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

Prognostic Value of Germline DNA Repair Gene Mutations in De Novo Metastatic and Castration-Sensitive Prostate Cancer

BACKGROUND

Germline DNA damage repair gene mutations (gDDRm) have been found in approximately 12% of patients with metastatic prostate cancer (mPCa). Previous studies of the clinical impact of gDDRm have mainly been in the setting of metastatic castration-resistant prostate cancer (mCRPC). This study aimed to determine the prognostic value of gDDRm in de novo metastatic and castration-sensitive prostate cancer (mCSPC).

MATERIALS AND METHODS

We retrospectively collected the records of 139 consecutive men with de novo mCSPC who initially received systemic therapies following guidelines. This included 128 patients who underwent genetic testing at our center and 11 patients referred to our center after being identified as gDDRm carriers. Time to mCRPC was collected. Kaplan-Meier and log-rank analysis were used to analyze the association between gDDRm and clinical outcomes. Survival outcomes were adjusted using multivariable Cox regression models.

RESULTS

Of the 139 patients with de novo mCSPC, 28 gDDRm carriers were identified. Median time progressing to mCRPC was significantly shorter in patients carrying gDDRm than in those without mutations (8.3 vs 13.2 months; hazard ratio [HR], 2.37; p < .001). Moreover, median progression time was almost halved in BRCA2 carriers (6.3 vs. 13.2 months; HR, 3.73; p < .001). Subgroup analysis revealed that the presence of gDDRm indicated poor therapy response regardless of disease volume and prostate-specific antigen nadir within the first 7 months. Presence of gDDRm remained independently associated with increased risk of progression to mCRPC in multivariate analysis (adjusted HR, 1.98; p = .006).

CONCLUSION

Our study suggested that positive gDDRm status predicted rapid progression to castration resistance in patients with de novo mCSPC. We propose identifying gDDRm status at the time of diagnosis for mCSPC patients, considering it is the first step of tailoring individualized treatment. In addition, DNA repair genes were a good therapeutic target for poly (ADP-ribose) polymerase inhibitors, and our results call for more frontline targeted therapy trials in gDDRm carriers to prolong the progression time.

IMPLICATIONS FOR PRACTICE

Results of this study suggested that positive germline DNA damage repair gene mutation (gDDRm) status predicted earlier progression to castration resistance in patients with de novo metastatic and castration-sensitive prostate cancer (mCSPC). These findings indicated the importance of intense therapy for some subgroups of mCSPC, especially for mCSPC harboring gDDRm with low-volume disease. Moreover, gDDRm was a good therapeutic target for poly (ADP-ribose) polymerase inhibitors, and these findings call for more molecular marker driven trials moving to the mTNPC setting.

Genetic Testing in Prostate Cancer

PURPOSE OF REVIEW

This review summarizes recent advances in prostate cancer (PCa) genetics.

RECENT FINDINGS

Upwards of 20% of metastatic castration-resistant prostate tumors (mCRPC) carry homologous recombination (HR) repair gene mutations, of which ~ 10% are germline (inherited). Another ~ 5% exhibit microsatellite instability (MSI-H) and/or mismatch repair deficiency (MMRd). Pembrolizumab is approved for tumors with MMRd, thus patients with mCRPC and MMRd are candidates for pembrolizumab. Emerging data indicate that platinum chemotherapy and poly ADP-ribose polymerase inhibitors (PARPi) are effective in PCa exhibiting HR deficiency. NCCN guidelines now recommend germline and somatic tumor testing in specific clinical scenarios due to treatment and family implications. Genetic testing in PCa patients may inform prognosis, treatment options, and have implications for family counseling. PARPi, platinum chemotherapy, and immune checkpoint inhibitors are promising targeted therapies for PCa with specific molecular features. Therapeutic advances, along with importance to relatives, are driving genetic testing in prostate cancer.

