Clinical outcome of maximum androgen blockade using flutamide as second-line hormonal therapy for hormone-refractory prostate cancer

Prostate Cancer Review: Genetics, Diagnosis, Treatment Options, and Alternative Approaches

Prostate cancer is one of the malignancies that affects men and significantly contributes to increased mortality rates in men globally. Patients affected with prostate cancer present with either a localized or advanced disease. In this review, we aim to provide a holistic overview of prostate cancer, including the diagnosis of the disease, mutations leading to the onset and progression of the disease, and treatment options. Prostate cancer diagnoses include a digital rectal examination, prostate-specific antigen analysis, and prostate biopsies. Mutations in certain genes are linked to the onset, progression, and metastasis of the cancer. Treatment for localized prostate cancer encompasses active surveillance, ablative radiotherapy, and radical prostatectomy. Men who relapse or present metastatic prostate cancer receive androgen deprivation therapy (ADT), salvage radiotherapy, and chemotherapy. Currently, available treatment options are more effective when used as combination therapy; however, despite available treatment options, prostate cancer remains to be incurable. There has been ongoing research on finding and identifying other treatment approaches such as the use of traditional medicine, the application of nanotechnologies, and gene therapy to combat prostate cancer, drug resistance, as well as to reduce the adverse effects that come with current treatment options. In this article, we summarize the genes involved in prostate cancer, available treatment options, and current research on alternative treatment options.

Novel combination therapy of prostate cancer cells with arsenic trioxide and flutamide: An in-vitro study

OBJECTIVE

The study objective was to assess the therapeutic potential of Arsenic Trioxide (ATO) and Flutamide combination for metastatic prostate cancer (PCa) treatment.

MATERIAL AND METHOD

LNCaP and PC3 cell lines were treated with different concentrations of ATO and PCa conventional drug Flutamide alone and/or in combination to find effective doses and IC₅₀ values. Percentages of apoptotic cells were evaluated by Annexin/PI staining and the proliferative inhibitory effect was assessed by Micro Culture Tetrazolium Test (MTT). Expression of SNAIL, KLK2, E-cadherin, and angiogenesis genes (VEGFA and VEGFC), and apoptosis genes (Bcl₂, and P53) were examined by real-time PCR.

RESULTS

The combination of Flutamide and ATO significantly increased the percentage of apoptotic cells and inhibited PCa cells proliferation compared with each drug alone in LNCaP and PC3 cell lines. Generally, both cell lines treated with the combination of Flutamide and ATO showed a decrease in expression of KLK2, angiogenesis genes (VEGFA and VEGFC), and apoptosis gene (Bcl₂), and an increase in expression of E-cadherin and P53 genes; however, contradictory findings were found regarding SNAIL expression in LNCaP and PC3 cells.

CONCLUSION

The combination therapy with ATO and flutamide has augmented the anti-tumor effect on LNCaP and PC3 cells, which probably originates from their potential to induce apoptosis and inhibit the proliferation of PCa cells simultaneously.

Enzalutamide + androgen deprivation therapy (ADT) versus flutamide + ADT in Japanese men with castration‐resistant prostate cancer: AFTERCAB study

Objectives

The objective of the study is to compare the efficacy and safety of alternative androgen therapy (AAT) with enzalutamide + androgen deprivation therapy (ADT) and flutamide + ADT in the treatment of Japanese men with metastatic or nonmetastatic castration‐resistant prostate cancer (CRPC) who progressed despite combined androgen blockade (CAB) with bicalutamide + ADT. AAT treatment sequence was also investigated.

Materials and methods

The open‐label, Phase 4 AFTERCAB study (NCT02918968) was conducted from November 2016 to March 2020 in Japanese men aged ≥20 years with asymptomatic or mildly symptomatic CRPC. Patients were initially randomized to enzalutamide (160 mg/day) + ADT (enzalutamide first) or flutamide (375mg/day [125mg three times daily]) + ADT (flutamide first) as first‐line therapy. Following prostate‐specific antigen (PSA) progression, other disease progression, or discontinuation of first‐line therapy due to an adverse event (AE), patients switched to the other treatment as second‐line therapy. The primary endpoint was time to PSA progression with first‐line therapy (TTPP1). Secondary endpoints included TTPP2 (TTPP1 + time to PSA progression with second‐line therapy). AEs were monitored to assess safety.

Results

Overall, 206 men were randomized (enzalutamide first, n = 102; flutamide first, n = 104) and stratified by study site and disease stage; 133 patients transitioned to second‐line therapy (enzalutamide first, n = 48; flutamide first, n = 85). TTPP1 was significantly improved with enzalutamide first versus flutamide first (median 21.4 months vs. 5.8 months; hazard ratio [HR] 0.42; 95% confidence interval [CI] [0.29, 0.61]). TTPP2 was numerically improved with enzalutamide first versus flutamide first (median not reached vs. 21.2 months; HR 0.76; 95% CI [0.48, 1.19]). Both treatments were generally well tolerated, with AEs consistent with their known safety profiles.

Conclusion

First‐line AAT with enzalutamide + ADT provided a significant improvement in time to PSA progression versus flutamide + ADT. Enzalutamide + ADT may therefore be the preferred first‐line AAT option in Japanese men with metastatic or nonmetastatic CRPC who progress despite CAB with bicalutamide + ADT.

Efficacy and safety of abiraterone acetate plus prednisolone in patients with early metastatic castration-resistant prostate cancer who failed first-line androgen-deprivation therapy: a single-arm, phase 4 study

Aim

The aim was to evaluate the efficacy and safety of abiraterone acetate plus prednisolone in patients with chemotherapy-naïve early metastatic castration-resistant prostate cancer who failed first-line androgen deprivation therapy.

Methods

Patients with early metastatic castration-resistant prostate cancer with confirmed prostate-specific antigen progression within 1-year or prostate-specific antigen progression without having normal prostate-specific antigen level (<4.0 ng/mL) during first-line androgen deprivation therapy were enrolled and administered abiraterone acetate (1000 mg) plus prednisolone (10 mg). A minimum of 48 patients were required according to Simon’s minimax design. The primary endpoint was prostate-specific antigen response rate (≥50% prostate-specific antigen decline by 12 weeks), secondary endpoints included prostate-specific antigen progression-free survival and overall survival. Safety parameters were also assessed.

