Estramustine and vinblastine for patients with progressive androgen-independent adenocarcinoma of the prostate

Crosstalk between Microtubule Stabilizing Agents and Prostate Cancer

A variety of microtubule-stabilizing cytotoxic agents (MSA) with diverse chemical scaffolds have been discovered from marine sponges, microorganisms, and plants. Two MSAs, docetaxel and cabazitaxel, are the exclusive chemotherapeutics that convey a survival benefit in patients with castration-resistant prostate cancer (CRPC). Additional MSAs have been investigated for their potential in treating prostate cancer in both clinical and preclinical settings. Independent of promoting mitotic arrest, MSAs can suppress the nuclear accumulation of androgen receptor (AR), which is the driving force for prostate cancer cell growth and progression. The alternative mechanism not only helps to better understand the clinical efficacy of docetaxel and cabazitaxel for AR-driven CRPC but also provides an avenue to seek better treatments for various forms of prostate cancer. The dual mechanisms of action enable MSAs to suppress AR-null prostate cancer cell proliferation by cell mitosis pathway and to interfere with the AR signaling pathway in AR positive cells. MSA chemotherapeutics, being administered alone or in combination with other therapeutics, may serve as the optimal therapeutic option for patients with either castration-sensitive or castration-resistant prostate cancer. This review provides an overview of the anti-prostate cancer profiles (including preclinical and clinical studies, and clinical use) of diverse MSAs, as well as the mechanism of action.

Tubulin-targeted agents including docetaxel and cabazitaxel

Microtubules are dynamic filamentous cytoskeletal proteins that are responsible for cellular integrity and architecture, mitosis, intracellular transport, cell signaling, and gene expression. Tubulin exists in the cell as dimers of α and β subunits, which complexes with a variety of regulatory proteins. There is a dynamic equilibrium between free and polymerized tubulin causing a state called "dynamic instability," which is a target of anticancer drugs, which inhibit tubulin through polymerization (taxanes, epothilones) or depolymerization (vinca alkaloids). Docetaxel-based therapy was the first such treatment to demonstrate a survival benefit in men with castration-resistant prostate cancer. Cabazitaxel, an antitubulin agent, which demonstrates activity in multidrug- and docetaxel-resistant cancer cell lines, demonstrates a survival benefit over mitoxantrone and prednisone in patients who have failed docetaxel-based chemotherapy. This article reviews the use of antitubulin agents in patients with castration-resistant prostate cancer.

A phase II trial of androgen deprivation therapy (ADT) plus chemotherapy as initial treatment for local failures or advanced prostate cancer

PURPOSE

Long-term hormonal ablation in prostate cancer is associated with decreased overall health and quality of life. Few reports emphasized the role of chemotherapy in the management of early stage prostate cancer. This study analyzed the safety and efficacy of androgen deprivation therapy (ADT) plus chemotherapy as initial treatment for patients identified as local failures or not eligible for prostatectomy or radiation therapy due to advanced disease presentation.

METHODS

Enrolled patients received ADT in the form of leuprolide every 12 weeks for 24 months with bicalutamide initiating after the completion of chemotherapy. Chemotherapy consisted of ketoconazole and doxorubicin for weeks 1, 3, and 5 and estramustine and docetaxel and for weeks 2, 4 and 6. During weeks 7 and 8, no treatment was received.

RESULTS

Forty-six patients were enrolled, and forty-five patients were evaluable. Median progression-free survival (PFS) was 23.4 months. Median overall survival (OS) was 53.7 months. Out of 45 patients with measurable disease, 22 patients had an objective response: 9 patients achieved a complete response; 2 patients achieved a partial response; 10 patients achieved stable disease. Frequent grade 3 adverse events included elevated ALT (17 %), hypokalemia (13 %), and hypophosphatemia (13 %). Grade 4 adverse events were rare and included low bicarbonate (2 %), hypokalemia (2 %), leukocytopenia (2 %), and neutropenia (2 %).

