Deferred combined androgen blockade therapy using bicalutamide in patients with hormone-refractory prostate cancer during androgen deprivation monotherapy

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

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

Management of nonmetastatic castration-resistant prostate cancer

PURPOSE OF REVIEW

The widespread use of prostate-specific antigen (PSA) resulted in stage migration of prostate cancer where androgen deprivation therapy (ADT) is administered for biochemical recurrence in patients following primary treatment. A proportion of these patients progress to a disease state termed nonmetastatic castration-resistant prostate cancer (nmCRPC), with a rising PSA despite ADT and without evidence of metastases on conventional imaging. We will review the treatment options in nmCRPC, especially in light of recent trials showing significant improvement in metastasis-free survival with newer agents.

RECENT FINDINGS

Historically, nmCRPC patients were followed-up if PSA doubling-time (PSADT) exceeded 10 months. Treatment options for patients with shorter PSADT included hormonal manipulations that often resulted in transient PSA decline. Denosumab was found to delay the onset of bone metastasis but did not impact survival. Recently, phase 3 trials showed that second-generation antiandrogens resulted in a significant delay in metastasis and a trend toward survival improvement in a select group of nmCRPC patients.

SUMMARY

The importance of reducing mortality and morbidity associated with metastasis has led to the acceptance of new primary endpoints in the design of trials for nmCRPC and might result in widespread approval of new agents for this disease state.

Effectiveness of Deferred Combined Androgen Blockade Therapy Predicts Efficacy in Abiraterone Acetate Treated Metastatic Castration-Resistant Prostate Cancer Patients after Docetaxel

Introduction: Conventional anti-androgen regimens were widely used as an initiation or combined androgen blockade (CAB) therapy in advanced prostate cancer patients. Currently, new androgen pathway inhibitors such as abiraterone acetate (AA) and enzalutamide had been proven effective in metastatic castration resistant prostate cancer. In this study, we attempt to analyze the role of conventional anti-androgen drugs as deferred CAB therapy in castration-resistant prostate cancer patients.

Materials and Methods: From 2012 to 2017, 48 metastatic castration-resistant prostate cancer (CRPC) patients who received sequential treatments with primary androgen blockade, oral anti-androgen regimens, and docetaxel followed by AA treatment were included. We defined effective deferred CAB as any decline of PSA after add-on antiandrogen after CRPC. Patients were separated into effective and ineffective deferred CAB. Comparison between two groups in the first line androgen deprivation therapy duration, CRPC PSA level, pre-AA PSA level, chemotherapy dosages, duration, and patients progression free survival and overall survival after AA treatment were analyzed.

Results: Twenty-three patients (47.9%) achieved PSA decline after deferred CAB. Among total 48 patients, 24 patients experienced PSA decline more than 50% after AA treatment. The median PSA progression-free survival and overall survival after AA treatment in the total cohort of 48 patients were 4.4 and 24.3 months, respectively. The effective deferred CAB group showed significantly lower PSA level, lower percentage of PSA progression, higher total follow-up duration, higher percentage of surviving patients, better progression free survival, and overall survival estimate after AA treatment. Of the eight variables analyzed, effectiveness in deferred CAB showed positive association to progression free survival (HR 0.29, 95% CI 0.12–0.67, p = 0.004) and overall survival (HR 0.24, 95% CI 0.07–0.81, p = 0.022). First line androgen deprivation therapy (ADT) duration also showed positive association to overall survival (HR 0.95, 95% CI 0.91–0.99, p = 0.023).

Conclusions: Effectiveness of deferred CAB therapy was positively associated with progression free survival and overall survival of AA treatment after docetaxel. It can be used as a pre-treatment predictor.

Castration-resistant prostate cancer: AUA Guideline

PURPOSE

This Guideline is intended to provide a rational basis for the management of patients with castration-resistant prostate cancer based on currently available published data.

MATERIALS AND METHODS

A systematic review and meta-analysis of the published literature was conducted using controlled vocabulary supplemented with keywords relating to the relevant concepts of prostate cancer and castration resistance. The search strategy was developed and executed by reference librarians and methodologists to create an evidence report limited to English-language, published peer-reviewed literature. This review yielded 303 articles published from 1996 through 2013 that were used to form a majority of the guideline statements. Clinical Principles and Expert Opinions were used for guideline statements lacking sufficient evidence-based data.

RESULTS

Guideline statements were created to inform clinicians on the appropriate use of observation, androgen-deprivation and antiandrogen therapy, androgen synthesis inhibitors, immunotherapy, radionuclide therapy, systemic chemotherapy, palliative care and bone health. These were based on six index patients developed to represent the most common scenarios encountered in clinical practice.