Results

For efficacy, 49/50 patients were evaluable. Median age was 73 (range: 55–86) years. The median duration of initial androgen deprivation therapy was 32.4 (range: 13.4–84.1) weeks and 48 patients experienced prostate-specific antigen progression within 1-year after initiation of androgen deprivation therapy. prostate-specific antigen response rate was 55.1% (95% confidence interval: 40.2%–69.3%), median prostate-specific antigen–progression-free survival was 24.1 weeks, and median overall survival was 102.9 weeks (95% confidence interval: 64.86 not estimable [NE]). Most common adverse event was nasopharyngitis (15/50 patients, 30.0%). The most common ≥grade 3 adverse event was alanine aminotransferase increased (6/50 patients, 12.0%).

Conclusions

Abiraterone acetate plus prednisolone demonstrated a high prostate-specific antigen response rate of 55.1%, suggesting tumor growth still depends on androgen synthesis in patients with early metastatic castration-resistant prostate cancer. However, prostate-specific antigen–progression-free survival was shorter than that reported in previous studies. Considering the benefit–risk profile, abiraterone acetate plus prednisolone would be a beneficial treatment option for patients with chemotherapy-naive metastatic prostate cancer who show early castration resistance.

Enzalutamide for the treatment of nonmetastatic castration-resistant prostate cancer

INTRODUCTION

Enzalutamide is the first characterized second-generation nonsteroidal androgen receptor inhibitor (ARi). Its efficacy has been established in several clinical trials evaluating its role in different settings of prostate cancer. Recently, enzalutamide has been approved for the treatment of nonmetastatic castration-resistant prostate cancer (nmCRPC).

AREAS COVERED

In this paper, the authors describe the chemical structure and pharmacologic characteristics of enzalutamide, providing a summary of clinical trials evaluating its efficacy and safety in prostate cancer patients.

EXPERT OPINION

Enzalutamide adds to the growing arsenal of ARi used in nmCRPC. An improvement in metastasis-free survival was observed with the use of these new treatment options; recently released preliminary data report also an OS benefit. These novel agents are generally well tolerated, but their safety profiles differ slightly. Since head-to-head comparisons between ARi in nmCRPC are lacking, the adverse events profile, as well as drug availability, costs, and considerations on treatment-sequencing, would most likely influence the selection of the individual agent in this setting. Further research is needed to improve treatment selection and clarify many unsolved issues. Abbreviations ARi: nonsteroidal androgen receptor inhibitor; nmCRPC: nonmetastatic castration resistant prostate cancer; ADT: androgen deprivation therapy; OS: overall survival; PSA: prostate specific antigen; FDA: Food and Drug Administration; AR: Androgen Receptor; MFS: metastasis free survival; PSA-DT: PSA doubling time; HR: hazard ratio; CI: confidence interval; AEs: adverse events; mCRPC: metastatic castration resistant prostate cancer; mHSPC: metastatic hormone-sensitive prostate cancer; rPFS: radiographic progression-free survival; OR: odds ratio.

Enzalutamide versus flutamide for castration-resistant prostate cancer after combined androgen blockade therapy with bicalutamide: the OCUU-CRPC study

BACKGROUND

Before the androgen target therapy era, flutamide was widely used for castration-resistant prostate cancer in Japan. Enzalutamide is currently the recommended treatment; however, the efficacy and safety of enzalutamide and flutamide after combined androgen blockade therapy with bicalutamide, has not been compared.

METHODS

Patients with castration-resistant prostate cancer who received combined androgen blockade therapy with bicalutamide were randomly assigned to receive either enzalutamide or flutamide. The primary endpoint for efficacy was the 3-month prostate-specific antigen response rate. This trial is registered with ClinicalTrials.gov (NCT02346578) and the University hospital Medical Information Network (UMIN000016301).

RESULTS

Overall, 103 patients were enrolled. The 3- (80.8% vs. 35.3%; p < 0.001) and 6-month (73.1% vs. 31.4%; p < 0.001) prostate-specific antigen response rates were higher in the enzalutamide than in the flutamide group. The 3-month disease progression rates (radiographic or prostate-specific antigen progression) were 6.4% and 38.8% in the enzalutamide and flutamide groups, respectively [hazard ratio (HR): 0.16; 95% confidence interval (CI): 0.05-0.47; p < 0.001]; the 6-month rates were 11.4% and 51.1%, respectively (HR 0.22; 95% CI 0.09-0.50; p < 0.001). Enzalutamide provided superior prostate-specific antigen progression-free survival compared with flutamide (HR 0.29; 95% CI 0.15-0.54; p < 0.001). Median time to prostate-specific antigen progression-free survival was not reached and was 6.6 months in the enzalutamide and flutamide groups, respectively.

CONCLUSIONS

As an alternative anti-androgen therapy in patients with castration-resistant prostate cancer who fail bicalutamide-combined androgen blockade therapy, enzalutamide provides superior clinical outcomes compared with flutamide. Enzalutamide should be preferred over flutamide in these patients.

Predictors of poor response to first-generation anti-androgens as criteria for alternate treatments for patients with non-metastatic castration-resistant prostate cancer

PURPOSE

There are no criteria for administering first- or second-generation anti-androgens (FGA and SGA, respectively) to patients with non-metastatic castration-resistant prostate cancer (nmCRPC). This study aimed to assess the efficacy of alternative FGA therapy in nmCRPC patients and the prognosis of these patients and to identify factors for predicting patients potentially responsive to FGA.

METHODS

Data from 63 men with nmCRPC who underwent alternative FGA therapy (bicalutamide, flutamide, or chlormadinone acetate) as first-line therapy after failure of primary androgen-deprivation therapy (PADT) between 2004 and 2017 at Hiroshima University Hospital and affiliated hospitals were retrospectively investigated. The associations of clinicopathological parameters with overall survival (OS) and prostate-specific antigen (PSA) progression-free survival (PFS) of alternative FGA-treated patients were analyzed.

