Finasteride and flutamide therapy in patients with advanced prostate cancer: response to subsequent castration and long-term follow-up

Treatment of Metastatic Prostate Cancer in Older Adults

The aging of the population, along with rising life expectancy, means that increasing numbers of older men will be diagnosed with prostate cancer, and a large proportion of these men will present with metastatic disease. In this paper, we discuss recent advances in prostate cancer treatment. In particular, we review management approaches for older patients with metastatic prostate cancer based on the decision tree developed by the International Society of Geriatric Oncology, which categorized older men as "fit," "vulnerable," and "frail" according to comprehensive geriatric assessment.

Androgen suppression strategies for prostate cancer: is there an ideal approach?

Androgen suppression therapy (AST) was first described in 1941 as a treatment of prostate cancer (PCa) and remains the mainstay of therapy in patients with hormone-naïve metastatic disease. It also is used in locally advanced or recurrent disease and in combination with radiation therapy in patients with higher-risk features. Several approaches to AST have been developed as a result of increased understanding of the pathways controlling testosterone production. Increased recognition of the side effects has resulted in strategies to minimize complications associated with AST. Attempts to reduce AST adverse effects include intermittent hormonal therapy and methods to reduce amount of intracellular androgens without reducing the circulating testosterone levels.

Key targets of hormonal treatment of prostate cancer. Part 2: the androgen receptor and 5alpha-reductase

OBJECTIVE

The inhibition of 5alpha-reductase (5AR) blocks the synthesis of the most powerful intracellular androgen, dihydrotestosterone (DHT). The prostate has two 5AR isoenzymes (5AR1 and 5AR2) that change in expression and cellular location during the development of prostate cancer and tumour progression. The objective of this review is to provide an understanding of the pharmacological properties and the potential clinical benefits of 5AR inhibition.

METHODS

We searched Pubmed for data obtained from pharmacological, preclinical and clinical studies.

RESULTS

5AR1 expression increases with increasing aggressiveness and extension of malignant prostatic disease. Conversely, 5AR2 expression decreases from benign prostatic tissue to localized prostate cancer. The efficacy of 5AR2 monotherapy with finasteride alone or in combination with an androgen receptor antagonist on more final outcome measures seems to be limited. Combining an androgen receptor antagonist with a 5AR inhibitor in patients with asymptomatic, locally advanced or recurrent prostate cancer might be a reasonable first therapeutic hormonal approach. As plasma testosterone levels are maintained, beneficial effects on quality of life, potency and sexual function are expected. From studies on the dual 5AR inhibitor dutasteride, the drug produces a biochemical response in some men who progressed under androgen-deprivation therapy, and is generally well tolerated.

CONCLUSIONS

Achieving more potent suppression of intracellular DHT synthesis by 5AR inhibition is expected to provide clinical benefit to patients. Previous studies have shown that 5AR inhibition, by dutasteride in particular, halts/delays the progression of disease, and might even cause regression of disease in patients with advanced prostate cancer.

Role of 5 alpha-reductase inhibitors in the management of prostate cancer

Prostate cancer is one of the most complex and enigmatic oncologic problems in medicine. It is highly prevalent, particularly in elderly males. Unfortunately, its generally protracted and variable clinical course and high association with treatment-related morbidity raise serious questions about the ideal treatment strategy for the individual patient. 5 alpha-reductase (5AR) inhibitors have a dramatic effect on benign prostatic disease with low toxicity. Thus, there is much interest in the potential role of 5AR inhibitors in the prevention and treatment of prostate cancer. Finasteride is the only agent that has been shown in a randomized clinical trial to decrease the risk of prostate cancer with a reduction of almost 25%. Additionally, a recent analysis of the Prostate Cancer Prevention Trial (PCPT) has found that finasteride improves the performance characteristics of prostate-specific antigen (PSA) blood test as a screening tool for prostate cancer, for both cancer detection as well as for detection of high risk disease. Finally, 5AR inhibitors have been studied as a component of multimodal therapy for all stages of prostate cancer, with the goal of improving oncologic outcomes while avoiding the toxicity of medical and surgical castration.

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.

