), NBN1 (3), BRCA1 (2), PALB2 (2), PMS2 (2), and MSH6 (1). Participants were more likely to complete the testing process if they were non-Hispanic White, married, highly educated, or from a higher-income bracket.

CONCLUSION

Here, we show the feasibility of delivering germline (inherited) genetic testing by a voluntary, patient-driven, Internet-based platform to men with mPC. Preliminary results show rates of germline DNA repair mutations, consistent with other cohorts. Although feasible for some, reduced steps for participation, more dedicated diverse outreach and participant support, and identification and addressing of additional barriers is needed to ensure equitable access and optimization.

Development of PARP Inhibitors in Targeting Castration-Resistant Prostate Cancer

Prostate cancer is a genetically heterogenous disease and a subset of prostate tumors harbor alterations in DNA damage and repair (DDR) genes. Prostate tumor DDR gene alterations can arise via germline or somatic events and are enriched in high-grade and advanced disease. Alterations in genes in the homologous recombination (HR) repair pathway are associated with sensitivity to PARP inhibition in breast and ovarian cancer, and data from recently completed randomized trials also demonstrate benefit of PARP inhibitor therapy in patients with advanced metastatic castration-resistant prostate cancer (mCRPC) and tumor HR gene alterations. PARP inhibitors have been investigated in first-line mCRPC in biomarker-selected and unselected populations, and are currently under study in earlier disease states in patients with DDR gene alterations. This chapter focuses on the current state of PARP inhibitor development in prostate cancer with particular emphasis on biomarkers and combination therapy approaches.

How the Analysis of the Pathogenetic Variants of DDR Genes Will Change the Management of Prostate Cancer Patients

Herein, we analyze answers achieved, open questions, and future perspectives regarding the analysis of the pathogenetic variants (PV) of DNA damage response (and repair) (DDR) genes in prostate cancer (PC) patients. The incidence of PVs in homologous recombination repair (HRR) genes among men with metastatic PC varied between 11% and 33%, which was significantly higher than that in non-metastatic PC, and BRCA2 mutations were more frequent when compared to other DDR genes. The determination of the somatic or germline PVs of BRCA2 was able to define a tailored therapy using PARP inhibitors in metastatic castration-resistant prostate cancer (mCRPC) progression after first-line therapy, with significant improvements in the radiologic progression-free survival (rPFS) and overall survival (OS) rates. We propose testing all metastatic PC patients for somatic and germline HRR mutations. Somatic determination on the primary site or on historic paraffin preparations with a temporal distance of no longer than 5 years should be preferred over metastatic site biopsies. The prognostic use of DDR PVs will also be used in selected high-risk cases with non-metastatic stages to better arrange controls and therapeutic primary options. We anticipate that the use of poly-ADP-ribose polymerase (PARP) inhibitors in hormone-sensitive prostate cancer (HSPC) and in combination with androgen receptor signaling inhibitors (ARSI) will be new strategies.

Mainstream germline genetic testing in men with metastatic prostate cancer: design and protocol for a multicenter observational study

BACKGROUND

In international guidelines, germline genetic testing is recommended for patients with metastatic prostate cancer. Before undergoing germline genetic testing, these patients should receive pre-test counseling. In the standard genetic care pathway, pre-test counseling is provided by a healthcare professional of a genetics department. Because the number of patients with metastatic prostate cancer is large, the capacity in the genetics departments might be insufficient. Therefore, we aim to implement so-called mainstream genetic testing in the Netherlands for patients with metastatic prostate cancer. In a mainstream genetic testing pathway, non-genetic healthcare professionals discuss and order germline genetic testing. In our DISCOVER study, we will assess the experiences among patients and non-genetic healthcare professionals with this new pathway.

METHODS

A multicenter prospective observational cohort study will be conducted in 15 hospitals, in different regions of the Netherlands. We developed an online training module on genetics in prostate cancer and the counseling of patients. After completion of this module, non-genetic healthcare professionals will provide pre-test counseling and order germline genetic testing in metastatic prostate cancer patients. Both non-genetic healthcare professionals and patients receive three questionnaires. We will determine the experience with mainstream genetic testing, based on satisfaction and acceptability. Patients with a pathogenic germline variant will also be interviewed. We will determine the efficacy of the mainstreaming pathway, based on time investment for non-genetic healthcare professionals and the prevalence of pathogenic germline variants.

DISCUSSION

This study is intended to be one of the largest studies on mainstream genetic testing in prostate cancer. The results of this study can improve the mainstream genetic testing pathway in patients with prostate cancer.

TRIAL REGISTRATION

The study is registered in the WHO's International Clinical Trials Registry Platform (ICTRP) under number NL9617.

The Prognostic Significance of Homologous Recombination Repair Pathway Alterations in Metastatic Hormone Sensitive Prostate Cancer

INTRODUCTION

The homologous recombination repair (HRR) pathway is a frequently mutated pathway in advanced prostate cancer. The clinical course of patients with HRR gene alterations who have metastatic hormone sensitive prostate cancer (mHSPC) has not been fully characterized. Here, we examine the outcomes of men with mHSPC with HRR alterations.

METHODS

We conducted a single-center retrospective analysis of men with mHSPC who underwent next generation sequencing. The primary objective was to assess the time from diagnosis of mHSPC to metastatic castrate resistance prostate cancer (mCRPC) in patients with pathogenic HRR alterations compared to individuals lacking these alterations. Key secondary objectives included time to mCRPC in prespecified cohorts, PSA response, and overall survival.

RESULTS

151 men with mHSPC were identified for the study. 24% (N = 37) had pathogenic HRR gene alterations detected with the most common alterations found in BRCA2 (n = 15), ATM (n = 10), and CDK12 (n = 7). Time to mCRPC was significantly decreased in patients with HRR gene alterations versus those without such alterations (12.7 vs. 16.1 months, HR 1.95, P = .02). In multivariate analysis, the effect of HRR gene alterations on time to CRPC remained significant when adjusting for age, mHSPC therapy, the volume of disease, the presence of visceral metastases, and PSA (adjusted HR 1.69, P = .02). Stratified by specific HRR gene alteration, patients with BRCA2 or CDK12 had significantly decreased time to mCRPC compared to other HRR alterations.

CONCLUSION

HRR gene alterations are associated with the worse outcomes in mHSPC with significantly shorter time to mCRPC. Given the established role of Poly (ADP-ribose) Polymerase (PARP) inhibitors in mCRPC, these data highlight an opportunity to examine PARP inhibitors earlier in the clinical course for prostate cancer patients. Ongoing prospective studies will further validate the role of PARP inhibitors in mHSPC patients.