CONCLUSIONS

As a direct result of the significant increase in FDA-approved therapeutic agents for use in patients with metastatic CRPC, clinicians are challenged with a multitude of treatment options and potential sequencing of these agents that, consequently, make clinical decision-making more complex. Given the rapidly evolving nature of this field, this guideline should be used in conjunction with recent systematic literature reviews and an understanding of the individual patient's treatment goals. In all cases, patients' preferences and personal goals should be considered when choosing management strategies.

The long-term results with delayed-combined androgen blockade therapy in local or locally advanced prostate cancer

OBJECTIVE

To evaluate long-term clinical outcomes in cT1c-T3a prostate cancer patients following delayed-combined androgen blockade therapy.

METHODS

From January 2001 to December 2004, 92 cT1c-T3a prostate cancer cases were enrolled. Medical castration and anti-androgen treatment were used sequentially as delayed-combined androgen blockade therapy. Time to prostate-specific antigen biochemical failure was estimated, and risk factors for prostate-specific antigen biochemical failure were evaluated.

RESULTS

The average patient age was 76.4 years (range, 59-91 years), the median observation period was 52.8 months (range, 26-106.6 months) and the median pre-treatment prostate-specific antigen level was 14 ng/ml (range, 3.68-492 ng/ml). The TNM classification distribution was as follows: T1c, n= 27; T2a, n = 39; T2b, n = 20; and T3a, n = 6. In the multivariate analysis, Gleason's score ≥8 (P < 0.05; hazard ratio, 3.02), prostate-specific antigen nadir >1.4 ng/ml (P = 0.001; hazard ratio, 8.76) and a half-life of the prostate-specific antigen level >1.2 months (P < 0.005; hazard ratio, 6.3) during the initial 6 months of luteinizing hormone-releasing hormone agonist monotherapy were significant independent risk factors for prostate-specific antigen biochemical failure with luteinizing hormone-releasing hormone agonist monotherapy. The high-risk group, which had at least one of these three risk factors, had a shorter time to prostate-specific antigen biochemical failure than the low-risk group, during luteinizing hormone-releasing hormone agonist monotherapy (P < 0.0001). For the total delayed-combined androgen blockade therapy observation period, the free-prostate-specific antigen biochemical failure rate was 88.3% at 5 years. Only a maintenance period following luteinizing hormone-releasing hormone agonist monotherapy (P < 0.005; hazard ratio, 16.8) was revealed to be a significant independent risk factor for prostate-specific antigen biochemical failure with total delayed-combined androgen blockade.

CONCLUSIONS

The free-prostate-specific antigen biochemical failure rate of delayed-combined androgen blockade therapy in our study was as valuable as those in other androgen deprivation therapy of previous reports.

Biological properties of androgen receptor pure antagonist for treatment of castration-resistant prostate cancer: optimization from lead compound to CH5137291

BACKGROUND

Castration-resistant prostate cancer (CRPC) is still dependent on androgen receptor (AR) signaling. We previously reported that a novel nonsteroidal AR pure antagonist, CH4933468, which is a thiohydantoin derivative with a sulfonamide side chain, provided in vitro proof of concept but did not in vivo.

METHODS

We developed other derivatives, CH5137291, CH5138514, and CH5166623, and their pharmacological properties were compared with CH4933468 and bicalutamide. Agonist/antagonist activities in AR-mediated transactivation, cell proliferation against LNCaP and LNCaP-BC2, and AR translocation were evaluated. Agonist metabolite was monitored in liver microsomes and in pharmacokinetics experiments. Antitumor activities in CRPC xenograft models were examined using LNCaP-BC2 and VCaP-CRPC.

RESULTS

All CH compounds completely inhibited AR-mediated transactivation and proliferation of LNCaP and LNCaP-BC2. In contrast bicalutamide showed a partial inhibition of AR-mediated transactivation and a proliferation of LNCaP-BC2. AR translocation to nucleus was inhibited by CH compounds, but stimulated by bicalutamide. In the LNCaP-BC2 xenograft model, however, only CH5137291 showed significant inhibition of plasma PSA level and antitumor activity. The other three CH compounds were metabolized to their core structure which had agonist activity. CH5137291 also exhibited antitumor activity in a VCaP-CRPC xenograft model, but bicalutamide did not.

CONCLUSIONS

The molecular mechanism of the CH compounds, inhibition of AR translocation, was different from bicalutamide and this action could contribute to AR pure antagonist activity. Agonist metabolite diminished the antitumor activity of AR pure antagonist. CH5137291 exhibited antitumor activity in LNCaP-BC2 and VCaP-CRPC xenograft models, suggesting that the compound has potential for the treatment of CRPC.

