Flutamide in the treatment of metastatic carcinoma of the prostate

Targeting the relaxin hormonal pathway in prostate cancer

Targeting the androgen signalling pathway has long been the hallmark of anti-hormonal therapy for prostate cancer. However, development of androgen-independent prostate cancer is an inevitable outcome to therapies targeting this pathway, in part, owing to the shift from cancer dependence on androgen signalling for growth in favor of augmentation of other cellular pathways that provide proliferation-, survival- and angiogenesis-promoting signals. This review focuses on the role of the hormone relaxin in the development and progression of prostate cancer, prior to and after the onset of androgen independence, as well as its role in cancers of other reproductive tissues. As the body of literature expands, examining relaxin expression in cancerous tissues and its role in a growing number of in vitro and in vivo cancer models, our understanding of the important involvement of this hormone in cancer biology is becoming clearer. Specifically, the pleiotropic functions of relaxin affecting cell growth, angiogenesis, blood flow, cell migration and extracellular matrix remodeling are examined in the context of cancer progression. The interactions and intercepts of the intracellular signalling pathways of relaxin with the androgen pathway are explored in the context of progression of castration-resistant and androgen-independent prostate cancers. We provide an overview of current anti-hormonal therapeutic treatment options for prostate cancer and delve into therapeutic approaches and development of agents aimed at specifically antagonizing relaxin signalling to curb tumor growth. We also discuss the rationale and challenges utilizing such agents as novel anti-hormonals in the clinic, and their potential to supplement current therapeutic modalities.

Design and synthesis of 4-[3,5-dioxo-11-oxa-4,9-diazatricyclo[5.3.1.0(2,6)]undec-4-yl]-2-trifluoromethyl-benzonitriles as androgen receptor antagonists

A novel series of 4-[3,5-dioxo-11-oxa-4,9-diazatricyclo[5.3.1.0(2,6)]undec-4-yl]-2-trifluoromethyl-benzonitriles has been synthesized. The ability of these compounds to act as antagonists of the androgen receptor was investigated and several were found to have potent activity in vitro and in vivo.

[Androgen deprivation for advanced prostate cancer]

Androgen deprivation (ADT) by medical or surgical castration represents the standard therapeutic approach for managing prostate cancer (PCA) with systemic or locoregional metastases. Although ADT has been successfully used for more than 60 years, there are still major controversies with regard to the initiation (early versus delayed), type (complete versus monotherapy), and duration (continuous versus intermittent) of treatment. It is the purpose of this review to critically present the results of the various ADT options. Bilateral orchiectomy and subcutaneous application of luteinising hormone-releasing hormone (LHRH) analogues represent the guideline-recommended standard treatment for metastatic PCA, whereas estrogens are no longer recommended because of significant cardiovascular side effects despite comparable therapeutic efficacy. Antiandrogen monotherapy with bicalutamide is comparable to LHRH analogues in men with minimal tumour burden. However, survival rates are inferior in patients with extensive metastatic disease, in whom medical or surgical castration should be favoured. Complete ADT results in a median survival benefit of about 5% in men with low metastatic tumour burden, and it cannot be recommended for routine use. Early ADT is associated with a significant advantage in terms of symptom-free survival and prevention of metastasis-associated complications, but it does not result in a prolonged progression-free and overall survival when compared with delayed ADT. Despite encouraging results, intermittent ADT remains an experimental therapeutic approach that should be considered on an individual basis in carefully selected patients. Adjuvant ADT is still discussed controversially for men after radical prostatectomy, whereas it has become the standard approach in patients who undergo external beam radiation for locally advanced PCA.

4-(Anilino)pyrrole-2-carboxamides: Novel non-steroidal/non-anilide type androgen antagonists effective upon human prostate tumor LNCaP cells with mutated nuclear androgen receptor

Various 4-(anilino)pyrrole-2-carboxamides were designed and synthesized as novel androgen receptor (AR) antagonists without steroidal or anilide structure, based on our strategy for developing full antagonists of nuclear receptors. Introduction of a bulky N-alkyl group, such as a cyclohexylmethyl or benzyl group, increased the binding affinity for wild-type AR and the potency for growth inhibition of androgen-dependent SC-3 cells. Among the compounds obtained, N-[4-[(benzyl)(4-nitrophenyl)amino]-1-methylpyrrole-2-carbonyl]pyrrolidine (22) is as potent an AR antagonist as the typical anilide-type AR antagonists hydroxyflutamide and bicalutamide. Further, compound 22 had potent binding affinity for T877A mutated AR, and dose-dependently inhibited the testosterone-induced production of prostate-specific antigen in LNCaP cells bearing T877A AR.

