High dose bicalutamide for androgen independent prostate cancer: effect of prior hormonal therapy

Androgen receptor: role and novel therapeutic prospects in prostate cancer

Androgen receptor (AR) signaling is necessary for the development of prostate cancer. Androgen-deprivation therapy (ADT) for prostate cancer was described over 50 years ago and ADT remains the mainstay of systemic therapy. AR signaling remains intact as the disease evolves to castration-resistant prostate cancer (CRPC). Through cellular adaptations, CRPC continues to rely on androgens and AR growth signaling, and thus AR remains an important therapeutic target. CRPC cells upregulate enzymes used in androgen synthesis, thus providing an intracellular source of androgen despite systemic castration. Compounds in development, such as antiandrogens, lyase inhibitors, heat-shock protein-90 inhibitors, histone deacetylase inhibitors and others, will provide new tools to more effectively reduce ligand, inhibit AR and/or inhibit costimulatory pathways and result in improved clinical outcomes.

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.

A phase II study of mifepristone (RU-486) in castration-resistant prostate cancer, with a correlative assessment of androgen-related hormones

OBJECTIVE

To evaluate mifepristone (RU-486) in patients with castration-resistant prostate cancer (CRPC), with a correlative assessment of serum androgens and androgen metabolites

PATIENTS AND METHODS

The androgen receptor (AR) is critical in the development and progression of prostate cancer, but available antiandrogens incompletely abrogate AR signalling. Mifepristone is a potent AR antagonist that functions by competing with androgen, preventing AR coactivator binding and by enhancing binding of AR corepressors. Patients with CRPC were treated with mifepristone 200 mg/day oral until disease progression. Testosterone, dihydrotestosterone (DHT), androstenedione, dihydroepiandrosterone sulphate and the testosterone metabolite 3 alpha-diol G, were measured at baseline and during therapy.

RESULTS

Nineteen patients were enrolled between April and August 2005; they were treated for a median (range) of 85 (31-338) days. The median prostate-specific antigen (PSA) level at enrollment was 22.0 (3.0-937.2) ng/mL. No patient had a PSA response (>50% reduction in PSA). Six patients had stable disease for a median of 5.5 months. After 1 month, adrenal androgens were increased and testosterone and DHT increased by 91% and 80%, respectively, compared to baseline.

CONCLUSION

Mifepristone had limited activity in patients with CRPC, and stimulated a marked increase in adrenal androgens, testosterone and DHT. We hypothesise that inhibition of glucocorticoid receptor by mifepristone resulted in an increase in adrenocorticotropic hormone and subsequent increase in adrenal androgens, and that their conversion by tumour cells to testosterone and DHT probably limited the efficacy of mifepristone. These data emphasize the continued importance of alternative androgen sources in AR signalling in CRPC.

Activity of androgen receptor antagonist bicalutamide in prostate cancer cells is independent of NCoR and SMRT corepressors

The mechanisms by which androgen receptor (AR) antagonists inhibit AR activity, and how their antagonist activity may be abrogated in prostate cancer that progresses after androgen deprivation therapy, are not clear. Recent studies show that AR antagonists (including the clinically used drug bicalutamide) can enhance AR recruitment of corepressor proteins [nuclear receptor corepressor (NCoR) and silencing mediator of retinoid and thyroid receptors (SMRT)] and that loss of corepressors may enhance agonist activity and be a mechanism of antagonist failure. We first show that the agonist activities of weak androgens and an AR antagonist (cyproterone acetate) are still dependent on the AR NH(2)/COOH-terminal interaction and are enhanced by steroid receptor coactivator (SRC)-1, whereas the bicalutamide-liganded AR did not undergo a detectable NH(2)/COOH-terminal interaction and was not coactivated by SRC-1. However, both the isolated AR NH(2) terminus and the bicalutamide-liganded AR could interact with the SRC-1 glutamine-rich domain that mediates AR NH(2)-terminal binding. To determine whether bicalutamide agonist activity was being suppressed by NCoR recruitment, we used small interfering RNA to deplete NCoR in CV1 cells and both NCoR and SMRT in LNCaP prostate cancer cells. Depletion of these corepressors enhanced dihydrotestosterone-stimulated AR activity on a reporter gene and on the endogenous AR-regulated PSA gene in LNCaP cells but did not reveal any detectable bicalutamide agonist activity. Taken together, these results indicate that bicalutamide lacks agonist activity and functions as an AR antagonist due to ineffective recruitment of coactivator proteins and that enhanced coactivator recruitment, rather than loss of corepressors, may be a mechanism contributing to bicalutamide resistance.

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.

Castration resistant, taxane naïve metastatic prostate cancer: current clinical approaches and future directions

PURPOSE

With the wide use of prostate specific antigen to detect response and disease progression resistance to androgen deprivation is being detected at an increasingly earlier stage. We focused on the current management and novel investigational strategies for the chemonaïve patient population with castration resistant metastatic disease.

MATERIALS AND METHODS

We reviewed standard and investigational hormonal, chemotherapeutic, biological and immune based strategies for patients with castration resistant metastatic prostate cancer who have not yet received taxane based chemotherapy.

RESULTS

Our understanding of the natural history of this group of patients is evolving. A variety of standard and experimental treatment options are available for this group of patients. Manipulating the androgen receptor signaling axis, targeting antiapoptotic pathways, using antiangiogenic strategies, harnessing the immune system and optimizing docetaxel based regimens and novel cytotoxic agents are under investigation.

CONCLUSIONS

Multiple agents currently under development offer a promise of palliation and prolongation of survival above and beyond that of docetaxel. In the absence of guidance from randomized trials with regard to chemotherapy timing, and considering the modest effects of docetaxel on survival, decisions regarding choice of therapy (standard chemotherapy or experimental therapies) must be based on careful consideration of the functional status of each individual, presence of symptoms, comorbidities and overall therapeutic objectives.

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.

Clinical efficacy of alternative antiandrogen therapy in Japanese men with relapsed prostate cancer after first-line hormonal therapy

BACKGROUND

To confirm the effectiveness of alternative antiandrogen therapy (AAT) in Japanese patients with prostate cancer relapse after first-line hormonal therapy.

