Sex Hormones and Prostate Cancer

The prostate is an androgen-dependent organ that develops only in male mammals. Prostate cancer is the most common nonskin malignancy in men and the second leading cause of cancer deaths. Metastatic prostate cancer initially retains its androgen dependence, and androgen-deprivation therapy often leads to disease control; however, the cancer inevitably progresses despite treatment as castration-resistant prostate cancer, the lethal form of the disease. Although it was assumed that the cancer became androgen independent during this transition, studies over the last two decades have shown that these tumors evade treatment via mechanisms that augment acquisition of androgens from circulating precursors, increase sensitivity to androgens and androgen precursors, bypass the androgen receptor, or a combination of these mechanisms. This review summarizes the history of prostate cancer research leading to the contemporary view of androgen dependence for prostate cancers and the current treatment approaches based on this modern paradigm.

Combining prostate cancer radiotherapy with therapies targeting the androgen receptor axis

Background

Prostate cancer (pca) is the most common non-dermatologic cancer and the 3rd leading cause of male cancer mortality in Canada. In patients with high-risk localized or recurrent pca, management typically includes the combination of long-term androgen deprivation therapy (adt) and radiotherapy (rt). New androgen-receptor-axis targeted therapies (arats), which await validation, offer an option to intensify therapy.

Methods

In this narrative review, we report the relevant history that has supported combining adt with rt. The literature in PubMed was searched for studies involving pca and novel arats (abiraterone acetate, enzalutamide, apalutamide, darolutamide) published between 1995 and 2019. Literature discussing clinical trials in which those modalities were combined was extracted and synthesized into a combined molecular and clinical discussion. Potential treatment intensification mechanisms and rationales are explored.

Results

Early results from three phase i/ii trials demonstrated that concurrent abiraterone acetate, adt, and rt is safe, improves the extent of chemical castration, and is associated with limited treatment failures. A single in vitro study implies synergy for radiosensitization beyond that facilitated by conventional adt. Studies investigating the combination of other arats with rt are under way, including multiple phase iii trials, but short-term results are not yet available.

Current Treatment Options for Metastatic Hormone-Sensitive Prostate Cancer

The possible treatments options for metastatic hormone-sensitive prostate cancer (mHSPC) have dramatically increased during the last years. The old backbone, which androgen-deprivation therapy (ADT) is the exclusive approach for hormone-naïve patients, has been disrupted. Despite the fact that several high-quality, randomized, controlled phase 3 trials have been conducted in this setting, no direct comparison is currently available among the different strategies. Inadequate power, absence of preplanning and small sample size frequently affect the subgroup analyses according to disease volume or patient's risk. The choice between ADT alone and ADT combined with docetaxel, abiraterone acetate, enzalutamide, apalutamide or radiotherapy to the primary tumor remains challenging. Factors that are related to the tumor, patient or drug side effects, currently guide these clinical decisions. This comprehensive review aims to indirectly compare the phase 3 trials in the mHSPC setting, in order to extrapolate data useful for treatment selection, providing also perspectives on future biomarkers.

Second-Generation Antiandrogens: From Discovery to Standard of Care in Castration Resistant Prostate Cancer

Prostate cancer is the most commonly diagnosed cancer affecting men in the United States. The prostate is a hormone-dependent gland in which androgen hormones testosterone and dihydrotestosterone bind to and activate the androgen receptor, initiating nuclear translocation of androgen receptor and a subsequent signaling cascade. Due to the androgen dependency of the prostate, androgen deprivation therapies have emerged as first line treatment for aggressive prostate cancer. Such therapies are effective until the point at which prostate cancer, through a variety of mechanisms including but not limited to generation of ligand-independent androgen receptor splice variants, or intratumoral androgen production, overcome hormone deprivation. These cancers are androgen ablation resistant, clinically termed castration resistant prostate cancer (CRPC) and remain incurable. First-generation antiandrogens established androgen receptor blockade as a therapeutic strategy, but these therapies do not completely block androgen receptor activity. Efficacy and potency have been improved by the development of second-generation antiandrogen therapies, which remain the standard of care for patients with CRPC. Four second-generation anti-androgens are currently approved by the Food and Drug Administration (FDA); abiraterone acetate, enzalutamide, and recently approved apalutamide and darolutamide. This review is intended to provide a thorough overview of FDA approved second-generation antiandrogen discovery, treatment application, strategies for combination therapy to overcome resistance, and an insight for the potential future approaches for therapeutic inhibition of androgen receptor.

