Antiandrogen withdrawal syndrome in prostate cancer after treatment with steroidal antiandrogen chlormadinone acetate

Parameter identification of a model for prostate cancer treated by intermittent therapy

Adenocarcinoma is the most frequent cancer affecting the prostate walnut-size gland in the male reproductive system. Such cancer may have a very slow progression or may be associated with a "dark prognosis" when tumor cells are spreading very quickly. Prostate cancers have the particular properties to be marked by the level of prostate specific antigen (PSA) in blood which allows to follow its evolution. At least in its first phase, prostate adenocarcinoma is most often hormone-dependent and, consequently, hormone therapy is a possible treatment. Since few years, hormone therapy started to be provided intermittently for improving patient's quality of life. Today, durations of on- and off-treatment periods are still chosen empirically, most likely explaining why there is no clear benefit from the survival point of view. We therefore developed a model for describing the interaction between the tumor environment, the PSA produced by hormone-dependent and hormone-independent tumor cells, respectively, and the level of androgens. Model parameters were identified using a genetic algorithm applied to the PSA time series measured in a few patients who initially received prostatectomy and were then treated by intermittent hormone therapy (LHRH analogs and anti-androgen). The measured PSA time series is quite correctly reproduced by free runs over the whole follow-up. Model parameter values allow for distinguishing different types of patient (age and Gleason score) meaning that the model can be individualized. We thus showed that the long-term evolution of the cancer can be affected by durations of on- and off-treatment periods.

Treatment of hormone-refractory prostate cancer

Objective. An increasing number of patients with prostate cancer develop hormone-refractory disease after standard treatment modalities. In these patients, early clinical trials with chemotherapy produced disappointing response rates. However, clinical trials that employ response criteria such as prostate-specific antigen (PSA) and clinical benefit response have produced encouraging responses. This article reviews current and future treatment options for the management of hormone-refractory prostate cancer.

Data Sources. A MEDLINE search for the years 1978 to 1998 was completed. The following terms were used in our search: prostate cancer, hormone-refractory, treatment, and chemotherapy. Relevant articles referenced in the literature obtained in our MEDLINE search were reviewed.

Study Selection. Randomized and nonrandomized clinical trials were used in our review. Clinical trials using prostate-specific antigen or a palliation of symptoms as primary criteria for response were given priority.

Data Synthesis. Several genetic alterations, including the overexpression of bcl-2 or mutations in p53, may lead to the development of hormone-refractory prostate cancer. Agents such as estramustine and taxanes, which affect microtubule function and potentially modulate bcl-2, appear to be particularly active in the treatment of hormone-refractory prostate cancer. In addition, mitoxantrone as well as other agents has been shown to be beneficial in improving the quality of life in patients with hormone-refractory prostate cancer.

Conclusion. Hormone-refractory prostate cancer is not a chemotherapy-resistant disease as once believed; significant progress in the treatment of hormone-refractory prostate cancer has been made with new combinations of chemotherapy agents. Promising new treatments are currently under evaluation to assess their potential benefit over the standard treatment modalities that are currently available.

Switching and withdrawing hormonal agents for castration-resistant prostate cancer

The antiandrogen withdrawal syndrome (AAWS) is characterized by tumour regression and a decline in serum PSA on discontinuation of antiandrogen therapy in patients with prostate cancer. This phenomenon has been best described with the withdrawal of the nonsteroidal antiandrogens, bicalutamide and flutamide, but has also been reported with a wide range of hormonal agents. Mutations that occur in advanced prostate cancer and induce partial activation of the androgen receptor (AR) by hormonal agents have been suggested as the main causal mechanism of the AAWS. Corticosteroids, used singly or in conjunction with abiraterone, docetaxel and cabazitaxel might also be associated with the AAWS. The discovery of the Phe876Leu mutation in the AR, which is activated by enzalutamide, raises the possibility of withdrawal responses to novel hormonal agents. This Review focusses on the molecular mechanisms responsible for withdrawal responses, the role of AR mutations in the development of treatment resistance, and the evidence for the sequential use of antiandrogens in prostate cancer therapy. The implications of AR mutations for the development of novel drugs that target the AR are discussed, as are the challenges associated with redefining the utility of older treatments in the current therapeutic landscape.