Management of asymptomatic rise in prostatic-specific antigen in patients with prostate cancer

Biochemical failure after curative-intent therapies is an increasingly common dilemma confronting patients and physicians. No definition of biochemical failure exists that can be applied to all forms of treatment and that is not to some degree affected by the follow-up interval, pretreatment prognostic factors, or the frequency of prostatic-specific antigen (PSA) testing. Available imaging techniques lack sensitivity in detection of occult micrometastases. Prognostic factors such as tumor characteristics and PSA kinetics should be considered when recommending second-line therapies. For those patients with suspected localized recurrence, second-line treatment with salvage therapies may provide long-term disease control. Hormonal therapy, although most commonly employed for PSA recurrence, is of palliative benefit only. Currently, the most appropriate therapeutic intervention for asymptomatic patients with evidence of biochemical failure remains undefined.

Optimal treatment of locally advanced prostate cancer

The treatment of clinically locally advanced prostate cancer (cT3-4) is subject to controversies. Patients with lymph node metastases as well as patients with overstaged localized and thus curable disease fall into this category. Radical prostatectomy, external beam radiotherapy and early or deferred hormonal therapy are possible treatment options. Multimodal treatment (i.e., a combination of these options) is frequently used. After radical prostatectomy, Gleason score-adjusted disease-specific survival does not differ meaningfully between the tumor stages pT2 and pT3-4. In the case of lymph node metastases after radical prostatectomy, but not in node-negative disease, adjuvant hormonal treatment seems to improve survival. Adjuvant radiotherapy may improve biochemical and local control in locally advanced prostate cancer, a survival benefit has, however, not yet been proven. External beam radiotherapy alone provides unfavourable survival rates in locally advanced prostate cancer. Adjuvant hormonal treatment may improve outcome in this setting. When no curative treatment is chosen, early hormonal treatment seems to provide modest benefit compared with deferred therapy.

Guidelines and counselling for treatment options in the management of prostate cancer

Prostate cancer is often a complex disease and one in which many aspects of the disease and the affected patient must be taken into consideration before decisions about diagnostic work-up, treatments, follow-up, etc. can be made. The current chapter reflects the current recommendations of the European Prostate Cancer Guideline Group made on the basis of criteria of evidence-based medicine after extensive review of the literature available up to December 2005.

Treatment of Locally Advanced Prostate Cancer – The Case for Radical Prostatectomy

The treatment of clinically locally advanced prostate carcinoma (stage cT3) remains controversial. One of the main reasons for this controversy results from the substantial staging error attached to the clinical diagnosis cT3 with overstaged T2 tumors and understaged node-positive cases. Treatment options in this situation include radical prostatectomy, external beam radiotherapy, immediate or delayed androgen deprivation treatment and the so-called 'watchful waiting'. Acceptable and often surprisingly good tumor-specific survival rates have been reported for radical prostatectomy in pT3 series--based on good clinical case selection--approaching those of pT2 series. In lymph node-positive pT3 cases, adjuvant hormone deprivation seems to prolong survival which it does not in lymph node-negative pT3 disease. A benefit of adjuvant external beam radiotherapy after radical prostatectomy for pT3 cases in prolonging overall survival has not been shown, despite the fact that it can prevent or delay biochemical and local recurrence. External beam radiotherapy as the only treatment for cT3 disease results in unfavorable tumor-specific survival rates, which can be significantly improved with adjuvant hormonal treatment with LHRH agonists. If, in case of advanced age and/or significant comorbidity, primary hormonal treatment is chosen, early hormonal deprivation therapy seems to offer marginal benefits in survival compared to delayed treatment.

Synthesis and biological evaluation of a nonsteroidal bromine-76-labeled androgen receptor ligand 3-[76Br]bromo-hydroxyflutamide

INTRODUCTION

Androgen receptors (ARs) are overexpressed in normal tissues and in most primary and metastatic prostate cancers. In our efforts to develop a nonsteroidal AR-specific imaging agent, we synthesized (+/-)-3-[(76)Br]bromo-hydroxyflutamide ((76)Br-), an analog of hydroxyflutamide, the active metabolite of the AR antagonist ligand flutamide.

MATERIALS AND METHODS

(76)Br- was synthesized in three steps, starting with commercially available compounds. Labeling of (76)Br- was achieved through the nucleophilic opening of an epoxide intermediate, and a labeled compound was obtained in high specific activity and good radiochemical yield.

RESULTS AND DISCUSSION

(+/-)-3-Bromo-hydroxyflutamide has a significantly higher affinity for ARs compared to hydroxyflutamide, its parent compound. The androgen target-tissue uptake of (76)Br- in diethylstilbestrol-treated male rats was examined; however, AR-mediated uptake was minimal due most likely to the rapid metabolic debromination of the radiolabeled ligand.