RESULTS

Time to CRPC [p = 0.007, hazard ratio (HR) = 4.77], regional lymph node involvement at the diagnosis of CRPC (p = 0.022, HR = 2.42), and PSA-PFS of alternative FGA therapy ≤ 6 months (p = 0.020, HR = 2.39) were identified as prognostic factors using a multivariate analysis. Additionally, Cox proportional hazard models revealed that PSA nadir value > 1 ng/mL during PADT (p = 0.034, HR = 2.40) and time from starting PADT to PSA nadir ≤ 1 year (p = 0.047, HR = 1.85) were predictive factors for worse PSA-PFS in alternative FGA therapy.

CONCLUSIONS

Shorter time to CRPC, regional lymph node involvement, PSA nadir during PADT > 1 ng/mL, and time from starting PADT to PSA nadir ≤ 1 year might suggest the potential benefit of immediate commencement of SGA, compared to FGA administration after nmCRPC diagnosis.

Treatment of non-metastatic castration-resistant prostate cancer: focus on apalutamide

Androgen deprivation therapy (ADT) is an important component of systemic therapy in advanced prostate cancer; however, resistance to ADT is inevitable. Three large studies demonstrated the efficacy of novel androgen receptor (AR)-targeted therapies in prolonging metastasis-free survival and time to symptomatic progression in patients with non-metastatic castration-resistant prostate cancer (nmCRPC). Enzalutamide and apalutamide have been approved by the FDA in the nmCRPC setting. This review discusses the role of AR and ADT in prostate cancer, mechanism of ADT resistance and the nmCRPC stage. In addition, pharmacologic characteristics and clinical development of apalutamide, role of apalutamide in nmCRPC, and ongoing clinical studies of apalutamide in different stages of prostate cancer are discussed.

Enzalutamide versus flutamide for castration-resistant prostate cancer after combined androgen blockade therapy with bicalutamide: study protocol for a multicenter randomized phase II trial (the OCUU-CRPC study)

Background

Enzalutamide is an oral androgen receptor targeted agent that has been shown to improve survival in PREVAIL trials and has been approved for patients with chemo-naïve metastatic castration-resistant prostate cancer (CRPC). Meanwhile, flutamide is a non-steroidal oral anti-androgen that was commonly used before the approval of bicalutamide. The objective of the OCUU-CRPC study is to compare the efficacy and safety between second-line hormonal therapy of enzalutamide and flutamide as alternative anti-androgen therapy (AAT) after combined androgen blockade (CAB) therapy that included bicalutamide in patients with CRPC.

Methods

A total of 100 patients with CRPC with or without distant metastases after disease progression who received CAB therapy with bicalutamide were randomly assigned at a 1:1 ratio according to distant metastases to the enzalutamide (160 mg/day, 4 × 40 mg capsules once daily) and flutamide (375 mg/day; 3 × 125 mg tablets thrice daily) groups. The primary endpoint for the drug efficacy is the response rate of prostate-specific antigen (PSA) (i.e., the ratio of patients whose PSA declined by ≥50% from baseline) at 3 months. Meanwhile, the secondary endpoints are PSA progression rate at 3 and 6 months, PSA response rate at 6 months, change in quality of life, PSA progression-free survival, and safety. The patient registration started in January 2015 and will end in March 2018, and the follow-up period is 6 months after the last patient registration. The main result will be reported in March 2019.

Discussion

In the OCUU-CRPC study, we compare the efficacy and safety of enzalutamide or alternative AAT with flutamide in participants with CRPC who were previously treated with a CAB therapy with bicalutamide. The expected results of this study will be that enzalutamide is superior to flutamide in terms of PSA response. A longer time to disease progression with enzalutamide over flutamide may translate to better overall survival. However, flutamide may be more accessible for patients owing to its lower cost than enzalutamide.

Trial registration

The OCUU-CRPC study was prospectively registered at clinicaltrials.gov (NCT02346578, January 2015) and University Hospital Medical Information Network (UMIN000016301, January 2015).

Medical management of metastatic prostate cancer

Androgen deprivation therapy has an important role in the medical treatment of advanced and metastatic prostate cancer

The treatment of metastatic prostate cancer is influenced by whether the patient’s disease has progressed on androgen deprivation therapy or not It is considered to be castrate-resistant disease if the cancer has progressed despite adequate suppression of androgens

Chemotherapy using docetaxel or cabazitaxel and anti-androgen drugs such as abiraterone and enzalutamide can be used to treat castrate-resistant disease Radium-223 is an option for patients with bony metastases

Metastatic castrate-resistant prostate cancer is now considered a chronic illness as the life expectancy of patients has almost doubled due to the new treatments General practitioners are therefore more likely to encounter patients with disease- and treatment-related complications

Efficacy of Immediate Switching from Bicalutamide to Flutamide as Second-Line Combined Androgen Blockade

We determined whether prostate specific antigen (PSA) would decrease with immediate antiandrogen switching from bicalutamide (BCL) to flutamide (FLT) in patients receiving combined androgen blockade for advanced prostate cancer. From 2002 to 2006, 20 patients who showed PSA failure after first-line hormonal therapy with a luteinizing hormone-release hormone (LH-RH) agonist and BCL were enrolled. All patients were immediately switched from BCL to FLT, administered with an LH-RH agonist, as second-line combined androgen blockade (CAB). We evaluated the PSA response to second-line CAB. Eight patients (40%) were responsive, showing PSA decreases of at least 50%. The median (range) duration of the PSA response was 18.4 (3–26) months. Second-line CAB using FLT was effective in 40% of patients who received first-line CAB using BCL. The lower Gleason scores at the initial prostate biopsy probably reflect the response to second-line CAB. Responders showed significantly better OS and CSS in the determination of any PSA decline and 40% PSA decline. The median OS duration in nonresponders and responders (40% PSA decline) was 1433 days versus 3617 days. It is concluded that an immediate switch from BCL to FLT is effective for some CRPC patients after first-line CAB using BCL.

