Distinct Prognostic Role of Prostate-Specific Antigen Doubling Time and Velocity at Emergence of Androgen Independence in Patients Treated with Chemotherapy

Baseline Plasma Tumor DNA (ctDNA) Correlates with PSA Kinetics in Metastatic Castration-Resistant Prostate Cancer (mCRPC) Treated with Abiraterone or Enzalutamide

Background: Baseline high circulating tumor DNA (ctDNA) fraction in plasma and androgen receptor (AR) copy number (CN) gain identify mCRPC patients with worse outcomes. This study aimed to assess if ctDNA associates with PSA kinetics. Methods: In this prospective biomarker study, we evaluate ctDNA fraction and AR CN from plasma samples. We divided patients into high and low ctDNA level and in AR gain and AR normal. Results: 220 baseline samples were collected from mCRPC treated with abiraterone (n = 140) or enzalutamide (n = 80). A lower rate of PSA decline ≥ 50% was observed in patients with high ctDNA (p = 0.017) and AR gain (p = 0.0003). Combining ctDNA fraction and AR CN, we found a different median PSA progression-free survival (PFS) among four groups: (1) low ctDNA/AR normal, (2) high ctDNA/AR normal, (3) low ctDNA/AR gain, and (4) high ctDNA/AR gain (11.4 vs. 5.0 vs. 4.8 vs. 3.7 months, p < 0.0001). In a multivariable analysis, high ctDNA, AR gain, PSA DT, PSA DT velocity remained independent predictors of PSA PFS. Conclusions: Elevated ctDNA levels and AR gain are negatively and independently correlated with PSA kinetics in mCRPC men treated with abiraterone or enzalutamide.

Stereotactic ablative radiotherapy in castration-resistant prostate cancer patients with oligoprogression during androgen receptor-targeted therapy

OBJECTIVES

To report outcomes of stereotactic body radiotherapy (SBRT) in metastatic castration-resistant prostate cancer (mCRPC) patients with oligoprogression (≤ 5 metastases) during first-line treatment with androgen receptor-targeted therapy (ARTT).

PATIENTS AND METHODS

Retrospective multi-institutional analysis of mCRPC patients treated with SBRT to oligoprogressive lesions during ARTT. End-points were time to next-line systemic treatment (NEST), radiological progression-free survival (r-PFS) and overall survival (OS). Toxicity was registered according to Common Terminology Criteria for Adverse Events (CTCAE) v4.0. Survival analysis was performed using the Kaplan-Meier method, univariate and multivariate analysis (MVA) were performed.

RESULTS

Data from 34 patients were analyzed. Median NEST-free survival, r-PFS, and OS were 16.97, 13.47, and 38.3 months, respectively. At MVA, factors associated with worse NEST-free survival and r-PFS were polymetastatic burden at diagnosis of metastatic hormone-sensitive disease (hazard ratio [HR] 3.66, p = 0.009; HR 3.03, p = 0.034), PSA ≤ 7 ng/ml at mCRPC diagnosis (HR 0.23, p = 0.017; HR 0.19, p = 0.006) and PSADT ≤ 3 months at mCRPC diagnosis (HR 3.39, p = 0.026; HR 2.79, p = 0.037). Polymetastatic state at mHSPC diagnosis was associated with a decreased OS (HR 4.68, p = 0.029). No patient developed acute or late grade ≥ 2 toxicity.

CONCLUSION

Our results suggest that SBRT in oligoprogressive mCPRC is safe, effective and seems to prolong the efficacy of the ongoing systemic treatment positively affecting disease progression. Prospective trials are needed.

Using medical claims database to develop a population disease progression model for leuprorelin-treated subjects with hormone-sensitive prostate cancer

Androgen deprivation therapy (ADT) is a widely used treatment for patients with hormone-sensitive prostate cancer (PCa). However, duration of treatment response varies, and most patients eventually experience disease progression despite treatment. Leuprorelin is a luteinizing hormone-releasing hormone (LHRH) agonist, a commonly used form of ADT. Prostate-specific antigen (PSA) is a biomarker for monitoring disease progression and predicting treatment response and survival in PCa. However, time-dependent profile of tumor regression and growth in patients with hormone-sensitive PCa on ADT has never been fully characterized. In this analysis, nationwide medical claims database provided by Humana from 2007 to 2011 was used to construct a population-based disease progression model for patients with hormone-sensitive PCa on leuprorelin. Data were analyzed by nonlinear mixed effects modeling utilizing Monte Carlo Parametric Expectation Maximization (MCPEM) method in NONMEM. Covariate selection was performed using a modified Wald’s approximation method with backward elimination (WAM-BE) proposed by our group. 1113 PSA observations from 264 subjects with malignant PCa were used for model development. PSA kinetics were well described by the final covariate model. Model parameters were well estimated, but large between-patient variability was observed. Hemoglobin significantly affected proportion of drug-resistant cells in the original tumor, while baseline PSA and antiandrogen use significantly affected treatment effect on drug-sensitive PCa cells (Ds). Population estimate of Ds was 3.78 x 10⁻² day^-1. Population estimates of growth rates for drug-sensitive (Gs) and drug-resistant PCa cells (G_R) were 1.96 x 10⁻³ and 6.54 x 10⁻⁴ day^-1, corresponding to a PSA doubling time of 354 and 1060 days, respectively. Proportion of the original PCa cells inherently resistant to treatment was estimated to be 1.94%. Application of population-based disease progression model to clinical data allowed characterization of tumor resistant patterns and growth/regression rates that enhances our understanding of how PCa responds to ADT.