CONCLUSIONS

This study is part of our first look at a novel class of nonsteroidal AR antagonists as positron emission tomography (PET) imaging agents, which are alternatives to steroidal AR agonist-based imaging agents. Although (76)Br- has a significant affinity for ARs, it showed limited promise as a PET imaging agent because of its poor target-tissue distribution properties.

[Treatment of locally advanced prostate cancer]

The management of clinically locally advanced prostate carcinoma (cT3) remains a controversial issue. The clinical stage cT3 consists of a mixture of overstaged T2 carcinomas but also contains lymph node-positive cases. Treatment options consist of radical prostatectomy, external beam radiotherapy, hormonal deprivation (early or delayed) and the so-called watchful waiting. In many cases multimodal therapy is used. Radical prostatectomy in the clinical stage T3 can achieve acceptable tumour-specific survival rates if patients are well selected. In this way, tumour-specific survival rates can be reached for pT3 patients which closely approach those of pT2 cases. In lymph node-positive cases after radical prostatectomy adjuvant hormonal treatment can prolong survival, but not in lymph node-negative cases. A benefit of adjuvant radiotherapy after radical prostatectomy has not been proven. Although it can postpone or prevent biochemical recurrence, it does not prolong overall survival. Treatment of stage cT3 by external beam radiotherapy alone results in unfavourable tumour-specific survival rates. In these cases definite improvement can be achieved by adjuvant androgen deprivation with LHRH analogues. If in case of severe comorbidity or advanced age primary hormonal treatment is chosen, early vs deferred treatment seems to prolong survival marginally.

Biochemical recurrence after definitive prostate cancer therapy. Part II: Treatment strategies for biochemical recurrence of prostate cancer*

PURPOSE OF REVIEW

Through the prostate-specific antigen era, the proportion of men less than 55 years old with newly diagnosed prostate cancer more than doubled to almost 15%. As increasing numbers of men are living longer with prostate cancer, larger proportions will eventually present to our collective practices with rising prostate-specific antigen levels. Such prostate-specific antigen relapses, conservatively estimated to affect approximately 50 000 men each year, have become the most common form of advanced prostate cancer in the current period.

RECENT FINDINGS

Increasing evidence suggests that early hormonal therapy improves progression-free survival and may alter the cancer-specific survival. However, there is a cost to pay in side-effects when androgen deprivation is administered over prolonged periods. The non-steroidal anti-androgen bicalutamide may offer an equivalent progression-free survival to castration without the complications of androgen deprivation. Observational data seem to indicate that high-risk individuals (i.e. those with high-grade, high-stage disease or a prostate-specific antigen doubling time less than 12 months) may also receive benefit from early therapy.

SUMMARY

The definition of advanced prostate cancer has changed. Multimodal therapy improves cancer-specific outcomes especially in men with high-risk disease. The potential opportunities for novel therapeutic agents with low associated morbidity are great.

Rising prostate-specific antigen after primary prostate cancer therapy

An estimated 20-40% of men experience a biochemical recurrence within 10 years of definitive prostate cancer treatment. No single prostate-specific antigen (PSA) value is invariably associated with clinical metastasis or cancer-specific survival; PSA kinetics might prove to be a more important predictor of eventual progression-free survival and cancer-specific survival than absolute PSA level alone. With only one-third of patients progressing from biochemical recurrence to clinical disease, therapeutic morbidity should not outpace risk of disease progression. Salvage radiation therapy following radical prostatectomy has widely variable long-term biochemical control rates (from 18 to 64% depending on the follow-up period). Early hormonal therapy delivered as castration or complete androgen blockade might delay clinical metastasis in patients with high-risk pathologic disease; however, the adverse effects and morbidity of long-term therapy must not be underestimated. Non-steroidal antiandrogens as monotherapy for early biochemical recurrence, particularly for younger men who wish to preserve their libido and sexual potency, have received considerable attention, but there are conflicting data on long-term outcomes. Because of their favorable adverse-effect profiles, non-traditional therapies that exert localized hormonal or cellular effects are receiving considerable attention for treatment of early, PSA-only recurrence. Data from animal models provide a rationale for the use of these therapies, but there is a lack of evidence to support prolongation of progression-free survival or cancer-specific survival.