Prognostic significance of third-line treatment for patients with metastatic castration-resistant prostate cancer: comparative assessments between cabazitaxel and other agents

Current Status of Sequential Treatment for Castration-resistant Prostate Cancer: A Retrospective Analysis

Background/Aim

Although multiple treatments are available for metastatic castration-resistant prostate cancer, data to determine the optimal treatment sequence are limited. This study aimed to investigate the current status of drug therapy for castration-resistant prostate cancer and clarify the sequential treatment in actual clinical practice.

Patients and Methods

This retrospective study included 425 patients diagnosed with castration-resistant prostate cancer at Showa University Hospital and affiliated hospitals between January 2014 and December 2021, who were treated with any of the following four drugs: novel androgen receptor signal inhibitors (abiraterone acetate and enzalutamide) and anticancer drugs (docetaxel and cabazitaxel). We investigated the actual treatment choices for castration-resistant prostate cancer, focusing on the order of administration of the four drugs. This analysis was visualized using a Sankey diagram.

Results

Regarding the number of drugs administered, most patients received one type of drug, with androgen receptor signal inhibitors being the most commonly administered (total, 179; enzalutamide, 139 and abiraterone acetate, 40). Enzalutamide was the most frequently selected first-line drug (58.4%). The most common sequence for second-line treatment was androgen receptor signal inhibitor-androgen receptor signal inhibitor (n=96), followed by androgen receptor signal inhibitor-docetaxel (n=85), docetaxel-androgen receptor signal inhibitor (n=59), and docetaxel-cabazitaxel (n=6).

Conclusion

Androgen receptor signal inhibitors is the most commonly used drug category for first-line treatment of castration-resistant prostate cancer, with enzalutamide being the most commonly used drug. Further investigations are required regarding patient background and prognosis.

The Cost-Effectiveness of Germline BReast CAncer Gene Testing in Metastatic Prostate Cancer Followed by Cascade Testing of First-Degree Relatives of Mutation Carriers

OBJECTIVES

Patients with metastatic prostate cancer (mPCa) with BReast CAncer gene (BRCA) mutations benefit from targeted treatments (eg, olaparib). In addition, family members of affected patients have increased risk of hereditary cancers and benefit from early detection and prevention. International guidelines recommend genetic testing in mPCa; however, the value for money of testing patients with mPCa and cascade testing of blood-related family members has not been assessed. In this context, we evaluated the cost-effectiveness of germline BRCA testing in patients with mPCa followed by cascade testing of first-degree relatives (FDRs) of mutation carriers.

METHODS

We conducted a cost-utility analysis of germline BRCA testing using 2 scenarios: (1) testing patients with mPCa only and (2) testing patients with mPCa and FDRs of those who test positive. A semi-Markov multi-health-state transition model was constructed using a lifetime time horizon. The analyses were performed from an Australian payer perspective. Decision uncertainty was characterized using probabilistic analyses.

RESULTS

Compared with no testing, BRCA testing in mPCa was associated with an incremental cost of AU$3731 and a gain of 0.014 quality-adjusted life-years (QALYs), resulting in an incremental cost-effectiveness ratio of AU$265 942/QALY. Extending testing to FDRs of variant-positive patients resulted in an incremental cost-effectiveness ratio of AU$16 392/QALY. Probability of cost-effectiveness at a willingness-to-pay of AU$75 000/QALY was 0% in the standalone mPCa analysis and 100% in the cascade testing analysis.

CONCLUSION

BRCA testing when performed as a standalone strategy in patients with mPCa may not be cost-effective but demonstrates significant value for money after the inclusion of cascade testing of FDRs of mutation carriers.

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.

The prognostic value of Eastern Cooperative Oncology Group performance status on overall survival among patients with metastatic prostate cancer: a systematic review and meta-analysis

Background

There is heterogeneity in the literature regarding the strength of association between Eastern Cooperative Oncology Group performance status (ECOG PS) and mortality. We conducted a systematic review and meta-analysis of studies reporting the prognostic value of ECOG PS on overall survival (OS) in metastatic prostate cancer (mPC).