Role of the DNA damage response in prostate cancer formation, progression and treatment

BACKGROUND

Clinical and preclinical studies have revealed that alterations in DNA damage response (DDR) pathways may play an important role in prostate cancer (PCa) etiology and progression. These alterations can influence PCa responses to radiotherapy and anti-androgen treatment. The identification of DNA repair gene aberrations in PCa has driven the interest for further evaluation whether these genetic changes may serve as biomarkers for patient stratification.

METHODS

In this review, we summarize the current knowledge on DDR alterations in PCa, their potential impact on clinical interventions and prospects for improved management of PCa. We particularly focus on the influence of DDR gene mutations on PCa initiation and progression and describe the underlying mechanisms.

RESULTS AND CONCLUSIONS

A better understanding of these mechanisms, will contribute to better disease management as treatment strategies can be chosen based on the specific disease properties, since a growing number of treatments are targeting DDR pathway alterations (such as Poly(ADP-ribose) polymerase inhibitors). Furthermore, the recently discovered crosstalk between the DDR and androgen receptor signaling opens a new array of possible strategies to optimize treatment combinations. We discuss how these recent and ongoing studies will help to improve diagnostic, prognostic and therapeutic approaches for PCa management.

BRCA2 gene mutation and prostate cancer risk. Comprehensive review and update

The second most common type of tumor worldwide is prostate cancer (PCa). Certain genetic factors contribute to a risk of developing PCa of as much as 40%. BRCA1 and BRCA2 mutations have linked with an increased risk for breast, ovarian, and PCa. However, BRCA2 is the most common gene found altered in early-onset of PCa in males younger than 65. BRCA2 mutation has a higher chance of developing an advanced stage of the disease, resulting in short survival time. This review aimed to describe the genetic changes in BRCA2 that contribute to the risk of PCa, to define its role in the early diagnosis in a man with a strong family history, and to outline the purpose of genetic testing and counseling. Also, the review summarizes the impact of BRCA2 gene mutation in localized PCa, and the treatment strategies have used for PCa patients with a BRCA2 modification.

Molecular Biomarkers in Localized Prostate Cancer: ASCO Guideline

PURPOSE

This guideline provides recommendations for available tissue-based prostate cancer biomarkers geared toward patient selection for active surveillance, identification of clinically significant disease, choice of postprostatectomy adjuvant versus salvage radiotherapy, and to address emerging questions such as the relative value of tissue biomarkers compared with magnetic resonance imaging.

METHODS

An ASCO multidisciplinary Expert Panel, with representatives from the European Association of Urology, American Urological Association, and the College of American Pathologists, conducted a systematic literature review of localized prostate cancer biomarker studies between January 2013 and January 2019. Numerous tissue-based molecular biomarkers were evaluated for their prognostic capabilities and potential for improving management decisions. Here, the Panel makes recommendations regarding the clinical use and indications of these biomarkers.

RESULTS

Of 555 studies identified, 77 were selected for inclusion plus 32 additional references selected by the Expert Panel. Few biomarkers had rigorous testing involving multiple cohorts and only 5 of these tests are commercially available currently: Oncotype Dx Prostate, Prolaris, Decipher, Decipher PORTOS, and ProMark. With various degrees of value and validation, multiple biomarkers have been shown to refine risk stratification and can be considered for select men to improve management decisions. There is a paucity of prospective studies assessing short- and long-term outcomes of patients when these markers are integrated into clinical decision making.

RECOMMENDATIONS

Tissue-based molecular biomarkers (evaluating the sample with the highest volume of the highest Gleason pattern) may improve risk stratification when added to standard clinical parameters, but the Expert Panel endorses their use only in situations in which the assay results, when considered as a whole with routine clinical factors, are likely to affect a clinical decision. These assays are not recommended for routine use as they have not been prospectively tested or shown to improve long-term outcomes-for example, quality of life, need for treatment, or survival. Additional information is available at www.asco.org/genitourinary-cancer-guidelines.