METHODS

A total of 80 patients who had successive serum prostate-specific antigen (PSA) progression after first-line hormonal therapy (luteinizing hormone-releasing hormone agonist alone: 21 cases; combined antiandrogen blockade therapy: 59 cases) were enrolled. We evaluated the positive ratio of antiandrogen withdrawal syndrome (AWS), the PSA responses with second- and third-line AAT, and cause-specific survival in terms of the effectiveness of AAT.

RESULTS

The overall positive AWS ratio after first-line therapy was 33%, while that after second-line therapy was 7%. There was no correlation between the first-line PSA response and the positive AWS. Of the 10 positive and the 20 negative AWS cases, secondary antiandrogen administration was effective in 50% and 60% of cases, respectively. The positive PSA responders at second- and third-line therapy were 51% and 13%, respectively. For second-line therapy, the effective rates from steroidal to non-steroidal, from non-steroidal to non-steroidal antiandrogen, and from non-steroidal to steroidal were 83%, 43%, and 14%, respectively. The cause-specific survival of the second-line responders was significantly better than that of the non-responders.

CONCLUSION

There was a substantial number of patients who found second-line AAT to be modestly effective. Flutamide was effective as an alternative antiandrogen for the patients' relapse treatment with bicalutamide in Japanese men.

Drug Insight: role of the androgen receptor in the development and progression of prostate cancer

Functional androgen receptor (AR) signaling is necessary for the development of prostate cancer. The therapeutic effect of androgen deprivation therapy for prostate cancer was described over 60 years ago and this treatment remains the mainstay of systemic therapy despite its transient response duration. It has become clear that AR expression and signaling remains intact as the disease evolves from androgen-sensitive cancer to classically (but perhaps inaccurately) termed hormone refractory prostate cancer. Through several genetic and epigenetic adaptations, prostate tumors continue to rely on AR growth signaling and they thus remain targets of 'hormonal' therapy. The development of new strategies and drugs that can abrogate AR signaling will probably result in important clinical benefits. The biology of androgen independence and the development of new approaches targeting AR signaling are reviewed herein.

The case for secondary hormonal therapies in the chemotherapy age

PURPOSE

Virtually all patients with high risk localized and metastatic prostate cancer who are treated with androgen deprivation therapy eventually have progressive clinical or biochemical disease despite this therapy. Despite this fact numerous therapies are available that target the interaction of androgen and androgen receptor in the castrate testosterone milieu and many clinical investigations are under way in this area.

MATERIALS AND METHODS

This literature review focuses on the current clinical literature in support of secondary hormonal therapy.

RESULTS

Despite low androgen levels the androgen receptor remains active through the amplification, mutation or alteration of coactivator function. These observations suggest that secondary hormonal therapies remain a reasonable clinical approach. Such approaches can be receptor or ligand directed. Receptor directed approaches to secondary hormonal therapy are antiandrogen withdrawal, sequential use of antiandrogens and estrogenic compounds. Ligand directed therapies are adrenal cortex inhibitors, such as ketoconazole and others in clinical development. Furthermore, in the context of androgen independent tumor growth in patients with metastatic disease clinicians are now faced with the choice of using chemotherapy or secondary hormonal manipulations. Appropriate patient selection is a critical component to the effective use of these agents.

CONCLUSIONS

The modest activity of these secondary therapies challenges the notion that advancing prostate cancer uniformly becomes hormone refractory. It offers an alternative to the early use of chemotherapy in patients with androgen independent disease.

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.

Androgen receptor remains critical for cell-cycle progression in androgen-independent CWR22 prostate cancer cells

The majority of prostate cancers (PCa) that relapse after androgen deprivation therapy (androgen-independent PCa) continue to express androgen receptor (AR). To study the functional importance of AR in these tumors, we derived androgen-independent CWR22 PCa xenografts in castrated mice and generated a cell line from one of these xenografts (CWR22R3). Similarly to androgen-independent PCa in patients, the relapsed xenografts and cell line expressed AR and were resistant to treatment with bicalutamide. However, expression of the AR-regulated PSA gene in the CWR22R3 cell line was markedly decreased compared to the relapsed xenografts in vivo. Transfections with androgen-regulated reporter genes further indicated that the cells lacked androgen-independent AR transcriptional activity and were not hypersensitive to low androgen concentrations despite constitutive activation of the Erk/MAP kinases. Nonetheless, AR remained essential for androgen-independent growth because retroviral shRNA-mediated AR down-regulation resulted in marked long-term growth suppression. This was associated with increased levels of p27(kip1) and hypophosphorylation of retinoblastoma protein but not with decreases in D-type cyclin levels or MAP kinase activation. These results reveal a potentially critical function of AR in androgen-independent PCa that is distinct from its previously described transcriptional or nontranscriptional functions.

[Hormone-refractory prostate cancer. Modifications of the therapeutic strategies since chemotherapy proved its usefulness]

Back in the 90's it was difficult to have access to the conclusions of publications on HRPC. Homogeneity was very scarce regarding issues as significant as the definition of HRPC itself, patient selection, or evaluation of the responses to therapy. Consensus has currently been reached on such matters, and it is described in this text. Two works were published in late 2004 showing that docetaxel-based chemotherapy improved metastatic HRPC survival. Until then, the different treatments used could only provide symptomatic relief. But probably not all of the HRPC patients are eligible for primary docetaxel chemotherapy. The current debate focuses on determinating to which patients should chemotherapy be administered and at which time should it start, in order to exclude those patients at risk of experiencing its adverse effects without benefitting from its clinical advantages. Non-metastatic HRPC patients may be candidates to receiving secondary hormone manoeuvres before starting with chemotherapy. We will analyse in this review the changes occurred in the therapeutic strategies ever since chemotherapy showed its value, and we shall also disclose our attitude regarding treatment of these patients in daily practice.

Secondary Hormonal Manipulations in Prostate Cancer

Targeting AIPC with therapies that affect the mechanisms of androgen receptor signaling despite a castrate testosterone milieu is an active and growing area of clinical research. At present, for patients with AIPC, the data support the maintenance of the castrate state, recognition of the AAWD phenomenon,the sequential use of oral antiandrogens, and a trial of estrogens or adrenal androgen-targeted therapies. Novel agents are being developed that seek to prolong the duration of clinical responses and the overall response rate.

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

OBJECTIVE

To assess the effect of adding bicalutamide on serum prostate-specific antigen (PSA) levels in patients with hormone-refractory prostate cancer (HRPC) during androgen deprivation monotherapy (ADMT).