CONCLUSIONS

The treatment demonstrated clinical benefit in all patient subsets with minimal reversible treatment-related adverse events. Subgroup analysis suggests that having prior local therapy resulted in greater PFS and OS.

Combination chemotherapy with docetaxel, estramustine and suramin for hormone refractory prostate cancer

PURPOSE

To investigate more effective chemotherapy against hormone refractory prostate cancer (HRPC) with the combination of estramustine (EM), docetaxel, and suramin.

PATIENTS AND METHODS

A total of 42 patients with symptomatic, progressive HRPC were included in this study. We evaluated the activity of the following schedule: EM 10 mg/kg orally daily on Days 1 to 21 every 28 days, docetaxel 70 mg/m(2) IV on Day 2 every 28 days and a total doses of 2150 mg of suramin in every cycle. Treatment was continued until disease progression or excessive toxicity.

RESULTS

Median follow-up was 23.4 months. A median of 8.8 consecutive cycles was administered per patient. In the 25 patients with lymphadenopathy, there were three (12%) complete and 18 (72%) partial responses for a measurable disease response rate of 84%. Levels of prostatic specific antigen (PSA) decreased by greater than 50% in 100% of patients and by greater than 90% in 76.2%. The median time to progression was 57 weeks and median overall survival was 132 weeks. A decline in PSA of > or =50% lasting > or =30 days was significantly associated with a prolonged median time to progression and median overall survival. Tumor volume reduction and/or antitumor treatment effects were observed in 88% of patients. A significant decrease in mean pain score from 7.8 (range, 6-10) to 2.2 (range, 0-4) (P < 0.001) was achieved in 78%. Of patients with bone metastasis, 30.5% demonstrated a partial response. The mean Eastern Cooperative Oncology Group (ECOG) performance score improved from 2.8 to 1.5 at the end of treatment period. There was no therapy-related death. The predominant toxicities were Grade 3 or 4 leukopenia in 33.3%, anemia in 21%, thrombocytopenia in 21.4%, cardiac ischemia in 4.7%, and rash in 4.7%.

CONCLUSION

The combination of docetaxel, EM, and suramin is a highly effective regimen for HRPC. Although hematologic and gastrointestinal toxicities were modest, these were easily managed medically.

A phase II study of vinorelbine and estramustine in patients with hormone-resistant prostate cancer

INTRODUCTION

This phase II study was designed to evaluate the efficacy of vinorelbine in combination with estramustine in patients with chemotherapy-naïve hormone-refractory prostate cancer.

MATERIAL AND METHODS

Patients received vinorelbine (i.v. 25 mg/m2) on days 1 and 8 every 3 weeks and estramustine (oral, 600 mg/m2) daily. Eligible patients were required to have progressive metastatic disease following the first hormonal manipulation.

RESULTS

Of the 51 patients enrolled (median age = 69 years), 84% presented bone involvement and 75% had at least two organs involved at the time of study entry and 47 were evaluable for treatment efficacy. Prostate specific antigen (PSA) response (> or =50% decrease) which was the primary efficacy criterion was reported in 21 patients (41.2%) in the intent-to-treat (ITT) population and in 20 patients (48.8%) in the per protocol (PP) population. Of the 7 patients with measurable disease, 2 achieved partial response. Median progression-free survival and overall survival were 4.7 months (range: 1.9-8.6) and 14.3 months (range: 4.2-21.2), respectively. Grade 3-4 neutropenia was reported in 6.1% of patients and in 1% of cycles. The incidence of complicated neutropenia (febrile neutropenia reported in 1 patient and septic shock with severe neutropenia reported in 2 patients) was 5.8%. The most frequent grade 3-4 non-haematological events (% of patients > or =5%) included anorexia (10%), thrombosis/embolism (8%), vomiting and hypotension (6% each). There were 3 toxic deaths (5.9 %) resulting from pulmonary embolism, angina pectoris, and septic shock. The impact of combined chemotherapy on the quality-of-life (QL) of the patients was assessed between baseline and the first evaluation scheduled at 6 weeks indicated a marked reduction in pain while the rest of the symptoms remained stable. Overall, health status improved slightly over the treatment period.