Significance of BRCA2 and RB1 Co-loss in Aggressive Prostate Cancer Progression

PURPOSE

Previous sequencing studies revealed that alterations of genes associated with DNA damage response (DDR) are enriched in men with metastatic castration-resistant prostate cancer (mCRPC). BRCA2, a DDR and cancer susceptibility gene, is frequently deleted (homozygous and heterozygous) in men with aggressive prostate cancer. Here we show that patients with prostate cancer who have lost a copy of BRCA2 frequently lose a copy of tumor suppressor gene RB1; importantly, for the first time, we demonstrate that co-loss of both genes in early prostate cancer is sufficient to induce a distinct biology that is likely associated with worse prognosis.

EXPERIMENTAL DESIGN

We prospectively investigated underlying molecular mechanisms and genomic consequences of co-loss of BRCA2 and RB1 in prostate cancer. We used CRISPR-Cas9 and RNAi-based methods to eliminate these two genes in prostate cancer cell lines and subjected them to in vitro studies and transcriptomic analyses. We developed a 3-color FISH assay to detect genomic deletions of BRCA2 and RB1 in prostate cancer cells and patient-derived mCRPC organoids.

RESULTS

In human prostate cancer cell lines (LNCaP and LAPC4), loss of BRCA2 leads to the castration-resistant phenotype. Co-loss of BRCA2-RB1 in human prostate cancer cells induces an epithelial-to-mesenchymal transition, which is associated with invasiveness and a more aggressive disease phenotype. Importantly, PARP inhibitors attenuate cell growth in human mCRPC-derived organoids and human CRPC cells harboring single-copy loss of both genes.

CONCLUSIONS

Our findings suggest that early identification of this aggressive form of prostate cancer offers potential for improved outcomes with early introduction of PARP inhibitor-based therapy.See related commentary by Mandigo and Knudsen, p. 1784.

An evaluation of current prostate cancer diagnostic approaches with emphasis on liquid biopsies and prostate cancer

Introduction: Knowledge of the complex biology of prostate cancer is constantly growing, opening the field up to new therapeutic advances. The selection of patients on the basis of prognostic and predictive biomarkers is a challenging and emerging clinical need, not yet completely fulfilled. In this scenario, liquid biopsy offers a noninvasive and attractive approach to give important information about tumor biology and eventual resistance to treatments.Areas covered: The aim of this review of the literature is to evaluate the current knowledge and the promising value of liquid biopsy in prostate cancer. Circulating tumor cells and circulating tumor DNA identified by liquid biopsies are currently under evaluation to guide therapeutic decisions in prostate cancer management, even though practical applications of these approaches are still very limited. We examined the current areas of interest in which circulating tumor cells and circulating tumor DNA are being investigated, such as their prognostic and predictive role in response to chemotherapy or androgen receptor signaling inhibition, especially in the castration-resistant setting.Expert opinion: As the body of knowledge on liquid biopsy rapidly grows, we need to identify which can be the real applications of this technique in clinical practice and to overcome the problems that are limiting its routinely use.

Clinical Outcomes in Cyclin-dependent Kinase 12 Mutant Advanced Prostate Cancer

BACKGROUND

Cyclin-dependent kinase 12 (CDK12) loss occurs in 3-7% of metastatic prostate cancer patients and is characterized by a genomic instability signature, but the clinical implications of CDK12 loss are not well established.

OBJECTIVE

To determine the clinical course of patients with CDK12 mutant advanced prostate cancer compared with other genomic subtypes.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective analysis of data from three academic medical centers, including 317 patients with advanced prostate cancer and prior next-generation sequencing from tumor tissue (n = 172) or circulating tumor DNA (n = 145), was performed. Forty-six patients had CDK12 mutations; 34 had biallelic CDK12 loss (79%).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Patients were stratified by mutation status (CDK12, homologous recombination deficiency [HRD; BRCA1/2 and ATM], TP53, and other cohort). The Kaplan-Meier method was used to evaluate time to event outcomes: time to development of metastatic disease, time to development of castration resistance, and time to prostate-specific antigen (PSA) progression after first-line androgen receptor pathway inhibitor (ARPI) therapy in a patient subset.