Complexities of Prostate Cancer

Prostate cancer has a long disease history and a wide variety and uncertainty in individual patients' clinical progress. In recent years, we have seen a revolutionary advance in both prostate cancer patient care and in the research field. The power of deep sequencing has provided cistromic and transcriptomic knowledge of prostate cancer that has not discovered before. Our understanding of prostate cancer biology, from bedside and molecular imaging techniques, has also been greatly advanced. It is important that our current theragnostic schemes, including our diagnostic modalities, therapeutic responses, and the drugs available to target non-AR signaling should be improved. This review article discusses the current progress in the understanding of prostate cancer biology and the recent advances in diagnostic and therapeutic strategies.

Role of Rucaparib in the Treatment of Prostate Cancer: Clinical Perspectives and Considerations

Prostate cancer is one of the most common types of cancer worldwide and has strong genetic associations. This is important for the development of therapeutics for the condition, as metastatic castrate-resistant prostate cancer (mCRPC) is resistant to standard androgen deprivation therapy (ADT) and has a relatively poor prognosis. We conducted a literature review on rucaparib, a poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor that is currently indicated for the treatment of patients with mCRPC who harbor mutations in BRCA1/2 (homologous recombination repair [HRR] genes) and who have already tried androgen receptor-axis-targeted therapies (ARAT) and a taxane chemotherapy. We describe rucaparib's FDA approval, which was based on the results of the single-arm, open-label, Phase II TRITON2 clinical trial, which found an objective response rate (ORR) of 43.5%, a duration of response (DOR) of over six months in length and an acceptable safety profile. Rucaparib's dosage and clinical considerations for use were also discussed. We also compared rucaparib's use and safety profile with Olaparib, niraparib and talazoparib, three other PARP inhibitors tested for the treatment of mCRPC. Overall, initial results show that the safety profile of all four drugs in mCRPC was relatively similar, and further testing is currently indicated for all four. Differences in their metabolism, however, also warrant further research. The clinical validity of rucaparib will be tested by the follow-up TRITON3 clinical trial, which is comparing the effect of rucaparib compared to standard therapies for mCRPC harboring BRCA1/2 or ATM mutations. Other than TRITON3, other clinical trials are testing rucaparib's ability against other cancers (prostate or otherwise) with HRR mutations, and also the efficacy of combination therapies involving rucaparib. Finally, more research is needed to elucidate rucaparib's effect on HRR mutations other than BRCA1/2. Advancements in understanding the genetic landscape of mCRPC will also assist in understanding rucaparib's full therapeutic potential.

Characteristics of BRCA2 Mutated Prostate Cancer at Presentation

Genetic alterations of DNA repair genes, particularly BRCA2 in patients with prostate cancer, are associated with aggressive behavior of the disease. It has reached consensus that somatic and germline tests are necessary when treating advanced prostate cancer patients. Yet, it is unclear whether the mutations are associated with any presenting clinical features. We assessed the incidences and characteristics of BRCA2 mutated cancers by targeted sequencing in 126 sets of advanced prostate cancer tissue sequencing data. At the time of diagnosis, cT3/4, N1 and M1 stages were 107 (85%), 54 (43%) and 35 (28%) samples, respectively. BRCA2 alterations of clinical significance by AMP/ASCO/CAP criteria were found in 19 of 126 samples (15.1%). The BRCA2 mutated cancer did not differ in the distributions of TNM stage, Gleason grade group or histological subtype compared to BRCA2 wild-type cancers. Yet, they had higher tumor mutation burden, and higher frequency of ATM and BRCA1 mutations (44% vs. 10%, p = 0.002 and 21% vs. 4%, p = 0.018, respectively). Of the metastatic subgroup (M1, n = 34), mean PSA was significantly lower in BRCA2 mutated cancers than wild-type (p = 0.018). In the non-metastatic subgroup (M0, n = 64), PSA was not significantly different (p = 0.425). A similar trend was noted in multiple metastatic prostate cancer public datasets. We conclude that BRCA2 mutated metastatic prostate cancers may present in an advanced stage with relatively low PSA.

Prognostic significance of pathogenic variants in BRCA1, BRCA2, ATM and PALB2 genes in men undergoing hormonal therapy for advanced prostate cancer

BACKGROUND

The prognostic significance of germline variants in homologous recombination repair genes in advanced prostate cancer (PCa), especially with regard to hormonal therapy, remains controversial.

METHODS

Germline DNA from 549 Japanese men with metastatic and/or castration-resistant PCa was sequenced for 27 cancer-predisposing genes. The associations between pathogenic variants and clinical outcomes were examined. Further, for comparison, DNA from prostate biopsy tissue samples from 80 independent patients with metastatic PCa were analysed.

RESULTS

Forty-four (8%) patients carried germline pathogenic variants in one of the analysed genes. BRCA2 was most frequently altered (n = 19), followed by HOXB13 (n = 9), PALB2 (n = 5) and ATM (n = 5). Further, the BRCA1, BRCA2, PALB2 and ATM variants showed significant association with a short time to castration resistance and overall survival (hazard ratio = 1.99 and 2.36; 95% CI, 1.15-3.44 and 1.23-4.51, respectively), independent of other clinical variables. Based on log-rank tests, the time to castration resistance was also significantly short in patients with BRCA1, BRCA2, PALB2 or ATM somatic mutations and TP53 mutations.

CONCLUSIONS

Germline variants in BRCA1, BRCA2, PALB2 or ATM are independent prognostic factors of the short duration of response to hormonal therapy in advanced PCa.

Integration of Liquid Biopsies in Clinical Management of Metastatic Prostate Cancer

PURPOSE OF REVIEW

The field of liquid biopsies is constantly evolving through novel technologies. This review outlines current data on liquid biopsies and application to clinical management of metastatic prostate cancer.

RECENT FINDINGS

To date, there are three platforms with FDA approval for use in the setting of metastatic prostate cancer and others which have been clinically validated. There is substantial evidence supporting the use of circulating tumor cell (CTC) enumeration to guide prognosis in metastatic castration-resistant prostate cancer (mCRPC). Additional evidence supports targeted sequencing of CTC and cell-free DNA (cfDNA) to guide androgren-directed therapy, identify candidates for treatment with PARP inhibitors, and monitor development of resistance. As a real-time and minimally invasive approach, utilization of liquid biopsies has the potential to drastically impact the treatment of metastatic prostate cancer and improve overall survival. With further clinical validation, additional liquid biopsy is likely to enter standard clinical practice.