The Present and Future of Biomarkers in Prostate Cancer: Proteomics, Genomics, and Immunology Advancements

Prostate cancer (PC) is the second most common form of cancer in men worldwide. Biomarkers have emerged as essential tools for treatment and assessment since the variability of disease behavior, the cost and diversity of treatments, and the related impairment of quality of life have given rise to a need for a personalized approach. High-throughput technology platforms in proteomics and genomics have accelerated the development of biomarkers. Furthermore, recent successes of several new agents in PC, including immunotherapy, have stimulated the search for predictors of response and resistance and have improved the understanding of the biological mechanisms at work. This review provides an overview of currently established biomarkers in PC, as well as a selection of the most promising biomarkers within these particular fields of development.

The utility of prostate-specific antigen in the management of advanced prostate cancer

To review current prostate-specific antigen (PSA) metrics used in monitoring treatment of advanced prostate cancer, with a specific focus on castration-resistant prostate cancer (CRPC) therapies. Explore what is known about the correlation between PSA and androgen levels as well as underlying reasons for persistent PSA expression and serum elevation in CRPC, and outline suggestions for use of PSA in managing patients with advanced prostate cancer. A comprehensive search of the PubMed database for English language articles through April 2012 was performed using the following Medical Subject Headings (MeSH) keywords or terms, alone or in combination: 'prostate cancer'; 'prostate cancer treatment'; 'prostate cancer outcomes'; 'prostate-specific antigen'; 'androgen receptor'; 'advanced prostate cancer'; 'castration-resistant prostate cancer'; 'biomarkers'. Bibliographies of relevant articles were searched for additional references. Relevant medical society and regulatory agency web sites from the USA and Europe were accessed for issued guidance on PSA use. PSA doubling time (PSADT) is a useful metric for determining which patients should be considered for androgen-deprivation therapy (ADT) after failing local treatment or for second-line therapies after failing ADT. However, it is not a validated surrogate for survival and no therapy has received regulatory approval based upon PSADT characteristics. PSA nadir and time-to-nadir have been identified as possible prognostic markers for patients receiving ADT. There is no universally accepted definition for PSA progression, nor is PSA progression a regulatory-approved surrogate for clinical progression in drug approval trials. PSA responses to second-line therapies can vary and are not considered by regulatory agencies as valid surrogates for clinical endpoints, so they must be assessed in the context of each individual therapy and trial design. PSA expression in CRPC is often a reflection of persistent androgen receptor activity. While we can provide guidance for use of PSA monitoring in managing patients with advanced prostate cancer based on the data at hand, there is an urgent need for prospective analyses of refined PSA metrics in conjunction with newer prostate cancer biomarkers in clinical trials to provide stronger evidence for their roles as surrogate endpoints.

The effectiveness of the TAX 327 nomogram in predicting overall survival in Chinese patients with metastatic castration-resistant prostate cancer

Based on the results of TAX 327, a nomogram was developed to predict the overall survival of metastatic castration-resistant prostate cancer (mCRPC) after first-line chemotherapy. The nomogram, however, has not been validated in an independent dataset, especially in a series out of clinical trials. Thus, the objective of the current study was to validate the TAX 327 nomogram in a community setting in China. A total of 146 patients with mCRPC who received first-line chemotherapy (docetaxel or mitoxantrone) were identified. Because clinical trials are limited in mainland China, those patients did not receive investigational treatment after the failure of first-line chemotherapy. The predicted overall survival rate was calculated from the TAX 327 nomogram. The validity of the model was assessed with discrimination, calibration and decision curve analysis. The median survival of the cohort was 21 months (docetaxel) and 19 months (mitoxantrone) at last follow-up. The predictive c-index of the TAX 327 nomogram was 0.66 (95% CI: 0.54-0.70). The calibration plot demonstrated that the 2-year survival rate was underestimated by the nomogram. Decision curve analysis showed a net benefit of the nomogram at a threshold probability greater than 30%. In conclusion, the present validation study did not confirm the predictive value of the TAX 327 nomogram in a contemporary community series of men in China, and further studies with a large sample size to develop or validate nomograms for predicting survival and selecting therapies in advanced prostate cancer are necessary.