PATIENTS AND METHODS

Forty-four patients with HRPC were treated with deferred combined androgen blockade (CAB) therapy, administering bicalutamide 80 mg once daily. HRPC was defined biochemically as three consecutive rises in PSA level during ADMT. The treatment response was defined as a > or = 50% decline in PSA levels. Prognostic values of various pretreatment variables for responsiveness to deferred CAB were determined statistically. When the disease relapsed during deferred CAB, bicalutamide was discontinued and the patients were evaluated for the antiandrogen withdrawal syndrome (AWS).

RESULTS

Of the 44 patients, 29 (66%) had a PSA response; the median PSA failure-free survival was 9.2+ months. Biopsy Gleason score was the only pretreatment variable predictive of a PSA response (mean Gleason score 7.9 in responders and 8.7 in nonresponders). The PSA doubling time (PSA-DT) was the only statistically significant variable of PSA failure-free survival in a multivariate analysis. The 1- and 2-year PSA failure-free survival rates were 43% and 31% in patients with a PSA-DT of >4 months, while it was 21% and none, respectively, in those with a PSA-DT of <4 months. Responders to deferred CAB had a statistically longer cancer-specific survival than nonresponders. None of 20 patients who were evaluated for AWS had the condition.

CONCLUSIONS

Deferred CAB therapy using bicalutamide is effective in patients with progression during ADMT, particularly in those with lower Gleason score tumours or a longer PSA-DT. AWS after deferred CAB is uncommon.

New approaches in hormone refractory prostate cancer

Effective therapeutic options have not existed for prostate cancer progressing after androgen deprivation therapy until very recently. Docetaxel based chemotherapy has been demonstrated to extend survival in 2 large randomized trials. These studies have provided the impetus to combine docetaxel with novel biologic agents to further consolidate the gains in long-term outcome. With the arrival of exciting agents including vaccines, monoclonal antibodies, bone-targeted drugs, antisense oligonucleotides, antiangiogenic drugs, and small molecule receptor tyrosine kinase inhibitors, the future of prostate cancer therapy appears promising.

Increased expression of genes converting adrenal androgens to testosterone in androgen-independent prostate cancer

Androgen receptor (AR) plays a central role in prostate cancer, and most patients respond to androgen deprivation therapies, but they invariably relapse with a more aggressive prostate cancer that has been termed hormone refractory or androgen independent. To identify proteins that mediate this tumor progression, gene expression in 33 androgen-independent prostate cancer bone marrow metastases versus 22 laser capture-microdissected primary prostate cancers was compared using Affymetrix oligonucleotide microarrays. Multiple genes associated with aggressive behavior were increased in the androgen-independent metastatic tumors (MMP9, CKS2, LRRC15, WNT5A, EZH2, E2F3, SDC1, SKP2, and BIRC5), whereas a candidate tumor suppressor gene (KLF6) was decreased. Consistent with castrate androgen levels, androgen-regulated genes were reduced 2- to 3-fold in the androgen-independent tumors. Nonetheless, they were still major transcripts in these tumors, indicating that there was partial reactivation of AR transcriptional activity. This was associated with increased expression of AR (5.8-fold) and multiple genes mediating androgen metabolism (HSD3B2, AKR1C3, SRD5A1, AKR1C2, AKR1C1, and UGT2B15). The increase in aldo-keto reductase family 1, member C3 (AKR1C3), the prostatic enzyme that reduces adrenal androstenedione to testosterone, was confirmed by real-time reverse transcription-PCR and immunohistochemistry. These results indicate that enhanced intracellular conversion of adrenal androgens to testosterone and dihydrotestosterone is a mechanism by which prostate cancer cells adapt to androgen deprivation and suggest new therapeutic targets.

The androgen receptor pathway is by-passed in prostate cancer cells generated after prolonged treatment with bicalutamide

BACKGROUND

Experimental work in various prostate cancer models revealed that the androgen receptor is frequently upregulated and implicated in tumor progression. However, little attention has been paid to the androgen receptor-signaling pathway in the development of therapy resistance in patients who receive chronic treatment with a non-steroidal anti-androgen.

METHODS

We have generated a novel subline, LNCaP-Bic, after prolonged treatment with androgen and bicalutamide in vitro. Proliferation of LNCaP-Bic cells in the absence or presence of androgen, tocopherol succinate, and/or bicalutamide was assessed by cell counting. Androgen receptor expression was determined by Western blot. Luciferase activity was measured in cells transfected with an androgen-responsive reporter.

RESULTS

In basal conditions, proliferation of LNCaP-Bic cells increased more than threefold over that of control LNCaP cells. Neither synthetic androgen R1881 nor bicalutamide showed any effect on LNCaP-Bic growth in vitro. Androgen receptor expression did not differ between the cell subline generated in the presence of bicalutamide and parental LNCaP cells. The ability of R1881 to induce reporter gene activity in LNCaP-Bic cells was reduced by 56%. Tocopherol succinate caused inhibition of proliferation only in the parental cell line although the androgen receptor and prostate-specific antigen were down regulated by the vitamin E derivative in both parental LNCaP and LNCaP-Bic cells.

CONCLUSIONS

Androgen receptor-mediated signal transaction is not enhanced in cells selected in the presence of bicalutamide. Our data may suggest that a more differentiated approach in targeting the androgen receptor is needed in prostate cancers that become resistant to classic endocrine treatment.

Hormone refractory prostate cancer: Management and advances

Effective therapeutic options have not existed for prostate cancer progressing after androgen deprivation therapy until very recently. Secondary hormonal manipulations offer marginal benefits. Docetaxel based chemotherapy has been demonstrated to extend survival and change the natural history of the disease in two large randomized trials. These studies have provided the impetus to combine docetaxel with novel biologic agents to further consolidate the gains in long-term outcome. With the arrival of exciting agents including vaccines, monoclonal antibodies, bone-targeted drugs, antisense oligonucleotides, anti-angiogenic drugs and small molecule receptor tyrosine kinase inhibitors, the future treatment of prostate cancer appears promising.

Secondary Hormonal Therapy for Advanced Prostate Cancer

PURPOSE

Androgen ablation remains the cornerstone of management for advanced prostate cancer. Therapeutic options in patients with progressive disease following androgen deprivation include antiandrogen withdrawal, secondary hormonal agents and chemotherapy. Multiple secondary hormonal agents have clinical activity and the sequential use of these agents may lead to prolonged periods of clinical response. We provide a state-of-the-art review of the various agents currently used for secondary hormonal manipulation and discusses their role in the systemic treatment of patients with prostate cancer.