Talazoparib, a Poly(ADP-ribose) Polymerase Inhibitor, for Metastatic Castration-resistant Prostate Cancer and DNA Damage Response Alterations: TALAPRO-1 Safety Analyses

BACKGROUND

The phase II TALAPRO-1 study (NCT03148795) demonstrated durable antitumor activity in men with heavily pretreated metastatic castration-resistant prostate cancer (mCRPC). Here, we detail the safety profile of talazoparib.

PATIENTS AND METHODS

Men received talazoparib 1 mg/day (moderate renal impairment 0.75 mg/day) orally until radiographic progression, unacceptable toxicity, investigator decision, consent withdrawal, or death. Adverse events (AEs) were evaluated: incidence, severity, timing, duration, potential overlap of selected AEs, dose modifications/discontinuations due to AEs, and new clinically significant changes in laboratory values and vital signs.

RESULTS

In the safety population (N = 127; median age 69.0 years), 95.3% (121/127) experienced all-cause treatment-emergent adverse events (TEAEs). Most common were anemia (48.8% [62/127]), nausea (33.1% [42/127]), decreased appetite (28.3% [36/127]), and asthenia (23.6% [30/127]). Nonhematologic TEAEs were generally grades 1 and 2. No grade 5 TEAEs or deaths were treatment-related. Hematologic TEAEs typically occurred during the first 4-5 months of treatment. The median duration of grade 3-4 anemia, neutropenia, and thrombocytopenia was limited to 7-12 days. No grade 4 events of anemia or neutropenia occurred. Neither BRCA status nor alteration origin significantly impacted the safety profile. The median (range) treatment duration was 6.1 (0.4-24.9) months; treatment duration did not impact the incidence of anemia. Only 3 of the 15 (11.8% [15/127]) permanent treatment discontinuations were due to hematologic TEAEs (thrombocytopenia 1.6% [2/127]; leukopenia 0.8% [1/127]).

CONCLUSION

Common TEAEs associated with talazoparib could be managed through dose modifications/supportive care. Demonstrated efficacy and a manageable safety profile support continued evaluation of talazoparib in mCRPC.

CLINICALTRIALS.GOV IDENTIFIER

NCT03148795.

PARP Inhibitors in Advanced Prostate Cancer in Tumors with DNA Damage Signatures

Simple Summary

This review paper seeks to summarize the current literature on the role of PARP Inhibitors in Advanced Prostate Cancer in tumors with defects in genes associated with DNA damage repair. It will give particular attention to the role of PARPi in tumors with non-BRCA DNA damage repair genes. The aim of this review is to summarize the literature on PARPi and their activity treating BRCA and non BRCA tumors with DNA damage signatures.

Abstract

Since 2010, significant progress has been made in the treatment of metastatic castrate resistant prostate cancer (mCRPC). While these advancements have improved survival, mCRPC remains a lethal disease, with a precision medicine framework that is lagging behind compared to other cancers. Poly (ADP-ribose) polymerase (PARP) inhibitor (PARPi) studies in prostate cancer (PCa) have focused primarily on the homologous recombination repair (HRR) genes, specifically BRCA1 and BRCA2. While homologous recombination deficiency (HRD) can be prompted by germline or somatic BRCA1/2 genetic mutations, it can also exist in tumors with intact BRCA1/BRCA2 genes. While the sensitivity of PARPi in tumors with non-BRCA DNA damage signatures is not as well established, it has been suggested that genomic alterations in DNA damage repair (DDR) genes other than BRCA may confer synthetic lethality with PARPI in mCRPC. The aim of this review is to summarize the literature on PARPi and their activity treating BRCA and non BRCA tumors with DNA damage signatures.

Whole-exome sequencing reveals a comprehensive germline mutation landscape and identifies twelve novel predisposition genes in Chinese prostate cancer patients

Prostate cancer is the most inheritable cancer with approximately 42% of disease risk attributed to inherited factors by studies of twins, indicating the importance of additional genetic screening to identify predisposition variants. However, only DNA damage repair (DDR) genes have been investigated thoroughly in prostate cancer. To determine the comprehensive germline mutation landscape in Chinese prostate cancer patients, we performed whole exome sequencing in 100 Han Chinese patients with prostate cancer in Hong Kong and identified deleterious germline mutations. A total of 36 deleterious germline variants in 25 genes were identified in 29% patients. Variants were found in eight pathways, including DNA methylation, DDR, and tyrosine-protein kinase. These findings were validated in an independent Chinese cohort of 167 patients with prostate cancer in Shanghai. Seven common deleterious-variant-containing genes were found in discovery cohort (7/25, 28%) and validation cohort (7/28, 25%) with three genes not described before (LDLR, MYH7 and SUGCT) and four genes previously reported (FANCI, ITGA6, PABPC1 and RAD54B). When comparing with that of a cohort of East Asian healthy individuals, 12 non-DDR novel potential predisposition genes (ADGRG1, CHD4, DNMT3A, ERBB3, GRHL1, HMBS, LDLR, MYH7, MYO6, NT5C2, NUP98 and SUGCT) were identified using the discovery and validation cohorts, which have not been previously reported in prostate cancer patients in all ethnic groups. Taken together, this study reveals a comprehensive germline mutation landscape in Chinese prostate cancer patients and discovers 12 novel non-DDR predisposition genes to lay the groundwork for the optimization of genetic screening.

Prostate cancer is the most inheritable cancer with about 42% of disease risk attributed to inherited factors, indicating the importance of additional genetic screening to identify predisposition variants. However, only DNA damage repair (DDR) genes have been studied thoroughly in prostate cancer. To determine the comprehensive germline mutation landscape in Chinese prostate cancer patients, we performed whole exome sequencing in 100 Han Chinese patients with prostate cancer in Hong Kong and identified deleterious germline mutations. A total of 36 deleterious germline variants in 25 genes were identified in 29% patients. Variants were found in eight pathways, including DNA methylation, DDR, and tyrosine-protein kinase. These findings were validated in an independent Chinese cohort of 167 patients with prostate cancer in Shanghai. Seven common deleterious-variant-containing genes were found in discovery cohort and validation cohort with three genes not described before (LDLR, MYH7 and SUGCT) and four genes previously reported. When comparing with that of a cohort of East Asian healthy individuals, 12 non-DDR novel potential predisposition genes were identified using the discovery and validation cohorts, which have not been previously reported in prostate cancer patients in all ethnic groups.