Pharmacodynamic and Clinical Results from a Phase I/II Study of the HSP90 Inhibitor Onalespib in Combination with Abiraterone Acetate in Prostate Cancer

PURPOSE

Onalespib is a potent, fragment-derived second-generation HSP90 inhibitor with preclinical activity in castration-resistant prostate cancer (CPRC) models. This phase I/II trial evaluated onalespib in combination with abiraterone acetate (AA) and either prednisone or prednisolone (P) in men with CRPC progressing on AA/P.

PATIENTS AND METHODS

Patients with progressing CRPC were randomly assigned to receive 1 of 2 regimens of onalespib combined with AA/P. Onalespib was administered as intravenous infusion starting at 220 mg/m2 once weekly for 3 of 4 weeks (regimen 1); or at 120 mg/m2 on day 1 and day 2 weekly for 3 of 4 weeks (regimen 2). Primary endpoints were response rate and safety. Secondary endpoints included evaluation of androgen receptor (AR) depletion in circulating tumor cells (CTC) and in fresh tumor tissue biopsies.

RESULTS

Forty-eight patients were treated with onalespib in combination with AA/P. The most common ≥grade 3 toxicities related to onalespib included diarrhea (21%) and fatigue (13%). Diarrhea was dose limiting at 260 and 160 mg/m2 for regimens 1 and 2, respectively. Transient decreases in CTC counts and AR expression in CTC were observed in both regimens. HSP72 was significantly upregulated following onalespib treatment, but only a modest decrease in AR and GR was shown in paired pre- and posttreatment tumor biopsy samples. No patients showed an objective or PSA response.

CONCLUSIONS

Onalespib in combination with AA/P showed mild evidence of some biological effect; however, this effect did not translate into clinical activity, hence further exploration of this combination was not justified.

Safety of Abiraterone Acetate Administration in Elderly Patients Receiving Peritoneal Dialysis with Castration-Resistant Prostate Cancer: Two Case Reports

We report two elderly patients receiving peritoneal dialysis with castration-resistant prostate cancer (CRPC). Herein, we show that the patients were safely treated using abiraterone acetate (750 mg/day orally once daily) and prednisolone (5 mg/day orally once daily). Although the prostate-specific antigen (PSA) level increased in both cases, there was no manifestation of disease progression (clinical and radiographic) for 22 months in case 1 and 8 months in case 2. In case 2, the only adverse event was hypokalemia, which was treated using potassium preparations.

Quantification of Bone Metastasis of Castration-resistant Prostate Cancer After Enzalutamide and Abiraterone Acetate Using Bone Scan Index on Bone Scintigraphy

BACKGROUND/AIM

This study aimed to evaluate the therapeutic effect of enzalutamide (ENZ) or abiraterone acetate (ABI) on bone metastasis in castration-resistant prostate cancer (CRPC), using bone scan index (BSI).

MATERIALS AND METHODS

Treatment outcomes for 31 patients who had undergone ENZ or ABI treatment were examined for CRPC with bone metastases. Cox proportional-hazards regression models were used to investigate the association between overall survival (OS) and clinical characteristics.

RESULTS

Median OS after ENZ or ABI treatment was 29 months. Considering the flare phenomenon, BSI in 17 (55%) patients decreased following treatment. In multivariate analysis, low baseline BSI value and a decrease in BSI following treatment were associated with longer OS (hazard ratio [HR]=8.009; p=0.35 and HR=7.025; p=0.045*, respectively).

CONCLUSION

Low BSI value before ENZ/ABI treatment and a decrease in BSI following ENZ or ABI treatment are independent predictors of longer OS. BSI could be useful for risk assessment of CRPC patients with bone metastases.

External validation and newly development of a nomogram to predict overall survival of abiraterone-treated, castration-resistant patients with metastatic prostate cancer

Abiraterone acetate is approved for the treatment of castration-resistant prostate cancer (CRPC); however, its effects vary. An accurate prediction model to identify patient groups that will benefit from abiraterone treatment is therefore urgently required. The Chi model exhibits a good profile for risk classification, although its utility for the chemotherapy-naive group is unclear. This study aimed to externally validate the Chi model and develop a new nomogram to predict overall survival (OS). We retrospectively analyzed a cohort of 110 patients. Patients were distributed among good-, intermediate-, and poor-risk groups, according to the Chi model. The good-, intermediate-, and poor-risk groups had a sample size of 59 (53.6%), 34 (30.9%), and 17 (15.5%) in our dataset, and a median OS of 48.4, 29.1, and 10.5 months, respectively. The C-index of external validation of Chi model was 0.726. Univariate and multivariate analyses identified low hemoglobin concentrations (<110 g l⁻¹), liver metastasis, and a short time interval from androgen deprivation therapy to abiraterone initiation (<36 months) as predictors of OS. Accordingly, a new nomogram was developed with a C-index equal to 0.757 (95% CI, 0.678–0.836). In conclusion, the Chi model predicted the prognosis of abiraterone-treated, chemotherapy-naive patients with mCRPC, and we developed a new nomogram to predict the overall survival of this group of patients with less parameters.

