Switch from abiraterone plus prednisone to abiraterone plus dexamethasone at asymptomatic PSA progression in patients with metastatic castration-resistant prostate cancer

Evolution-based mathematical models significantly prolong response to abiraterone in metastatic castrate-resistant prostate cancer and identify strategies to further improve outcomes

Background

Abiraterone acetate is an effective treatment for metastatic castrate-resistant prostate cancer (mCRPC), but evolution of resistance inevitably leads to progression. We present a pilot study in which abiraterone dosing is guided by evolution-informed mathematical models to delay onset of resistance.

Methods

In the study cohort, abiraterone was stopped when PSA was <50% of pretreatment value and resumed when PSA returned to baseline. Results are compared to a contemporaneous cohort who had >50% PSA decline after initial abiraterone administration and met trial eligibility requirements but chose standard of care (SOC) dosing.

Results

17 subjects were enrolled in the adaptive therapy group and 16 in the SOC group. All SOC subjects have progressed, but four patients in the study cohort remain stably cycling (range 53-70 months). The study cohort had significantly improved median time to progression (TTP; 33.5 months; p<0.001) and median overall survival (OS; 58.5 months; hazard ratio, 0.41, 95% confidence interval (CI), 0.20-0.83, p<0.001) compared to 14.3 and 31.3 months in the SOC cohort. On average, study subjects received no abiraterone during 46% of time on trial. Longitudinal trial data demonstrated the competition coefficient ratio (αRS/αSR) of sensitive and resistant populations, a critical factor in intratumoral evolution, was two- to threefold higher than pre-trial estimates. Computer simulations of intratumoral evolutionary dynamics in the four long-term survivors found that, due to the larger value for αRS/αSR, cycled therapy significantly decreased the resistant population. Simulations in subjects who progressed predicted further increases in OS could be achieved with prompt abiraterone withdrawal after achieving 50% PSA reduction.

Conclusions

Incorporation of evolution-based mathematical models into abiraterone monotherapy for mCRPC significantly increases TTP and OS. Computer simulations with updated parameters from longitudinal trial data can estimate intratumoral evolutionary dynamics in each subject and identify strategies to improve outcomes.

Funding

Moffitt internal grants and NIH/NCI U54CA143970-05 (Physical Science Oncology Network).

Metronomic Chemotherapy in Prostate Cancer

Despite the significant expansion of the therapeutic armamentarium associated with the introduction of novel endocrine therapies, cytotoxic agents, radiopharmaceuticals, and PARP inhibitors, progression of metastatic castration-resistant prostate cancer (mCRPC) beyond treatment options remains the leading cause of death in advanced prostate cancer patients. Metronomic chemotherapy (MC) is an old concept of wise utilization of cytotoxic agents administered continuously and at low doses. The metronomic is unique due to its multidimensional mechanisms of action involving: (i) inhibition of cancer cell proliferation, (ii) inhibition of angiogenesis, (iii) mitigation of tumor-related immunosuppression, (iv) impairment of cancer stem cell functions, and (v) modulation of tumor and host microbiome. MC has been extensively studied in advanced prostate cancer before the advent of novel therapies, and its actual activity in contemporary, heavily pretreated mCRPC patients is unknown. We have conducted a prospective analysis of consecutive cases of mCRPC patients who failed all available standard therapies to find the optimal MC regimen for phase II studies. The metronomic combination of weekly paclitaxel 60 mg/m² i.v. with capecitabine 1500 mg/d p.o. and cyclophosphamide 50 mg/d p.o. was selected as the preferred regimen for a planned phase II study in heavily pretreated mCRPC patients.