RESULTS AND LIMITATIONS

The median follow-up was 66.6 mo. Patients with CDK12 mutant prostate cancer exhibited shorter time to metastasis (median = 34.9 mo, p =  0.004) and development of castration-resistant disease (median = 32.7 mo, p <  0.001), compared with other genomic subtypes, with shorter time to PSA progression on first-line ARPI treatment of metastatic castration-resistant disease (median = 3.6 mo, p =  0.0219). CDK12 mutant patients did not have overall shorter time on treatment compared with other mutation subgroups, and CDK12 status did not demonstrate statistical significance in multivariate analysis. Limitations include variable center-dependent practice patterns and heterogeneity due to combining tumor and liquid biopsy data.

CONCLUSIONS

Our data suggest that advanced prostate cancers harboring CDK12 mutations display aggressive clinical behavior, underscoring the need to fully delineate the molecular and clinical characteristics, and appropriate therapeutic approaches for distinct subtypes of advanced prostate cancers.

PATIENT SUMMARY

In this report, we evaluate the clinical characteristics and outcomes of patients with prostate cancer and CDK12 mutation in their tumors. These patients seem to have more aggressive disease, with more high-grade Gleason ≥8 cancers and shorter time to developing metastatic cancer. Cases of advanced CDK12-mutated prostate cancer may warrant consideration of therapy intensification or combination approaches.

Germline mutation in DNA-repair genes is associated with poor survival in BRCA1/2-negative breast cancer patients

BRCA1/2 genes are the most frequently germline mutated DNA‐repair genes, and the survival of BRCA1/2 carriers has been extensively explored in breast cancer. However, the prevalence of germline mutations in non‐BRCA1/2 DNA‐repair genes and the survival of carriers are largely unknown in a large cohort of unselected breast cancer patients. Germline mutations in 16 DNA‐repair genes were determined using a multigene panel in 7657 BRCA1/2‐negative breast cancer patients who were unselected for family history of cancer or age at diagnosis. Among the 7657 BRCA1/2‐negative breast cancer patients, 257 (3.4%) carried at least 1 pathogenic germline mutation in the 16 DNA‐repair genes. The prevalence of DNA‐repair gene mutations was significantly higher in familial breast cancers (5.2%, P = 0.002) and early‐onset breast cancers (diagnosed at and before the age of 40) (4.5%, P = 0.003) than that of sporadic breast cancers (2.9%) (diagnosed above age of 40), respectively. The DNA‐repair gene mutation carriers were significantly more likely to have a larger tumor (P = 0.04) and axillary lymph node metastasis (P = 0.03). Moreover, DNA‐repair gene mutation was an independent unfavorable factor for recurrence‐free survival (adjusted hazard ratio [HR] = 1.38, 95% CI: 1.00‐1.91, P = 0.05) and disease‐specific survival (adjusted HR=1.63, 95% CI: 1.04‐2.57, P = 0.03) in this cohort. Overall, 3.4% of BRCA1/2‐negative breast cancer patients carried germline mutations in the 16 DNA‐repair genes, and the DNA‐repair gene mutation carriers exhibited an aggressive phenotype and had poor survival compared with noncarriers.

Effect of DNA damage response mutations on prostate cancer prognosis: a systematic review

The prognosis of men with prostate cancer (PC) with mutations in DNA damage response (DDR) genes undergoing different treatments is unclear. This systematic review compared clinical outcomes in PC patients with DDR mutations (DDR⁺) versus no mutations (DDR^-). 14 resources plus gray literature were searched for studies in PC and subgroups (castration-resistant PC, metastatic PC and metastatic castration-resistant PC) by DDR gene (ATM, ATR, BRCA1, BRCA2, CHEK2, FANCA, MLH1, MRE11A, NBN, PALB2, RAD51C) mutation status. From 11,648 records, 26 studies were included. For mCRPC, six studies reported comparative efficacy for key outcomes. Improvements in several clinical outcomes were observed for DDR⁺ (vs DDR^-) after PARP inhibitor therapy or immunotherapy. DDR⁺ PC patients may have improved outcomes depending on the treatment they undergo.