Bone Health Management in the Continuum of Prostate Cancer Disease

Prostate cancer (PCa) is the second-leading cause of cancer-related deaths in men. PCa cells require androgen receptor (AR) signaling for their growth and survival. Androgen deprivation therapy (ADT) is the preferred treatment for patients with locally advanced and metastatic PCa disease. Despite their initial response to androgen blockade, most patients eventually will develop metastatic castration-resistant prostate cancer (mCRPC). Bone metastases are common in men with mCRPC, occurring in 30% of patients within 2 years of castration resistance and in >90% of patients over the course of the disease. Patients with mCRPC-induced bone metastasis develop lesions throughout their skeleton; the 5-year survival rate for these patients is 47%. Bone-metastasis-induced early changes in the bone that proceed the osteoblastic response in the bone matrix are monitored and detected via modern magnetic resonance and PET/CT imaging technologies. Various treatment options, such as targeting osteolytic metastasis with bisphosphonates, prednisone, dexamethasone, denosumab, immunotherapy, external beam radiation therapy, radiopharmaceuticals, surgery, and pain medications are employed to treat prostate-cancer-induced bone metastasis and manage bone health. However, these diagnostics and treatment options are not very accurate nor efficient enough to treat bone metastases and manage bone health. In this review, we present the pathogenesis of PCa-induced bone metastasis, its deleterious impacts on vital organs, the impact of metastatic PCa on bone health, treatment interventions for bone metastasis and management of bone- and skeletal-related events, and possible current and future therapeutic options for bone management in the continuum of prostate cancer disease.

DNA damage repair gene germline profiling for metastatic prostate cancer patients of different ancestries

BACKGROUND

Germline and somatic mutations in DNA damage repair genes (DDRg) are now recognized as new biomarkers for the management of metastatic prostate cancers (mPC). We evaluate the frequency of germline DDRg mutations among French mPC patients of European and African ancestries.

METHODS

Targeted next-generation sequencing of 21 DDRg was performed on germline DNA from 557 mPC patients, including 15.1% of cases with an African origin.

RESULTS

Forty-seven germline mutations in 11 DDR genes were identified in 46 patients of the total cohort (8.3%). BRCA2 (4.1%) and ATM (2.0%) were the most frequently mutated genes. There was no difference in DDRg mutation frequency between mPC patients of European ancestry and those of African origin. Germline mutations of BRCA2 were associated with a positive family history of breast cancer (p = 0.02). The mean age at metastatic stage (59.7 vs. 67.0; p = 0.0003) and the mean age at death (65.2 vs. 73.9; p = 0.0003) were significantly earlier for carriers of BRCA2 mutation than for non-carriers. Moreover, the Cox model showed that BRCA2 positive status was statistically associated with poorer survival (hazard ratio: 0.29; 95% confidence interval 0.18-0.48; p < 0.0001).

CONCLUSION

We showed that, in France, BRCA2 and ATM are the main predisposing DDR genes in mPC patients, with a particular aggressiveness for BRCA2 leading to early metastatic stage and death.

Factors influencing survival in metastatic castration resistant prostate cancer therapy

INTRODUCTION

The number of patients with metastatic castration resistant prostate cancer (mCRPC) is expecting to increase due to the long-life expectancy of those with advanced disease who are also more commonly diagnosed today because of stage migration. Several compounds are available for treating these patients.

AREAS COVERED

We reviewed currently available treatments for mCRPC, their mechanism of action and resistance and we explored possible predictors of treatment success useful to predict survival in mCRPC patients.

EXPERT OPINION

A combination of molecular, clinical, pathological, and imaging features is necessary to correctly estimate patients' risk of death. The combination of these biomarkers may allow clinicians to tailor treatments based on cancer history and patients' features. The search of predictive biomarkers remains an unmet medical need for most patients with mCRPC.

BRCA Mutations in Ovarian and Prostate Cancer: Bench to Bedside

Simple Summary

DNA damage is one of the hallmarks of cancer. Epithelial ovarian cancer (EOC) —especially the high-grade serous subtype—harbors a defect in at least one DNA damage response (DDR) pathway. Defective DDR results from a variety of lesions affecting homologous recombination (HR) and nonhomologous end joining (NHEJ) for double strand breaks, base excision repair (BER), and nucleotide excision repair (NER) for single strand breaks and mismatch repair (MMR). Apart from the EOC, mutations in the DDR genes, such as BRCA1 and BRCA2, are common in prostate cancer as well. Among them, BRCA2 lesions are found in 12% of metastatic castration-resistant prostate cancers, but very rarely in primary prostate cancer. Better understanding of the DDR pathways is essential in order to optimize the therapeutic choices, and has led to the design of biomarker-driven clinical trials. Poly(ADP-ribose) polymerase (PARP) inhibitors are now a standard therapy for EOC patients, and more recently have been approved for the metastatic castration-resistant prostate cancer with alterations in DDR genes. They are particularly effective in tumours with HR deficiency.

Abstract

DNA damage repair (DDR) defects are common in different cancer types, and these alterations can be exploited therapeutically. Epithelial ovarian cancer (EOC) is among the tumours with the highest percentage of hereditary cases. BRCA1 and BRCA2 predisposing pathogenic variants (PVs) were the first to be associated with EOC, whereas additional genes comprising the homologous recombination (HR) pathway have been discovered with DNA sequencing technologies. The incidence of DDR alterations among patients with metastatic prostate cancer is much higher compared to those with localized disease. Genetic testing is playing an increasingly important role in the treatment of patients with ovarian and prostate cancer. The development of poly (ADP-ribose) polymerase (PARP) inhibitors offers a therapeutic strategy for patients with EOC. One of the mechanisms of PARP inhibitors exploits the concept of synthetic lethality. Tumours with BRCA1 or BRCA2 mutations are highly sensitive to PARP inhibitors. Moreover, the synthetic lethal interaction may be exploited beyond germline BRCA mutations in the context of HR deficiency, and this is an area of ongoing research. PARP inhibitors are in advanced stages of development as a treatment for metastatic castration-resistant prostate cancer. However, there is a major concern regarding the need to identify reliable biomarkers predictive of treatment response. In this review, we explore the mechanisms of DDR, the potential for genomic analysis of ovarian and prostate cancer, and therapeutics of PARP inhibitors, along with predictive biomarkers.