Prostate-specific antigen kinetics as a surrogate endpoint in clinical trials of metastatic castration-resistant prostate cancer: a review

Prostate cancer is the most common cancer in men. Overall survival is considered the best endpoint for clinical trials, but it is difficult to use in phase-2 studies. Although the reduction of PSA after cytotoxic chemotherapy has been identified as a valid surrogate for overall survival, it has not proven reliable for the evaluation of many biologics. Moreover, the PSA progression-free survival at 3 months was validated only for cytotoxic drugs, and the various measures of progression/delay have not been confirmed by large studies. Ultimately, outside of overall survival, no measure has been validated as a surrogate endpoint after treatment with targeted therapies and vaccine therapy. The PSA levels have a great variability and, theoretically, the use of measures of cell kinetics and PSA may be the most reliable approach to estimate the behavior of metastatic disease. Some measures of PSA kinetics have been well developed in the clinical castration-resistant prostate cancer, the PSA doubling time and the growth rate constant. The studies about the kinetics of PSA measures are reviewed and discussed. To date, studies that consider the measures of PSA kinetics as surrogate endpoints are still very few. However in the near future, the drug evaluation can not proceed separately, with distinct endpoints between cytotoxic and non-cytotoxic agents. Therefore, extensive analysis and validation of measures of kinetics derived from PSA, and candidates for a role for surrogate endpoint, will be needed in phase-3 studies, in order to test their effectiveness in different disease scenarios.

Prostate-specific antigen half-life: a new predictor of progression-free survival and overall survival in Chinese prostate cancer patients

We investigated the potential value of prostate-specific antigen half-life (PSAHL) and decreasing velocity (PSAVd) to predict progression-free survival (PFS) and overall survival (OS) in Chinese patients with prostate cancer. A total of 153 patients treated with hormonal therapy were included in the study. Of these, 78 patients progressed to hormone-refractory prostate cancer (HRPC) and 24 patients died by the end of follow-up. PSAHL was defined as the time during which prostate-specific antigen (PSA) concentration became half of the initial value during the first hormonal therapy. PSAVd reflected the decreasing velocity of PSA during the first hormonal therapy. PFS was defined as the interval from the beginning of hormonal therapy to HRPC. Cox proportional hazards regression analysis was used to evaluate whether PSAHL and PSAVd were significantly associated with PFS and OS. The median PSAHL and PSAVd were 0.50 months and 33.8 ng mL(-1) per month. The median PFS and OS were 22.7 months (95% confidence interval [CI], 22.0-29.6 months) and 43.5 months (95% CI, 37.9-48.4 months), respectively. On univariate and multivariate analysis, long PSAHL (> 0.5 months), metastatic disease, high biopsy Gleason scores (>or= 8) and high nadir PSA (> 0.4 ng mL(-1)) were all found to be significantly associated with short PFS. Long PSAHL, high nadir PSA and short PSA doubling time (PSADT Collapse

Key Words

• predictor
• prognosis
• prostate cancer
• prostate-specific antigen decreasing velocity
• prostate-specific antigen half-life

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MESH Headings

• Adult
• Aged
• Aged, 80 and over
• China
• Disease Progression
• Half-Life
• Humans
• Male
• Middle Aged
• Proportional Hazards Models
• Prostate-Specific Antigen/blood
• Prostatic Neoplasms/blood
• Prostatic Neoplasms/immunology
• Prostatic Neoplasms/pathology
• Survival Analysis

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Affiliation(s)

Guo-Wen Lin Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Xu-Dong Yao Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Shi-Lin Zhang Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Bo Dai Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Chun-Guang Ma Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Hai-Liang Zhang Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Yi-Jun Shen Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Yao Zhu Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Yi-Ping Zhu Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Guo-Hai Shi Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Xiao-Jian Qin Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Ding-Wei Ye Department of Urology, Cancer Hospital, Fudan University, Shanghai 200032, China Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China

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Current applications for prostate-specific antigen doubling time

OBJECTIVE

To review the current status of prostate-specific antigen doubling time (PSADT) as it pertains to the evolution of prostate cancer (PCa), specifically assessing its role in the following four stages: before diagnosis, prior to definitive treatment, following treatment including salvage therapy after recurrence, and lastly, after onset of androgen-insensitive PCa.

METHODS

We searched PubMed literature for current articles on PSADT using the key words listed for this review and, where possible, selected those with significant levels of evidence that were deemed relevant, seminal, or controversial. We summarized the data regarding PSADT as a marker for diagnosis and disease characterization, as well as a predictor of progression, response to treatment, and mortality.

RESULTS

PSADT may offer an advantage in providing a more dynamic picture of tumor behavior, providing clues regarding the relative aggressiveness of the underlying pathology. Evidence points toward a role for PSADT in the management of PCa, specifically in active surveillance, disease recurrence after treatment, and in androgen-independent PCa. PSADT is an important prognostic factor that may serve as an auxiliary end point for cancer-specific survival; however, optimal cut-off points denoting risk remain debatable.

CONCLUSIONS

PCa management requires risk stratification with a combination of variables, PSADT being one of the most reliable predictors. It is now a parameter included in many predictive nomograms and in treatment guidelines for expectant management and salvage therapy.