Clinical outcomes of anti-androgen withdrawal and subsequent alternative anti-androgen therapy for advanced prostate cancer following failure of initial maximum androgen blockade

The present study aimed to investigate the significance of anti-androgen withdrawal and/or subsequent alternative anti-androgen therapy in patients with advanced prostate cancer (PC) who relapsed after initial maximum androgen blockade (MAB). The present study evaluated the clinical outcomes of 272 consecutive advanced PC patients undergoing anti-androgen withdrawal and/or subsequent alternative anti-androgen therapy with flutamide following the failure of initial MAB using bicalutamide. With the exception of 41 patients (15.1%) who did not undergo anti-androgen withdrawal due to the characteristics of PC suggesting aggressive diseases, prostate-specific antigen (PSA) declined from the baseline value in 83 patients (35.9%), including 18 (7.8%) with PSA decline >50%, but not in the remaining 148 (64.1%). No significant difference in the overall survival (OS) or cancer-specific survival (CSS) among the three groups was observed based on the response to anti-androgen withdrawal. Following the introduction of alternative anti-androgen therapy with flutamide, PSA decline was observed in 185 patients (68.0%), including 103 (37.9%) who achieved a PSA reduction of >50%; however, the PSA level continued to elevate in the remaining 87 (32.0%). Furthermore, of the numerous factors examined, only the duration of the initial MAB therapy was shown to be significantly correlated with the PSA decline following alternative anti-androgen therapy. Multivariate analysis of several factors identified revealed that only PSA decline following alternative anti-androgen therapy was an independent predictor of CSS and OS. If initial MAB is effective, the introduction of alternative anti-androgen therapy may be considered; however, anti-androgen withdrawal should be omitted, irrespective of the characteristics of advanced PC.

Prospective study on the relationship between clinical efficacy of secondary hormone therapy with flutamide and neuroendocrine differentiation in patients with relapsed prostate cancer after first line hormone therapy

OBJECTIVE

The aim of this study was to prospectively verify the relationship between the clinical efficacies of secondary hormone therapy for castration-resistant prostate cancer (CRPC) following first line hormone therapy and neuroendocrine differentiation (NED).

MATERIAL AND METHODS

Forty-six consecutive patients with CRPC following first line hormone therapy who were treated with flutamide as secondary hormone therapy were prospectively assessed with a median follow-up of 21 months. Serum chromogranin A (CgA), as a marker of NED, was measured using an immunoradiometric assay.

RESULTS

Of the 46 patients, 22 (48%) responded to the secondary hormone therapy as a 50% or more reduction from baseline prostate-specific antigen (PSA) with a median response duration of 9.2 months. The PSA response group was correlated with significantly favorable cancer-specific survival (CSS) (92% vs 59% at 5 years, p = 0.0146) compared with the non-response group. Above-normal CgA levels at study entry were detected in 15 patients (33%), but no association with CSS was identified. Data on CgA kinetics were available in 35 patients. The CgA levels before and at 3 months during the treatment were similar. However, eight patients (23%) with an increase in CgA level of a quarter or more from baseline had a tendency for worse CSS (63% vs 84% at 5 years, p = 0.0507) compared with the remaining patients.

CONCLUSION

Within limitations, in this study secondary hormone therapy with flutamide was effective for CRPC following first line hormone therapy. The above-normal CgA level in the first hormone resistance phase is mostly unrelated to prognosis. However, some patients with a remarkable increase in CgA in a short duration may have an unfavorable prognosis caused by NED as well.

Development of nomogram to non-steroidal antiandrogen sequential alternation in prostate cancer for predictive model

OBJECTIVES

To clarify clinical predictors for a prostate-specific antigen decrease ≥50% in response to alternative non-steroidal antiandrogen therapy and to develop a nomogram to predict the prostate-specific antigen decrease ≥50% in response to alternative non-steroidal antiandrogen therapy in patients with advanced prostate cancer that relapsed after initial combined androgen blockade. We previously reported that combined androgen blockade with an alternative non-steroidal antiandrogen is effective for advanced prostate cancer that has relapsed after initial combined androgen blockade.

METHODS

We enrolled 161 patients from 14 medical institutions with histologically confirmed prostate cancer who had been treated with combination therapy and in whom cancer progressed after first-line combined androgen blockade therapy. A nomogram for the prostate-specific antigen decrease ≥50% from baseline prostate-specific antigen in response to alternative non-steroidal antiandrogen therapy was developed based on the final logistic regression model.

RESULTS

Overall prostate-specific antigen decreased ≥50% in 75 of 161 patients (46.6%) in response to alternative non-steroidal antiandrogen therapy. Using five independent risk factors (initial serum level of prostate-specific antigen, hemoglobin, C-reactive protein, prostate-specific antigen nadir to second hormone therapy and Gleason sum), a nomogram was developed for the prediction of prostate-specific antigen decrease ≥50% in response to alternative non-steroidal antiandrogen therapy. The receiver operating characteristic curve showed that the accuracy of the predicted probability was 72.5% for the model.

CONCLUSIONS

This predictive nomogram could predict the prostate-specific antigen decrease ≥50% in response to alternative non-steroidal antiandrogen therapy and might be of benefit to determine the sequential treatment strategy in patients with relapse after first combined androgen blockade.

Efficacy of tegafur-uracil (UFT) administration in castration-resistant prostate cancer patients with a history of both alternative antiandrogen therapy and estramustine phosphate sodium hydrate therapy

PURPOSE

The purpose of this study was to evaluate the efficacy of tegafur-uracil (UFT) administration as a fourth-line therapy in patients with castration-resistant prostate cancer (CRPC) who had already received combined androgen blockade (CAB) therapy (first-line), alternative antiandrogen therapy (second-line), and estramustine phosphate sodium hydrate (EMP) therapy (third-line), in order to determine who would benefit from UFT therapy.

METHODS

UFT was administered at a daily dose of 300 mg/m(2) to 26 patients, and the response to UFT 4 weeks after its induction and its toxicity were evaluated.