Addition of Germline Testing to Tumor-Only Sequencing Improves Detection of Pathogenic Germline Variants in Men With Advanced Prostate Cancer

PURPOSE

Guidelines recommend somatic and germline testing for men with advanced prostate cancer (PCa). Barriers to widespread implementation result in underutilization of germline testing. Somatic testing alone risks missing pathogenic germline variants (PGVs). We sought to determine whether the addition of germline testing to tumor-only sequencing improves detection of PGVs in men with advanced PCa. Secondarily, we sought to define the added value of combining somatic and germline testing to optimize detection of clinically actionable alterations.

PATIENTS AND METHODS

We analyzed results of independent germline testing and tumor-only sequencing from 100 men with advanced PCa from a prospective clinical trial (ClinicalTrials.gov identifier: NCT03328091). The primary outcome was the proportion of PGVs not reported with tumor-only sequencing. The secondary outcome was the association of locus-specific loss of heterozygosity for PGVs in homologous recombination genes with clinical-genomic features.

RESULTS

In the 100 men who underwent germline testing and tumor-only sequencing, 24 PGVs were identified, 17 of which were clinically actionable, in 23 patients. Tumor-only sequencing failed to report four (17%) of the PGVs. One additional PGV (4.2%) had variant allele frequency on tumor-sequencing below the threshold for follow-up germline testing. When integrating tumor-only sequencing with germling testing results, 33% of patients harbored clinically actionable alterations. Rates of locus-specific loss of heterozygosity were higher for BRCA2 PGVs in castration-resistant PCa than PGVs in other homologous recombination genes in hormone-sensitive PCa (P = .029).

CONCLUSION

Tumor-only sequencing failed to report more than 20% of PGVs in men with advanced PCa. These findings strongly support guideline recommendations for universal germline and somatic testing in this population. Combining tumor and germline sequencing doubled the chance of detecting a clinically actionable alteration.

Germline genetics of prostate cancer

BACKGROUND

An important fraction (>/~10%) of men with high-risk, localized prostate cancer and metastatic prostate cancer carry germline (heritable) pathogenic and likely pathogenic variants (also known as mutations) in DNA repair genes. These can represent known or suspected autosomal dominant cancer predisposition syndromes. Growing evidence suggests that pathogenic variants in key genes involved in homologous recombination and mismatch DNA repair are important in prostate cancer initiation and/or the development of metastases.

AIMS

Here we provide a comprehensive review regarding individual genes and available literature regarding risks for developing prostate cancer, and discuss current national guidelines for germline genetic testing in the prostate cancer population and treatment implications.

RESULTS

The association with prostate cancer risk and treatment implications is best understood for those with germline mutations of BRCA2, with emerging data supporting associations with ATM, CHEK2, BRCA1, HOXB13, MSH2, MSH6, PALB2, TP53 and NBN. Treatment implications in the metastatic castration resistant prostate cancer setting include rucaparib and olaparib, and pembrolizumab with potential clinical trial opportunities in earlier disease settings.

DISCUSSION

The data summarized in this review has led to the expansion of national guidelines for germline genetic testing in prostate cancer. We review these guidelines, and discuss the importance of cascade genetic testing of relatives, diverse populations with attention to inclusion, as well as prostate cancer screening updates and clinical trial opportunities for men who carry genetic risk factors for prostate cancer.

Clinical implications of homologous recombination repair mutations in prostate cancer

Prostate cancer is a disease with significant interpatient genomics, with a proportion of patients presenting mutations in key homologous recombination repair (HRR) gene aberrations, particularly in late-stage disease. A better understanding of the genomic landscape of prostate cancer and the prognostic and predictive value of HRR mutations could lead to more precise care for prostate cancer patients. BRCA1/2 mutations are associated with a more aggressive disease course and higher risk of developing lethal prostate cancer, but also identify patients who could benefit from directed therapeutic strategies with PARP inhibitors. Other HRR mutations are also frequent but their prognostic and predictive value for prostate cancer patients is less clear. Moreover, a proportion of these mutations are associated with inherited germline defects, being relevant for the patients' risk of second malignancies but also to inform their relatives' risk of cancer through cascade testing. In this manuscript, we review current knowledge of the prognostic and predictive value for different HHR alterations across the different prostate cancer disease states. Additionally, we assess the challenges to implement genomic testing in clinical practice for prostate cancer patients.

Genomic Profiling of Prostate Cancer: An Updated Review

Understanding the genomic profiling of prostate cancer is crucial, owing to the emergence of precision medicine to guide therapeutic approaches. Over the last decade, integrative genomic profiling of prostate tumors has provided insights that improve the understanding and treatment of the disease. Minimally invasive liquid biopsy procedures have emerged to investigate cancer-related molecules with the advantage of detecting heterogeneity as well as acquired resistance in cancer. The metastatic castration-resistant prostate cancer (mCRPC) tumors have a highly complex genomic landscape compared to primary prostate tumors; a number of mCRPC harbor clinically actionable molecular alterations, including DNA damage repair (e.g., BRCA1/2 and ATM) and PTEN/phosphoinositide 3-kinase signaling. Heterogeneity in the genomic landscape of prostate cancer has become apparent and genomic alterations of TP53, RB1, AR, and cell cycle pathway are associated with poor clinical outcomes in patients. Prostate cancer with mutant SPOP shows a distinct pattern of genomic alterations, associating with better clinical outcomes. Several genomic profiling tests, which can be used in the clinic, are approved by the U.S. Food and Drug Administration, including MSK-IMPACT, FoundationOne CDx, and FoundationOne Liquid CDx. Here, we review emerging evidence for genomic profiling of prostate cancer, especially focusing on associations between genomic alteration and clinical outcome, liquid biopsy, and actionable molecular alterations.

An appraisal of genetic testing for prostate cancer susceptibility

Most criteria for genetic testing for prostate cancer susceptibility require a prior diagnosis of prostate cancer, in particular cases with metastatic disease are selected. Advances in the field are expected to improve outcomes through tailored treatments for men with advanced prostate cancer with germline pathogenic variants, although these are not currently offered in the curative setting. A better understanding of the value of genetic testing for prostate cancer susceptibility in screening, for early detection and prevention is necessary. We review and summarize the literature describing germline pathogenic variants in genes associated with increased prostate cancer risk and aggressivity. Important questions include: what is our ability to screen for and prevent prostate cancer in a man with a germline pathogenic variant and how does knowledge of a germline pathogenic variant influence treatment of men with nonmetastatic disease, with hormone-resistant disease and with metastatic disease? The frequency of germline pathogenic variants in prostate cancer is well described, according to personal and family history of cancer and by stage and grade of disease. The role of these genes in aggressive prostate cancer is also discussed. It is timely to consider whether or not genetic testing should be offered to all men with prostate cancer. The goals of testing are to facilitate screening for early cancers in unaffected high-risk men and to prevent advanced disease in men with cancer.