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.

Structure based approach to the design of bicyclic-1H-isoindole-1,3(2H)-dione based androgen receptor antagonists

A novel series of isoindoledione based compounds were identified as potent antagonists of the androgen receptor (AR). Co-crystallization of members of this family of inhibitors was successfully accomplished with the T877A AR LBD. A working model of how this class of compounds functions to antagonize the AR was created. Based on this model, it was proposed that expanding the bicyclic portion of the molecule should result in analogs which function as effective antagonists against a variety of AR isoforms. In contrast to what was predicted by the model, SAR around this new series was dictated by the aniline portion rather than the bicyclic portion of the molecule.

Identification of a novel class of androgen receptor antagonists based on the bicyclic-1H-isoindole-1,3(2H)-dione nucleus

A novel series of isoindoledione based compounds were identified as potent antagonists of the androgen receptor (AR). SAR around this series revealed dramatic differences in binding and function in mutant variants (MT) of the AR as compared to the wild type (WT) receptor. Optimization of the aniline portion revealed substitution patterns, which yielded potent antagonist activity against the WT AR as well as the MT AR found in the LNCaP and PCa2b human prostate tumor cell lines.

The synthesis and evaluation of [2.2.1]-bicycloazahydantoins as androgen receptor antagonists

A novel series of [2.2.1]-azahydantoins has been designed and synthesized in an enantiospecific manner. The ability of these compounds to act as antagonists to the androgen receptor was investigated and several were found to have potent activity in vitro.

Effect of soluble and insoluble fiber diets on serum prostate specific antigen in men

PURPOSE

We assess whether high fiber diets influence serum prostate specific antigen (PSA) related to effects on serum sex hormone levels and fecal steroid excretion.

MATERIALS AND METHODS

A randomized crossover controlled trial was performed on 14 healthy men with hyperlipidemia on 2 metabolic diets 4 months in duration with each containing foods high in soluble or insoluble fiber and approximately 25 to 30 gm. dietary fiber per 1,000 kilocalories. Serum PSA, free testosterone and estradiol, and fecal bile acid and neutral sterol excretion were evaluated.

RESULTS

Mean serum PSA was lower with the soluble than the insoluble fiber diet (0.07+/-0.03 ng./ml., p = 0.035). No treatment difference was seen in free testosterone or estradiol, although the latter decreased significantly with the insoluble fiber diet (9+/-3 pmol./l., p = 0.004). After 16 weeks total fecal bile acid output was greater with the soluble (341+/-56 mg. daily) compared to the insoluble (203+/-35, p = 0.001) fiber diet but no differences were seen in fecal neutral sterol elimination. The treatment difference in fecal lithocholic acid output related to the difference in serum PSA (r = 0.57, p = 0.035).

CONCLUSIONS

A small but statistically significantly lower serum PSA was seen in healthy men consuming soluble fiber, which was not related to changes in serum sex hormones but was related to the increased lithocholic acid output as a possible marker of increased fecal steroid elimination. The effect of soluble fiber on prostatic disease may warrant further investigation.

Tamoxifen for flutamide/finasteride-induced gynecomastia

OBJECTIVES

Current therapies for advanced prostate carcinoma lead to a marked decrease in serum testosterone levels, which renders patients impotent. In preliminary studies, combination therapy with flutamide and finasteride has been used as an alternative therapy for the treatment of prostate carcinoma because potency can be preserved. Both of these agents can cause gynecomastia and breast/nipple tenderness.

METHODS

Six men being treated for advanced prostate carcinoma with flutamide/finasteride combination therapy developed painful gynecomastia, which was treated with tamoxifen 10 to 30 mg/day for 1 month. Clinical follow-up included breast measurements and determination of prostate-specific antigen (PSA), testosterone, and estradiol levels.

RESULTS

While on this combination therapy for prostate carcinoma, 4 of 6 patients experienced a decrease in PSA level to less than 0.5 ng/mL. All patients remained potent. Serum testosterone increased in each patient who had a baseline level drawn. Estradiol levels were noted to be elevated in 4 of 6 patients at the time of evaluation for gynecomastia. After treatment with tamoxifen, circulating estradiol levels increased in 3 patients from 1.3 to 2.2 times the baseline level. Five patients experienced complete resolution of breast and nipple pain on tamoxifen 10 mg/day within the first month. The other patient had to be treated with 30 mg/day for 1 additional month, which subsequently resulted in pain resolution.