RESULTS

A reduction in the serum prostate-specific antigen (PSA) value was observed in 12 patients (46.2 %), while two cases (7.7 %) achieved more than 50 % reduction in PSA. Two patients (7.7 %) required discontinuation of UFT administration because of side effects (grade 2 exanthema in one patient and grade 2 nausea in one patient). A PSA response to UFT was observed, especially in patients older than 75 years and/or whose Gleason score was 8 or less.

CONCLUSIONS

Our data indicate that UFT administration as a fourth-line therapy was tolerable and effective to some degree in patients with CRPC who had already received CAB therapy, alternative antiandrogen therapy, and EMP therapy. It can be used, even in patients aged more than 75 years old, without any loss of efficacy or effect on their activities of daily life, and can be regarded as a treatment option for patients with advanced prostate cancer.

[Hormonal treatment in prostate cancer]

AIM

To describe drugs used in the hormonal treatment (hormonotherapy) of prostate cancer.

MATERIAL

Bibliographical search was performed from the database Medline (National Library of Medicine, PubMed) and websites of the HAS and the ANSM. The search was focused on the characteristics, the mode of action, the efficiency and the side effects of the various drugs concerned.

RESULTS

LHRH analogs and the antiandrogens remain the cornerstone in the treatment of locally advanced and metastatic prostate cancer. New therapeutic classes emerged recently (inhibitor of the synthesis of the androgen, the new antiandrogens) and allowed to grow again the limits of the hormone resistance and define the concept castration-resistant prostate cancer.

CONCLUSION

The hormonal treatment of the prostate cancer grew rich of new therapeutic classes which are going to change the medical care of the prostate cancer in the coming years and the urologist must play its full part.

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.

Novel therapeutic strategies for malignant salivary gland tumors: lessons learned from breast cancer

Malignant salivary gland tumors (MSGTs) account for 2–6% of all head and neck cancers. Despite the rarity, MSGTs have been of great interest due to a wide variety of pathological features and high metastasis rates resulting in poor prognosis. Surgical resection followed by radiation therapy represents the main treatment of this malignancy. Adjuvant therapy is reserved for the management of local recurrence, no longer amenable to additional local therapy, and for metastasis. Based on the studies from other types of tumors, particularly breast cancer, the expression and function of sex steroid hormone receptors in cancer have been extensively studied and applied to diagnosis and treatment. Although a number of studies in MSGTs have been published, the rationale for hormone therapy is still controversial due to the disparate results and insufficient number of cases. However, some recent reports have demonstrated that certain salivary gland neoplasms are similar to breast cancer, not only in terms of the pathological features, but also at the molecular level. Here, we shed light on the biological similarity between MSGTs and certain types of breast cancer, and describe the potential use of hormone and additional therapies for MSGTs.

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.

The Evolution and Current Paradigm of Chemotherapy for Metastatic Castrate-Resistant Prostate Cancer

While hormonal manipulation has a pivotal role in the management of advanced prostate cancer, most patients eventually become refractory to such intervention. Until 2004, no treatment had been shown to increase survival in this group of men. Then the demonstration that docetaxel-based chemotherapy improved overall survival, compared with mitoxantrone-based chemotherapy, ushered in a new era of prostate cancer management—and a new treatment pathway. Questions persisted over optimal use of multiple lines of hormone manipulation, and the ideal time in the pathway to offer chemotherapy. The pathway now looks set to change again, as a new generation of treatments emerges from phase III clinical trials. The next challenge facing healthcare professionals in prostate cancer will be to determine the optimal way in which these new agents can be used, in sequence and/or in combination.

Efficacy of alternative antiandrogen therapy for prostate cancer that relapsed after initial maximum androgen blockade

PURPOSE

We evaluated the effectiveness of second-line maximum androgen blockade (MAB) with an alternative antiandrogen in patients who relapsed after initial MAB.

MATERIALS AND METHODS

We retrospectively analyzed 47 patients with prostate cancer who relapsed after initial MAB, including surgical or medical castration combined with antiandrogens, from January 1998 to December 2009. When the serum prostate-specific antigen (PSA) level was increased on three consecutive occasions, we discontinued the antiandrogen and then administered an alternative antiandrogen. Seven patients were assessed for antiandrogen withdrawal syndrome (AWS). The effect of the second-line MAB was evaluated by the serum PSA level, and response was subdivided into ≥50% and <50% PSA reductions from the baseline PSA at the start of second-line MAB.

RESULTS

PSA reduction was observed in 32 patients (68.1%). Among them, 23 (48.9%) achieved ≥50% PSA reductions with a mean response duration of 13.4±5.4 months. Nine (19.2%) patients reached <50% PSA reductions with a mean response duration of 12.2±6.2 months. The time to nadir PSA level after first-line MAB in the ≥50% PSA reduction group, <50% PSA reduction group, and PSA elevation group was 15.6±12.9 months, 11.8±6.0 months, and 8±6.5 months, respectively. That is to say, it was significantly longer in the responder groups (p=0.038).

CONCLUSIONS

Second-line MAB using an alternative antiandrogen is an effective treatment option before cytotoxic chemotherapy in patients who relapse after initial MAB.

Alternative antiandrogen therapy in patients with castration-resistant prostate cancer: a single-center experience

Outcomes of alternative (second-line) antiandrogen therapy in 112 patients with relapsing prostate cancer after first-line hormonal therapy were analyzed. A good response (prostate-specific antigen [PSA] decrease 50%) and a partial response (PSA decrease of 0–50%) by switching from bicalutamide (BCL) to flutamide (FLT) and from FLT to BCL were achieved in 35.4% (28/79) and 30.4% (24/79), and in 45.0% (9/20) and 20.0% (4/20) of cases, respectively. A good response and a partial response with the change from chlormadinone acetate (CMA) to a non-steroidal antiandrogen (FLT or BCL)and from a non-steroidal antiandrogen to CMA were obtained in 25.0% (2/8) and 37.5% (3/8), and in 20.0% (1/5) and 0% (0/5)of cases, respectively. In multivariate analyses, a second-line good response was significantly predictive of cause-specific survival from first therapy relapse to cancer death in all patients. Patients (52/112, 46.4%) with 30% decrease in PSA levels were associated with significantly better cause-specific survival as measured from the start of first-line treatment and first-line relapse.