Contribution of Inherited DNA-Repair Gene Mutations to Hormone-Sensitive and Castrate-Resistant Metastatic Prostate Cancer and Implications for Clinical Outcome

PURPOSE

To compare the prevalence of germline mutations in metastatic hormone-sensitive prostate cancer (mHSPC) and metastatic castrate-resistant prostate cancer (mCRPC) and assess the impact of mutations on progression to castration resistance and overall survival.

METHODS

Targeted sequencing of germline DNA from 704 men (221 at the time of mHSPC and 483 at the time of mCRPC) enrolled in two advanced prostate cancer registries at Mayo Clinic between 2003 and 2013 was performed for 21 predisposition genes. Frequencies of pathogenic mutations were compared in patients and reference controls to identify genes enriched in metastatic prostate cancer. Multivariable Cox proportional hazards regression was used to identify predictors of progression to mCRPC and overall survival.

RESULTS

Sixty-eight germline mutations in 12 genes were identified in 66 men (9.4%). Mutations in ATM, BRCA2, CHEK2, FANCM, and TP53 were significantly enriched (odds ratio greater than 2.0) in the metastatic cohorts compared with reference controls. The frequency of germline mutations was similar for patients with mHSPC and mCRPC (11.8% v 8.3%; P = .16). The median time to progression from mHSPC to mCRPC was 23.1 and 32.5 months for patients with and without mutations, respectively (P = .96). Although older age at diagnosis, Gleason score greater than 7, elevated alkaline phosphatase level, and high volume of disease were associated with shorter duration of progression to mCRPC and poor overall survival, mutation status was not (progression to mCRPC hazard ratio, 0.81; 95% CI, 0.61 to 1.09; P = .17; overall survival hazard ratio, 1.00; 95% CI, 0.75 to 1.34; P = .98).

CONCLUSION

Similarly elevated rates of germline predisposition gene mutations in mHSPC and mCRPC suggest that germline genetic testing may help to guide medical management for all patients with advanced metastatic prostate cancer. Mutation status was not associated with shorter progression to mCRPC or poor overall survival.

Current Treatment Options for Metastatic Hormone-Sensitive Prostate Cancer

The possible treatments options for metastatic hormone-sensitive prostate cancer (mHSPC) have dramatically increased during the last years. The old backbone, which androgen-deprivation therapy (ADT) is the exclusive approach for hormone-naïve patients, has been disrupted. Despite the fact that several high-quality, randomized, controlled phase 3 trials have been conducted in this setting, no direct comparison is currently available among the different strategies. Inadequate power, absence of preplanning and small sample size frequently affect the subgroup analyses according to disease volume or patient's risk. The choice between ADT alone and ADT combined with docetaxel, abiraterone acetate, enzalutamide, apalutamide or radiotherapy to the primary tumor remains challenging. Factors that are related to the tumor, patient or drug side effects, currently guide these clinical decisions. This comprehensive review aims to indirectly compare the phase 3 trials in the mHSPC setting, in order to extrapolate data useful for treatment selection, providing also perspectives on future biomarkers.

Emerging therapeutic agents for genitourinary cancers

The treatment of genitourinary malignancies has dramatically evolved over recent years. Renal cell carcinoma, urothelial carcinoma of the bladder, and prostate adenocarcinoma are the most commonly encountered genitourinary malignancies and represent a heterogeneous population of cancers, in both histology and approach to treatment. However, all three cancers have undergone paradigm shifts in their respective therapeutic landscapes due to a greater understanding of their underlying molecular mechanisms and oncogenic drivers. The advance that has gained the most recent traction has been the advent of immunotherapies, particularly immune checkpoint inhibitors. Immunotherapy has increased overall survival and even provided durable responses in the metastatic setting in some patients. The early success of immune checkpoint inhibitors has led to further drug development with the emergence of novel agents which modulate the immune system within the tumor microenvironment. Notwithstanding immunotherapy, investigators are also developing novel agents tailored to a variety of targets including small-molecule tyrosine kinase inhibitors, mTOR inhibitors, and novel fusion proteins to name a few. Erdafitinib has become the first targeted therapy approved for metastatic bladder cancer. Moreover, the combination therapy of immune checkpoint inhibitors with targeted agents such as pembrolizumab or avelumab with axitinib has demonstrated both safety and efficacy and just received FDA approval for their use. We are in an era of rapid progression in drug development with multiple exciting trials and ongoing pre-clinical studies. We highlight many of the promising new emerging therapies that will likely continue to improve outcomes in patients with genitourinary malignancies.