Biochemical and objective response to abiraterone acetate withdrawal: incidence and clinical relevance of a new scenario for castration-resistant prostate cancer

OBJECTIVE

To describe the incidence and clinical relevance of biochemical and objective responses to abiraterone acetate (AA) withdrawal (AAWD) in patients with castration-resistant prostate cancer (CRPC).

MATERIALS AND METHODS

Twenty-six patients with progressive CRPC treated with first-line docetaxel-based chemotherapy were administered with AA at the standard dose of 1000 mg/day in combination with prednisone until progression. The patients were regularly followed up during treatment and after AAWD.

RESULTS

Nineteen of the 26 patients discontinued AA because of progression. Three of the patients undergoing AAWD experienced a biochemical response, which was accompanied by a metabolic and radiological response as revealed by choline positron emission tomography in 2 cases.

CONCLUSION

Regardless of the underlying molecular bases, AAWD response does not occur rarely. It is sometimes long-lasting and accompanied by a metabolic and radiographic improvement. AAWD response should be taken into account when further therapeutic strategies are planned in patients with CRPC with progressive disease during abiraterone therapy.

Oral low-dose dexamethasone for androgen-independent prostate cancer patients

We retrospectively evaluated the outcome of oral low-dose dexamethasone (DXM) therapy for androgen-independent prostate cancer (AIPC). Between January 1999 and April 2006, 99 consecutive patients with AIPC were enrolled in this study. The median patient age was 70 years (range 46-86), and the median pretreatment prostate-specific antigen (PSA) level was 243 ng/ml (range 8.2-29600). Median follow-up was 41.9 months (range 11.4-170.4). Upon biochemical failure, patients were treated with oral low-dose DXM. A total of 40 of the 99 cases (40.4%) showed a ≥50% decrease in serum PSA levels (PSA responders). Twenty-five cases (25.2%) showed a <50% decrease in PSA, and the remaining 34 cases (34.3%) had increased PSA levels (PSA non-responders). The median PSA progression-free survival was 3.0 (range 0-27) and 8.0 months (range 2-27) for the entire cohort and PSA responders, respectively. The PSA responders had a significantly increased survival (median 30.1 months) compared to the non-responders (median 8.8 months, P<0.001). Of the 34 patients who were under pain control for bone metastases before the administration of DXM, 23 (67.6%) were able to discontinue the regular use of analgesics. The PSA responders also showed an increase in hemoglobin levels. The change in serum interleukin-6 levels was significantly associated with a response to DXM (P=0.0065). Severe adverse events of DXM were rare. Clinicopathological factors predicting the PSA response to DXM were age, time from initial androgen deprivation therapy to DXM and PSA velocity prior to DXM. In conclusion, oral low-dose DXM led to an acceptable PSA response in patients with AIPC. Thus, this therapy may be an effective and safe alternative for the treatment of AIPC, particularly for patients who are not favourable candidates for chemotherapy.

Molecular basis for the antiandrogen withdrawal syndrome

In patients with prostate cancer who manifest disease progression during combined androgen blockade therapy, discontinuation of antiandrogen treatment might result in prostate-specific antigen decline, often associated with clinical improvement. The response called antiandrogen withdrawal syndrome is thus acknowledged as a general phenomenon. However, molecular mechanisms responsible for this syndrome are not completely understood. This article outlines the proposed mechanisms, including alterations of androgen receptor gene and its coregulatory proteins and activation of the signal transduction pathway, and the potential therapeutic approaches based on the specific mechanisms.

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.