Efficacy and toxicity of mitoxantrone and oral etoposide in the treatment of hormone-refractory prostate cancer: pilot study

OBJECTIVE

To evaluate the efficacy and toxicity of the association of mitoxantrone and oral etoposide.

METHODS

Twelve consecutive patients with metastatic hormone-refractory prostate cancer were treated with mitoxantrone and oral etoposide. Toxicity, response rate and response duration were assessed.

RESULTS

Partial response was observed in two patients (response duration of seven and four months) and one patient had stable disease (during four months). Mitoxantrone and oral Etoposide were well tolerated and did not affect tolerability to subsequent chemotherapy.

CONCLUSION

Mitoxantrone and oral etoposide association is an active and well-tolerated regimen in hormone-refractory prostate cancer.

Complete androgen blockade safely allows for delay of cytotoxic chemotherapy in castration refractory prostate cancer

PURPOSE

Complete androgen blockade (CAB) does not prolong overall survival (OS) in patients with castration refractory prostate cancer (CRPC). Although there is variable clinical benefit with second-line hormone manipulation, we do not know which patients might benefit the most.

OBJECTIVES

To identify clinical predictors of benefit of complete androgen blockade.

MATERIALS AND METHODS

We reviewed the records for 54 patients who received treatment with CAB in the setting of disease progression despite castration. We evaluated progression-free survival (PFS) and OS according to PSA at diagnosis, Gleason scores, age, testosterone level, and duration of prior disease control during castration in first line treatment.

RESULTS

Among 54 patients who received CAB, the median PFS was 9 months (CI 4.3-13.7) and OS was 36 months (CI 24-48). We did not find an effect of PSA at diagnosis (p = 0.32), Gleason score (p = 0.91), age (p = 0.69) or disease control during castration (p = 0.87) on PFS or OS. Thirty-four patients subsequently received chemotherapy, with a mean OS of 21 months (CI 16.4-25.5, median not reached).

CONCLUSION

Age, Gleason score, PSA at diagnosis and length of disease control with castration did not affect PFS or OS. In the absence of predictors of benefit, CAB should still be considered in CRPC.

Adrenal androgen levels as predictors of outcome in castration-resistant prostate cancer patients treated with combined androgen blockade using flutamide as a second-line anti-androgen

OBJECTIVES

To analyze the clinical effects of flutamide as a second-line anti-androgen for combined androgen blockade in patients with castration-resistant prostate cancer (CRPC) initially treated with bicalutamide as a first-line anti-androgen.

METHODS

Our study population consisted of 16 patients with CRPC who were treated with flutamide (375 mg daily) as second-line hormonal therapy. Dehydroepiandrosterone (DHEA), androstenedione, androstenediol, testosterone and dihydrotestosterone were measured to investigate the relationship between plasma androgens and outcome following treatment. Furthermore, adrenal androgen levels in a medium of adrenal cancer cell line were also measured.

RESULTS

Second-line hormonal therapy using flutamide resulted in a reduction of the prostate-specific antigen (PSA) level in 14 (87.5%) of 16 patients. A PSA decline greater than 50% was observed in 8 (50%) of the 16 patients. The duration of median responsiveness was 6.25 months. PSA elevation of baseline androstenediol level was a predictive factor of PSA responsiveness. The lower DHEA group improved the duration of responsiveness to flutamide. In vitro, 3 micromol/L flutamide suppressed DHEA, androstenedione and androstenediol synthesis compared with bicalutamide in a medium of adrenal cancer cell line.

CONCLUSIONS

Our data show that flutamide suppresses the adrenal androgens in comparison with bicalutamide. The responsiveness and response duration of flutamide can be predicted in patients with a higher baseline androstenediol level and a lower DHEA level. Metabolites from adrenal androgens contribute to the progression of prostate cancer.

Antiandrogen withdrawal syndrome and alternative antiandrogen therapy associated with the W741C mutant androgen receptor in a novel prostate cancer xenograft

BACKGROUND

The mechanisms underlying antiandrogen withdrawal syndrome (AWS) and alternative antiandrogen therapy (AAT) effectiveness were assumed to be mutations in the androgen receptor (AR), which resulted in an altered response to antiandrogens. The aim of the present study was to test this assumption using the novel prostate cancer xenograft model KUCaP-1 harboring the W741C mutant AR (Yoshida et al., Cancer Res 2005; 65(21): 9611-9616).

METHODS

Mice bearing xenograft tumors were castrated, and the long-term sequential changes in tumor volume were observed. To determine whether AWS was observed in this model, bicalutamide (BCL) was orally administered to the castrated mice and then withdrawn. The effect of flutamide (FLT) on the W741C mutant AR was examined with transactivation assays in vitro and with the oral administration of FLT to non-castrated mice harboring KUCaP-1 in vivo. The AAT efficacy against KUCaP-1 was evaluated by changing BCL with FLT.

RESULTS

KUCaP-1 regressed significantly after castration and did not re-grow. KUCaP-1 treated with BCL continued to grow even after castration and started regressing 2 months after BCL withdrawal, replicating clinically recognized AWS. The antagonistic effect of FLT against the W741C mutant AR was revealed in vitro and in vivo. AAT with FLT suppressed tumor growth after BCL withdrawal.

CONCLUSIONS

KUCaP-1 was an entirely androgen-dependent xenograft and mimicked the clinical phenomena of AWS and AAT caused by the agonistic and antagonistic activity of BCL and FLT, respectively. KUCaP-1 could be an in vivo model for screening novel antiandrogens for the treatment of BCL resistant prostate cancer harboring the W741C mutation in the AR.

[Management of metastatic androgeno-independent prostate cancer]

After first line hormonal therapy (agonist LHRH), metastasic prostate cancer becomes androgen independent in a period of 18 months on average. After this period and after having verified the castration by blood testosterone level, a few options are possible: either inhibit adrenal androgens by maximum androgen blockage (+anti androgens) or by specific adrenal androgen inhibitors. It is also possible to use estrogen or, in a few cases, to propose chemotherapy.