The tumor mutational landscape of BRCA2-deficient primary and metastatic prostate cancer

Carriers of germline BRCA2 pathogenic sequence variants have elevated aggressive prostate cancer risk and are candidates for precision oncology treatments. We examined whether BRCA2-deficient (BRCA2d) prostate tumors have distinct genomic alterations compared with BRCA2-intact (BRCA2i) tumors. Among 2536 primary and 899 metastatic prostate tumors from the ICGC, GENIE, and TCGA databases, we identified 138 primary and 85 metastatic BRCA2d tumors. Total tumor mutation burden (TMB) was higher among primary BRCA2d tumors, although pathogenic TMB did not differ by tumor BRCA2 status. Pathogenic and total single nucleotide variant (SNV) frequencies at KMT2D were higher in BRCA2d primary tumors, as was the total SNV frequency at KMT2D in BRCA2d metastatic tumors. Homozygous deletions at NEK3, RB1, and APC were enriched in BRCA2d primary tumors, and RB1 deletions in metastatic BRCA2d tumors as well. TMPRSS2-ETV1 fusions were more common in BRCA2d tumors. These results identify somatic alterations that hallmark etiological and prognostic differences between BRCA2d and BRCA2i prostate tumors.

The Homologous Recombination Deficiency Scar in Advanced Cancer: Agnostic Targeting of Damaged DNA Repair

BRCA1 and BRCA2 are the most recognized tumor-suppressor genes involved in double-strand DNA break repair through the homologous recombination (HR) system. Widely known for its role in hereditary cancer, HR deficiency (HRD) has turned out to be critical beyond breast and ovarian cancer: for prostate and pancreatic cancer also. The relevance for the identification of these patients exceeds diagnostic purposes, since results published from clinical trials with poly-ADP ribose polymerase (PARP) inhibitors (PARPi) have shown how this type of targeted therapy can modify the long-term evolution of patients with HRD. Somatic aberrations in other HRD pathway genes, but also indirect genomic instability as a sign of this DNA repair impairment (known as HRD scar), have been reported to be relevant events that lead to more frequently than expected HR loss of function in several tumor types, and should therefore be included in the current diagnostic and therapeutic algorithm. However, the optimal strategy to identify HRD and potential PARPi responders in cancer remains undefined. In this review, we summarize the role and prevalence of HRD across tumor types and the current treatment landscape to guide the agnostic targeting of damaged DNA repair. We also discuss the challenge of testing patients and provide a special insight for new strategies to select patients who benefit from PARPi due to HRD scarring.

PARP Inhibitors: A New Horizon for Patients with Prostate Cancer

The introduction of PARP inhibitors (PARPi) in prostate cancer is a milestone and provides a pathway to hope in fighting this disease. It is the first time that drugs, based on the concept of synthetic lethality, have been approved for prostate cancer. In addition, it is also the first time that genetic mutation tests have been included in the therapeutic algorithm of this disease, representing a significant step forward for precision and personalized treatment of prostate cancer. The objectives of this review are: (1) understanding the mechanism of action of PARPi in monotherapy and combinations; (2) gaining insights on patient selection for PARPi; (3) exposing the pivotal studies that have allowed its approval, and; (4) offering an overview of the ongoing trials. Nevertheless, many unsolved questions remain, such as the number of patients who could potentially benefit from PARPi, whether to use PARPi in monotherapy or in combination, and when is the best time to use them in advanced or localized disease. To answer these and other questions, many clinical trials are underway. Some of them have recently demonstrated promising results that may favor the introduction of new combinations in metastatic castration-resistant prostate cancer.

Germline Mutations in Patients With Early-Onset Prostate Cancer

Objective

To investigate the inherited mutations and their association with clinical features and treatment response in young-onset prostate cancer patients.

Method

Targeted gene sequencing on 139 tumor susceptibility genes was conducted with a total of 24 patients diagnosed with PCa under the age of 63 years old. Meanwhile, the related clinical information of those patients is collected and analyzed.

Results

Sixty-two germline mutations in 45 genes were verified in 22 patients. BRCA2 (20.8%) and GJB2 (20.8%) were found to be the most frequently mutated, followed by CHEK2, BRCA1, PALB2, CDKN2A, HOXB13, PPM1D, and RECQL (8.3% of each, 2/24). Of note, 58.3% (14/24) patients carry germline mutations in DNA repair genes (DRGs). Four families with HRR (homologous recombination repair)-related gene mutations were described and analyzed in detail. Two patients with BRCA2 mutation responded well to the combined treatment of androgen deprivation therapy (ADT) and radiotherapy/chemotherapy.

Conclusion

Mutations in DRGs are more prevalent in early-onset PCa with advanced clinical stages, and these patients had shorter progression-free survival. ADT Combined with either radiotherapy or chemotherapy may be effective in treating PCa caused by HRR-related gene mutations.

Ataxia-telangiectasia mutated and ataxia telangiectasia and Rad3-related kinases as therapeutic targets and stratification indicators for prostate cancer

The DNA damage response is an integral part of a cells' ability to maintain genomic integrity by responding to and ameliorating DNA damage, or initiating cell death for irrepairably damaged cells. This response is often hijacked by cancer cells to evade cell death allowing mutant cells to persist, as well as in the development of treatment resistance to DNA damaging agents such as chemotherapy and radiation. Prostate cancer (PCa) cells often exhibit alterations in DNA damage response genes including ataxia telangiectasia mutated (ATM), correlating with aggressive disease phenotype. The recent success of Poly (ADP-ribose) polymerase (PARP) inhibition has led to several clinically approved PARP inhibitors for the treatment of men with metastatic PCa, however a key limitation is the development of drug resistance and relapse. An alternative approach is selectively targeting ATM and ataxia telangiectasia and Rad3-related (ATR) which, due to their position at the forefront of the DDR, represent attractive pharmacological targets. ATR inhibition has been shown to act synergistically with PARP inhibition and other cancer treatments to enhance anti-tumour activity. ATM-deficiency is a common characteristic of PCa and a synthetic lethal relationship exists between ATM and ATR, with ATR inhibition inducing selective cell death in ATM-deficient PCa cells. The current research highlights the feasibility of therapeutically targeting ATR in ATM-deficient prostate tumours and in combination with other treatments to enhance overall efficacy and reduce therapeutic resistance. ATM also represents an important molecular biomarker to stratify patients into targeted treatment groups and aid prognosis for personalised medicine.