Androgen hypersensitivity in prostate cancer: molecular perspectives on androgen deprivation therapy strategies

Androgen deprivation therapy is initially successful in treating advanced prostate cancer. However, after a period of time tumors inevitably recur. Improved understanding of the various biochemical causes of resistance to hormonal therapy is of crucial importance for developing more effective therapeutic strategies in this cohort of patients. This review discusses the preclinical evidence for androgen hypersensitivity (AH), as a mechanism by which tumors become hormone-refractory (HR). We propose that the growth of some such tumors may be not only stimulated by, but also dependent on low hormone levels, and furthermore, that normal hormone concentrations can have an inhibitory effect on growth. The incidence and importance of AH merits further investigation both in preclinical studies and during clinical trials of intermittent androgen withdrawal or testosterone replacement. We suggest that a subset of HR prostate cancer patients who have androgen-hypersensitive tumors could be particularly amenable to these treatments. Finally, potential approaches for developing biomarkers to identify such patients are explored.

Prostate Cancer-Specific Survival and Clinical Progression-Free Survival in Men with Prostate Cancer Treated Intermittently with Testosterone Inactivating Pharmaceuticals

OBJECTIVES

More than 85% of men with prostate cancer die of other causes. An effective method is needed to distinguish fatal forms of prostate cancer from benign variants.

METHODS

We performed a retrospective chart review from a medical oncology practice specializing in prostate cancer. All men with negative bone scans, prostate-specific antigen (PSA) level less than 100 ng/mL, adequate records for review, and who started taking testosterone inactivating pharmaceutical (TIP) agents before January 2000 were included in the study. Six factors were evaluated as potential predictors of prostate cancer-specific mortality: PSA nadir greater than 0.05 ng/mL while taking TIP, PSA doubling time of less than 12 months, Gleason score, stage, baseline PSA level greater than 20 ng/mL, and age.

RESULTS

The study criteria were met by 160 men. The median follow-up was 10 years. The median age, PSA level, PSA nadir, and PSA doubling time was 65.6 years, 9.6 ng/mL, 0.03 ng/mL, and 10 months, respectively. Of the 160 men, 39 died of prostate cancer. Death from prostate cancer was far more common (78% versus 11%) and accelerated (median of 4 years versus 7 years) for men with a PSA nadir greater than 0.05 ng/mL than for those with a lower nadir. Multivariate Cox regression analysis indicated that the hazard ratio for prostate cancer-specific mortality in men with a PSA nadir greater than 0.05 ng/mL was 11.6 (P <0.0001). The hazard ratio for men with a PSA doubling time of less than 12 months was 2.9 (P = 0.04). Gleason score, stage, baseline PSA level greater than 20 ng/mL, and age were not statistically significant.

CONCLUSIONS

Of the factors studied, the PSA nadir while taking a TIP was the best predictor of prostate cancer-specific mortality.

Prostate-specific antigen half-life and pretreatment prostate-specific antigen: Crucial predictors for prostate-specific antigen trend in delayed-combined androgen blockade therapy

PURPOSE

To elucidate the crucial predictors for prostate-specific antigen (PSA) trends and determine the usage of anti-androgen treatment during delayed-combined androgen blockade (CAB) leading to a PSA level below 0.2 ng/mL.

MATERIALS AND METHODS

From January 2001 to December 2004, 105 prostate cancer patients were enrolled. Medical castration and anti-androgen treatment were used sequentially and termed delayed-CAB. The first goal was to maintain an undetectable PSA level. The nadir PSA was determined after medical castration only. Anti-androgen was given if a PSA level of more than 0.2 ng/mL was observed and the subsequent PSA response was assessed. All cases were divided into two groups based on whether the PSA was lower (n = 59) or higher (n = 46) than 0.2 ng/mL. An analysis of the difference between the two groups was calculated.

RESULTS

The median of the initial PSA level in the lower group was lower than in the higher group with a 95% cut-off level of 40 ng/mL. The median PSA half-life in the lower group was also reduced with a 95% cut-off of 3.6 months. In a multivariate analysis, the pretreatment PSA level and the PSA half-life exhibited a significant correlation between the two groups. Anti-androgen treatment was given to 26 cases in the higher group. The PSA increased in one case, decreased to less than 0.2 ng/mL in 17 cases and remained over 0.2 ng/mL in eight cases.

CONCLUSION

Both the PSA half-life and the pretreatment PSA level were useful markers for predicting the PSA trends to determine the optimal use of anti-androgen treatment during delayed-CAB.