Androgen receptor mutations in carcinoma of the prostate: significance for endocrine therapy

Endocrine therapy for advanced prostate cancer involves androgen ablation (orchiectomy or application of luteinizing hormone releasing hormone analogs) and/or blockade of the androgen receptor (AR) with either steroidal (cyproterone acetate) or nonsteroidal (hydroxyflutamide, bicalutamide and nilutamide) antiandrogens. These antagonists prevent androgen-induced conformational change and activation of the AR. During long term androgen ablation, the AR adapts to an environment with low androgen concentrations and becomes hypersensitive to low concentrations of androgens, either alone or in combination with various cellular regulators. Bicalutamide can switch from antagonist to agonist during long-term androgen withdrawal, as shown in prostate cancer LNCaP cells. AR point mutations were detected in metastatic lesions from human prostate cancer more frequently than in primary tumors. Although functional characterization of only some mutant AR detected in prostate cancer tissue has been performed, data available suggest that they are activated by dihydrotestosterone, its precursors and metabolites, synthetic androgens, estrogenic and progestagenic steroids and hydroxyflutamide. A direct association between AR mutations and endocrine withdrawal syndrome has been investigated in only one study thus far. There is no evidence at present that activation of any of the mutant AR genes detected in prostate cancer is enhanced in the presence of a nonsteroidal AR stimulator. Coactivators of the AR are proteins that associate with the receptor, possess histone acetylase activity and facilitate AR activation. The coregulatory proteins ARA70 and ARA160 differentially affected the activity of the mutated AR Glu(231)-->Gly, which was discovered in a mouse authochthonous prostate tumor. ARA70 enhanced receptor activation by both androgen and estradiol, whereas ARA160 augmented only androgen-induced AR activity. Novel experimental therapies that down-regulate AR expression have been developed; they include the application of ribozymes and antisense oligonucleotides.

Secondary hormonal manipulation of prostate cancer

Prostate cancer is the second leading cause of cancer mortality among men in Western countries. The initial treatment of advanced prostate cancer is suppression of testicular androgen production by medical or surgical castration, but nearly all men with metastases develop disease progression. Patients with hormone-resistant prostate cancer (HRPC) have a median survival of approximately 18 months, and no therapy has yet demonstrated a definitive survival advantage. However, in the past several years, a number of promising new treatment strategies have emerged. One of the most important new treatment strategies involves secondary hormonal manipulation after the failure of primary androgen deprivation. This approach is predicated on the recognition that HRPC is a heterogeneous disease, and some patients may respond to alternative hormonal interventions despite the presence of castrate levels of testosterone.

Hormonal treatment for prostate cancer

For nearly six decades the preferred primary treatment for advanced prostate cancer has been continuous suppression of testicular androgen production by medical or surgical castration. While androgen deprivation is effective in inducing tumour regression in the large majority of cases, essentially all patients will develop progressive disease. In addition androgen deprivation may be associated with a variety of side effects. Thus, strategies that minimise the use of these agents could potentially lower the morbidity and cost associated with the treatment of advanced prostate cancer. In the era of prostate-specific antigen (PSA) testing, hormonal therapy is being used earlier in the course of the disease when the only evidence of recurrent disease is an elevated PSA. These men may survive for many years and thus have the potential for long periods of exposure to hormonal therapy and its side effects. It has been hoped that the development of alternative hormonal interventions might lead to both enhanced antitumour efficacy as well as improvements in side effect profile.

New treatment strategies in advanced prostate cancer

The treatment of advanced prostate cancer has evolved rapidly in the last 5 years. Therapeutic options for patients with advanced disease, once essentially limited to the use of androgen deprivation, have expanded to include a number of interventions, including secondary hormonal manipulations, chemotherapy, and a variety of investigational approaches. Novel therapeutic approaches in prostate cancer patients are likely to be undertaken in patients with disease that is at or below the limits of detection by current imaging technology, so novel methods will be essential to the successful evaluation and use of these agents.

"Decoy" of androgen-responsive element induces apoptosis in LNCaP cells

BACKGROUND

In an androgen-dependent manner, the androgen receptor (AR) binds to the androgen-responsive element (ARE) in the regulatory region of target genes. We hypothesize that an "ARE decoy, " a double-stranded oligonucleotide containing the same DNA sequence as ARE, can inhibit prostatic proliferation by competitive inhibition of AR transcriptional activity.