An exploratory first-in-man study to investigate the pharmacokinetics and safety of liposomal dexamethasone at a 2- and 1-week interval in patients with metastatic castration resistant prostate cancer

Dexamethasone has antitumor activity in metastatic castration resistant prostate cancer (mCRPC). We aimed to investigate intravenous liposome-encapsulated dexamethasone disodium phosphate (liposomal dexamethasone) administration in mCRPC patients. In this exploratory first-in-man study, patients in part A received a starting dose of 10 mg followed by five doses of 20 mg liposomal dexamethasone at 2-week intervals. Upon review of part A safety, patients in part B received 10 weekly doses of 18.5 mg. Primary outcomes were safety and pharmacokinetic profile, secondary outcome was antitumor efficacy. Nine mCRPC patients (5 part A, 4 part B) were enrolled. All patients experienced grade 1-2 toxicity, one (part B) patient experienced grade 3 toxicity (permanent bladder catheter-related urosepsis). No infusion-related adverse events occurred. One patient had upsloping glucose levels ≤9.1 mmol/L. Trough plasma concentrations of liposomal- and free dexamethasone were below the lower limit of quantification (LLOQ) in part A, and above LLOQ in three patients in part B (t1/2 ~50 h for liposomal dexamethasone), trough concentrations of liposomal- and free dexamethasone increased toward the end of the study. In seven of nine patients (78%) patients, stable disease was observed in bone and/or CT scans at follow-up, and in one (part B) of these seven patients a >50% PSA biochemical response was observed. Bi- and once weekly administrations of IV liposomal dexamethasone were well-tolerated. Weekly dosing enabled trough concentrations of liposomal- and free dexamethasone >LLOQ. The data presented support further clinical investigation in well-powered studies. Clinical trial registration: ISRCTN 10011715.

Corticosteroid switch from prednisone to dexamethasone in metastatic castration-resistant prostate cancer patients with biochemical progression on abiraterone acetate plus prednisone

Background

To assess the efficacies and potential predictors of a corticosteroid switch in metastatic castration-resistant prostate cancer (mCRPC) patients with biochemical progression on abiraterone acetate plus prednisone (A + P).

Methods

Patients with mCRPC treated between April 2016 and August 2020, who experienced biochemical progression on A + P and then switched to A plus dexamethasone (D), were retrospectively identified. The primary endpoint was progression-free survival (PFS), and the secondary endpoints were PSA response, overall survival (OS), and safety.

Results

One hundred and thirty consecutive cases were enrolled. The median PFS and OS on A + D were 5.0 and 18.7 months, respectively. The best PSA decline of ≥50% (PSA50) and ≥ 30% (PSA30) were observed in 29.2 and 46.2% patients, respectively. Lower PSA at corticosteroid switch (≤ 20 ng/mL; median PFS, HR 0.63, p = 0.019; median OS, HR 0.38, p = 0.001) and longer mCRPC-free survival (≥ 18 months; median PFS, HR 0.61, p = 0.013; median OS, HR 0.51, p = 0.015) were identified as independent prognostic predictors associated with longer PFS and OS. A risk stratification tool was developed to select candidates for corticosteroid switch based on the independent prognostic predictors of PFS and OS.

Conclusions

A corticosteroid switch from prednisone to dexamethasone is effective for mCRPC which progressed on A + P treatment. Patients with lower PSA at corticosteroid switch and/or longer mCRPC-free survival may gain more benefits by the corticosteroid switch.

Steroid switch after progression on abiraterone plus prednisone in patients with metastatic castration-resistant prostate cancer: A systematic review

BACKGROUND

Emerging evidence indicates that patients with metastatic castration-resistant prostate cancer could respond to steroid switch from prednisone (P) to dexamethasone (D) following progression on abiraterone acetate plus prednisone (AA+P).

OBJECTIVES

Conducting a systematic review to evaluate the efficacy, safety, and prognostic factors of steroid switch.

MATERIALS AND METHODS

We systematically searched Pubmed, Web of Science, and American Society of Clinical Oncology annual meeting abstracts published up to October 2020. Literature review, study selection, and data extraction were conducted by two reviewers. Risk of bias (RoB) and quality of evidence were assessed. A systematic review and pooled analysis were performed.