CONCLUSIONS

This study confirmed that the combination of vinorelbine and estramustine is an active regimen in patients with hormone-resistant prostate cancer who had not been treated previously with chemotherapy. Main toxicities included complicated neutropenia even though the incidence of severe neutropenia was low. We observed a higher incidence of toxic deaths which could have been related to the regimen of estramustine used in the study.

Randomized Phase II trial assessing estramustine and vinblastine combination chemotherapy vs estramustine alone in patients with progressive hormone-escaped metastatic prostate cancer

Based on the results of combined data from three North American Phase II studies, a randomised Phase II study in the same patient population was performed, using combination chemotherapy with estramustine phosphate (EMP) and vinblastine (VBL) in hormone refractory prostate cancer patients. In all, 92 patients were randomised into a Phase II study of oral EMP (10 mg kg day continuously) or oral EMP in combination with intravenous VBL (4 mg m² week for 6 weeks, followed by 2 weeks rest). The end points were toxicity and PSA response in both groups, with the option to continue the trial as a Phase III study with time to progression and survival as end points, if sufficient responses were observed. Toxicity was unexpectedly high in both treatment arms and led to treatment withdrawal or refusal in 49% of all patients, predominantly already during the first treatment cycle. The mean treatment duration was 10 and 14 weeks, median time to PSA progression was 27.2 and 30.8 weeks, median survival time was 44 and 50.9 weeks, and PSA response rate was only 24.6 and 28.9% in the EMP/VBL and EMP arms, respectively. There was no correlation between PSA response and survival. While the PSA response in the patients tested was less than half that recorded in the North American studies, the toxicity of EMP monotherapy or in combination with VBL was much higher than expected. Further research on more effective and less toxic treatment strategies for hormone refractory prostate cancer is mandatory.

Phase II trial of paclitaxel, estramustine, etoposide, and carboplatin in the treatment of patients with hormone-refractory prostate carcinoma

BACKGROUND

Preclinical data suggest that the combination of intravenous (i.v.) paclitaxel, carboplatin, oral etoposide, and oral estramustine (TEEC) has significant activity in patients with advanced, hormone-refractory prostate carcinoma. The authors conducted this clinical trial to evaluate the addition of carboplatin to the three-drug combination of paclitaxel, estramustine, and etoposide (TEE).

METHODS

Twenty patients with carcinoma of the prostate that was progressing despite hormone therapy were enrolled on this Phase II trial. Patients were treated with oral estramustine, 280 mg three times daily, and oral etoposide, 50 mg/m2, once daily on Days 1-7, with i.v. paclitaxel, 135 mg/m2, over 1 hour followed by carboplatin (area under the curve, 5) on Day 2 of each 21-day treatment cycle. Patients were evaluated for response after three cycles, and three additional cycles were given to responding or stable patients.

RESULTS

Nineteen patients were evaluable for response, and 12 patients had measurable disease at baseline. The measurable response rate was 58% (7 of 12 patients; 95% confidence interval [95% CI], 28-85%), and all of those were partial responses. Eleven patients had decreases >50% from their baseline prostate specific antigen levels during therapy, for a response rate of 58% (95% CI, 34-80%) by this criterion. The median time to disease progression was 5.5 months, with a median survival of 14.2 months. Major toxicities included Grade (according to version 2 of the National Cancer Institute Common Toxicity Criteria) 4 neutropenia in 4 patients, Grade 4 thrombocytopenia in 4 patients, and anemia > or = Grade 3 in 4 patients. One patient had a deep vein thrombosis.

