The cost-effectiveness of germline BRCA testing-guided olaparib treatment in metastatic castration resistant prostate cancer.

BACKGROUND: Olaparib targets the DNA repair pathways and has revolutionized the management of metastatic castration resistant prostate cancer (mCRPC). Treatment with the drug should be guided by genetic testing; however, published economic evaluations did not consider olaparib and genetic testing as codependent technologies. This study aims to assess the cost-effectiveness of BRCA germline testing to inform olaparib treatment in mCRPC. METHODS: We conducted a cost-utility analysis of germline BRCA testing-guided olaparib treatment compared to standard care without testing from an Australian health payer perspective. The analysis applied a decision tree to indicate the germline testing or no testing strategy. A Markov multi-state transition approach was used for patients within each strategy. The model had a time horizon of 5 years. Costs and outcomes were discounted at an annual rate of 5 percent. Decision uncertainty was characterized using probabilistic and scenario analyses. RESULTS: Compared to standard care, BRCA testing-guided olaparib treatment was associated with an incremental cost of AU$7,841 and a gain of 0.06 quality-adjusted life-years (QALYs). The incremental cost-effectiveness ratio (ICER) was AU$143,613 per QALY. The probability of BRCA testing-guided treatment being cost effective at a willingness-to-pay threshold of AU$100,000 per QALY was around 2 percent; however, the likelihood for cost-effectiveness increased to 66 percent if the price of olaparib was reduced by 30 percent. CONCLUSION: This is the first study to evaluate germline genetic testing and olaparib treatment as codependent technologies in mCRPC. Genetic testing-guided olaparib treatment may be cost-effective with significant discounts on olaparib pricing.

Longitudinal assessment of plasma androgen receptor copy number predicts overall survival in subsequent treatment lines in castration-resistant prostate cancer: analysis from a prospective trial.

BACKGROUND: Baseline plasma androgen-receptor copy number (AR-CN) is a promising biomarker for metastatic castration-resistant prostate cancer (mCRPC) outcome and treatment response; however, the role of its longitudinal testing is unproven. We aimed to evaluate the prognostic role of AR-CN assessed before subsequent treatment lines in mCRPC patients. METHODS: A subgroup analysis of a prospective multicenter biomarker trial (IRSTB030) was carried out. Plasma AR-CN status (classified as normal or gain, cut-off value = 2) was assessed with digital PCR before each treatment line. RESULTS: Forty mCRPC patients receiving sequentially docetaxel, cabazitaxel and an AR signaling inhibitor (abiraterone or enzalutamide) were analyzed. At multivariate analysis, at each assessment overall survival (OS) was independently correlated with AR-CN status [first line: hazard ratio (HR) 4.1 [95% confidence interval (CI) 1.6-10.5]; second line: HR 2.4 (95% CI 1.1-5.3); third line: HR 2.1 (95% CI 1.0-4.3)] and median prostate-specific antigen [first line: HR 4.4 (95% CI 1.8-10.9); second line: HR 3.4 (95% CI 1.6-7.2); third line: HR 2.5 (95% CI 1.2-5.6)]. In the three subsequent assessments, AR-CN status changed from normal to gain in 15 (38%) patients. These patients had longer OS (47 months) compared with patients presenting AR-CN gain from first assessment (36 months), but shorter than those maintaining normal AR-CN (69 months) (P = 0.003). CONCLUSIONS: Plasma AR-CN correlates with survival not only at baseline (before first treatment), but also in the assessments before the following lines. Interestingly, AR-CN status may change from normal to gain across subsequent treatments in a significant number of cases, identifying a group of patients with intermediate outcomes. Longitudinal assessment of AR-CN status could represent a promising method to capture mCRPC intrinsic heterogeneity and to improve clinical management.

Prediction of Resistance to 177Lu-PSMA Therapy by Assessment of Baseline Circulating Tumor DNA Biomarkers.