Current topics and perspectives relating to hormone therapy for prostate cancer

Prostate cancer is androgen-dependent, and hormone therapy, mainly achieved by androgen deprivation, has been one of the main treatment modalities in the clinical management of prostate cancer patients for more than six decades. In the 1980s, luteinizing hormone-releasing hormone agonists, which reduce testosterone to castration levels, were introduced Also, after the 1980s, nonsteroidal antiandrogens were developed in addition to steroidal antiandrogens. Since then, so-called maximum androgen blockade (MAB)/combined androgen blockade (CAB), which is a combination of surgical or medical castration and oral antiandrogens, has been developed. More recently, novel treatment modalities have been developed, such as intermittent androgen suppression, nonsteroidal antiandrogen monotherapy, and alternative antiandrogen therapy after relapse from initial MAB/CAB, The present article focuses on these treatment modalities to review current topics and perspectives with respect to hormone therapy for prostate cancer.

Alternative nonsteroidal antiandrogen therapy for advanced prostate cancer that relapsed after initial maximum androgen blockade

PURPOSE

Large meta-analyses have documented that maximum androgen blockade with nonsteroidal antiandrogens for advanced prostate cancer confers survival benefits, although it remains controversial. Also, we and others have reported the effectiveness of second line hormonal therapy for prostate cancer that relapses after initial hormone therapy. However, there is little clinical evidence of the effectiveness of the latter treatment strategy. Therefore, in this multicenter trial in Japan we analyzed clinical outcomes following alternative changing from 1 nonsteroidal antiandrogen to another, ie bicalutamide to flutamide and flutamide to bicalutamide, for advanced prostate cancer that relapsed after initial maximum androgen blockade.

MATERIALS AND METHODS

The study included 232 patients with advanced prostate cancer who were initially treated with maximum androgen blockade, including surgical or medical castration combined with nonsteroidal antiandrogens. If a patient relapsed while on first line therapy, we discontinued antiandrogen and evaluated the patient for antiandrogen withdrawal syndrome. We then administered an alternative antiandrogen and evaluated its effect.

RESULTS

The incidence of antiandrogen withdrawal syndrome after initial maximum androgen blockade was 15.5% for bicalutamide and 12.8% for flutamide. A prostate specific antigen decrease after antiandrogen withdrawal was a prognostic factor. Nonsteroidal antiandrogens as alternative therapy in patients with relapse after the initial maximum androgen blockade were effective (prostate specific antigen decrease greater than 50%) as second line maximum androgen blockade. Of 232 patients 142 (61.2%) showed a prostate specific antigen decrease in response to an alternative antiandrogen. These responders had significantly better survival than nonresponders, suggesting that responsiveness to second line therapy predicts increased survival.

CONCLUSIONS

Following maximum androgen blockade with an alternative nonsteroidal antiandrogen is effective for advanced prostate cancer that has relapsed after initial maximum androgen blockade. Even a partial response to second line maximum androgen blockade was associated with improved survival. Our data support the notion that responders to second line regimens are androgen independent but still hormonally sensitive.

Current perspectives in the treatment of advanced prostate cancer

Prostate cancer (PC) continues to be an important world health problem for men. Patients with locally confined PC are treated with either radiotherapy or surgery. However, treatment of more advanced stages of the disease is problematic. Initially, androgen deprivation offers a period of clinical stability, which is however invariably followed by progression to non-responsiveness to hormonal manipulation. Current management of patients with androgen-independent prostate cancer (AIPC) displays modest response rates and achieves only short-term benefit. Recently, knowledge in the complex pathophysiology of advanced PC has led to the identification of mechanisms and target molecules permitting the introduction of new therapies. Consequently, many investigational treatments are ongoing for AIPC in Phase-II and Phase-III trials aiming at the combination of chemotherapeutic regimens along with immunotherapy targeting PC-associated antigens. Other attractive options are gene therapy, as well as the targeting of survival signaling, differentiation, and apoptosis of the malignant PC cells. Further treatment modalities are directed against the tumor microenvironment, bone metastasis, or both. Collectively, the aforementioned efforts introduce a new era in the management of advanced PC. Novel pharmaceutical compounds and innovative approaches, integrated into the concept of individualized therapy will hopefully, during the next decade, improve the outcome and survival for hundreds of thousands of men worldwide.

Rising prostate-specific antigen after primary treatment of prostate cancer: sequential hormone manipulation

OBJECTIVE

To evaluate systematically the current endocrine treatment options for patients with biochemical recurrence after radical prostatectomy or radiation therapy for localized prostate cancer.

METHODS

Literature search of PubMed documented publications and abstracts from international meetings. Key items included timing and type of salvage hormone therapy, length of its application and handling of side effects.

RESULTS

The majority of patients with isolated prostate-specific antigen (PSA) relapse are not candidates for salvage treatment with curative intent. The PSA threshold that triggers initiation of hormonal therapy is debatable and should be based also on pretreatment risk assessment. Intermittent androgen suppression is an emerging concept to circumvent the unresolved controversy of early versus deferred endocrine therapy. Since the tumor load at time of recurrence is low, peripheral androgen blockade with an antiandrogen and a 5alpha-reductase inhibitor is an acceptable first choice. In case of progression, addition of a LHRH analogue would be the next step. Antiandrogen withdrawal and second-line antiandrogens are clinically of limited value.

CONCLUSIONS

Biochemical-only progression after definitive treatment in curative intent is different from objective or even symptomatic relapse and allows for sequential hormonal therapy with a variety of compounds.