CONCLUSIONS

The combination of TEEC was active in patients with hormone-refractory prostate carcinoma. The regimen was tolerable, with primarily hematologic toxicity. The addition of carboplatin to TEE did not appear to add to the efficacy of the three-drug combination of antimicrotubule agents.

The combination of estramustine and mitoxantrone in hormone-refractory prostate cancer: a phase II feasibility study conducted by the Hellenic Cooperative Oncology Group

OBJECTIVES

To consider the safety profile and therapeutic value of the combination of estramustine and mitoxantrone in a bimonthly schedule to treat hormone-refractory prostate cancer. The survival of patients with prostate cancer who relapse after androgen ablation is limited and the therapeutic options are restricted.

METHODS

Twenty-nine patients with relapse after previous treatment were included in the study; however, 3 patients who refused to start treatment were not included in the analysis, leaving 26 eligible patients. The median age was 64 years (range 44 to 82), the World Health Organization performance status ranged from 1 to 3, and the mean prostate-specific antigen level was 103 ng/mL (range 1 to 620). The Gleason score ranged from 2 to 9. The patients received a total of 208 therapeutic cycles (mean 8, range 3 to 24). Every cycle consisted of oral estramustine 140 mg, 3 times a day continuously, and intravenous mitoxantrone 20 mg (total dose). The regimen was repeated every 2 weeks.

RESULTS

Twenty-seven percent of patients with measurable soft-tissue disease demonstrated an objective response, which included one complete and six partial responses. Thirteen patients (50%) had a greater than 50% reduction in serum prostate-specific antigen level. The median duration of response was 9.2 months, and the median survival for all patients was 15 months. The most common side effects were neutropenia and thrombocytopenia.

CONCLUSIONS

The combination of estramustine and mitoxantrone is safe, well tolerated, and relatively active in patients with hormone-refractory prostate cancer. More patients are needed to partake in Phase III studies to establish the survival benefit that this combination may offer.

Estramustine and Vinblastine (EV) Regimen for Advanced Hormone-Refractory Prostate Cancer

The increasing complexity of cancer chemotherapy makes it mandatory that pharmacists be familiar with these highly toxic agents. This column reviews various issues related to the preparation, dispensing, and administration of cancer chemotherapy, both commercially available and investigational.

Treatment options in hormone-refractory prostate cancer: current and future approaches

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 will develop disease progression. Patients with hormone refractory 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. Until recently, cytotoxic chemotherapy was felt to be relatively ineffective in the treatment of HRPC. Combination regimens incorporating new active agents have demonstrated significant activity in this setting, renewing interest in the use of chemotherapy to treat HRPC. Recent advances in the understanding of prostate cancer biology have led to the development of drugs directed against precise molecular alterations in the prostate tumour cell. Biologic agents now in development include those capable of altering signal transduction, blocking angiogenesis, inhibiting cell cycle progression, and stimulating apoptosis. In addition, many types of immune therapies are showing promise. Evaluating these agents, and incorporating them into existing regimens, are major goals of ongoing clinical research in advanced prostate cancer.

The treatment of prostate cancer: an overview of current options

PURPOSE

The purpose of this report is to discuss the current treatment options available to the patient with prostate cancer in all stages of the disease.

OVERVIEW

With the exception of skin cancer, prostate cancer is the most common cancer in men in the United States. Most patients in the current era will present with organ-confined disease, amenable to curative treatment. Treatment for organ-confined disease includes watchful waiting, radical prostatectomy, radiation therapy, and cryosurgery in selective cases. Hormone therapy is the cornerstone of treatment of patients with advanced prostate cancer. There is no curative treatment for hormone-refractory prostate cancer.