MATERIALS AND METHODS

A comprehensive review of the peer reviewed literature was performed on the topic of secondary hormonal therapies, including oral antiandrogens, adrenal androgen inhibitors, corticosteroids, estrogenic compounds, gonadotropin-releasing hormone antagonists and alternative hormonal therapies for advanced prostate cancer.

RESULTS

Secondary hormonal therapies can provide a safe and effective treatment option in patients with AIPC. The use of steroids and adrenolytics, such as ketoconazole and aminoglutethimide, has resulted in symptomatic improvement and a greater than 50% prostate specific antigen decrease in a substantial percent of patients with AIPC. A similar clinical benefit has been demonstrated with estrogen based therapies. Furthermore, these therapies have demonstrated a decrease in metastatic disease burden. Other novel hormonal therapies are currently under investigation and they may also show promise as secondary hormonal therapies. Finally, guidelines from the United States Food and Drug Administration Prostate Cancer Endpoints Workshop were reviewed in the context of developing new agents.

CONCLUSIONS

Secondary hormonal therapy serves as an excellent therapeutic option in patients with AIPC in whom primary hormonal therapy has failed. Practicing urologists should familiarize themselves with these oral medications, their indications and their potential side effects.

Biology of progressive, castration-resistant prostate cancer: directed therapies targeting the androgen-receptor signaling axis

Prostate cancers that are progressing on medical and surgical therapies designed to ablate the action of androgens continue to express androgen receptor (AR) and to depend on signaling through the receptor for growth. A more clinically relevant classification of castration-resistant disease focuses on the mechanisms of receptor activation, which include (1) changes in the level of ligand(s) in tumor tissue; (2) increased levels of the protein due to gene amplification or altered mRNA expression; (3) activating mutations in the receptor that affect structure and function; (4) changes in coregulatory molecules including coactivators and corepressors; and (5) factors that lead to activation of the receptor independent of the level of ligand or receptor allowing kinase cross talk. From an AR perspective, the term "hormone refractory" is inappropriate. On the basis of this schema, we discuss strategies that are focused on the AR either directly or indirectly, as single agents or in combination, that are in clinical development.

Diethylstilboestrol versus bicalutamide in hormone refractory prostate carcinoma: a prospective randomized trial

OBJECTIVE

To compare the efficacy of diethylstilboestrol (DES) with bicalutamide in the treatment of hormone refractory prostate cancer in relation to its effect on prostate-specific antigen (PSA) and survival.

METHODS

Patients on LHRH analogues for prostate carcinoma with evidence of biochemical or clinical progression were randomized into one of the treatment arms (n=58). The first group (group A, n=26) received 1 mg of DES with 75 mg of aspirin per day in addition to the primary hormonal treatment. The second group (group B, n=32) received bicalutamide at a dose of 50 mg/day in addition to the primary treatment. Patients were followed up every 3 months with their PSA being checked and were also monitored for any clinical progression and adverse effects as a result of treatment. Any adverse event occurring after patients were started on treatment was attributed to the drug and patients were clinically assessed at each visit. Failure of treatment was defined as a 50% or greater increase in PSA after commencing treatment. Once randomized, all patients were followed up for survival regardless of failure of second-line hormonal manipulation.

RESULTS

The mean age of the patients was 76.7 years (60-88, SD 7.4) in group A and 76 years (67-86, SD 6.9) in group B. Twelve patients in each group had metastatic disease. The median follow-up periods for both groups were 24 months (range 6-48 in group A, range 3-54 in group B). 65% of the patients in group A (17/26) and 43.5% (14/32) in group B had a fall in their PSA levels (p=0.08, Fisher's exact test) with 23% (6/26) and 31% (10/32) having a >50% response respectively (p=0.34, Fisher's exact test). Mean PSA nadir in those who responded were 20.6 ng/ml (range 1.6-59.4) and 7.41 ng/ml (range 0.1-42.6) in groups A and B respectively. The median duration of response was 9 months (3-18 months) for group A and 12 months (3-18 months) for group B. Seven patients in group A and 6 in group B experienced adverse events. Three of the 7 in the group A experienced cardiovascular related adverse effects (1 congestive cardiac failure, 1 pulmonary embolism and 1 stroke). At the end of the study period, 14 (54%) of group A patients were alive and 12 (46%) were dead. In group B, 15 (47%) were alive, 16 (50%) were dead and 1 (3%) lost to follow-up. At the completion of the study, 3 patients in each group were still on treatment.

CONCLUSION

Low-dose DES and 50 mg of bicalutamide per day are equally effective in hormone refractory prostate carcinoma with respect to biochemical response, although DES has more severe adverse effects. This is a small sample and larger multicentre trials are needed to give us a definite conclusion.

A phase II study of nilutamide in men with prostate cancer after the failure of flutamide or bicalutamide therapy

OBJECTIVE

To determine the prostate-specific antigen (PSA) response and time to PSA or radiographic progression in men with prostate cancer refractory to bicalutamide and/or flutamide therapy.

PATIENTS AND METHODS

Men with histologically confirmed prostate cancer not amenable to curative surgery or radiation therapy were eligible for the study if they had radiographic or PSA progression on at least one antiandrogen (not nilutamide) despite continued androgen suppression and standard antiandrogen withdrawal periods. All men received nilutamide 150 mg/day orally for > or = 8 weeks unless there was unacceptable toxicity or disease progression. All men were evaluated for response, safety and toxicity. Baseline PSA levels, chest X-ray, bone scan and abdominopelvic computed tomography studies were obtained; the re-evaluation included PSA levels every 4 weeks and repeated imaging every 8 weeks in those with baseline abnormalities. The chest X-ray was repeated if there were pulmonary symptoms. Nineteen men were consented and 16 were evaluable for response.

RESULTS

The median (range) Gleason score was 7 (6-9) and the median number of previous second-line therapies was 2 (1-4). Bicalutamide therapy had failed in all patients. At baseline, 13 (of 16 men) had radiographically evident disease, nine with diffuse osseous and four with radiographically measurable metastases. There was no grade 3/4 toxicity; the commonest grade 1/2 toxicities were constipation (three), sensory neuropathy (four), fatigue (six), and visual changes (two) involving transiently altered colour vision and sensitivity to light, respectively. Responses included three partial and 13 with progressive disease.

