Phase II evaluation of oral estramustine and oral etoposide in hormone-refractory adenocarcinoma of the prostate

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.

Oral chemotherapy for hormone refractory prostate cancer. The University of Michigan experience

The use of oral chemotherapy for the treatment of malignant disease is expanding. The authors' experience with oral chemotherapy for hormone-refractory prostate cancer continues to grow. These therapies are well-tolerated and effective. Already, these regimens are being improved by hybridizing them with intravenous agents such as paclitaxel. Also, oral novel agents are being tested that may offer new options for the treatment of hormone-refractory prostate cancer.

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.

Prognostic indicators in hormone refractory prostate cancer

Prognostic factors in hormone refractory prostate cancer currently are of limited use to clinicians. Although studies have identified several factors that predict for poor survival in patients, most are either retrospective, or nonrandomized. Therefore, large prospective, randomized trials are needed to validate the significance of these factors. In addition, these indicators are largely descriptive of the patients' condition or the extent of disease. As more treatment options are developed for these patients, functionally relevant and prognostic molecular markers are needed to direct their care.

Prostate-specific antigen and other markers of therapeutic response

Several new agents and combinations demonstrate significant activity in the treatment of patients with hormone refractory prostate cancer. Prostate-specific antigen (PSA) is being used increasingly as the key marker of a therapeutic response in trials of new agents. This article reviews data that support this marker as a surrogate endpoint, and it discusses the issues around the appropriateness of PSA as an intermediate marker with evolving noncytotoxic agents. Other biomarkers of prostate cancer progression are not uniformly elevated in men with advanced disease; to date, they are of limited clinical use. This article also discusses the rationale and results of novel and alternative biomarkers of prostate cancer progression.

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.

Pyrazoloacridine for the treatment of hormone-refractory prostate cancer

There is a pressing need for new agents for the treatment of hormone-resistant prostate cancer (HRPC). Pyrazoloacridine (PZA) has antitumor activity in several in vitro and in vivo tumor systems, and was selected for testing in clinical trials by the National Cancer Institute (NCI). We conducted a phase II trial of PZA for the treatment of HRPC. Seventeen male patients with HRPC were treated with PZA at 750 mg/m2 i.v. given over a period of 3 hr every 3 weeks. Response to therapy was assessed with serial measurements of serum prostate-specific antigen (PSA) and sequential imaging studies. The 17 patients were treated and fully evaluable. One patient experienced a significant decrease in PSA, from over 10,000 ng/ml to 423 ng/ml, along with an improvement in bone scan findings. However, no other patient obtained an objective or PSA response (overall PSA response rate = 5.9%). Median survival duration was 15.3 months. Toxicity was moderate. If PSA is used as a marker of response, single-agent PZA appears to lack efficacy in the treatment of HRPC. However, the one unambiguous response, and the favorable toxicity profile observed, may warrant further evaluation of this agent.

Phase II study of estramustine and vinorelbine in hormone-refractory prostate carcinoma patients

The purpose of this study was to evaluate the antitumor activity of vinorelbine and oral estramustine phosphate in patients with metastatic, hormone-refractory prostate cancer. We evaluated the activity of this association using the following schedule: estramustine phosphate 600 mg/m2/day orally days 1-42 and vinorelbine 25 mg/m1 days 1, 8, 22, 29 cycles repeated every 56 days. Twenty-five patients were included in the study, 24 being evaluable for response and 25 for toxicity. Out of 5 patients with measurable disease, none had an objective response. Of the 24 assessable patients with bone metastases, 9 patients had a > or = 65% decline in pretreatment prostate-specific antigen (PSA) level, stable disease was observed in 10 and 5 patients progressed. Toxicities were minimal. Anemia was observed in 5 patients, alopecia in 4 and nausea and vomiting was observed in 6 patients. Anorexia and weight loss of more than 10% were observed in 2 patients. This combination is active and well tolerated in hormone-resistant prostate cancer. These results support the therapeutic strategy of combining agents that impair microtubule function.

Early clinical experience with liarozole (Liazal) in patients with progressive prostate cancer

Liarozole (Liazal) is the first retinoic acid (RA) metabolism blocking agent (RAMBA) in clinical practice. RAMBA therapy promotes differentiation and inhibits proliferation by increasing endogenous RA in tumours. Liarozole was investigated in two open-label pilot studies of 100 patients with progressive prostate cancer in relapse despite previous androgen ablation. Liarozole (150-300 mg twice daily, for > or = 1 month) produced > or = 50% reduction in prostate specific antigen (PSA) serum levels in 15 of 30 evaluable patients in study 1 (50%) and 10 of 55 patients in study 2 (18%). PSA responders had more marked reductions in prostatic acid phosphatase, alkaline phosphatase and symptom scores for bone pain and urological symptoms, and improved general well being. Plasma levels of adrenal androgens did not alter during chronic treatment with liarozole nor at adrenocorticotrophic hormone (ACTH) stimulation test. Liarozole did not alter plasma levels of adrenal androgens or cortisol. Cortisol response to ACTH stimulation was slightly blunted. Liarozole was generally well tolerated. Dermatological adverse events were probably related to increased intracellular RA. Liarozole appears to be a promising treatment option in prostate cancer.