METHODS

We synthesized a 23-mer ARE decoy based on the deduced ARE sequence at the promoter region of the human prostate-specific antigen (PSA) gene. The nuclear extract was prepared from LNCaP cells, and DNA-protein interactions were examined by gel shift assay. Then the antiandrogen effect of the ARE decoy was studied in LNCaP cells transfected with the ARE decoy by lipofection. After 24-hr incubation with 10(-9) M dihydrotestosterone (DHT), induction of apoptosis was examined by DNA fragmentation.

RESULTS

The gel shift assay demonstrated specific binding of the ARE decoy to the LNCaP nuclear protein which is most likely AR. The transfection experiment showed DNA fragmentation in the ARE decoy-transfected cells despite the presence of DHT, though not in the cells transfected with the control decoy.

CONCLUSIONS

The ARE decoy had an antiandrogen effect and induced apoptosis in LNCaP cells. This ARE decoy may become a potential therapeutic tool for prostate cancers when combined with a highly efficient transfection method.

Secondary hormonal manipulations in hormone refractory prostate cancer

Hormone refractory prostate cancer is clinically heterogeneous, and many patients retain sensitivity to subsequent hormonal manipulations, even after combined androgen blockage. Antiandrogen withdrawal is a mandatory first step. Subsequent treatment with an alternate antiandrogen, adrenal androgen inhibitor (such as ketoconazole), or glucocorticoid may provide both subjective and objective clinical benefit in up to 65% of patients.

Antiandrogen withdrawal syndrome with cyproterone acetate

OBJECTIVES

To determine whether the antiandrogen withdrawal syndrome occurs with the steroidal antiandrogen cyproterone acetate.

METHODS

Cyproterone acetate was withheld in 12 patients with progressing androgen-independent metastatic prostate cancer. Eight patients had been receiving cyproterone acetate concomitant with androgen ablation, and in 4 patients it was prescribed after failure of androgen suppression. Time to response and to disease progression were defined by serum prostate-specific antigen (PSA) levels and imaging studies.

RESULTS

PSA levels decreased in 5 of the 1 2 patients; in 4 of them (33%), the decrease exceeded 50%. The decline lasted a median of 24 weeks (range 9 to 37.8). All 5 patients had received initial concomitant exposure to androgen ablation and cyproterone acetate.

CONCLUSIONS

We recommend that the steroidal antiandrogen cyproterone acetate be added to the list of agents capable of inducing antiandrogen withdrawal syndrome.

Androgen deprivation for prostatic carcinoma: a rationale for choosing components

Ever since prostatic carcinoma was discovered to be dependent on the hormone androgen for its proliferation, androgen deprivation has been the treatment of choice for advanced cases of prostate cancer. Originally, treatment was limited to surgical castration or estrogen therapy. However, the introduction of luteinizing hormone-releasing hormone analogues, antiandrogens, and newer treatment modalities, such as combined androgen blockade, has made choosing a treatment strategy more complex. Assuming that each modality is equally effective, emphasis should be placed on increasing patient tolerance and compliance by the use of long-acting, nontoxic treatments with simple dosing regimens and minimal side effects. This review focuses on the factors influencing the final choice of treatment strategy.

Endocrine therapy of prostate cancer

Endocrine therapy is effective treatment for patients with metastatic prostate cancer. Most patients will benefit from androgen withdrawal in terms of symptomatic relief and delay in progression of diseases. It does not, however, cure patients with metastatic prostate cancer. This finding emphasizes the need for the development of effective nonendocrine therapies.

Hormone/antihormone withdrawal and dexamethasone for hormone-refractory prostate cancer

BACKGROUND

Flutamide withdrawal has been reported to benefit patients with hormone-refractory prostate cancer. Several studies have also demonstrated that a combination of corticosteroids and testicular androgen ablation lowers serum androgen levels and improves clinical response. The purpose of this study was to examine the effect of withdrawal of oral hormonal agents and administration of dexamethasone in stage D3 prostate cancer patients.