Clinically complete response to abiraterone acetate in a patient with metastatic castration-resistant prostate cancer

Introduction

Abiraterone acetate in combination with prednisone is now widely used for the treatment of castration‐resistant prostate cancer.

Case presentation

A 62‐year‐old patient with a bone metastatic castration‐resistant prostate cancer was started on abiraterone acetate at a dose of 1000 mg a day along with 10 mg prednisone. In spite of castrate testosterone level, the laboratory test showed a relatively high level of serum testosterone, which was 21 ng/dL. Within 6 months, the patient achieved a complete prostate‐specific antigen response. Follow‐up bone scintigraphy demonstrated no area of intense uptake. He had a history of hyperlipidemia and was started on atorvastatin at home just after starting abiraterone acetate.

Conclusion

This report is a rare case of a clinically complete response to abiraterone acetate in a patient with metastatic castration‐resistant prostate cancer.

Real-World Treatment Patterns in Patients with Castrate-Resistant Prostate Cancer and Bone Metastases

BACKGROUND

Prostate cancer is the most frequently diagnosed cancer in men in the United States. There is scant real-world evidence characterizing the care utilization and clinical outcomes associated with the use of therapies currently approved by the US Food and Drug Administration (FDA) for patients with metastatic castrate-resistant prostate cancer (CRPC).

OBJECTIVE

To describe the real-world treatment patterns, healthcare costs, and survival rates of patients with metastatic CRPC and bone metastases who have commercial or Medicare coverage.

METHODS

This retrospective observational study was conducted using medical and pharmacy claims from the Humana research database for male patients who had Medicare or commercial coverage and were aged 55 to 89 years at the initiation of treatment for metastatic CRPC. Three inclusion criteria were used to identify appropriate patients for the 2 cohorts, including (1) a diagnosis of prostate cancer (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] code 185.x); (2) a diagnosis of bone metastasis (ICD-9-CM code 198.5) between 2013 and 2014; and (3) a healthcare insurance claim indicating a prescription for an FDA-approved first-line treatment for metastatic CRPC. Subsequent lines of treatment were also identified through the healthcare claims data. The 2-year survival rate was calculated and controlled for demographic and clinical characteristics, and the total costs (medical plus pharmacy) were calculated for the 6 months postindex.

RESULTS

A total of 1855 patients met the study inclusion criteria. Of these patients, 660 (35.6%) received at least 1 medication. The patient count by line of treatment was 660 (100%) who received first-line therapy, 380 (57.6%) who received second-line treatment, 204 (30.9%) who received third-line therapy, and 107 (16.2%) who received fourth-line therapy. The medication distribution by line of treatment (using first-, second-, third-, or fourth-line therapy for each drug) was abiraterone acetate (50.5%, 61.3%, 68.6%, 75.7%); enzalutamide (15.6%, 39.2%, 54.4%, 71.0%); sipuleucel-T (9.2%, 13.9%, 20.1%, 20.6%); radium-223 dichloride (1.7%, 2.6%, 7.4%, 13.1%); cabazitaxel (2.3%, 5.5%, 16.2%, 19.6%); and docetaxel (22.1%, 32.1%, 42.6%, 48.6%). The total monthly unadjusted healthcare costs for patients who received an FDA-approved treatment was much higher ($9435) than for patients with metastatic prostate cancer who did not receive an FDA-approved treatment ($5055), and the 2-year survival rate for patients who received an FDA-approved treatment was 57.1% (25th percentile, 250 days; 50th percentile, 541 days).

CONCLUSIONS

The most common first-line treatment for patients with commercial or Medicare coverage who had metastatic CRPC was abiraterone or enzalutamide. Hormone therapies used as monotherapy were the most frequently used treatment, and their concomitant administration with other treatments was the second most common treatment pattern. Additional clinical studies are needed to further elucidate the treatment sequencing for patients with metastatic CRPC.