CONCLUSIONS

The study was discontinued after a planned interim analysis because nilutamide had no apparent activity. Although well tolerated, nilutamide offers benefit to few men with prostate cancer in whom bicalutamide has failed.

An objective assessment of the results of hypospadias surgery

OBJECTIVE

To compare the cosmetic result of tubularized incised-plate urethroplasty (Snodgrass method) with that of two established techniques, the meatal-based flap and onlay island flap repair.

SUBJECTS AND METHODS

Photographs of the penis after hypospadias repair in 32 boys were assessed by a panel of five independent health professionals, including four surgeons with variable paediatric urological experience and a urology nurse. Twenty patients had a distal and 12 a proximal meatus. The Snodgrass technique was applied by one paediatric urologist for either distal (10) or proximal (six) hypospadias. A Mathieu repair was used for distal hypospadias (10) and an onlay preputial island flap for proximal hypospadias (six) by a second paediatric urologist. The panel was asked to grade cosmesis as poor, unsatisfactory, satisfactory or very good (points 1-4) for each of the following aspects of penile appearance: meatus, glans, shaft and overall appearance. Photographs were taken in a standard way, with a standard distance, lighting and two views, one of the dorsal surface and one ventral, for each patient. Signed written consent for the study was obtained from each family.

RESULTS

The mean assessment score for any aspect of cosmesis was significantly higher for the Snodgrass technique (P < 0.05). The mean score (95% confidence interval) for the meatus was 0.76 (0.4-1.1) points higher for the patients with a Snodgrass repair than those with a Mathieu or onlay island flap repair (P = 0.002). Correspondingly, the values for the glans were 0.67 (0.38-0.97) (P = 0.003), shaft 0.42 (0.16-0.69) (P = 0.01) and overall appearance 0.62 (0.24-1.0) (P = 0.01) points higher for the Snodgrass repair. The Snodgrass technique was more effective in producing a vertically orientated meatus (87.5%) than the Mathieu and Duckett onlay repairs (37.5%; P = 0.009).

CONCLUSION

The Snodgrass technique, as assessed by this panel, had a better cosmetic outcome than the Mathieu and Duckett onlay island flap repairs. The assessment of cosmesis in hypospadias surgery is potentially more objective when several health professionals, not involved in the surgery, compared the various methods of repair.

An interdisciplinary approach to treating prostate cancer

Urologists often are faced with challenges in treating men with metastatic prostate cancer. Although historically chemotherapy has had limited utility in treating this disease, therapeutic nihilism surrounding its use is no longer warranted, as demonstrated by results of 2 recent randomized clinical trials showing that docetaxel-based chemotherapy improves survival in patients with hormone-refractory prostate cancer (HRPC). Although the survival benefit was a modest 2 months, the results hold the promise that docetaxel-based treatment in earlier-stage disease may provide a longer survival advantage. The Cancer and Leukemia Group B (CALGB) 90203 and TAX 3501 studies are phase 3 neoadjuvant and adjuvant radical prostatectomy trials designed to assess the role of docetaxel in patients with high-risk localized disease. These 2 trials, along with the Southwest Oncology Group (SWOG) 9921 trial, which will assess the potential for adjuvant mitoxantrone, are paving the way for earlier systemic treatment. The need for better therapies for patients routinely seen in the urology clinic and the potential for improvements with chemotherapy necessitate an increasing collaboration between urologists and oncologists. Referral to a medical oncologist for a full discussion of treatment options is in the best interest of patients with HRPC, and patients at high-risk for treatment failure should be encouraged to consider clinical trial enrollment.

Secondary hormonal manipulations in prostate cancer

Virtually all patients treated with androgen deprivation eventually develop progressive clinical or biochemical disease despite this therapy. Despite low levels of androgen, the androgen receptor remains active, making secondary hormonal therapies a reasonable clinical approach. Considerations for such patients include antiandrogen withdrawal, sequential use of antiandrogens, adrenal cortex inhibitors, and estrogenic compounds. Collectively, the modest activity of these therapies challenges the notion that advancing prostate cancer will uniformly become "hormone refractory."

Prolonged Response to Nilutamide in a Patient with Stage D0.5 Prostate Cancer Who Previously Failed Androgen Deprivation Therapy

There is currently no standard therapy for patients with prostate cancer who have progressive rise in PSA levels despite treatment with hormonal ablation and antiandrogen withdrawal (stage D0.5). One potential treatment option is the use of a different androgen receptor antagonist (ARA), such as nilutamide. We report a case of a 66-year-old gentleman with greater than a 46 month sustained response to nilutamide therapy after failing bicalutamide therapy and its subsequent withdrawal. The patient continues to have undetectable PSA levels and an excellent performance status. This case demonstrates the prolonged response to a second-line ARA in patients deemed to have androgen insensitive prostate cancer. Further investigation of the potential role of nilutamide therapy as second-line antiandrogen therapy is warranted as monotherapy and/or in combination with other promising novel approaches including PSA-based vaccines.

An update on bicalutamide in the treatment of prostate cancer

In this update, bicalutamide (Casodex, Zeneca Pharmaceuticals) has been confirmed as an effective, well-tolerated and convenient non-steroidal anti-androgen for advanced prostate cancer. Preclinical and clinical studies have indicated its potential as monotherapy, with quality of life advantages compared with castration. A head-to-head comparison with flutamide, where both anti-androgens were used as part of combined androgen blockade, has suggested that the choice of components in this regimen can influence outcome, and has demonstrated that bicalutamide is better tolerated than flutamide. There is also preliminary evidence to support the potential use of bicalutamide in treatment of early-stage disease and tumours that are refractory to other non-steroidal anti-androgens.