CLINICAL IMPLICATIONS

The availability of several therapeutic options for localized prostate cancer warrants careful consideration when planning treatment with curative intent. Patients need to be active participants in decision making, and they must be aware of the benefits and possible complications of the different types of treatment. Patients with advanced prostate cancer need to be aware that hormone treatment will provide temporization and palliation in the majority of cases. Hormone-resistant prostate cancer is refractory to most forms of conventional and experimental therapy.

Progressing prostate carcinoma

In the Karnell Cancer Center Grand Rounds, we present a patient who underwent radical prostatectomy with bilateral pelvic lymphadenectomy, but had positive margins and subsequently developed local recurrence and then systemic disease. Pathologic and radiologic aspects of his disease are discussed. Therapeutic options at different stages of the disease are examined from the point of view of the urologist, radiation oncologist, and medical oncologist. The surgical portion of the discussion focuses on the selection of initial therapy. Both the selection of surgical candidates and choice of pre- or post-operative therapy in patients can be aided by prognostic tools looking at several variables, including prostate-specific antigen (PSA) level, Gleason score of the tumor, seminal vesicle invasion, extracapsular invasion, and lymph node involvement. Low-risk patients can be treated with monotherapy, such as radical prostatectomy, external beam radiation therapy, prostate brachytherapy, or cryosurgical ablation of the prostate. Higher risk patients may require adjuvant and possibly neoadjuvant therapy in addition. The radiation portion of the discussion focuses on the use of radiation therapy as salvage for relapsing disease. Of particular importance is the point that treating high-risk patients whose PSA levels have started to rise but are less than 1 ng/ml results in a long-term PSA control rate as high as 75%, but that limiting the use of salvage radiation therapy to patients with high PSA levels or biopsy confirmation of local recurrence in the face of a negative bone scan results in biochemical long-term control of less than 40%. In the medical oncology part of the discussion, the major focus is on the use of chemotherapy to treat patients whose disease has become resistant to hormonal therapy. Mitoxantrone plus a corticosteroid has been found to offer significant palliation for such patients. Combination therapy with estramustine plus taxanes, other microtubule inhibitors, or other agents such as topoisomerase II inhibitors, has been found to cause shrinkage of measurable soft tissue disease and diminution of serum PSA levels. The development of effective hormonal and chemotherapeutic drugs for treatment of metastatic disease has led to new interest in adjuvant and neoadjuvant therapy of high-risk patients.

Paclitaxel and docetaxel in prostate cancer

Although their ultimate value in prostate cancer therapy remains to be defined in randomized trials, docetaxel and paclitaxel are active agents in HRPC. Combination therapies using either of these taxanes plus oral EMP show reproducible antitumor activity that appears to be greater and more durable than that of single-agent treatment. Although the optimal combination and schedule have not been determined, weekly paclitaxel and EMP and docetaxel given every 3 weeks or by weekly infusion with EMP are useful treatment options for patients with progressive HRPC. The gastrointestinal toxicity of EMP has been reduced by intermittent rather than continuous administration, and other toxicities may be reduced further by use of intravenous EMP. Although there has been progress, the median time to progression of 5 to 6 months for current taxane-based therapies suggests that they will not have major impact on overall survival for patients with HRPC. Greater benefit may be possible earlier in the course of prostate cancer, and the activity of the taxane-EMP combinations is sufficient to justify clinical trials of adjuvant or neoadjuvant chemotherapy for selected groups of patients with locally advanced and poor-prognosis tumors. Armed with many new molecularly targeted agents that may interact favorably with taxanes, it should be possible to build on current antimicrotubule regimens to improve activity in HRPC. Taxane-EMP combinations provide a platform on which to test additional agents that may enhance the apoptotic response or circumvent cellular stress adaptations that confer drug resistance. Further elucidation of signaling pathways that regulate microtubule dynamics and programmed cell death after exposure to microtubule inhibitors would provide a more rational guide for integrating specific inhibitors of signal transduction with current taxane-based therapies. Pharmacokinetic and pharmacodynamic studies will play a key role in the development of future taxane-based therapies for prostate cancer.