[CLINICAL OUTCOMES OF ABIRATERONE ACETATE FOR TREATMENT OF CASTRATION-RESISTANT PROSTATE CANCER: A RETROSPECTIVE ANALYSIS]

(Objective) We retrospectively evaluated the clinical efficacy and safety of abiraterone acetate (AA) in patients with castration-resistant prostate cancer (CRPC). (Methods) We analyzed the clinical records of 50 patients who had received AA in Gunma Cancer Center between October 2014 and June 2017. We assessed the response of prostate-specific antigen (PSA) to AA, and analyzed the association between overall survival and various parameters, including the types of primary hormonal therapy, PSA level, Gleason score, time to CRPC, prior treatment with enzalutamide (Enz) and docetaxel, and sites of metastases. (Results) The median patient age was 74.5 years and median PSA level at baseline was 15.9 ng/ml; 39 (78%) patients had Gleason score ≥8. Eleven (45.8%) of the 24 docetaxel-naïve patients achieved >50% reduction in PSA level from baseline as opposed to one (4.5%) of the 22 patients previously treated with docetaxel.Eleven (55%) of the 20 Enz-naïve patients achieved >50% reduction in PSA level from baseline compared to one (3.8%) of the 26 patients previously treated with Enz. The overall survival of the group with time to CRPC >12 months was significantly longer than that of the group with time to CRPC <12 months (p=0.035). In general, AA was tolerated; the most frequently reported adverse events included liver dysfunction (22%) and fatigue (6%). (Conclusion) Our results suggest that AA is tolerated and may be suitable for patients with time to CRPC >12 months.

Medical resource utilization of abiraterone acetate plus prednisone added to androgen deprivation therapy in metastatic castration-naive prostate cancer: Results from LATITUDE

BACKGROUND

Abiraterone acetate plus prednisone (AA+P), when added to androgen deprivation therapy (ADT), demonstrated significant improvements in overall survival and disease progression over dual placebos added to ADT in the LATITUDE clinical trial (NCT01715285). The objective of this study was to assess event-driven medical resource utilization (MRU) of ADT plus AA+P (ADT+AA+P) versus ADT plus dual placebos (ADT+placebos) in LATITUDE.

METHODS

Event-driven MRU data from LATITUDE while patients were on treatment were used for analyses. Types of MRU included overnight hospitalizations and length of stay (LOS), emergency room (ER) visits, radiotherapy, surgery, imaging, and specialist and general practitioner (GP) visits. Rates by treatment (per 100 person-years) and rate ratios comparing ADT+AA+P with ADT+placebos were estimated with zero-inflated Poisson regression. The difference in the average hospital LOS between arms was assessed with repeated measures regression analyses. Reasons for hospitalization were explored. Sensitivity analyses were conducted to assess the robustness of the results.

RESULTS

A total of 1199 patients were enrolled in LATITUDE. Significantly lower rates of hospitalization (a 24% reduction), imaging (a 36% reduction), and radiotherapy (a 50% reduction) were observed with ADT+AA+P versus ADT+placebos. There was a nonsignificant trend of lower rates of specialist visits and surgery. The rates of ER and GP visits and the average LOS per hospitalization episode were similar across arms. The most common hospitalization reasons were genitourinary, musculoskeletal, and respiratory tract symptoms/disorders. The results remained consistent in a sensitivity analysis.

CONCLUSIONS

Adding AA+P to ADT does not increase MRU and leads to lower rates of hospitalization, imaging, and radiotherapy. This likely reflects the more favorable clinical outcomes with ADT+AA+P therapy.

Abiraterone acetate for early stage metastatic prostate cancer: patient selection and special considerations

In recent years, therapeutic advances, together with new medication sequences and combinations, have improved outcomes for prostate cancer. For a long time, androgen deprivation therapy (ADT) has been the standard of care for newly diagnosed, metastatic prostate cancer, first as a standalone therapy and then in combination with taxane-based regimens. More recently, the addition of abiraterone acetate to ADT to achieve complete androgen blockade has proven beneficial for the treatment of metastatic hormone-resistant prostate cancer and metastatic hormone-sensitive prostate cancer (mHSPC). In this review, we summarize recent findings on the early use of abiraterone in mHSPC and discuss survival benefits as reported in clinical trials. On the basis of existing data, abiraterone in combination with ADT could be considered a new standard of care for patients affected by mHSPC.

Remarkable response to abiraterone acetate in castration-resistant prostate cancer patient with aggressive liver metastasis

Introduction

The number of treatment options for metastatic castration-resistant prostate cancer has increased in recent years. Abiraterone, which selectively inhibits CYP17 in the androgen synthesis pathway, is widely used. Liver metastasis is one of the worst prognostic factors in metastatic castration-resistant prostate cancer. Only a few case reports have shown abiraterone successfully treated the liver metastasis of metastatic castration-resistant prostate cancer.