The androgen receptor recruits nuclear receptor CoRepressor (N-CoR) in the presence of mifepristone via its N and C termini revealing a novel molecular mechanism for androgen receptor antagonists

The androgen receptor (AR) activates target gene expression in the presence of agonist ligands via the recruitment of transcriptional coactivators, but recent work shows that overexpression of the nuclear corepressors NCoR and SMRT attenuates this agonist-mediated AR activation. Here we demonstrate using NCoR siRNA and chromatin immunoprecipitation that endogenous NCoR is recruited to and represses the dihydrotestosterone (DHT)-liganded AR. Furthermore this study shows that NCoR and coactivators compete for AR in the presence of DHT. AR antagonists such as bicalutamide that are currently in use for prostate cancer treatment can also mediate NCoR recruitment, but mifepristone (RU486) at nanomolar concentrations is unique in its ability to markedly enhance the AR-NCoR interaction. The RU486-liganded AR interacted with a C-terminal fragment of NCoR, and this interaction was mediated by the two most C-terminal nuclear receptor interacting domains (RIDs) present in NCoR. Significantly, in addition to the AR ligand binding domain, the AR N terminus was also required for this interaction. Mutagenesis studies demonstrate that the N-terminal surface of the AR-mediating NCoR recruitment was distinct from tau5 and from the FXXLF motif that mediates agonist-induced N-C-terminal interaction. Taken together these data demonstrate that NCoR is a physiological regulator of the AR and reveal a new mechanism for AR antagonism that may be exploited for the development of more potent AR antagonists.

Management of patients with hormone refractory prostate cancer

Prostate cancer is the second most common cancer in men in the UK, and the incidence of prostate cancer has increased dramatically over the past two decades. Although most men are diagnosed at early stage, more than 50% develop locally advanced or metastatic disease. Androgen ablation with luteinising hormone-releasing hormone (LHRH) agonists alone, or in combination with anti-androgens, is the standard treatment for men with metastatic prostate cancer. Unfortunately, almost all men develop progressive disease after a variable time period, despite the maximal androgen blockade. The management of hormone refractory prostate cancer (HRPC) is challenging, as there is no uniformly accepted strategy. Various treatment options, including second-line hormone therapy, are discussed. Chemotherapy is being increasingly used and, importantly, docetaxel and estramustine may play an important role in the near future. The role of radiotherapy, strontium-89, bisphosphonates, novel agents and future therapies are also outlined.

Expression and function of androgen receptor coactivators in prostate cancer

Human androgen receptor (AR) associates with coactivator or corepressor proteins that modulate its activation in the presence of ligand. Early studies on AR coactivators in carcinoma of the prostate were hampered because of lack of respective antibodies. Investigations at mRNA level revealed that most benign and malignant prostate cells express common coactivators. AR coactivators SRC-1 and TIF-2 are up-regulated in tissue specimens obtained from patients who failed prostate cancer endocrine therapy. Increased expression of these coactivators is associated with enhanced activation of the AR by the adrenal androgen dehydroepiandrosterone. Similar association between AR coactivator expression and high prostate cancer grade and stage was reported for RAC-3 (SRC-3). The transcriptional integrator CBP was detected in clinical specimens representing organ-confined prostate cancer, lymph node metastases and tumour cell lines. Agonistic effect of the nonsteroidal antiandrogen hydroxyflutamide was strongly potentiated in prostate cells transfected with CBP cDNA. A functional homologue of CBP, p300, is implicated in ligand-independent AR activation by interleukin-6. The AR coactivator Tip60, which is up-regulated by androgen ablation, is recruited to the promoter of the prostate-specific antigen gene in the absence of androgen in androgen-independent prostate cancer sublines. It was proposed that the cofactor ARA70 is a specific enhancer of AR action. However, research from other laboratories has demonstrated interaction between ARA70 and other steroid receptors. Although in some cases dominant-negative coactivator mutants inhibited proliferation of prostate cancer cells in vitro, confirmation from in vivo tumour models is missing. In summary, several abnormalities in AR coactivator expression and function are associated with prostate cancer progression.

Combination hormonal therapy: a reassessment within advanced prostate cancer

Combination hormonal therapy, comprising a luteinising hormone-releasing hormone analogue (LHRHa) with an antiandrogen, is widely used in the treatment of advanced prostate cancer. There is ongoing debate regarding the use of combination hormonal therapy as opposed to LHRHa monotherapy. The pivotal consideration is whether there are adequate benefits with combination hormonal therapy in terms of increased survival and decreased disease progression to outweigh the increased risk of adverse events and additional cost. The most recent meta-analysis by the Prostate Cancer Trialists' Collaborative Group indicates a small but statistically significant survival benefit with combination hormonal therapy using nonsteroidal antiandrogens. It is, however, noteworthy that combined conclusions derived from such meta-analyses may not apply across each of the individual antiandrogens. Individual studies have reported differences between antiandrogens in terms of both tolerability and efficacy-for example, bicalutamide has been shown to be better tolerated than flutamide, and may be associated with improved survival. In addition, it is essential that treatment decisions are taken in consultation with the patient. Owing to an increasing proportion of cases presenting with early-stage disease, combination hormonal therapy is increasingly used in the neoadjuvant or adjuvant setting with radiotherapy and, in cases of prostate-specific antigen recurrence after prior localised therapy. Further data are awaited to optimise the use of combination hormonal therapy in these new settings.

Androgen receptor down-regulation in prostate cancer with phosphorodiamidate morpholino antisense oligomers

PURPOSE

Androgen receptor (AR) has a pivotal role in the growth and proliferation of prostate cancer (PCa). Even in advanced stages of PCa AR continues to be expressed and appears to be functional. Since the mechanisms of AR activation in androgen independent PCa have yet to be clearly defined, the decrease in AR protein by antisense compounds is an attractive therapeutic option. In this study we evaluated a novel antisense phosphorodiamidate morpholino oligomer (PMO) targeting the translational start site of AR mRNA in vitro and in vivo in a PCa xenograft and murine prostate.

MATERIALS AND METHODS

AR antisense PMOs targeting the AR initiation AUG were tested in vitro and in LNCaP cells, and in vivo in LAPC-4 xenografts and normal mouse prostate. Effects on AR protein and PSA expression were assessed.

RESULTS

AR antisense PMOs specifically down-regulated AR protein levels in a plasmid based screening system and also decreased endogenous AR levels in androgen responsive LNCaP cells in culture compared to control nonspecific PMOs. Pretreatment and posttreatment biopsies in the LAPC-4 xenograft model demonstrated that the antisense AR PMO administered intraperitoneally specifically decreased AR protein levels and serum PSA. Analysis of tissue distribution of the AR PMO by high performance liquid chromatography based methodology showed significant PMO levels in tumor tissue and mouse prostate, and there was a dose dependent decrease in AR protein levels in murine AR antisense PMO treated mouse prostates.

CONCLUSIONS

An AR antisense PMO with unique chemical properties administered once daily can decrease AR protein levels and PSA in vivo. The reduction of AR protein with an antisense PMO may be an effective method of interfering with AR mediated growth in advanced human PCa.