Phase II study of docetaxel, estramustine, and low-dose hydrocortisone in men with hormone-refractory prostate cancer: a final report of CALGB 9780. Cancer and Leukemia Group B

PURPOSE

To investigate the combination of docetaxel, estramustine (EM), and low-dose hydrocortisone in men with hormone-refractory prostate cancer (HRPC).

PATIENTS AND METHODS

Combinations of EM with other antimitotic agents such as docetaxel are synergistic in vitro and show significant clinical activity in patients with HRPC. We studied intravenous administration of docetaxel 70 mg/m(2), oral estramustine, and low-dose daily hydrocortisone in men with HRPC who demonstrated progression after initial hormone therapy.

RESULTS

Of the 47 men enrolled onto this multicenter cooperative group study, 46 were assessable for response and/or toxicity. In the 24 patients with measurable disease, there were three complete and nine partial responses for a measurable disease response rate of 50% (12 of 24 patients; 95% confidence interval [CI], 27% to 73%). In the 44 patients in whom pretreatment prostate-specific antigen (PSA) was elevated, 30 (68%) had a 50% or greater decrease, and 25 (57%) had a 75% or greater decrease in PSA. The combined measurable disease and biochemical response rate in all 46 assessable patients was 54% (three complete responses, 22 partial responses, 95% CI, 37% to 71%). The predominant toxicity was neutropenia, with 26% of patients having grade 3 and 30% having grade 4 granulocytopenia; there were no episodes of febrile neutropenia. Other common but mild adverse effects included malaise/fatigue, peripheral edema, and hyperglycemia. The incidence of thromboembolic events during therapy was 9%. With a median follow-up of 17 months, the median survival was 20 months. The median time to disease progression was 8 months for all patients, and 10 months for those with measurable disease.

CONCLUSION

This therapy is efficacious and moderately well tolerated in HRPC and should be compared in a phase III trial with mitoxantrone and prednisone.

Bone-targeted therapy for advanced androgen-independent carcinoma of the prostate: a randomised phase II trial

BACKGROUND

Prostate carcinoma is linked to osteoblastic metastasis. We therefore investigated the value of bone-targeted consolidation therapy in selected patients with advanced androgen-independent carcinoma of the prostate.

METHODS

103 patients received induction chemotherapy, consisting of ketoconazole and doxorubicin alternating with estramustine and vinblastine. After two or three cycles of induction chemotherapy, we randomly assigned 72 patients who were clinically stable or responders to receive doxorubicin with or without strontium-89 (Sr-89) every week for 6 weeks.

FINDINGS

Overall 62 of the 103 (60%, 95% CI 50-70) patients had a 50% or greater reduction in serum prostate-specific antigen concentration that was maintained for at least 8 weeks, and 43 (42%, 32-52) had an 80% or greater reduction. 49 (52%) patients with bone pain at registration had complete resolution of pain. After follow-up of 67 patients until death, the estimated median survival for all 103 patients was 17.5 months (range 0.5-37.7). For the 36 patients randomly assigned to receive Sr-89 and doxorubicin, the median survival time was 27.7 months (4.9-37.7), and for the 36 who received doxorubicin alone it was 16.8 months (4.4-34.2) (p=0.0014). The hazard ratio was 2.76 (95% CI 1.44-5.29).

INTERPRETATION

Bone-targeted consolidation therapy consisting of one dose of Sr-89 plus doxorubicin once a week for 6 weeks, when given to patients with stable or responding advanced androgen-independent carcinoma of the prostate after induction chemotherapy, improved overall survival.

Chemotherapy in advanced androgen-independent prostate cancer 1990-1999: a decade of progress?

BACKGROUND AND PURPOSE

A great number of clinical research studies have been reported in the field of chemotherapy for advanced androgen-independent prostate cancer during the last ten years. The aims of the present review were to assess their impact on management of the disease and on survival of patients.