RESULTS

Nine studies were eligible for inclusion. All of the included patients were progression on AA+P. Pooled rates of PSA50 and PSA30 on abiraterone acetate plus dexamethasone (AA+D) were 0.24 (95%CI [0.18,0.30]) and 0.42 (95%CI [0.36,0.48]), respectively. Subgroup analysis indicated more favorable PSA50 and PSA30 rates on AA+D when switching from P to D only based on PSA progression. Median time to PSA progression on AA+D ranged from 2.73 to 11.38 months. Definitions of progression free survival were variable. Reported median progression free survival on AA+D ranged from 2.52 to 11.8 months. Median overall survival on AA+D varied from 4.11 to 20.9 months. All patients tolerated well on AA+D, and no grade 3 to 4 adverse events were reported. Baseline characteristics of patients, previous treatment and its response, and genetic alterations might all play roles in the response in the response toward the AA+D regimen.

CONCLUSIONS

The present systematic review suggested that steroid switch from P to D might be an effective and safe treatment strategy in a subset of patients with metastatic castration-resistant prostate cancer after PSA progression on AA+P.

Optimizing outcomes for patients with metastatic prostate cancer: insights from South East Asia Expert Panel

AIMS

Clinical decision making is challenging in men with metastatic prostate cancer (mPC), as heterogeneity in treatment options and patient characteristics have resulted in multiple scenarios with little or no evidence. The South East Asia Expert Panel 2019 addressed some of these challenges.

METHODS

Based on evidence in the literature and expert interviews, 19 statements were formulated for key challenges in the treatment of men with castration-sensitive and -resistant prostate cancer in clinical practice. A modified Delphi process was used to reach consensus among experts in the panel and develop clinical practice recommendations.

RESULTS

The majority of the panel preferred a risk-based stratification and recommended abiraterone or enzalutamide as first-line therapy for symptomatic chemotherapy naïve patients. Abiraterone is preferred over enzalutamide as a first-line treatment in these patients. However, the panel did not support the use of abiraterone in high risk lymph-node positive only (N+M0) or in non-metastatic (N0M0) patients. In select patients, low dose abiraterone with food may be used to optimize clinical outcomes. Androgen receptor gene splice variant status may be a useful guide to therapy. In addition, generic versions of approved therapies may improve access to treatment to a broader patient population. The choice of treatment, as well as sequencing are guided by both patient and disease characteristics, preferences, drug access, cost, and compliance.

CONCLUSION

Expert recommendations are key to guidance for the optimal management of mPC. Appropriate choice, timing, and sequence of treatment options can help to tailor therapy to maximize outcomes in men with mPC.

NCCN Guidelines Insights: Prostate Cancer, Version 1.2021

The NCCN Guidelines for Prostate Cancer address staging and risk assessment after a prostate cancer diagnosis and include management options for localized, regional, and metastatic disease. Recommendations for disease monitoring and treatment of recurrent disease are also included. The NCCN Prostate Cancer Panel meets annually to reevaluate and update their recommendations based on new clinical data and input from within NCCN Member Institutions and from external entities. This article summarizes the panel’s discussions for the 2021 update of the guidelines with regard to systemic therapy for metastatic castration-resistant prostate cancer.

Clinical Experience of Steroid Switch from Prednisone to Dexamethasone in Patients with Metastatic Castration-Resistant Prostate Cancer Treated with Abiraterone Acetate

OBJECTIVE

To evaluate the therapeutic efficacy of a steroid switch from prednisone to dexamethasone in Asians with metastatic castration-resistant prostate cancer (mCRPC) that progressed after docetaxel chemotherapy.

METHODS

This study included postdocetaxel patients with mCRPC treated with abiraterone acetate combined with prednisone (AA + P) who had experienced prostate-specific antigen (PSA) progression. All patients underwent a steroid switch from prednisone (10 mg/day) to dexamethasone (1 mg/day). The PSA level and clinical symptoms were recorded. Moreover, follow-up was conducted until patients were either lost to follow-up or death.

RESULTS

This study included 11 patients from a single center in Taiwan. The median follow-up time starting from AA + P treatment was 19.47 months. Seven patients (63.64%) had >30% PSA decline, and 6 patients (54.55%) had >50% PSA decline. The median percentage of PSA decline was 83.6%. The median time until PSA progression after the steroid switch was 11.38 months. No adverse events greater than grade 3 were noted.