Roles of androgen-dependent and -independent activation of signal transduction pathways for cell proliferation of prostate cancer cells

Prostate cancer is one of the most frequently diagnosed cancers in the western world and this malignant neoplasm is the second-leading cause of cancer death among men in the USA. In the early 1940s, Huggins and Hodges demonstrated that growth and survival of prostate cancer depends on androgens. The mainstay of treatment for advanced prostate cancer is currently androgen ablation. Over the past few decades, several compounds, such as luteinizing hormone-releasing hormone analogues and anti-androgens, were developed and widely used in clinics. Then, the new treatment strategy, maximum androgen blockade (MAB) was introduced. In fact, MAB improved the prognosis of patients with advanced prostate cancer to some extent; however, most of those patients finally relapse after a period of initial response to this therapy, developing androgen-independent prostate cancer (AIPC). Once patients develop AIPC, effective therapeutic modalities are extremely limited and, therefore, the prognosis of this disease is very poor. It is strongly desirable to explore novel therapeutic concepts for AIPC, based on detailed molecular mechanisms for progression to androgen independency. As for the molecular mechanisms involved in the emergence of AIPC, mutations in the androgen receptor have been examined most extensively. These days, evidence is accumulating that demonstrates activation of signal transduction pathways, such as Src, PI3K and mTOR/S6K, are involved in the acquisition of the androgen-independent cell proliferation of prostate cancer cells. In addition, animal models using transgenic and gene-knockout techniques have confirmed these results. The development of therapies targeting against the signal transduction pathways is critical for the improvement of the prognosis of patients with AIPC. In this article, we review recent understandings on molecular mechanisms of androgen-dependent proliferation of prostate cancer cells, whose aberrant activation is proposed as a critical event for progression to AIPC.

The role of hormonal treatment in prostate cancer

In 1941 Huggins and Hodges published for the first time the favorable effects of surgical castration and estrogen treatment on the progression of metastatic prostate cancer. However, this hormonal therapy is not without side effects. Since this pioneering milestone in history of prostate cancer, a further tremendous innovation did not take place. Today, due to intensive clinical, biochemical, nuclear-biological and molecular-biological research, many hormone active treatment variations are available. Besides traditional hormonal therapy, surgical or chemical castration, maximal androgen blockade, nontraditional forms of hormonal therapy, intermittent hormonal therapy, antiandrogens, 5-alpha-reductase inhibitors, and their combinations, we discuss options toward creating an increased number of side effect-oriented offers of hormonal treatment options, guaranteeing a longer and more comfortable exhaustion of the individual hormonal period of response and probably a longer survival. The prerequisite is a closer-than-ever monitoring by tumor marker and an early observation of symptomatic changes.

Effects of steroidal and non-steroidal antiandrogens on wild-type and mutant androgen receptors

BACKGROUND

Molecular basis for secondary antiandrogen therapy in prostate cancer with mutant androgen receptors (ARs) is not fully elucidated.

MATERIALS AND METHODS

Effects of steroidal and non-steroidal antiandrogens on transcriptional activities of wild-type and mutant (W741C, T877A, and W741C+T877A) ARs were measured. Crystal structure analysis and docking studies were performed using Molecular Operating Environment (MOE) package.

RESULTS

DHT-induced transcriptional activity of the T877A mutant and the W741C mutant was suppressed by bicalutamide and hydroxyflutamide, respectively. Nilutamide suppressed the W741C mutant and the double mutant. Cyproterone acetate modestly inhibited the W741C mutant and the double mutant. The structural studies suggested that nilutamide and cyproterone acetate retain their antiandrogenic properties against both the W741C mutant and the double mutant due to fact that mutation W741C does not permit formation of key hydrophobic interaction between ligand and AR ligand binding domain, which is necessary for their conversion into agonists.

CONCLUSIONS

Switching antiandrogens may be reasonable in prostate cancer with mutant ARs.

Effects of flutamide as a second-line agent for maximum androgen blockade of hormone refractory prostate cancer

We analyzed clinical effects of flutamide as a second-line agent for maximum androgen blockade (MAB) in patients with relapsing prostate cancer who received bicalutamide as the first-line MAB agent. This study included 13 patients with progressive prostate cancer who had relapsed after first-line MAB, with bicalutamide at 80 mg/day. After checking for antiandrogen withdrawal syndrome, they were given flutamide at 375 mg/day as second-line MAB. The effectiveness of that therapy was evaluated by changes in prostatic specific antigen (PSA) levels, with response defined as a decrease of greater than 50% from the start of therapy. We also compared several factors between responders and non-responders. Nine (69.2%) of the 13 patients showed a decrease in PSA levels, of whom five (38.5%) had a greater than 50% decrease and were defined as responders. The median duration of PSA response was 11.0 months (range 5-20 months). Patients who had a longer duration of response to first-line MAB had a significantly greater response to second-line MAB. For advanced prostate cancer patients who progressed on first-line MAB with bicalutamide, flutamide administration as a second-line antiandrogen was found to be relatively effective, especially for those who showed a longer duration of response to the first-line MAB. Our results confirm previous findings that MAB using flutamide is an effective second-line hormonal therapy.

Recent progress in hormonal therapy for advanced prostate cancer

PURPOSE OF REVIEW

Primary androgen deprivation therapy and secondary hormonal therapy remain the cornerstones of treatment for advanced prostate cancer. This review outlines the basic evidence for use of hormonal therapy while highlighting major research developments made in the past year.

RECENT FINDINGS

Recent research on androgen deprivation therapy has suggested that patients with high-risk features may have longer metastasis-free survival with early initiation of androgen deprivation therapy. Fracture risk has been shown to be significantly increased in patients on androgen deprivation therapy and is correlated with duration of treatment. In the treatment of androgen-independent prostate cancer, oral premarin has been shown to induce of prostate specific antigen responses more than 50% in 32% of patients, though thromboembolism remains a risk despite prophylactic low-dose warfarin. Transdermal estradiol has been associated with virtually no cardiovascular toxicity, but induced of prostate specific antigen responses more than 50% in only 12.5% of patients. Clinical studies of nilutamide, flutamide, and ketoconazole have further clarified efficacy of these secondary hormonal treatments.

SUMMARY

Optimal timing of androgen deprivation therapy awaits the results of randomized trials, but available evidence indicates that patients with high-risk features may benefit from early androgen deprivation therapy. New estrogen-based therapies have shown promising efficacy in the treatment of androgen-independent prostate cancer, with significantly less cardiovascular toxicity than traditional estrogens.