177Lu-PSMA-617 and 177Lu-PSMA I&T (collectively termed 177Lu-PSMA) are currently being used for the treatment of selected metastatic castration-resistant prostate cancer (mCRPC) patients with PSMA PET-positive disease, but biomarkers for these agents remain incompletely understood. Methods: Pretreatment circulating tumor DNA (ctDNA) samples were collected from 44 mCRPC patients receiving 177Lu-PSMA treatment. Prostate-specific antigen responders and nonresponders were assessed relative to the ctDNA findings at baseline. Results: The ctDNA findings indicated that nonresponders were more likely to have gene amplifications than were responders (75% vs. 39.2%, P = 0.03). In particular, amplifications in FGFR1 (25% vs. 0%, P = 0.01) and CCNE1 (31.2% vs. 0%, P = 0.001) were more likely to be present in nonresponders. CDK12 mutations were more likely to be present in nonresponders (25% vs. 3.6%, P = 0.05). Conclusion: Our analyses indicate that ctDNA assays may contain specific biomarkers predictive of response or resistance for 177Lu-PSMA-treated mCRPC patients. Additional confirmatory studies are required before clinicians can use these findings to make personalized treatment decisions.

Circulating Tumor DNA Biomarkers for Response Assessment in Prostate Cancer.

Circulating tumor DNA (ctDNA) is measurable in the majority of metastatic castration-resistant prostate cancer patients. Data indicate that ctDNA present at baseline can serve as a prognostic biomarker and changes in the ctDNA posttreatment can rapidly predict both time to progression and survival. See related article by Tolmeijer et al., p. 2835.

Preclinical patient-derived modeling of castration-resistant prostate cancer facilitates individualized assessment of homologous recombination repair deficient disease.

The use of mutation analysis of homologous recombination repair (HRR) genes to estimate PARP-inhibition response may miss a larger proportion of responding patients. Here, we provide preclinical models for castration-resistant prostate cancer (CRPC) that can be used to functionally predict HRR defects. In vitro, CRPC LNCaP sublines revealed an HRR defect and enhanced sensitivity to olaparib and cisplatin due to impaired RAD51 expression and recruitment. Ex vivo-induced castration-resistant tumor slice cultures or tumor slice cultures derived directly from CRPC patients showed increased olaparib- or cisplatin-associated enhancement of residual radiation-induced γH2AX/53BP1 foci. We established patient-derived tumor organoids (PDOs) from CRPC patients. These PDOs are morphologically similar to their primary tumors and genetically clustered with prostate cancer but not with normal prostate or other tumor entities. Using these PDOs, we functionally confirmed the enhanced sensitivity of CRPC patients to olaparib and cisplatin. Moreover, olaparib but not cisplatin significantly decreased the migration rate in CRPC cells. Collectively, we present robust patient-derived preclinical models for CRPC that recapitulate the features of their primary tumors and enable individualized drug screening, allowing translation of treatment sensitivities into tailored clinical therapy recommendations.

Prospective assessment of AR splice variant and multi-biomarker expression on circulating tumor cells of mCRPC patients undergoing androgen receptor targeted agents: interim analysis of PRIMERA trial (NCT04188275).

Circulating tumor cells detection and ARV7 expression are associated with worse clinical outcomes in metastatic Castration-Resistant Prostate Cancer (mCRPC) undergoing Androgen Receptor Targeted Agents. ARFL, PSMA and PSA may help to refine prognostic models. In our institution, a prospective observational trial testing CTC detection in mCPRC undergoing I line ARTA therapy terminated the planned enrollment in 2020. Here, we present a pre-planned interim analysis with 18 months of median follow-up. RT-qPCR was used to determine the CTC expression of PSA, PSMA, AR and ARV7 before starting ARTA. PSA-drop, Progression-Free and Overall Survival (PFS and OS) and their correlation with CTC detection were reported. Forty-four patients were included. CTC were detected in 43.2% of patients, of whom 8.94% expressed PSA, 15.78% showed ARV7, 63.15% and 73.68% displayed ARFL and PSMA, respectively. Biochemical response was significantly improved in CTC + vs CTC- patients, with median PSA-drop of 18.5 vs 2.5 ng/ml (p = 0.03). After a median follow-up of 18 months, 50% of patients progressed. PFS was significantly longer in CTC- patients (NR vs 16 months). Eight (18.2%) patients died, a non-significant trend in terms of OS was detected in favor of CTC- patients (NR vs 29 months, p = 0.05). AR, PSA and PSMA expression in CTC + had no significant impact on PSA-drop, PFS or OS. PRIMERA-trial confirmed the CTC detection predictive importance in mCRPC patients.

Assessment of Androgen Receptor Splice Variant-7 as a Biomarker of Clinical Response in Castration-Sensitive Prostate Cancer.