Sequencing strategies in the new treatment landscape of prostate cancer

Over the last 10 years, a number of new agents approved for the treatment of metastatic castration-resistant prostate cancer have led to a significant improvement in overall survival. The addition of new agents to androgen deprivation therapy has also allowed a paradigmatic change in the treatment of metastatic hormone-sensitive prostate cancer by improving overall survival in comparison with androgen deprivation therapy alone. Furthermore, recent data concerning the efficacy of three different androgen receptor-targeting agents in patients with nonmetastatic castration-resistant prostate cancer have opened up new scenarios for future patients' management. Defining the best sequencing strategies for men with prostate cancer is a currently unmet medical need, and choosing treatment is often challenging for clinicians because of the lack of direct comparisons of the available agents. The aim of this paper is to provide a comprehensive review of the literature concerning current sequencing strategies for prostate cancer patients.

Cellular and Molecular Mechanisms Underlying Prostate Cancer Development: Therapeutic Implications

Prostate cancer is the most frequent nonskin cancer and second most common cause of cancer-related deaths in man. Prostate cancer is a clinically heterogeneous disease with many patients exhibiting an aggressive disease with progression, metastasis, and other patients showing an indolent disease with low tendency to progression. Three stages of development of human prostate tumors have been identified: intraepithelial neoplasia, adenocarcinoma androgen-dependent, and adenocarcinoma androgen-independent or castration-resistant. Advances in molecular technologies have provided a very rapid progress in our understanding of the genomic events responsible for the initial development and progression of prostate cancer. These studies have shown that prostate cancer genome displays a relatively low mutation rate compared with other cancers and few chromosomal loss or gains. The ensemble of these molecular studies has led to suggest the existence of two main molecular groups of prostate cancers: one characterized by the presence of ERG rearrangements (~50% of prostate cancers harbor recurrent gene fusions involving ETS transcription factors, fusing the 5' untranslated region of the androgen-regulated gene TMPRSS2 to nearly the coding sequence of the ETS family transcription factor ERG) and features of chemoplexy (complex gene rearrangements developing from a coordinated and simultaneous molecular event), and a second one characterized by the absence of ERG rearrangements and by the frequent mutations in the E3 ubiquitin ligase adapter SPOP and/or deletion of CDH1, a chromatin remodeling factor, and interchromosomal rearrangements and SPOP mutations are early events during prostate cancer development. During disease progression, genomic and epigenomic abnormalities accrued and converged on prostate cancer pathways, leading to a highly heterogeneous transcriptomic landscape, characterized by a hyperactive androgen receptor signaling axis.

PARP Inhibitors in Prostate Cancer—The Preclinical Rationale and Current Clinical Development

Prostate cancer is globally the second most commonly diagnosed cancer type in men. Recent studies suggest that mutations in DNA repair genes are associated with aggressive forms of prostate cancer and castration resistance. Prostate cancer with DNA repair defects may be vulnerable to therapeutic targeting by Poly(ADP-ribose) polymerase (PARP) inhibitors. PARP enzymes modify target proteins with ADP-ribose in a process called PARylation and are in particular involved in single strand break repair. The rationale behind the clinical trials that led to the current use of PARP inhibitors to treat cancer was to target the dependence of BRCA-mutant cancer cells on the PARP-associated repair pathway due to deficiency in homologous recombination. However, recent studies have proposed therapeutic potential for PARP inhibitors in tumors with a variety of vulnerabilities generating dependence on PARP beyond the synthetic lethal targeting of BRCA1/BRCA2 mutated tumors, suggesting a wider potential than initially thought. Importantly, PARP-associated DNA repair pathways are also closely connected to androgen receptor (AR) signaling, which is a key regulator of tumor growth and a central therapeutic target in prostate cancer. In this review, we provide an extensive overview of published and ongoing trials exploring PARP inhibitors in treatment of prostate cancer and discuss the underlying biology. Several clinical trials are currently studying PARP inhibitor mono-and combination therapies in the treatment of prostate cancer. Integration of drugs targeting DNA repair pathways in prostate cancer treatment modalities allows developing of more personalized care taking also into account the genetic makeup of individual tumors.