Methods

PubMed was searched from inception to March 21, 2022. A meta-analysis pooling the effect of ECOG PS categories (≥2 vs. <2, 2 vs. <2, and ≥1 vs. <1) on OS was performed separately for studies including patients with metastatic castration-resistant prostate cancer (mCRPC) and metastatic castration-sensitive prostate cancer (mCSPC) using a random-effects model. Analyses were stratified by prior chemotherapy and study type.

Results

Overall, 75 studies, comprising 32,298 patients, were included. Most studies (72/75) included patients with mCRPC. Higher ECOG PS was associated with a significant increase in mortality risk, with the highest estimate observed among patients with mCRPC with an ECOG PS of ≥2 versus <2 (hazard ratio [HR]: 2.10, 95% confidence interval [CI]: 1.87-2.37). When stratifying by study type, there was a higher risk estimate of mortality among patients with mCRPC with an ECOG PS of ≥1 versus <1 in real-world data studies (HR: 1.98, 95% CI: 1.72-2.26) compared with clinical trials (HR: 1.32, 95% CI: 1.13-1.54; p < 0.001). There were no significant differences in the HR of OS stratified by previous chemotherapy.

Conclusion

ECOG PS was a significant predictor of OS regardless of category, previous chemotherapy, and mPC population. Additional studies are needed to better characterize the effect of ECOG PS on OS in mCSPC.

STEAP1 Knockdown Decreases the Sensitivity of Prostate Cancer Cells to Paclitaxel, Docetaxel and Cabazitaxel

The Six Transmembrane Epithelial Antigen of the Prostate 1 (STEAP1) protein has been indicated as an overexpressed oncoprotein in prostate cancer (PCa), associated with tumor progression and aggressiveness. Taxane-based antineoplastic drugs such as paclitaxel, docetaxel, or cabazitaxel, have been investigated in PCa treatment, namely for the development of combined therapies with the improvement of therapeutic effectiveness. This study aimed to evaluate the expression of STEAP1 in response to taxane-based drugs and assess whether the sensitivity of PCa cells to treatment with paclitaxel, docetaxel, or cabazitaxel may change when the STEAP1 gene is silenced. Thus, wild-type and STEAP1 knockdown LNCaP and C4-2B cells were exposed to paclitaxel, docetaxel or cabazitaxel, and STEAP1 expression, cell viability, and survival pathways were evaluated. The results obtained showed that STEAP1 knockdown or taxane-based drugs treatment significantly reduced the viability and survival of PCa cells. Relatively to the expression of proliferation markers and apoptosis regulators, LNCaP cells showed a reduced proliferation, whereas apoptosis was increased. However, the effect of paclitaxel, docetaxel, or cabazitaxel treatment was reversed when combined with STEAP1 knockdown. Besides, these chemotherapeutic drugs may stimulate the cell growth of PCa cells knocked down for STEAP1. In conclusion, this study demonstrated that STEAP1 expression levels might influence the response of PCa cells to chemotherapeutics drugs, indicating that the use of paclitaxel, docetaxel, or cabazitaxel may lead to harmful effects in PCa cells with decreased expression of STEAP1.

Sequencing impact and prognostic factors in metastatic castration-resistant prostate cancer patients treated with cabazitaxel: A systematic review and meta-analysis

BACKGROUND

Cabazitaxel is an effective treatment of post-docetaxel metastatic castration-resistant prostate cancer (mCRPC). We aimed to assess the sequencing impact and identify prognostic factors of oncologic outcomes in mCRPC patients treated with cabazitaxel.

METHODS

PUBMED, Web of Science, and Scopus databases were searched for articles published before January 2022 according to the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) statement. Studies were deemed eligible if they investigated pretreatment clinical or hematological prognostic factors of overall survival (OS) in mCRPC patients with progression after docetaxel treated with available treatments including cabazitaxel.