PARP Inhibition, a New Therapeutic Avenue in Patients with Prostate Cancer

Up to 25% of patients with metastatic prostate cancer present with germline or somatic DNA damage repair alterations, some of which are associated with aggressive disease and poor outcomes. New data have brought poly(ADP-ribose) polymerase (PARP) inhibitors into sharp focus in the treatment of metastatic castrate-resistant prostate cancer (mCRPC). Olaparib improved survival after at least one new hormonal therapy (NHT) in a cohort of patients harboring BRCA1, BRCA2 or ATM mutations in the PROfound trial, while rucaparib, talazoparib and niraparib demonstrated compelling activity in phase II trials. While patients with prostate cancer and BRCA1 or BRCA2 mutations may derive greatest benefit of PARP inhibition, the magnitude of benefit seems much lower in the context of most other homologous recombination gene mutations. Several PARP inhibitors are currently developed in combination with conventional therapy, including chemotherapy, NHT, and alpha-particle emitters, at different disease stages. Herein, we review the rationale for PARP inhibition in patients with prostate cancer, discuss the impact of PARP inhibitors on outcomes, and explore underlying challenges for future developments.

Implications of DNA damage repair alterations for the management of prostate cancer

PURPOSE OF REVIEW

In this review, we summarize the prevalence of alterations in DNA damage repair (DDR) genes in prostate cancer, their clinical significance, the therapeutic strategies developed to take advantage of the impaired tumour ability to repair DNA and the diagnostic approaches available to identify patients likely to benefit from DDR-targeting agents.

RECENT FINDINGS

DDR alterations are more frequent in metastatic than in localized prostate cancer and some of them associate with aggressive disease whereas the significance of others remain unclear. The most appropriate management approach for DDR-defective prostate cancer patients is unknown. Clinical trials have demonstrated the efficacy of different poly-ADP ribose polymerase inhibitors (PARPi) to treat metastatic castration-resistant prostate cancer patients with BRCA1/2 alterations, although there may be other DDR alterations that sensitize patients to these drugs. Multiple strategies to target DDR defects are being investigated, including PARPi in combination, platinum-based chemotherapy and immunotherapy, both in earlier and late disease stages. Optimization of molecular testing is paramount for the implementation of precision oncology in prostate cancer.

SUMMARY

Certain DDR defects present in prostate cancer have prognostic and therapeutic implications whereas the significance of other DDR alterations is yet to be elucidated.

The role of genetic testing in prostate cancer screening, diagnosis, and treatment

PURPOSE OF REVIEW

This review provides an overview of the current role of genetic testing in prostate cancer screening, diagnosis, and treatment.

RECENT FINDINGS

Recent studies have uncovered few but highly penetrant rare pathogenic mutations (RPMs), in genes, such as BRCA2, with strong prostate cancer risk and outcomes associations. Over 260 single nucleotide polymorphisms (SNPs) have also been identified, each associated with small incremental prostate cancer risk and when combined in a polygenic risk score (PRS), they provide strong prostate cancer risk prediction but do not seem to predict outcomes. Tumor tissue sequencing can also help identify actionable somatic mutations in many patients with advanced prostate cancer and inform on their risk of harboring a germline pathogenic mutation.

SUMMARY

RPM testing, PRS testing, and tumor sequencing all have current and/or potential future roles in personalized prostate cancer care.

Beyond BRCA: The Emerging Significance of DNA Damage Response and Personalized Treatment in Pancreatic and Prostate Cancer Patients

The BRCA1/2 germline and/or somatic pathogenic variants (PVs) are key players in the hereditary predisposition and therapeutic response for breast, ovarian and, more recently, pancreatic and prostate cancers. Aberrations in other genes involved in homologous recombination and DNA damage response (DDR) pathways are being investigated as promising targets in ongoing clinical trials. However, DDR genes are not routinely tested worldwide. Due to heterogeneity in cohort selection and dissimilar sequencing approaches across studies, neither the burden of PVs in DDR genes nor the prevalence of PVs in genes in common among pancreatic and prostate cancer can be easily quantified. We aim to contextualize these genes, altered in both pancreatic and prostate cancers, in the DDR process, to summarize their hereditary and somatic burden in different studies and harness their deficiency for cancer treatments in the context of currently ongoing clinical trials. We conclude that the inclusion of DDR genes, other than BRCA1/2, shared by both cancers considerably increases the detection rate of potentially actionable variants, which are triplicated in pancreatic and almost doubled in prostate cancer. Thus, DDR alterations are suitable targets for drug development and to improve the outcome in both pancreatic and prostate cancer patients. Importantly, this will increase the detection of germline pathogenic variants, thereby patient referral to genetic counseling.

Impact of DNA damage response defects in cancer cells on response to immunotherapy and radiotherapy

The DNA damage response (DDR) is a complex set of downstream pathways triggered in response to DNA damage to maintain genomic stability. Many tumours exhibit mutations which inactivate components of the DDR, making them prone to the accumulation of DNA defects. These can both facilitate the development of tumours and provide potential targets for novel therapeutic interventions. The inhibition of the DDR has been shown to induce radiosensitivity in certain cancers, rendering them susceptible to treatment with radiotherapy and improving the therapeutic window. Moreover, DDR defects are a strong predictor of patient response to immune checkpoint inhibition (ICI). The ability to target the DDR selectively has the potential to expand the tumour neoantigen repertoire, thus increasing tumour immunogenicity and facilitating a CD8+ T and NK cell response against cancer cells. Combinatorial approaches, which seek to integrate DDR inhibition with radiotherapy and immunotherapy, have shown promise in early trials. Further studies are necessary to understand these synergies and establish reliable biomarkers.