PURPOSE: Therapies targeting the androgen receptor (AR) have improved the outcome for patients with castration-sensitive prostate cancer (CSPC). Expression of the constitutively active AR splice variant-7 (AR-V7) has shown clinical utility as a predictive biomarker of AR-targeted therapy resistance in castration-resistant prostate cancer (CRPC), but its importance in CSPC remains understudied. EXPERIMENTAL DESIGN: We assessed different approaches to quantify AR-V7 mRNA and protein in prostate cancer cell lines, patient-derived xenograft (PDX) models, publicly available cohorts, and independent institutional clinical cohorts, to identify reliable approaches for detecting AR-V7 mRNA and protein and its association with clinical outcome. RESULTS: In CSPC and CRPC cohorts, AR-V7 mRNA was much less abundant when detected using reads across splice boundaries than when considering isoform-specific exonic reads. The RM7 AR-V7 antibody had increased sensitivity and specificity for AR-V7 protein detection by immunohistochemistry (IHC) in CRPC cohorts but rarely identified AR-V7 protein reactivity in CSPC cohorts, when compared with the EPR15656 AR-V7 antibody. Using multiple CRPC PDX models, we demonstrated that AR-V7 expression was exquisitely sensitive to hormonal manipulation. In CSPC institutional cohorts, AR-V7 protein quantification by either assay was associated neither with time to development of castration resistance nor with overall survival, and intense neoadjuvant androgen-deprivation therapy did not lead to significant AR-V7 mRNA or staining following treatment. Neither pre- nor posttreatment AR-V7 levels were associated with volumes of residual disease after therapy. CONCLUSIONS: This study demonstrates that further analytical validation and clinical qualification are required before AR-V7 can be considered for clinical use in CSPC as a predictive biomarker.

Is olaparib cost effective in metastatic castration-resistant prostate cancer patients with at least one favorable gene mutation in BRCA1, BRCA2 or ATM?

Aim: To compare the cost-effectiveness of olaparib versus control treatment in metastatic castration-resistant prostate cancer patients with at least one gene mutation in BRCA1, BRCA2 or ATM from the US payer perspective. Methods: A Markov model was constructed to assess the quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios. Sensitivity analyses and scenario analyses were conducted to explore the impact of uncertainties. Results: The base-case result indicated that, for patients with specific gene mutations, olaparib gained 1.26 QALYs and USD$157,732 total cost. Compared with control treatment, the incremental cost-effectiveness ratio of olaparib was USD$248,248/QALY. The price of olaparib was the most influential parameter. Conclusion: Olaparib is not cost effective in comparison with control treatment in metastatic castration-resistant prostate cancer patients with specific gene mutations.

Efficacy of systemic therapies in men with metastatic castration resistant prostate cancer harboring germline ATM versus BRCA2 mutations.

BACKGROUND: Among men with metastatic prostate cancer, about 10% have germline alterations in DNA damage response genes. Most studies have examined BRCA2 alone or an aggregate of BRCA1/2 and ATM. Emerging data suggest that ATM mutations may have distinct biology and warrant individual evaluation. The objective of this study is to determine whether response to prostate cancer systemic therapies differs between men with germline mutations in ATM (gATM) and BRCA2 (gBRCA2). METHODS: This is an international multicenter retrospective matched cohort study of men with prostate cancer harboring gATM or gBRCA2. PSA50 response (≥50% decline in prostate-specific antigen) was compared using Fisher's exact test. RESULTS AND LIMITATIONS: The study included 45 gATM and 45 gBRCA2 patients, matched on stage and year of germline testing. Patients with gATM and gBRCA2 had similar age, Gleason grade, and PSA at diagnosis. We did not observe differences in PSA50 responses to abiraterone, enzalutamide, or docetaxel in metastatic castration resistant prostate cancer between the two groups; however, 0/7 with gATM and 12/14 with gBRCA2 achieved PSA50 response to PARPi (p < .001). Median (95% confidence interval) overall survival from diagnosis to death was 10.9 years (9.5-not reached) versus 9.9 years (7.1-not reached, p = .07) for the gATM and gBRCA2 cohorts, respectively. Limitations include the retrospective design and lack of mutation zygosity data. CONCLUSIONS: Conventional therapies can be effective in gATM carriers and should be considered before PARPi, which shows limited efficacy in this group. Men with gATM mutations warrant prioritization for novel treatment strategies.