Risk Prediction Tools Available for Germline BRCA1/2 Mutations Underperform in Prostate Cancer Patients

Early identification of germline BRCA1/2 mutations may be relevant for the management of patients with prostate cancer (PC) and to prevent future breast and ovarian cancers in their relatives. Several prediction tools have been developed to estimate the likelihood of a germline BRCA1/2 mutation and are widely used to optimize screening in breast and ovarian cancer patients. We aimed to elucidate the proportion of PC patients with known BRCA1/2 mutations who would have qualified for testing using two risk calculation models (BRCAPRO and the Manchester scoring system [MSS]). We analyzed 106 families with known BRCA1/BRCA2 mutations, including 23 with PC cases. Only 30% and 48% of PC patients who were known BRCA1/BRCA2 mutations carriers would have qualified for testing using BRCAPRO and MSS, respectively. A median of two breast and/or ovarian cancer cases per family had occurred between the first PC identified in a carrier and the cancer case leading to germline testing. PATIENT SUMMARY: We tested two models developed to predict the probability of inherited BRCA1/BRCA2 mutations and found that these tools underperform in men with prostate cancer and should not be used to optimize testing in this population.

The Role of BRCA Testing in Hereditary Pancreatic and Prostate Cancer Families

Beyond breast and ovarian cancers, mutations in the BRCA1 and BRCA2 genes increase risks for pancreatic and prostate cancers and contribute to the prevalence of these cancers. Mutations in a number of other genes have also been shown to increase the risk for these cancers as well. Genetic testing is playing an increasingly important role in the treatment of patients with pancreatic and prostate cancer and is now recommended for all patients with pancreatic or metastatic prostate cancer, as well as patients with high Gleason grade prostate cancer and a remarkable family history. Identification of an inherited mutation can direct evaluation of the patient for other cancer risks as well as identification and management of disease in at-risk relatives. Growing evidence suggests improved responses to PARP inhibitors and other therapies in patients with mutations in the BRCA and other DNA repair genes. Although more work must be done to clarify the prevalence and penetrance of mutations in genes other than BRCA1 and BRCA2 in patients with pancreatic and prostate cancer, in most cases, testing is now being done with a panel of multiple genes. Because of the complexities in panel testing and the increased likelihood of finding variants of uncertain significance, pre- and post-test genetic counseling are essential.

Germline and Somatic Mutations in Prostate Cancer for the Clinician

It is increasingly important for clinicians involved in the management of prostate cancer to understand the relevance of heritable (germline) mutations that, for select patients, affect prostate cancer risk and cancer biology, and acquired (somatic) mutations that occur in prostate cancer cells. In the advanced disease setting, mutations in homologous recombination repair genes (eg, BRCA1, BRCA2, ATM, CHEK2, PALB2) suggest candidacy for platinum chemotherapy and PARP inhibitor trials. Similarly, microsatellite instability and mismatch repair deficiency, which may arise in the setting of MLH1, MSH2, MSH6, and PMS2 mutations, suggest potential vulnerability to PD-1 inhibitors. Germline genetic testing has potential importance in the treatment and assessment of familial risk, and tumor-directed somatic sequencing may guide treatment decision-making. This review provides clinicians with knowledge of basic genetic terminology, awareness of the importance of family history of cancer (not limited to prostate cancer), contrasts between the different but potentially related objectives of germline versus somatic testing of tumor tissue, and indications for genetic counseling. Specific clinical scenarios, objectives of testing, and nature of the assays are reviewed. Germline and somatic mutations of known and potential relevance to prostate cancer are discussed in the context of treatment options, and algorithms to assist clinicians in approaching this area are proposed.