Case presentation

A 62-year-old man with prostate-specific antigen of 16.69 ng/mL was diagnosed with Gleason 8 (3 + 5) poorly differentiated prostate adenocarcinoma. Androgen deprivation therapy and sequential anti-androgen replacement were performed; however, the disease advanced to castration-resistant prostate cancer with liver metastasis. Prior to docetaxel, abiraterone achieved marked improvements in liver metastasis and prostate-specific antigen.

Conclusion

Metastatic castration-resistant prostate cancer patients with visceral metastasis were excluded from COU-AA-302, which is phase III trial on abiraterone prior to docetaxel. Although docetaxel is the recommended treatment for the visceral metastasis of castration-resistant prostate cancer according to the European Association of Urology guidelines, abiraterone also has potential as a treatment option.

Corticosteroid switch in heavily pre-treated castration-resistant prostate cancer patients progressed on abiraterone acetate plus prednisone

The aim of this retrospective study is to evaluate the activity and safety of a steroidal switch from prednisone to dexamethasone in patients with advanced, heavily pre-treated, castration-resistant prostate cancer (CRPC) who progressed on abiraterone acetate. Treatment consisted of oral daily abiraterone plus dexamethasone (0.5 mg once daily) administered until disease progression or unacceptable toxicity. Thirty-six patients were evaluated: all men underwent a prior treatment with enzalutamide. A PSA decrease ≥50% was observed in 11% of patients; median progression-free survival was 10.8 weeks (95% CI: 9.2-16), and median survival was 17.6 weeks (95% CI: 15.8-28.8). Better efficacy and survival were observed in the subgroup of patients treated with abiraterone acetate prior for a period >3 months; treatment was well tolerated, and no grade 3-4 toxicities were observed. Our findings did not suggest the use of steroid switch in all CRPC who were heavily pre-treated. However, the switch could be an option for patients who responded well to prior abiraterone acetate treatment.

Impact of abiraterone acetate plus prednisone or enzalutamide on fatigue and cognition in patients with metastatic castration-resistant prostate cancer: initial results from the observational AQUARiUS study

Introduction

Abiraterone acetate plus prednisone (AAP) and enzalutamide (ENZ) are commonly prescribed for metastatic castration-resistant prostate cancer (mCRPC). Data comparing their effects on patient-reported outcomes (PROs) from routine clinical practice are limited.

Methods

AQUARiUS (NCT02813408) is an ongoing, two-cohort, prospective, observational, non-randomised, multicentre, phase IV European study assessing the effects of AAP and ENZ on PROs in 211 patients with mCRPC over 12 months. Patients receive AAP or ENZ per routine clinical practice. Data on cognition, fatigue, pain and health-related quality of life are measured using the Functional Assessment of Cancer Therapy-Cognitive Function, Brief Fatigue Inventory-Short Form, Brief Pain Inventory-Short Form and European Organization for Research and Treatment of Cancer Quality of Life-C30 questionnaires, respectively.

Results

This 3-month analysis was conducted in 105 patients; 46 received AAP and 59 received ENZ. There were statistically significant differences in mean change from baseline favouring AAP over ENZ at months 1, 2 and 3 for perceived cognitive impairments and cognitive functioning. At each time-point, ENZ-treated patients had a significantly higher risk of experiencing clinically meaningful worsening in perceived cognitive impairments versus those receiving AAP.

Statistically significant differences in mean change from baseline favouring AAP over ENZ were seen for usual level of fatigue and fatigue interference at months 2 and 3 and for current fatigue and worse level of fatigue at month 3. Differences favouring AAP versus ENZ were seen for the fatigue scale of the QLQ-C30 questionnaire (months 1 and 3). There was a significantly higher risk of clinically meaningful worsening in usual level of fatigue with ENZ versus AAP at month 3.

No significant differences between cohorts were observed for pain (BPI-SF) at any time-point.

Conclusion

This analysis suggests more favourable outcomes with AAP versus ENZ for cognition and fatigue in the first 3 months of treatment initiation for mCRPC. These findings require confirmation from future analyses of data from AQUARiUS from a larger number of patients with a longer follow-up period.

Abiraterone in chemotherapy-naive patients with metastatic castration-resistant prostate cancer: a systematic review of 'real-life' studies

Background

To assess the efficacy and safety of treatment with abiraterone acetate (AA) in chemotherapy-naïve men with metastatic castration-resistant prostate cancer (mCRPC) in the 'real-life' setting.

Methods

Data acquisition on the outcomes of the use of AA in chemotherapy-naive patients with mCRPC was performed by a MEDLINE comprehensive systematic literature search using combinations of the following key words: 'prostate cancer', 'metastatic', 'castration resistant', 'abiraterone', 'real life', and excluding controlled clinical trials (phase II and III studies). Identification and selection of the studies was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) criteria. Outcomes of interest were overall survival (OS), progression-free survival (PFS), 12-week 50% reduction in prostate-specific antigen (PSA), and grade 3 and higher adverse events. Data were narratively synthesized in light of methodological and clinical heterogeneity.