CONCLUSIONS

These preliminary results suggest that low-dose tamoxifen is useful in treating painful gynecomastia for those patients on flutamide/finasteride combination therapy for advanced prostate carcinoma.

Is prednisolone as good as flutamide in hormone refractory metastatic carcinoma of the prostate?

PURPOSE

There are no generally accepted rules for the second line treatment of prostate cancer and few prospective studies have attempted to compare 2 therapeutic strategies with different modes of action.

MATERIALS AND METHODS

We describe a prospective, randomized study of 40 patients comparing the second line response of flutamide to prednisolone in patients with known hormone refractory stage M1 prostate cancer.

RESULTS

The median survival of patients receiving either treatment was 32.9 weeks, with no difference between the 2 groups. In terms of biological response 11 of 20 patients (55%) receiving prednisolone and 10 of 20 (50%) receiving flutamide exhibited prostate specific antigen (PSA) suppression. Average minimum PSA was 54 and 52% of the initial PSA in patients receiving prednisolone and flutamide, respectively. There was no difference between the 2 treatment groups in terms of long-term survival, although 35% of all patients survived beyond 1 year and 3 survived beyond 2 years.

CONCLUSIONS

More patients taking prednisolone described better pain relief, although both medications were well tolerated and there was no difference in terms of performance status or analgesic requirements.

Codon 877 mutation in the androgen receptor gene in advanced prostate cancer: relation to antiandrogen withdrawal syndrome

The growth of prostate cancer is androgen responsive, and androgen receptor (AR) is thought to play an important role in the development of this cancer. Recently, some reports demonstrated that AR gene mutations were detected in human prostate cancer tissues. We have previously reported that one of eight endocrine therapy-resistant prostate cancer cases showed AR gene mutation [Suzuki et al: J Steroid Biochem Mol Biol 46:759-765, 1993]. To further investigate structural abnormality of the AR in a large number of human prostate cancers, exons B-H encoding DNA-and hormone-binding domains were examined by single-strand conformation polymorphism analysis of polymerase chain reaction products and direct sequencing. Tissues surgically removed from 30 cases of stage B or C prostate cancer and from 22 cases of endocrine therapy-resistant cancers obtained at autopsy were used in the study. Three out of 22 cancer death cases (14%) revealed AR gene mutations, one of which contained two different mutations-exon D in cancerous prostate and exon H in metastatic tissues. In the other two cases, AR gene mutations in exon H were found in metastatic tissues. All three cases in metastatic tissues showed the same mutation at codon 877 (877Thr-->Ala). In stage B or C cancer tissues and the other cancer death samples, no AR mutation was detected. The mutation in exon H was identical to that reported in a human prostate cancer cell line, LNCaP. These results indicate that AR gene mutation scarcely occurs in the early stage of prostate cancer and that the mutation is found in relation to endocrine therapy resistance. Two patients with an AR gene mutation at codon 877 revealed a remarkable fall in prostate-specific antigen after withdrawal of antiandrogen. Data on the other case were not available. These results indicate that a codon 877 mutation in the AR gene in advanced prostate cancer evokes the antiandrogen withdrawal syndrome. To our knowledge, this report is the first description of relationship between an AR mutation at codon 877 and the antiandrogen withdrawal syndrome.

Antiandrogenic agents as monotherapy in advanced prostatic carcinoma

Pure antiandrogens have a quality-of-life advantage over other androgen ablation methods in the treatment of patients with prostatic cancer because they do not reduce the serum testosterone and therefore do not have a marked inhibitory effect on libido and potency. The long half-life of two of the three currently studied pure antiandrogens permits once-a-day administration, which should enhance patient compliance. With continued administration, there is a gradual rise in serum testosterone, and the clinical impact of this requires additional study using randomized Phase III trials. Proper stratification of patients at entry into such studies with documentation of various prognostic factors will add statistical value and enable physicians to draw better conclusion on the relative efficacy of these agents.