Targeting DNA Repair Defects for Precision Medicine in Prostate Cancer

PURPOSE OF REVIEW

Genomic studies of localized and metastatic prostate cancer have identified a high prevalence of clinically actionable alterations including mutations in DNA repair genes. In this manuscript, we review the current knowledge on DNA repair defects in prostate cancer and provide an overview of how these alterations can be targeted towards a personalized prostate cancer management.

RECENT FINDINGS

Twenty to 25% of metastatic prostate cancers harbor defects in DNA repair genes, most commonly in the homologous recombination genes. These defects confer increased sensitivity to platinum chemotherapy or poly (ADP-ribose) polymerase (PARP) inhibitors. Recent trials also support a synergistic effect of combining these therapies with androgen receptor-targeting agents. Identification of mismatch-repair defects could result in defining a prostate cancer population who may benefit from immune checkpoint inhibitors. These data have implications for family testing and early diagnosis, as many of these mutations are linked to inherited risk of prostate cancer. The DNA damage repair pathways are clinically relevant in prostate cancer, being a target for precision medicine; combination with standard-of-care androgen receptor (AR)-targeting agents may be synergistic.

BRCA2 and Other DDR Genes in Prostate Cancer

Germline and somatic aberrations in DNA damage repair (DDR) genes are more prevalent in prostate cancer than previously recognized, with BRCA2 as the most commonly altered gene. Germline mutations in BRCA2 have been linked to poor prognosis when patients are managed under the protocols currently approved for prostate cancer. The impact of germline mutations in other DDR genes beyond BRCA2 remain unclear. Importantly, a quarter of prostate cancer patients identified as germline mutation carriers lack a family history of cancer. The clinical implications of somatic DDR defects are yet to be elucidated. Poly ADP-ribose polymerase (PARP) inhibitors and platinum-based chemotherapy have proven to be effective in the treatment of other tumor types linked to BRCA1 and BRCA2 alterations and several trials are currently evaluating their efficacy in prostate cancer. Here, we summarize the available evidence regarding the prevalence of somatic and germline DDR defects in prostate cancer; their association with clinical outcomes; the trials assessing the efficacy of new therapies that exploit DDR defects in prostate cancer and briefly discuss some uncertainties about the most appropriate management for these patients.

Biological Evolution of Castration-resistant Prostate Cancer

CONTEXT

Recent studies focused on the molecular characterization of metastatic prostate cancer have identified genomic subsets and emerging resistance patterns. Detection of these alterations in patients has potential implications for therapy selection and prognostication.

OBJECTIVE

The primary objective is to review the current landscape of clinical and molecular biomarkers in advanced prostate cancer and understand how they may reflect underlying tumor biology. We also discuss how these features may potentially impact earlier stages of the disease.

EVIDENCE ACQUISITION

A literature search was performed of recent clinical biomarker/genomic studies focused on advanced metastatic prostate cancer as well as relevant preclinical studies investigating how these alterations influence therapy response or resistance.

EVIDENCE SYNTHESIS

Metastatic castration-resistant prostate cancer is commonly driven by androgen receptor signaling even after progression on potent hormonal agents, but other alterations may also be present or emerge during therapy resistance such as DNA repair gene aberrations or combined loss of tumor suppressor genes. Biological implications of these changes are context dependent, which may affect their detection and interpretation.

CONCLUSIONS

Molecular changes occur during prostate cancer progression and treatment resistance. Detection of genomic alterations has potential to influence therapy choice. Additional studies are warranted to elucidate the evolution of these changes and their impact in earlier stages of the disease.

PATIENT SUMMARY

We review the biology of advanced prostate cancer, and highlight opportunities and challenges for using biological or molecular assays to help guide individualized treatment decisions for patients.