Prospective assessment of AR splice variant and PSMA detection on circulating tumor cells of mCRPC patients: preliminary analysis of patients enrolled in PRIMERA trial (NCT04188275).

In our institution, a prospective observational trial testing micro-RNA (miRNA) and ARV7 mutational status in metastatic, castration resistant prostate cancer (mCRPC), is currently recruiting (PRIMERA trial, NCT04188275). A pre-planned interim analysis was performed when 50% of the planned accrual was reached. In this report, we explored the predictive value of Circulating Tumor Cell (CTC) detection in mCRPC patients undergoing 1st line therapy. Moreover, ARV7, ARFL, PSMA and PSA expression on CTC was reported to explore potential correlation with patient prognosis and response to therapy. PRIMERA is a prospective observational trial enrolling mCRPC patients undergoing standard treatment (ARTA + ADT) after I line ADT failure. Clinical and pathological features were collected. Outcomes selected for this preliminary analysis were time to castration resistance (TTCR), PSA at 8 weeks after ARTA therapy start, PSA drop at 8 weeks, Overall PSA drop, PSA nadir. Correlation between these outcomes and CTC detection was tested. Expression of ARV7, ARFL, PSA and PSMA was explored in CTC+ patients to assess their prevalence in this cohort and their impact on selected outcomes. Median TTCR was significantly shorter in CTC+ vs CTC- patients (32.3 vs 75 months, respectively, p = 0.03) and in ARFL+ vs ARFL- patients (30.2 vs 51.1 months, respectively, p = 0.02). ARV7, PSMA and PSA expression on CTC had no impact on median TTCR, nor on biochemical response to therapy. Patients in whom CTC and ARFL expression were detected had significant reduced TTCR. However, PSA response was not influenced by CTCs detection and specific biomarkers expression.

Immunohistochemistry-based assessment of androgen receptor status and the AR-null phenotype in metastatic castrate resistant prostate cancer.

BACKGROUND: Molecular and immunohistochemistry-based profiling of prostatic adenocarcinoma has revealed frequent Androgen Receptor (AR) gene and protein alterations in metastatic disease. This includes an AR-null non-neuroendocrine phenotype of metastatic castrate resistant prostate cancer which may be less sensitive to androgen receptor signaling inhibitors. This AR-null non-neuroendocrine phenotype is thought to be associated with TP53 and RB1 alterations. Herein, we have correlated molecular profiling of metastatic castrate resistant prostate cancer with AR/P53/RB immunohistochemistry and relevant clinical correlates. DESIGN: Twenty-seven cases of metastatic castrate resistant prostate cancer were evaluated using histopathologic examination to rule out neuroendocrine differentiation. A combination of a hybridization exon-capture next-generation sequencing-based assay (n = 26), fluorescence in situ hybridization for AR copy number status (n = 16), and immunohistochemistry for AR (n = 27), P53 (n = 24) and RB (n = 25) was used to profile these cases. RESULTS: Of 27 metastatic castrate resistant prostate cancer cases, 17 had AR amplification and showed positive nuclear expression of AR by immunohistochemistry. Nine cases lacked AR copy number alterations using next-generation sequencing/fluorescence in situ hybridization. A subset of these metastatic castrate resistant prostate cancer cases demonstrated the AR-null phenotype by immunohistochemistry (five cases and one additional case where next-generation sequencing failed). Common co-alterations in these cases involved the TP53, RB1, and PTEN genes and all these patients received prior therapy with androgen receptor signaling inhibitors (abiraterone and/or enzalutamide). CONCLUSIONS: Our study suggests that AR immunohistochemistry may distinguish AR-null from AR-expressing cases in the metastatic setting. AR-null status informs clinical decision-making regarding continuation of therapy with androgen receptor signaling inhibitors and consideration of other treatment options. This might be a relevant and cost-effective diagnostic strategy when there is limited access and/or limited tumor material for molecular testing.

Cost-Savings Analysis of AR-V7 Testing in Patients With Metastatic Castration-Resistant Prostate Cancer Eligible for Treatment With Abiraterone or Enzalutamide.