CONCLUSIONS

Steroid switching is a feasible and effective therapy in docetaxel-treated Asian patients with mCRPC.

LncRNA GAS5 participates in the regulation of dexamethasone on androgen receptor -negative and -positive prostate cancer cell proliferation

BACKGROUND

Androgen receptor (AR) and long non-coding RNAs (lncRNA) play important roles in the initiation and progression of prostate cancer (PCa). The present study was designed to investigate whether lncRNA growth arrest-specific 5 (GAS5) is involved in the regulation of dexamethasone on the proliferation of AR⁺ PCa and AR^- PCa cell lines.

METHODS

Cell proliferation and cell cycle distribution were assessed using MTT assay and flow cytometry, respectively. GAS5 expression was examined by quantitative real-time PCR. AR protein level was examined by Western blot. RNA immunoprecipitation and RNA pull-down were performed to analyze the binding of GAS5 to AR.

RESULTS

In AR^- PCa cell line PC3, dexamethasone upregulated GAS5 expression, induced cell cycle arrest in the G0/G1 phase and inhibited cell proliferation, which were enhanced by GAS5 overexpression and attenuated by GAS5 silencing. However, in AR⁺ PCa cell line 22Rv1, dexamethasone had no obvious effects on GAS5 expression, cell cycle distribution and cell proliferation. AR was localized in the cytoplasm and bound to GAS5, counteracting the proliferation-inhibitory effect of GAS5.

CONCLUSION

Taken together, GAS5 participates in the regulation of dexamethasone on the proliferation of AR⁺ PCa and AR^- PCa cell lines.

Pharmacotherapeutic strategies for castrate-resistant prostate cancer

INTRODUCTION

Metastatic castration-resistant prostate cancer (CRPC) is a potentially symptomatic disease with an eventual lethal outcome. Novel pharmaceutical agents are continuously studied with encouraging results in CRPC.

AREAS COVERED

In this perspective, the authors present established and promising pharmacotherapeutic strategies for the management of CRPC; both with and without metastases. Apart from the different treatment strategies, the authors present the relevant sequence of treatment through disease progression.

EXPERT OPINION

Usually, docetaxel should be considered the first line treatment in mCRPC. Abiraterone acetate (AA) plus prednisone or enzalutamide (ENZ) could be alternative treatments in chemotherapy naïve patients. Sipuleucel-T has been approved for the treatment of asymptomatic or minimally symptomatic mCRPC. Ra-223 has been approved for patients with mCRPC with symptomatic bone metastases (not visceral metastases). Cabazitaxel has been approved as the second line treatment to docetaxel in mCRPC. No differences in the overall survival has been observed between sequences starting with docetaxel versus AA/ENZ. Between AA-to-ENZ and ENZ-to-AA sequence, the AA-to-ENZ sequence appeared to be more favorable than the ENZ-to-AA regarding progression-free survival but not overall survival. Carbazitaxel seemed to retain its activity regardless of the treatment sequence. Of note, ENZ and apalutamide have been approved in non-metastatic CRPC.

Corticosteroid switch after progression on abiraterone acetate plus prednisone

INTRODUCTION

Abiraterone acetate plus prednisone is approved in metastatic castration-resistant prostate cancer. There is some evidence in favour of the steroid switch from prednisone to dexamethasone in patients who progressed whilst on abiraterone acetate plus prednisone or prednisolone.

MATERIALS AND METHODS

The aim of this review is to discuss the results from the clinical studies available, examining potential mechanisms of action and patient selection criteria for this treatment option.

RESULTS

A total of four studies were evaluated. Among possible eligibility criteria for steroid switch, we found: PSA progression without any radiological or clinical progression during abiraterone acetate + prednisone; no high-grade adverse events related to CYP-17 inhibition; and unfitness for chemotherapy or radium-223.

CONCLUSION

Although large randomized prospective trials are warranted, steroid switch seems to offer a good option for certain patients treated with abiraterone acetate plus prednisone or prednisolone.