Results

Within the eight identified studies that fulfilled the criteria, a total of 801 patients were included in the meta-analysis. Baseline PSA ranged between 9.5 and 212.0 ng/ml. Most of the patients had bone metastases. Duration of treatment with AA was longer in the studies with lower baseline PSA levels. The median OS ranged between 14 and 36.4 months. The PFS, assessed according to different definitions, ranged from 3.9 to 18.5 months. A 50% PSA reduction at 12 weeks was reached by a variable percentage of patients ranging from 36.0% to 62.1%. Finally, the rate of grade 3 and higher adverse events was reported in three studies and ranged from 4.4% to 15.5%.

Conclusions

Despite the high grade of heterogeneity among studies, treatment with AA seems to ensure good survival outcomes in the 'real-life' setting. However, prospective studies based on patients' characteristics being more similar to 'real-life' patients are necessary.

Baseline prostate-specific antigen levels following treatment with abiraterone acetate as a prognostic factor in castration-resistant prostate cancer

The aim of the present study was to investigate the prognostic factors associated with progression-free survival (PFS) and overall survival (OS) times in patients with castration-resistant prostate cancer (CRPC) who received treatment with abiraterone acetate (AA) in routine clinical settings. A total of 93 patients treated with AA between September 2014 and February 2017 were selected and their medical records were analyzed retrospectively. The median PFS time of docetaxel (DTX)-naïve patients was 171 days, and that of post-DTX patients was 56 days. The OS time of DTX-naïve patients did not reach the median. The median OS time of post-DTX patients was 761 days. Multivariate analyses identified baseline prostate-specific antigen (PSA) level prior to treatment with AA and the PSA response rate as independent prognostic factors for PFS time, and baseline PSA prior to treatment with AA as the only independent prognostic factor for OS time. The results of the present study indicate that the baseline PSA level prior to treatment with AA is a notable prognostic factor in patients with CRPC.

Abiraterone acetate/androgen deprivation therapy combination versus docetaxel/androgen deprivation therapy combination in advanced hormone-sensitive prostate cancer: a network meta-analysis on safety and efficacy

BACKGROUND

A major, yet precisely studied, shift has occurred in the treatment of advanced hormone-sensitive prostate cancer (HSPC) by the addition of docetaxel to androgen deprivation therapy (ADT) in the first line. Recently, two landmark trials showed that abiraterone acetate (AA) can be an effective alternative along with ADT in the same setting. We implemented a network meta-analysis to compare the safety and efficacy of the two combinations.

METHODS

PubMed database, ASCO and ESMO meeting library databases of all results published until June 2017 were searched using the keywords: "prostate cancer" AND "docetaxel" OR "abiraterone acetate". Efficacy endpoints including progression-free survival (PFS) and overall survival (OS), and safety endpoints (including treatment related deaths and selected adverse events) were assessed.

RESULTS

Twenty relevant studies were retrieved and assessed for eligibility. Of those trials, eight were found potentially eligible. Inconsistent reporting of efficacy outcomes limited our analysis to M1 HSPC. The pooled hazard ratios (HRs) of OS and PFS of the direct comparison of abiraterone acetate plus ADT versus ADT were 0.63 (95% CI: 0.545-0.717) and 0.38 (95% CI: 0.34-0.43), respectively. Meanwhile, in the trials of docetaxel plus ADT the pooled HRs of OS and PFS were 0.75 (95% CI: 0.65-0.86) and 0.634 (95% CI: 0.57-0.70), respectively. The indirect comparison showed that the HRs of OS and PFS in DOC + ADT in comparison to AA + ADT were 1.2 (95% CI: 0.98-1.46) and 1.65 (1.40-1.94), respectively. The pooled RR of treatment-related mortality in docetaxel + ADT versus AA + ADT was 1.438 (95% CI: 0.508-4.075).

CONCLUSION

Patients with metastatic HSPC (mHSPC) who received abiraterone acetate with ADT had better PFS and less toxicity compared to those receiving docetaxel with ADT. A trend towards superior OS and fewer treatment-related deaths was also observed, but was statistically non-significant. In view of lacking clear OS advantage, the choice between docetaxel and AA should include a discussion with the patient about the potential toxicities and impact on quality of life of each regimen.