Flutamide in hormone-resistant prostatic cancer

Flutamide (250 mg. orally 3 times daily) yielded a subjective response in 5 of 25 fully evaluable patients with hormone-resistant prostatic cancer. Four additional patients had early progression. A 40% or greater decrease in the pre-treatment prostate specific antigen level was observed in 7 of 24 patients and this finding was correlated with improved survival. Toxicity was mainly gastrointestinal and resulted in permanent discontinuation of flutamide in 5 patients. Flutamide or similar antiandrogens may have a role in the management of hormone-resistant prostatic cancer when relief of subjective symptoms should be an important treatment goal together with improvement of survival. However, before the drug should be used routinely in the management of hormone-resistant prostatic cancer phase 3 studies must confirm its effectiveness, especially in comparison to less expensive drugs.

Antiandrogens alone or in combination for treatment of prostate cancer: the European experience

In Europe, antiandrogens have been used for many years to treat prostate cancer, either as monotherapy or as part of a "combination therapy" with either surgical or chemical castration. However, considerable debate still exists regarding the relative benefits of combination therapy versus antiandrogen monotherapy or castration alone. This article reviews the European experience with antiandrogen therapy, including the personal experiences of the authors.

Benefits of combination therapy with flutamide in patients relapsing after castration

Two hundred and nine patients with biopsy-proven stage D2 prostatic carcinoma showing disease progression after orchiectomy or treatment with DES (stilboestrol) or an LHRH agonist alone received combination therapy with the pure antiandrogen flutamide. In patients treated with DES, the oestrogen was replaced by the LHRH agonist [D-Trp6]LHRH ethylamide. The objective response to therapy was assessed according to the criteria of the US NPCP. Thirteen patients had a complete response to treatment, while partial and stable responses were achieved in 20 and 39 patients respectively (total objective response rate of 34.5%). The mean duration of response was 24 months. In the non-responders the median survival was 8.1 months with a 17% probability of survival at 2 years; the probabilities of survival at 2 years of the patients who showed partial and stable responses were 87 and 67% respectively. All patients who achieved a complete response are still alive. Combination therapy with Flutamide and castration (surgical or LHRH agonist) appears to be the treatment of choice for prostate cancer patients in relapse after standard endocrine therapy.

Flutamide and other antiandrogens in the treatment of advanced prostatic carcinoma

The various clinical trials suggest that the qualitative and quantitative responses of patients with Stage D prostatic carcinoma to antiandrogens are similar to those achieved with conventional endocrine therapy. These antiandrogens appear generally safe and many avoid the increased risks of cardiovascular or thromboembolic complications seen with estrogen therapy. Further, flutamide appears to have a lesser adverse effect on libido and sexual potency than do alternative therapies. Antiandrogens offer an alternative mode of therapy for previously untreated patients with advanced prostatic cancer but have produced no convincing benefits in hormonally refractory patients.

Carcinoma of the prostate. Hormonal therapy

A selective review of the literature regarding hormonal therapy for patients with carcinoma of the prostate is presented to assess the current status of the following: therapeutic advantages, disadvantages and risks of alternate approaches to hormonal therapy; observations to predict the magnitude and duration of response to therapy; indications for initiating hormone therapy; the short-term and long-term effects of therapy; and role of hormone therapy in patients with recurrent tumor activity after initial hormonal measures.

Combination therapy with flutamide and castration (orchiectomy or LHRH agonist): the minimal endocrine therapy in both untreated and previously treated patients

Patients (154) with clinical stage D2 prostate cancer with no previous endocrine therapy or chemotherapy received the combination therapy with the pure antiandrogen Flutamide and the LHRH agonist [D-Trp6]LHRH ethylamide for an average of 22 months (3-49 months). The objective response to the treatment was assessed according to the criteria of the US NPCP. There was a 6.3-fold increase (29.2 vs 4.6%) in the percentage of patients who achieved a complete response as compared to the results achieved in five recent studies limited to removal (orchiectomy) or blockade (DES or Leuprolide) of testicular androgens. Only 4.5% of patients did not respond to the combination therapy as compared to an average of 18% by standard therapy. The duration of response is also significantly increased in the patients who received the combination therapy. The death rate was decreased by approximately 2-fold between 2 and 3 yr of treatment. The marked (6.3-fold) improvement in the rate of complete objective responses coupled with the 4-fold decrease in the number of non-responders, the increased duration of the positive responses and the 2-fold decrease in the death rate at 2-3 yr of treatment are obtained with the combination therapy using Flutamide and castration with no or minimal secondary effects.