Bicalutamide (Casodex) in the treatment of prostate cancer

Prostate cancer is an important healthcare issue in men worldwide. With the advent of prostate-specific antigen screening and improved diagnostic techniques, prostate cancer is now being diagnosed in younger men and at earlier disease stages. As a result, patients often live with their disease for many years after diagnosis. This shift in the patient profile has focused attention to the impact of treatment on quality of life. Medical/surgical castration has traditionally been the mainstay of hormonal therapy but is associated with side effects including loss of libido and impotence. Nonsteroidal antiandrogens such as bicalutamide (Casodex) offer an effective alternative to castration with potential quality-of-life benefits. This paper reviews the evidence concerning the use of bicalutamide at all stages of the disease.

An evaluation of bicalutamide in the treatment of prostate cancer

Although prostate cancer is traditionally considered a disease of old age, improved diagnostic techniques have resulted in early diagnosis, and many men are now treated while still physically and sexually active. Current therapies for prostate cancer often include medical or surgical castration, which cause adverse effects on physical and sexual function; therefore, greater attention has been focused on quality of life. The nonsteroidal antiandrogen bicalutamide is an effective agent with a favorable tolerability profile and, in some settings, represents an alternative to castration. Mature survival data reveal that bicalutamide monotherapy provides survival benefits for untreated locally advanced disease that do not differ significantly from those of castration and maintains better physical capacity and sexual interest. Recent data from a prospective randomized trial demonstrate that bicalutamide given as immediate therapy, either alone or as adjuvant to therapy of curative intent, significantly reduces the risk of objective disease progression in patients with localized or locally advanced prostate cancer. Antiandrogens are also used in combination with castration, a treatment known as combined androgen blockade (CAB), for advanced disease. A randomized trial demonstrated that CAB with bicalutamide is associated with similar survival outcome to CAB with flutamide and is better tolerated. Current evidence demonstrates that bicalutamide currently has a favorable risk-benefit ratio in several stages of prostate cancer and that the role of bicalutamide will be further defined by ongoing studies.

Androgen receptor: a key molecule in the progression of prostate cancer to hormone independence

Despite earlier detection and recent advances in surgery and radiation, prostate cancer is second only to lung cancer in male cancer deaths in the United States. Hormone therapy in the form of medical or surgical castration remains the mainstay of systemic treatment in prostate cancer. Over the last 15 years with the clinical use of prostate specific antigen (PSA), there has been a shift to using hormone therapy earlier in the disease course and for longer duration. Despite initial favorable response to hormone therapy, over a period of time these tumors will develop androgen-independence that results in death. The androgen receptor (AR) is central to the initiation and growth of prostate cancer and to its response to hormone therapy. Analyses have shown that AR continues to be expressed in androgen-independent tumors and AR signaling remains intact as demonstrated by the expression of the AR regulated gene, PSA. Androgen-independent prostate cancers have demonstrated a variety of AR alterations that are either not found in hormone naïve tumors or found at lower frequency. These changes include AR amplification, AR point mutation, and changes in expression of AR co-regulatory proteins. These AR changes result in a "super AR" that can respond to lower concentrations of androgens or to a wider variety of agonistic ligands. There is also mounting evidence that AR can be activated in a ligand independent fashion by compounds such as growth factors or cytokines working independently or in combination. These growth factors working through receptor tyrosine kinase pathways may promote AR activation and growth in low androgen environments. The clinical significance of these AR alterations in the development and progression of androgen-independent prostate cancer remains to be determined. Understanding the changes in AR signaling in the evolution of androgen-independent prostate cancer will be key to the development of more effective hormone therapy.

Update on hormone-refractory prostate cancer

PURPOSE OF REVIEW

Androgen deprivation therapy is the cornerstone treatment for men with de novo or recurrent metastatic prostate cancer. Unfortunately, androgen deprivation therapy is primarily palliative, with nearly all men progressing to an androgen-independent state. Hormone-refractory prostate cancer presents significant management challenges and is the focus of this review.

RECENT FINDINGS

Investigations into the pathophysiology of hormone-refractory prostate cancer, the exploration of chemotherapeutic combinations, novel biological targets, skeletal protectants, and radiopharmaceuticals, as well as new prognostic tools are expanding the clinician's armamentarium and improving patient outcomes.

SUMMARY

Bisphosphonates and chemotherapy are providing effective palliative approaches. Phase II trials of taxane-based regimens show higher response rates and longer survival than has typically been achieved with existing standards. Two completed randomized phase III studies to be reported in mid-2004 will more definitively answer the question of whether currently available chemotherapy can improve survival.

Prostate-specific antigen doubling time predicts response to deferred antiandrogen therapy in men with androgen-independent prostate cancer

OBJECTIVES

To identify the pretreatment variables that are predictive of response and the duration of response to deferred antiandrogen therapy in men with androgen-independent prostate cancer (AIPC).

METHODS

A total of 375 patients receiving androgen deprivation therapy for advanced prostate cancer between 1977 and 2002 had medical records available for retrospective review. Of these 375 patients, 163 were diagnosed with AIPC. The inclusion criteria included (1) diagnosis of AIPC and (2) treatment with deferred antiandrogen therapy. AIPC was biochemically defined as two consecutive rises in the prostate-specific antigen (PSA) level during androgen deprivation therapy. The treatment response to deferred antiandrogen therapy was defined as a 50% or greater decline in the pretreatment PSA level. The prognostic value of various pretreatment parameters was determined with the appropriate statistical methods and tested with a Cox proportional hazards model.

RESULTS

Of the 163 patients with AIPC, 36 were treated with deferred antiandrogen therapy. Of these 36 patients, 12 (33.3%) experienced a PSA response. The median PSA failure-free survival was 9.0 months (95% confidence interval 5.2 to 12.9). The only pretreatment variable predictive of a PSA response was the PSA doubling time (PSADT). The mean PSADT in responders was 12.7 months versus 7.5 months in nonresponders (P = 0.037). Moreover, PSADT was the only statistically significant variable on univariate analysis of PSA failure-free survival in responders (hazard ratio 0.202, 95% confidence interval 0.041 to 0.990, P = 0.049). No statistically significant difference was found in cancer-specific survival between responders and nonresponders (P = 0.1501).

CONCLUSIONS

The PSADT predicted both the response and the duration of the response to deferred antiandrogen therapy in patients diagnosed with AIPC.