The IMAAGEN Study: Effect of Abiraterone Acetate and Prednisone on Prostate Specific Antigen and Radiographic Disease Progression in Patients with Nonmetastatic Castration Resistant Prostate Cancer

PURPOSE

We evaluated the use of abiraterone acetate (1,000 mg) plus prednisone (5 mg) in patients with high risk, nonmetastatic, castration resistant prostate cancer.

MATERIALS AND METHODS

Patients considered at high risk for progression to metastatic disease (prostate specific antigen 10 ng/ml or greater, or prostate specific antigen doubling time 10 months or less) received abiraterone acetate plus prednisone daily in 28-day cycles. The primary study end point was the proportion of patients in whom a 50% or greater prostate specific antigen reduction was achieved during cycles 1 to 6. Secondary end points included time to prostate specific antigen progression, time to radiographic evidence of disease progression and safety.

RESULTS

Of the 131 enrolled patients 44 (34%) remained on treatment with a median followup of 40.0 months. Median age was 72 years (range 48 to 90). Of the patients 82.4% were white and 14.5% were black. Median screening prostate specific antigen was 11.9 ng/dl and median prostate specific antigen doubling time was 3.4 months. Prostate specific antigen was significantly reduced (p <0.0001) with a 50% or greater prostate specific antigen reduction in 86.9% of cases and a 90% or greater reduction in 59.8%. Median time to prostate specific antigen progression was 28.7 months (95% CI 21.2-38.2). Median time to radiographic evidence of disease progression was not reached but on sensitivity analysis in 15 patients it was estimated to be 41.4 months (95% CI 27.6-not estimable). Baseline testosterone 12.5 ng/dl or greater and a 90% or greater prostate specific antigen reduction at cycle 3 were associated with longer time to prostate specific antigen progression and radiographic evidence of disease progression. Outcomes in black patients were similar to those in other patients. Adverse events, grade 3 or greater adverse events and serious adverse events were reported in 96.2%, 61.1% and 43.5% of patients, respectively.

CONCLUSIONS

In patients with high risk, nonmetastatic, castration resistant prostate cancer treatment with abiraterone acetate plus prednisone demonstrated a significant 50% or greater prostate specific antigen reduction with encouraging results for the secondary end points, including the safety of 5 mg prednisone.

Systemic immune-inflammation index predicts the combined clinical outcome after sequential therapy with abiraterone and docetaxel for metastatic castration-resistant prostate cancer patients

OBJECTIVE

To compare the antitumor effect of abiraterone (AA) followed by docetaxel-prednisone (DP) or vice versa in metastatic castration-resistant prostate cancer (mCRPC) patients, and explored factors that might predict combined PSA-PFS, combined rPFS and OS.

PATIENTS AND METHODS

We retrospectively analyzed mCRPC patients treated with sequential therapy using DP followed by AA or vice versa. Patients who had received enzalutamide or cabazitaxel were excluded. The primary outcome measure was overall survival (OS). The combined PSA progression-free survival (PSA-PFS), combined radiographic PFS (rPFS), and OS of AA-to-DP were compared to the reverse sequence using Kaplan-Meier curves with log-rank statistics. Univariable and multivariable Cox regression analyses were performed to determine prognostic factors that were associated with combined PSA-PFS, combined rPFS and OS.

RESULTS

A total of 104 mCRPC patients who began treatment between 2013 and 2017 were identified: 42 were in the DP-to-AA group and 62 were in the AA-to-DP group. There was no significant difference of baseline clinical characteristics between AA-to-DP and DP-to-AA group. In addition, there was no significant difference in combined PSA-PFS (AA-to-DP: 12.5 [11.4-13.6] vs DP-to-AA: 13.2 [10.9-15.5] months [P = 0.127]), combined rPFS (AA-to-DP: 12.2 [10.9-13.4] vs DP-to-AA: 11.2 [8.9-13.5] months [P = 0.183]) and OS (AA-to-DP: 23.3 [19.7-26.9] vs DP-to-AA: 22.9 [22.1-23.7] months [P = 0.213]) between the two treatment sequences in Kaplan-Meier analysis. In multivariate Cox regression analysis, high systematic Immune-Inflammation Index (SII) level, which was calculated by P (platelet) × N (neutrophil)/L(lymphocyte), remained significant predictors of OS, combined rPFS and combined PSA-PFS.

CONCLUSION

In this study, we did not observe differences in clinical outcomes based on alternative sequencing of AA and DP in mCRPC patients. The ability to tolerate side effects and patient preference may be used to determine the treatment sequencing. In addition, high pretreatment SII level is a negative independent prognosticator of survival outcomes in mCRPC with sequential therapy using DP followed by AA or vice versa, which might guide clinicians select the best treatment.