Clinical evaluation of flutamide and estramustine as initial treatment of metastatic carcinoma of prostate

The efficacy and side effects of flutamide were compared with estramustine in patients with advanced prostatic carcinoma. Thirty patients with metastatic cancers but with no serious cardiovascular (CV) conditions were randomly assigned to receive treatment either with flutamide (250 mg X 3) or with estramustine (280 mg X 2). Clinical examination, bone scan, laboratory measurements, including coagulation studies were performed prior to randomization, every three months during year one, and at six-month intervals thereafter. The two groups were comparable with respect to age and tumor characteristics. However, more patients presented with skeletal pain among those later treated with flutamide. During an observation period of between one and two and one-half years, flutamide was discontinued in 1 case (7%) because of icterus, and estramustine in 3 cases (20%) because of CV complications. Of the remaining 14 flutamide-treated patients, 13 responded initially. Eleven of them relapsed, and 5 died of cancer. In the corresponding group of 12 estramustine-treated patients, there were 11 primary responders. Of these, only 2 relapsed and died as did the only nonresponder. The difference between the two groups with regard to relapse is significant (P less than 0.01), but not with regard to mortality. All estramustine-treated patients lost their libido, whereas only 20 per cent of the patients treated with flutamide did so. In the present limited material there was an initial favorable response to flutamide without signs of CV complications and with maintained libido in most cases. However, due to significantly increased risk for relapse compared with estramustine, flutamide cannot be recommended as single therapy except in cases where estrogens are contraindicated or when interference with libido and potency is unacceptable.

Phase II trial with D-Trp-6-LH-RH in prostatic carcinoma: comparison with other hormonal agents

Various approaches to hormonal treatment of prostate carcinoma are discussed. Eighty-one patients with prostatic carcinoma, eight with stage B, nine with stage C, and 64 with stage D disease, were treated subcutaneously daily for 3 months with the LH-RH agonist D-Trp-6-LH-RH (Decapeptyl) in order to evaluate the incidence of remissions according to WHO recommendations for oncologic trials. The findings were compared to those obtained with other hormonal therapies of prostatic carcinoma according to the statistical method of "expected response rate" as adapted by Lee and Wesley for phase II trials. Treatment with D-Trp-6-LH-RH greatly reduced serum LH and testosterone levels without raising serum prolactin. After 1-2 weeks of therapy, there was relief of subjective symptoms and a reversal of the signs of prostatism as well as a marked decrease in bone pain. At 90 days 52 patients had complete relief of prostatism and 21 had only mild signs and symptoms. Seventy patients were experiencing no bone pain and an additional six had only mild pain. Prostatic size, evaluated by rectal examination and transabdominal ultrasonography, reverted to normal in 26.4% of patients (complete remission) and was reduced by more than 50% in an additional 17.6% (partial remission), the overall rate of complete plus partial regression of prostatic enlargement being 44%. Scans showed a major improvement of bone lesions in 14.8% of cases. This response increased to 37% after more than 6 months of follow-up. Prostatic acid phosphatase levels were decreased by more than 50% in 61% of the patients, but this test appears to be a less valid marker than the lipid-associated sialic acid (LASA). The increase in LASA before treatment and a reduction after treatment can frequently be correlated with the objective volume of the neoplasms. No flare-up of the disease was encountered, and there were no side effects except for impotence. Statistical analyses of results by the method of Lee and Wesley indicated that the incidence of complete and partial regression (CR and PR) observed with D-Trp-6-LH-RH was not significantly different from that recorded in previous studies for another LH-RH analog, Buserelin. However, CR and PR obtained with D-Trp-6-LH-RH (44%) were significantly higher than with subcapsular orchiectomy (22%). Hormonal effects and some other actions of D-Trp-6-LH-RH were compared and contrasted with those produced by castration, estrogens, antiandrogens, and progestogens.(ABSTRACT TRUNCATED AT 400 WORDS)

Human prostatic adenocarcinoma: comparative experimental treatment of the tumor line PC 82 in nude mice

A human prostatic adenocarcinoma, growing as a transplantable line in nude mice, was subjected comparatively to the usual endocrine treatment schedules including orchiectomy, estrogens, estramustine phosphate, and a study with flutamide (SCH 13521) and cyproterone acetate. The regression under treatment in tumor volume and in the histological pattern in demonstrated, and the possibilities and limitations of the nude mouse model are discussed.