Outcomes of Patients with Metastatic Castration-Resistant Prostate Cancer According to Somatic Damage DNA Repair Gene Alterations

(1) Background: In literature, approximately 20% of mCRPC present somatic DNA damage repair (DDR) gene mutations, and their relationship with response to standard therapies in mCRPC is not well understood. The objective was to evaluate outcomes of mCRPC patients treated with standard therapies according to somatic DDR status. (2) Methods: Eighty-three patients were recruited at Caen Cancer Center (France). Progression-free survival (PFS) after first-line treatment was analyzed according to somatic DDR mutation as primary endpoint. PFS according to first exposure to taxane chemotherapy and PFS2 (time to second event of disease progression) depending on therapeutic sequences were also analyzed. (3) Results: Median first-line PFS was 9.7 months in 33 mutated patients and 8.4 months in 50 non-mutated patients (p = 0.9). PFS of first exposure to taxanes was 8.1 months in mutated patients and 5.7 months in non-mutated patients (p = 0.32) and significantly longer among patients with ATM/BRCA1/BRCA2 mutations compared to the others (10.6 months vs. 5.5 months, p = 0.04). PFS2 was 16.5 months in mutated patients, whatever the sequence, and 11.7 months in non-mutated patients (p = 0.07). The mutated patients treated with chemotherapy followed by NHT had a long median PFS2 (49.8 months). (4) Conclusions: mCRPC patients with BRCA1/2 and ATM benefit from standard therapies, with a long response to taxanes.

Definitions of disease burden across the spectrum of metastatic castration-sensitive prostate cancer: comparison by disease outcomes and genomics

BACKGROUND

Several definitions have attempted to stratify metastatic castrate-sensitive prostate cancer (mCSPC) into low and high-volume states. However, at this time, comparison of these definitions is limited. Here we aim to compare definitions of metastatic volume in mCSPC with respect to clinical outcomes and mutational profiles.

METHODS

We performed a retrospective review of patients with biochemically recurrent or mCSPC whose tumors underwent somatic targeted sequencing. 294 patients were included with median follow-up of 58.3 months. Patients were classified into low and high-volume disease per CHAARTED, STAMPEDE, and two numeric (≤3 and ≤5) definitions. Endpoints including radiographic progression-free survival (rPFS), time to development of castration resistance (tdCRPC), and overall survival (OS) were evaluated with Kaplan-Meier survival curves and log-rank test. The incidence of driver mutations between definitions were compared.

RESULTS

Median OS and tdCRPC were shorter for high-volume than low-volume disease for all four definitions. In the majority of patients (84.7%) metastatic volume classification did not change across all four definitions. High volume disease was significantly associated with worse OS for all four definitions (CHAARTED: HR 2.89; p < 0.01, STAMPEDE: HR 3.82; p < 0.01, numeric ≤3: HR 4.67; p < 0.01, numeric ≤5: HR 3.76; p < 0.01) however, were similar for high (p = 0.95) and low volume (p = 0.79) disease across all four definitions. Those with discordant classification tended to have more aggressive clinical behavior and mutational profiles. Patients with low-volume disease and TP53 mutation experienced a more aggressive course with rPFS more closely mirroring high-volume disease.

CONCLUSIONS

The spectrum of mCSPC was confirmed across four different metastatic definitions for clinical endpoints and genetics. All definitions were generally similar in classification of patients, outcomes, and genetic makeup. Given these findings, the simplicity of numerical definitions might be preferred, especially when integrating metastasis directed therapy. Incorporation of tumor genetics may allow further refinement of current metastatic definitions.

A transcriptomic model for homologous recombination deficiency in prostate cancer

BACKGROUND

Tumors with mutations associated with homologous recombination deficiency (HRD) are uncommon in prostate cancer (PCa) and variably responsive to PARP inhibition. To better identify tumors with HRD, we developed a transcriptomic signature for HRD in PCa (HRD-P).

METHODS

By using an established mutational signature, we created and validated HRD-P in six independent PCa cohorts (primary PCa, n = 8224; metastatic castration-resistant PCa [mCRPC], n = 328). Molecular and clinical features were compared between HRD-P+ tumors and those with single HR-gene mutations.

RESULTS

HRD-P+ tumors were more common than tumors with single HR-gene mutations in primary (201/491, 41% vs 32/491 6.5%) and mCRPC (126/328, 38% vs 82/328, 25%) cases, and HRD-P+ was more predictive of genomic instability suggestive of HRD. HRD-P+ was associated with a shorter time to recurrence following surgery and shorter overall survival in men with mCRPC. In a prospective trial of mCRPC treated with olaparib (n = 10), all three men with HRD-P+ experienced prolonged (>330 days) PSA progression-free survival.

CONCLUSION

These results suggest transcriptomics can identify more patients that harbor phenotypic HRD than single HR-gene mutations and support further exploration of transcriptionally defined HRD tumors perhaps in conjunction with genomic markers for therapeutic application.

Apalutamide, Darolutamide and Enzalutamide for Nonmetastatic Castration-Resistant Prostate Cancer (nmCRPC): A Critical Review

Nonmetastatic castration-resistant prostate cancer (nmCRPC) represents a condition in which patients with prostate cancer show biochemical progression during treatment with androgen-deprivation therapy (ADT) without signs of radiographic progression according to conventional imaging. The SPARTAN, ARAMIS and PROSPER trials showed that apalutamide, darolutamide and enzalutamide, respectively, prolong metastasis-free survival (MFS) and overall survival (OS) of nmCRPC patients with a short PSA doubling time, and these antiandrogens have been recently introduced in clinical practice as a new standard of care. No direct comparison of these three agents has been conducted to support treatment choice. In addition, a significant proportion of nmCRPC on conventional imaging is classified as metastatic with new imaging modalities such as the prostate-specific membrane antigen positron emission tomography (PSMA-PET). Some experts posit that these "new metastatic" patients should be treated as mCRPC, resizing the impact of nmCRPC trials, whereas other authors suggest that they should be treated as nmCRPC patients, based on the design of pivotal trials. This review discusses the most convincing evidence regarding the use of novel antiandrogens in patients with nmCRPC and the implications of novel imaging techniques for treatment selection.

PARP Inhibitors as Monotherapy in Daily Practice for Advanced Prostate Cancers

Despite recent improvements in survival, metastatic castration-resistant prostate cancers (mCRPCs) remain lethal. Alterations in genes involved in the homologous recombination repair (HRR) pathway are associated with poor prognosis. Poly-ADP-ribose polymerase (PARP) inhibitors (PARPis) have demonstrated anti-tumoral effects by synthetic lethality in patients with mCRPCs harboring HRR gene alterations, in particular BRCA2. While both olaparib and rucaparib have obtained government approvals for use, the selection of eligible patients as well as the prescription of these treatments within the clinical urology community are challenging. This review proposes a brief review of the rationale and outcomes of PARPi treatment, then a pragmatic vision of PARPi use in terms of prescription and the selection of patients based on molecular screening, which can involve potential genetic counseling in the case of associated germinal alterations.