PTEN Loss Promotes Intratumoral Androgen Synthesis and Tumor Microenvironment Remodeling via Aberrant Activation of RUNX2 in Castration-Resistant Prostate Cancer

Purpose: Intratumoral androgen synthesis (IAS) is a key mechanism promoting androgen receptor (AR) reactivation and antiandrogen resistance in castration-resistant prostate cancer (CRPC). However, signaling pathways driving aberrant IAS remain poorly understood.Experimental Design: The effect of components of the AKT-RUNX2-osteocalcin (OCN)-GPRC6A-CREB signaling axis on expression of steroidogenesis genes CYP11A1 and CYP17A1 and testosterone level were examined in PTEN-null human prostate cancer cell lines. Pten knockout mice were used to examine the effect of Runx2 heterozygous deletion or abiraterone acetate (ABA), a prodrug of the CYP17A1 inhibitor abiraterone on Cyp11a1 and Cyp17a1 expression, testosterone level and tumor microenvironment (TME) remodeling in vivoResults: We uncovered that activation of the AKT-RUNX2-OCN-GPRC6A-CREB signaling axis induced expression of CYP11A1 and CYP17A1 and testosterone production in PTEN-null prostate cancer cell lines in culture. Deletion of Runx2 in Pten homozygous knockout prostate tumors decreased Cyp11a1 and Cyp17a1 expression, testosterone level, and tumor growth in castrated mice. ABA treatment also inhibited testosterone synthesis and alleviated Pten loss-induced tumorigenesis in vivoPten deletion induced TME remodeling, but Runx2 heterozygous deletion or ABA treatment reversed the effect of Pten loss by decreasing expression of the collagenase Mmp9.Conclusions: Abnormal RUNX2 activation plays a pivotal role in PTEN loss-induced IAS and TME remodeling, suggesting that the identified signaling cascade represents a viable target for effective treatment of PTEN-null prostate cancer, including CRPC. Clin Cancer Res; 24(4); 834-46. ©2017 AACR.

Baseline neutrophil-to-lymphocyte ratio predicts the prognosis of castration-resistant prostate cancer treated with abiraterone acetate

Abiraterone acetate (AA), a CYP17 inhibitor, now has a crucial role in the treatment of castration-resistant prostate cancer (CRPC), and previous studies have reported several prognostic clinical factors for AA treatment. The neutrophil-to-lymphocyte ratio (NLR) has also been investigated for a CRPC treatments in a few reports, however it has not been identified to be a prognostic factor for AA treatment in Japanese patients. The present study aimed to assess the association of the baseline NLR with the overall survival (OS) in CPRC patients treated by AA. The present study retrospectively reviewed a total of 90 consecutive patients with CRPC treated with AA from 2011 to 2016 at Yokohama City University Medical Center and National Cancer Center Hospital East. The primary endpoint of the study was the OS, which was defined as the survival from the start of AA administration. The secondary endpoint was the prostate-specific antigen (PSA) response. PSA response was defined as a reduction in antigen levels of >50%. Complete blood cell counts were performed, and the NLR was calculated using the neutrophil and lymphocyte counts obtained on the same day or a few days prior to the initiation of AA therapy. The NLR cut-off point was determined to be 3.76 for the OS, and divided into the high NLR group of 34 patients and the low NLR group of 56 patients. A PSA response was obtained in 8 patients (23.5%) in the high NLR group and in 24 (42.9%) in the low NLR group. The difference of PSA response between the two groups was significant (P=0.037). Kaplan-Meier curves demonstrated that a high NLR [NLR ≥3.76; median OS: 8.4 months; 95% confidence interval (CI): 6.325-10.475 months] was correlated with a risk of mortality compared with a low NLR (NLR <3.76; median OS not reached). A multivariate analysis demonstrated that the NLR was an independent predictor for the OS (hazard ratio: 2.682; 95% CI: 1.143-6.293; P=0.023). The findings suggest that the NLR may be a useful novel biomarker for predicting the prognosis of CRPC patients treated with AA.

Abiraterone acetate and its use in the treatment of metastatic prostate cancer: a review

Abiraterone acetate, which targets enzymatic complexes playing a central role in steroidogenesis, demonstrated to increase survival significantly in both chemo-naive and docetaxel pretreated, becoming one of the drugs of choice for metastatic castration-resistant prostate cancer. More recently, this agent in combination to androgen deprivation therapy demonstrated to be efficacious also in metastatic castration-sensitive prostate cancer. The present review is aimed to outline the clinical development of abiraterone acetate, the pivotal trials which led to its approval for the clinical practice, new evidence about its efficacy in metastatic castration-sensitive prostate cancer, its place in the therapeutic landscape of prostate cancer and future directions of development.