INTRODUCTION: Identification of cancer biomarkers that inform clinical decisions and reduce the use of ineffective therapies is a major goal of precision oncology. An abnormal splice variant of the androgen receptor, AR-V7, was recently found to confer resistance to novel hormonal therapies (abiraterone and enzalutamide) in men with metastatic castration-resistant prostate cancer (mCRPC), but did not negatively affect responses to taxane chemotherapies, suggesting that early use of chemotherapy may be a more effective option for AR-V7(+) patients. METHODS: We calculated the cost savings of performing AR-V7 testing in mCRPC patients prior to starting abiraterone/enzalutamide (and avoiding these drugs in AR-V7(+) men) versus treating all mCRPC patients empirically with abiraterone/enzalutamide (without use of the biomarker). RESULTS: We determined that AR-V7 testing would result in substantial cost savings as long as the true prevalence of AR-V7 was >5%. In our prior studies, we estimated that approximately 30% of mCRPC patients may have detectable AR-V7 in circulating tumor cells (CTCs). In this population, upfront testing of AR-V7 status (at a price of $1,000 per test) would result in a net cost savings of $150 Million in the United States per year. CONCLUSIONS: AR-V7 testing in mCRPC patients would be cost-beneficial when considering the current price of treatment, and may reduce the ineffective use of abiraterone/enzalutamide, leading to a significant net cost savings to the healthcare system. Clinical-grade AR-V7 testing is currently available at our institution. Prostate 76:1484-1490, 2016. © 2016 Wiley Periodicals, Inc.

Precision medicine for advanced prostate cancer.

PURPOSE OF REVIEW: Precision cancer medicine, the use of genomic profiling of patient tumors at the point-of-care to inform treatment decisions, is rapidly changing treatment strategies across cancer types. Precision medicine for advanced prostate cancer may identify new treatment strategies and change clinical practice. In this review, we discuss the potential and challenges of precision medicine in advanced prostate cancer. RECENT FINDINGS: Although primary prostate cancers do not harbor highly recurrent targetable genomic alterations, recent reports on the genomics of metastatic castration-resistant prostate cancer has shown multiple targetable alterations in castration-resistant prostate cancer metastatic biopsies. Therapeutic implications include targeting prevalent DNA repair pathway alterations with PARP-1 inhibition in genomically defined subsets of patients, among other genomically stratified targets. In addition, multiple recent efforts have demonstrated the promise of liquid tumor profiling (e.g., profiling circulating tumor cells or cell-free tumor DNA) and highlighted the necessary steps to scale these approaches in prostate cancer. SUMMARY: Although still in the initial phase of precision medicine for prostate cancer, there is extraordinary potential for clinical impact. Efforts to overcome current scientific and clinical barriers will enable widespread use of precision medicine approaches for advanced prostate cancer patients.

Phase II study of satraplatin and prednisone in patients with metastatic castration-resistant prostate cancer: a pharmacogenetic assessment of outcome and toxicity.

BACKGROUND: We assessed the effect of excision repair cross-complementing group 1 (ERCC1) and x-ray cross-complementing group 1 (XRCC1) gene polymorphisms on treatment outcomes with satraplatin and prednisone in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel-based therapy. PATIENTS AND METHODS: Twenty-four patients were enrolled in this single arm study. The primary objective was to determine if the presence of ERCC1 Asn118Asn (N118N, 500C>T, rs11615) and XRCC1 Arg399Gln (R399Q, 1301G>A, rs25487) genetic variants might be associated with an impact on progression-free survival (PFS); secondary objectives included overall response, survival, and toxicity. RESULTS: After population stratification by race, white patients carrying heterozygous or variant genotypes at the ERCC1 C>T locus had a >3-fold longer median PFS (5.8 vs. 1.8 months; 2P = .18, adjusted) and 5-fold longer median overall survival (OS) (15.7 vs. 3.2 months; 2P = .010, adjusted) than did patients carrying only wild-type alleles. For the XRCC1 G>A variant, without regard to race, patients carrying the wild-type GG alleles had a longer PFS (9.3 months) than those carrying GA or AA alleles (2.7 months; 2P = .02). Similarly, those carrying GG alleles did not reach median OS, whereas those carrying GA or AA alleles had a median OS of 9.6 months (2P = .12, adjusted). Multivariable analysis by using Cox proportional hazards modeling demonstrated that only XRCC1 was associated with PFS. CONCLUSIONS: To our knowledge, this is the first prospective study to date in patients with metastatic castration-resistant prostate cancer that describes predictive germline polymorphisms of ERCC1 and XRCC1 for assessing the clinical activity of satraplatin.