RESULTS

Overall, 22 studies were eligible for the meta-analysis. In mCRPC patients treated with docetaxel, subsequent treatment with cabazitaxel was associated with better OS compared to that without cabazitaxel (pooled hazard ratio [HR]: 0.70, 95% confidence interval [CI]: 0.56-0.89). Among the patients treated with cabazitaxel, several pretreatment clinical features and hematologic biomarkers were associated with worse OS as follows: poor performance status (PS) (pooled HR: 1.92, 95% CI: 1.33-2.77), presence of visceral metastasis (pooled HR: 2.13, 95% CI: 1.62-2.81), symptomatic disease (pooled HR: 1.47, 95% CI: 1.25-1.73), high PSA (pooled HR: 1.76, 95% CI: 1.27-2.44), high alkaline phosphatase (ALP) (pooled HR: 1.45, 95% CI: 1.28-1.65), high lactate dehydrogenase (LDH) (pooled HR: 1.54, 95% CI: 1.00-2.38), high c-reactive protein (CRP) (pooled HR: 4.40, 95% CI: 1.52-12.72), low albumin (pooled HR:1.09, 95% CI: 1.05-1.12) and low hemoglobin (pooled HR:1.55, 95% CI: 1.20-1.99).

CONCLUSIONS

Sequential therapy with cabazitaxel significantly improves OS in post-docetaxel mCRPC patients. In mCRPC patients treated with cabazitaxel, patients with poor PS, visceral metastasis, and symptomatic disease were associated with worse OS. Further, pretreatment high PSA, ALP, LDH or CRP as well as low hemoglobin or albumin, were blood-based prognostic factors for OS. These findings might help guide the clinical decision-making for the use of cabazitaxel and prognostication of its OS benefit.

Enzalutamide Versus Abiraterone plus Prednisolone Before Chemotherapy for Castration-resistant Prostate Cancer: A Multicenter Randomized Controlled Trial

Background

Enzalutamide (ENZ) and abiraterone plus prednisolone (ABI) improve survival in castration-resistant prostate cancer (CRPC). However, which agent is better for patients with CRPC remains unclear.

Objective

To evaluate whether ENZ or ABI is better as first-line treatment for CRPC.

Design, setting, and participants

An investigator-initiated, multicenter, randomized controlled trial was conducted in Japan. The study enrolled 203 patients with CRPC before chemotherapy between February 20, 2015, and July 31, 2019. Patients were randomly assigned 1:1 to the ENZ or ABI arm.

Outcome measurements and statistical analysis

The primary endpoint was time to prostate-specific antigen (PSA) progression. Secondary endpoints included the PSA response rate (≥50% decline from baseline), overall survival, and safety. A log-rank test was used for comparison of survival analyses between arms.

Results and limitations

After randomization, 92 patients in each arm were treated and analyzed. Time to PSA progression did not significantly differ between the arms (median 21.2 mo for ENZ and 11.9 mo for ABI; hazard ratio [HR] 0.81, 95% confidence interval [CI] 0.51–1.27; p = 0.1732). There was a significant difference in the PSA response rate between the arms (72% for ENZ and 57% for ABI; p = 0.0425). There was no significant difference in overall survival (median 32.9 mo for ENZA and 35.5 mo for ABI; HR 1.17, 95% CI 0.72–1.88; p = 0.5290). Grade ≥3 adverse events were observed in 11% of patients in the ENZA arm and 21% in the ABI arm (p = 0.1044).

Conclusions

ENZ did not show any survival benefit in comparison to ABI, but showed a better PSA response rate with a low rate of severe adverse events in CRPC.

Patient summary

Results from our study suggest that use of enzalutamide before abiraterone may have potential clinical benefits for patients with castration-resistant prostate cancer.