METHODS

The review of full published reports was facilited by the use of a MEDLINE computer search.

RESULTS

Clinical research studies have focused on defining guidelines for eligibility criteria and accurate endpoints for patients to be enrolled onto clinical trials and developing new agents or combination of drugs including estramustine phosphate. Any combination of current chemotherapy has no impact on overall survival of patients. Among drugs in development, only the promising activity observed with docetaxel deserves randomized trials to assess its impact on survival. The major innovative advance of the 90s is the demonstration of the impact of chemotherapy (mitoxantrone + prednisone) on quality of life as compared to prednisone alone. A greater and longer-lasting improvement in quality of life along with a concomitant decrease in costs was observed.

CONCLUSIONS

At the present time, chemotherapy should be considered as a palliative treatment in patients with symptomatic androgen-independent disease. The enrollment of patients into clinical trials dealing with quality of life as primary endpoint is strongly solicited. A standard methodology should be used in phase II trials with a primary goal of selection of agents which should progress to randomized trials using survival as an endpoint. Hopefully new specific strategies targeted to reverse the molecular changes that underlie prostate tumorigenesis should rapidly impact the multimodality management of AIPC in the third millenium.

Chemotherapy for advanced hormone refractory prostate cancer

Men with metastatic prostate cancer treated with androgen ablation respond rapidly and often dramatically to therapy, with improvement of bone pain, regression of soft tissue metastases, and declines in serum prostate-specific antigen (PSA). Unfortunately, few treatment options are available to men who progress after hormone therapy. Recent studies in the mechanism of anticancer drug action have focused on the proteins that regulate apoptosis or programmed cell death as a target for the treatment of hormone-resistant prostate cancer. New treatments are now being designed with both resistance and apoptotic pathways in mind. US Food and Drug Administration (FDA) approval of the combination of mitoxantrone and prednisone for the palliation of bone pain in men with hormone refractory prostate cancer demonstrates that chemotherapy can be effective. Two randomized trials have demonstrated the superiority of mitoxantrone combined with a corticosteroid over corticosteroid therapy in alleviating bone pain. The combination of estramustine with vinblastine, or VP-16, is commonly used in clinical practice with both regimens demonstrating significant PSA declines. When estramustine is combined with either paclitaxel or docetaxel in vitro, greater than additive in vitro cytotoxicity is noted. Phase I and II studies of taxane-based therapy in hormone refractory prostate cancer demonstrate improved survival when compared with historical controls, but phase III studies are necessary to confirm these preliminary observations.

Serologic tumor markers, clinical biology, and therapy of prostatic carcinoma

PSA has been a valuable tool in enhancing our understanding of the prevalence and virulence of prostate cancer. PSA also has contributed to the understanding of important phenomena related to the androgen regulation of the cancer; however, it has not been useful in detecting some forms of androgen-independent (neuroendocrine) progression and is of limited prognostic value in androgen-independent prostate cancer. PSA also has been valuable in the accelerated development of therapies for prostate cancer; however, it must be used cautiously for this purpose, because it may not reflect the most relevant clone. In addition, some agents may directly affect PSA release independent of their antitumor activity. Most importantly, before PSA is adopted as a surrogate end point in clinical trials in prostate cancer, it must be prospectively validated. Future studies must focus on the development of prospective serologic tumor markers that can predict virulence of disease and to reflect androgen-independent progression.

Chemotherapy for hormone refractory prostate cancer

New combinations have been developed that show significant activity in therapy for hormone refractory prostate cancer. Several of these are designed to address specific cellular targets unique to prostate cancer. To date, the major benefits of these therapies have been palliative in nature, resulting in an improvement in quality of life, particularly with the combination of mitoxantrone and prednisone. None of these agents or regimens have been shown to affect survival significantly, and none can be considered to be standard therapy for this disease. Nonetheless, the success of these regimens in inducing response has challenged the skepticism concerning the appropriateness of chemotherapy for patients with advanced prostate cancer. The ability to slow and even reverse the growth of far advanced disease raises the possibility that the application of these regimens earlier in the course of the disease will have a more significant impact on the morbidity and, in the long run, on the mortality of prostate cancer. It is hoped that the enrollment of patients into properly designed clinical trials of new agents and combinations will result in the development of therapy with proven efficacy in the near future.