Alternative Antiandrogens to Treat Prostate Cancer Relapse After Initial Hormone Therapy

PURPOSE

We studied the efficiency of second or third line hormonal therapy for prostate cancer relapse after hormone therapy.

MATERIALS AND METHODS

The study included 70 patients with advanced prostate cancer treated with hormonal therapy, androgen deprivation monotherapy or maximum androgen blockade including surgical or medical castration combined with steroidal antiandrogen, 100 mg chlormadinone acetate daily or nonsteroidal antiandrogens, 375 mg flutamide (FLT) daily or 80 mg bicalutamide (BCL) daily. When the disease relapsed, we discontinued the antiandrogen and evaluated the patient for the antiandrogen withdrawal syndrome (AWS). Thereafter we administrated an alternative antiandrogen and evaluated its effect.

RESULTS

The incidence of the AWS after first, second and third line hormonal therapy was 35.8%, 8.0% and 0%, respectively. The efficiency of subsequent hormonal therapy was not related to the occurrence of the AWS. Nonsteroidal antiandrogens as alternative therapies for disease relapse from primary therapy were effective in second line (FLT 38.1%, BCL 44.4%) or in third line (FLT 30.0%, BCL 28.6%) hormonal therapy. Of 5 (80%) patients who responded to second line therapy 4 (80%) had effective third line therapy, while only 1 of 12 (8.3%) second line nonresponders had effective third line therapy (p = 0.003). The survival of second line responders was significantly better than that of nonresponders (5-year survival rate 92.3% vs 23.9%, p <0.001), indicating a potential predictive value for second line responsiveness. No significant clinical factor identified second line responsiveness.

CONCLUSIONS

Subsequent nonsteroidal antiandrogen therapies were effective against prostate cancer relapse after hormonal therapy. The response to third line therapy was more effective and survival was improved from the time of first line therapy relapse among second line responders than that in nonresponders. Our data support the notion that second line responders are androgen independent but still hormonally sensitive.

Role of secondary hormonal therapy in the management of recurrent prostate cancer

Androgen ablation remains the cornerstone of the systemic management of prostate cancer. After initial androgen deprivation, clinical outcomes vary considerably. For the patient with progressive disease after androgen deprivation, multiple therapeutic options are available and include antiandrogen withdrawal, chemotherapy, and secondary hormonal agents. Multiple secondary hormonal agents have clinical activity and the sequential use of these agents may lead to prolonged periods of clinical response. In addition to the use of oral antiandrogens, active secondary hormonal therapies include adrenolytic agents such as ketoconazole and aminoglutethimide, corticosteroids and estrogenic compounds. This article reviews the clinical trial data for these various agents and discusses their role in the management of patients with advanced prostate cancer.

Androgen receptor mutations in androgen-independent prostate cancer: Cancer and Leukemia Group B Study 9663

PURPOSE

The mechanisms responsible for prostate cancer androgen independence are diverse. Mutations of the androgen receptor (AR) gene that broaden ligand specificity have been implicated. Bone marrow specimens containing prostate tumor were obtained from men undergoing antiandrogen withdrawal for AR sequence analysis and clinical correlation.

MATERIALS AND METHODS

Eligible men enrolled on a trial of antiandrogen withdrawal had a minimum prostate-specific antigen (PSA) level of 5 ng/dL that was increasing on castration therapy including an antiandrogen. With informed consent, marrow biopsies were obtained to collect prostate tumor. Additional samples were obtained from men enrolled on chemotherapy trials. AR cDNA or DNA was polymerase chain reaction-amplified, cloned, and sequenced. The AR CAG repeat length was recorded.

RESULTS

One hundred eighty-four bone marrow biopsies were obtained, and 48 had prostate tumor detected by light microscopy. The ARs from these 48 samples were sequenced. Overall, five (10%) of 48 tumors had mutated ARs. AR point mutations were detected in the hormone-binding domain involved in transcription factor binding. Three mutations were novel in prostate cancer. One tumor sample had a CAG repeat length of 21, compared with germline length of 22 repeats. There was no association between detectability of AR mutations and antiandrogen withdrawal response or survival.

CONCLUSION

These data suggest that AR mutations are present in approximately 10% of patients with prostate cancer who experience treatment failure with hormone therapy that included an antiandrogen. Mutations in the AR likely confer a growth advantage for a subset of progressive prostate cancers. Correlation of AR mutation with antiandrogen withdrawal response or survival could not be made.

Current strategies in the management of hormone refractory prostate cancer

Prostate cancer is the most common cancer diagnosed in American males, and is the second leading cause of cancer-related deaths. Most patients who develop metastatic disease will initially respond to androgen deprivation, but response is invariably temporary. Most patients will develop androgen-independent ("hormone-refractory") disease that results in progressive clinical deterioration and ultimately death. This progression to androgen independence is accompanied by increasingly evident DNA instability and alterations in genes and gene expression, including mutations in p53, over-expression of Bcl2, and mutations in the androgen receptor gene, among others. Treatment options for hormone refractory disease include intensive supportive care, radiotherapy, bisphosphonates, second-line hormonal manipulations, cytotoxic chemotherapy and investigational agents. A post-treatment reduction in the level of prostate specific antigen (PSA) by 50% has been shown to correlate with survival and has been accepted by consensus as a valid endpoint in clinical trials. Chemotherapeutic agents such as mitoxantrone, estramustine, and the taxanes have yielded improved response rates and palliative benefit, but not improved survival. Therefore, current efforts must be focused on enrolling patients onto clinical trials of investigational agents with novel mechanisms of action, and on using survival, time to progression, and quality of life as end points in routine clinical practice.

Selecting a secondary treatment

There is compelling evidence that early hormonal therapy prolongs life in many stages of prostate cancer. Large-scale trials to answer this question have not yet been conducted in surgically treated patients or in patients with PSA-only relapse. Thus, many physicians and patients use early hormone therapy in PSA-only relapse. Many unique new agents are being tested in this population and may offer benefits. Patients and physicians are encouraged to participate in such trials, with hormone therapy reserved for subsequent use. Following failure of primary hormone therapy, a standard algorithm of care exists: antiandrogen withdrawal, use of alternative or first-line anti-androgens. ketoconazole. and chemotherapy. At each interval, clinical trials should be offered since none of these maneuvers are proven to prolong life.