METHODS

Sixteen patients with hormone-refractory prostate cancer were enrolled in the study. All patients had osseous metastasis and elevated serum prostate-specific antigen. Nine had been treated with chlormadinone acetate, 4 with estramustine phosphate, and 3 with flutamide as first-line hormonal therapy. All patients had also been treated either with bilateral orchiectomy (13 cases) or a luteinizing hormone-releasing hormone (LH-RH) agonist (3 cases). Seven patients whose disease progressed following hormone withdrawal were treated with oral dexamethasone (initially 1.5 mg/day, then tapered to 0.5 mg/day).

RESULTS

Eight patients demonstrated a decrease in prostate-specific antigen of greater than 50% following hormone withdrawal. The time to cancer progression for these 8 patients was 2 to 15 months (mean, 4 months). Among the patients receiving dexamethasone, 4 showed a greater than 90% decrease in prostate-specific antigen after 3 months' treatment. The time to disease progression for these 4 patients was 3 to 11 months.

CONCLUSION

In treating hormone-refractory advanced prostate cancer, the first pharmacologic manipulation should be withdrawal of the oral component of combined hormonal therapy. Patients whose disease progresses after hormone withdrawal should then be treated with glucocorticoids such as dexamethasone.

Steroid hormone withdrawal syndromes. Pathophysiology and clinical significance

The steroid withdrawal syndrome has brought a new dimension to the treatment of advanced prostate cancer not only in the way we treat androgen-independent disease but also in terms of insights into the development of hormonal resistance. The data now confirm that 30% of cases have a meaningful subjective, biochemical, and objective response to the withdrawal of a steroid hormone as the first maneuver after primary hormonal therapy failure. Larger studies are needed to define further the withdrawal effect related to the other steroid hormone family members and to determine the objective response proportions. Although controversy surrounds the cause of the steroid withdrawal phenomenon, studies suggest that the androgen receptor plays a pivotal role. Molecular studies of the androgen receptors involving larger number of patients are paramount if we are going to develop a better understanding of the evolution of the withdrawal effect and hormone resistance.

The antiandrogen withdrawal syndrome

In 1989 the unanticipated agonist effect of antiandrogens on LNCaP prostate cancer cells was detected. A "flutamide withdrawal syndrome" was first described by Kelly and Scher [15], who reported a decrease in serum prostate-specific antigen (PSA) levels after the removal of flutamide from the treatment regimen. In the last few years the paradoxical response to antiandrogens has also been reported for bicalutamide, chlormadinone acetate and others. Therefore the name of the syndrome has changed to "antiandrogen withdrawal syndrome." Several reasons such as mutations in the androgen receptor or a direct stimulatory effect of the antiandrogen for this effect have been discussed, but the exact molecular mechanism remains unclear. However, in patients with hormonally relapsed prostate cancer, a trial of "withdrawal therapy" is required prior to the initiation of toxic therapies.

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.

Hormone and antihormone withdrawal: implications for the management of androgen-independent prostate cancer

OBJECTIVES

To analyze reported clinical outcomes for patients in whom an agent that acts via a steroid hormone receptor was "withdrawn."

METHODS

Published reports where agent(s) known to act via steroid hormone receptors were discontinued in patients with relapsing prostatic cancer were retrieved from MEDLINE listings. The trials included patients who progressed on steroidal and nonsteroidal antiandrogens, progestational agents, and estrogens. Included were the specifics of all treatments administered prior to discontinuation of the drugs, concomitant therapies, and factors that might predict a favorable response to "withdrawal."

RESULTS

Withdrawal responses were observed following the discontinuation of the antiandrogens flutamide and bicalutamide, flutamide plus aminoglutethimide, estrogens, and progestational agents. In most responding cases, responses were seen in patients with long exposure to the drug. No specific factors were predictive for response.

CONCLUSIONS

Withdrawal responses to agents that act via steroid hormone receptors represent a generalized phenomenon that can result in palliation for patients with hormonally relapsed prostate cancer. A trial of "withdrawal therapy" is warranted in patients with relapsing disease prior to the initiation of more toxic therapies. Failure to control for this phenomenon in clinical trials may lead to false attribution of response to a study agent. The data provide support for the concept that androgen independence does not necessarily mean that a tumor is resistant to further hormonal manipulations.