Phase I trial of docetaxel with estramustine in androgen-independent prostate cancer

PURPOSE

To evaluate the toxicity, efficacy, and pharmacokinetics of docetaxel when combined with oral estramustine and dexamethasone in a phase I study in patients with progressive metastatic androgen-independent prostate cancer.

PATIENTS AND METHODS

Thirty-four men were stratified into minimally pretreated (MPT) and extensively pretreated (EPT) groups. Estramustine 280 mg PO tid was administered 1 hour before or 2 hours after meals on days 1 through 5, with escalated doses of docetaxel from 40 to 80 mg/m2 on day 2. Treatment was repeated every 21 days.

RESULTS

Thirty-four patients were assessable for toxicity and 33 for response. In the MPT patients, dose-limiting myelosuppression was reached at 80 mg/m2, with six patients experiencing grade 3/4 granulocytopenia. In EPT patients, escalation above 70 mg/m2 was not attempted. Fourteen MPT (70%) and six EPT (50%) patients had a > or = 50% decline in serum PSA on two consecutive measurements taken at least 2 weeks apart. The overall 50% PSA response rate was 63% (95% confidence interval [CI], 28% to 81%). Of the 18 patients with bidimensionally measurable disease, five (28%; 95% CI, 11% to 54%) achieved a partial response. At the time of entry onto the study, 15 patients required narcotic analgesics for bone pain; after treatment, eight (53%) discontinued their pain medications. The area under the curve for docetaxel increased linearly from 40 to 70 mg/m2. At 80 mg/m2, the measured area under the curve was 8.37 (standard deviation, 0.724), which was significantly higher than the previously reported values.

CONCLUSION

The recommended phase II dose of docetaxel combined with estramustine is 70 mg/m2 in MPT patients and 60 mg/m2 in EPT patients. This combination is active in men with androgen-independent prostate cancer.

Post-therapy serum prostate-specific antigen level and survival in patients with androgen-independent prostate cancer

BACKGROUND

With an hypothesis that post-chemotherapy changes in serum prostate-specific antigen (PSA) levels might serve as a surrogate marker for assessing prostate cancer outcome (i.e., survival), we studied the relationship between pretherapy and post-therapy prognostic factors and survival in patients with androgen-independent prostate cancer.

METHODS

A prognostic model for survival based on pretherapy and post-therapy parameters was developed from the clinical data on 254 patients with androgen-independent prostate cancer treated with 11 different protocol therapies at Memorial Sloan-Kettering Cancer Center. The model was validated by use of an independent dataset of 541 patients enrolled in two randomized phase III trials.

RESULTS

In multivariate analysis, a post-therapy decline in PSA levels of 50% achieved in 12 weeks was a statistically significant factor associated with survival (two-sided P = .0012). A similar outcome was obtained with the use of an 8-week time frame. Elevated pretherapy level of serum lactate dehydrogenase (two-sided P = .0001), lower pretherapy level of hemoglobin (P = .0001), and younger age (two-sided P = .0430) had a statistically significant negative impact on outcome. Median survival times were 23, 17, and 9 months for low-, intermediate-, and high-risk groups of patients defined by the prognostic model, respectively.

CONCLUSION

This study confirms the prognostic value of a post-therapy decline in PSA of 50% or greater from baseline in relation to survival in patients with androgen-independent prostate cancer treated with a variety of therapies. Two consecutive determinations at 4-week intervals can be used as an end point for efficacy in phase II trials of therapies in this disease.