Oral estramustine and oral etoposide for hormone-refractory prostate cancer

OBJECTIVES

Estramustine and etoposide have been shown to inhibit the growth of prostate cancer cells in experimental models. An in vivo synergism of the two agents, when administered to patients with metastatic prostate cancer refractory to hormone therapy, has been reported. To confirm these results, we administered this combination to a large number of patients with hormone-refractory prostate cancer (HRPC).

METHODS

Fifty-six patients with metastatic HRPC were treated with oral estramustine 140 mg three times a day and oral etoposide 50 mg/m2/day for 21 days. Therapy was discontinued for 7 days and the cycle was then repeated. Therapy was continued until evidence of disease progression or unacceptable toxicity occurred. To control for the possible interference of an antiandrogen withdrawal effect, all patients discontinued antiandrogen therapy and were not enrolled in the study unless there was evidence of disease progression.

RESULTS

Forty-five percent of 33 patients with measurable soft tissue disease demonstrated an objective response, which included five complete and ten partial responses. Among 52 patients with osseous disease 17% showed improvement and 50% showed stability of bone scan. Thirty patients (58%) demonstrated a decrease of more than 50% in pretreatment prostate-specific antigen (PSA) levels. The median survival of all patients was 13 months. Good pretreatment performance status, measurable disease response, improvement or stability of bone scan, and PSA response were important predictors of longer survival.

CONCLUSIONS

We conclude that the combination of estramustine and etoposide is an active and well-tolerated oral regimen in HRPC.

A phase II trial of oral estramustine and oral etoposide in hormone refractory prostate cancer

OBJECTIVES

We previously demonstrated that the combination of oral estramustine (15 mg/kg/day) and oral etoposide (50 mg/m2/day) is effective first-line therapy for the treatment of hormone refractory prostate cancer. We initiated a new Phase II trial utilizing a lower dose of estramustine (10 mg/kg/day) and allowing previous chemotherapy treatment.

METHODS

Estramustine (10 mg/kg/day) and etoposide (50 mg/m2/day) were administered orally for 21 of 28 days. Sixty-two patients were enrolled with a minimum of 26 weeks of follow-up.

RESULTS

Of 15 patients with measurable soft tissue disease, 8 (53%) had a partial response (PR). Seven of these 8 patients also demonstrated a decrease in baseline prostate-specific antigen (PSA) of more than 50%. The median survival of all patients was 56 weeks. Of 47 patients with disease limited to the bone, 16 (34%) had a PR to therapy based on decrease in pretreatment PSA of more than 50%. Overall, 24 (39%) of 62 patients demonstrated a decrease in pretreatment PSA levels of at least 50% from baseline. Twenty-two patients received previous chemotherapy. There were no differences in survival or disease response in patients treated with previous chemotherapy compared with untreated patients. Pretreatment hemoglobin, PSA, alkaline phosphatase and lactate dehydrogenase levels were not significant prognostic factors, but performance status was an important predictor of survival.

CONCLUSIONS

We conclude that the combination of oral estramustine (10 mg/kg/day) and oral etoposide (50 mg/m2/day) is an active regimen for hormone refractory prostate cancer.

Anti-angiogenic treatment with linomide as adjuvant to surgical castration in experimental prostate cancer

PURPOSE

Escape from "castration inhibition," be it surgical or chemically induced, is still the major problem in prostate cancer treatment. New agents that can be given as adjuvant therapy are needed. Linomide has demonstrated both anti-tumor and anti-angiogenic activity with little toxicity in the Dunning R-3327 rat prostate tumor system. Therefore it was deemed essential to study the efficacy of this drug in the adjuvant situation.

MATERIALS AND METHODS

Linomide, roquinimex, was administered 3 times a week i.p. alone or in conjunction with castration to rats bearing the Dunning R-3327 PAP rat prostate tumor and its effect on tumor growth analyzed. Similar experiments, in which Linomide 25 mg./kg./day was given in the drinking water were carried out in rats with the Dunning R-3327 G tumor. The effect of treatment on blood vessel density and blood flow in the tumor was also assessed using an image analysis system.

RESULTS

Linomide, 2.5 & 40 mg./kg., administered from the day after castration inhibited the regrowth of the Dunning R-3327 PAP tumors In addition, Linomide 40 mg./kg. administered after tumor regrowth occurred following castration(week 10) inhibited further tumor growth. Inhibition of tumor regrowth after castration was also found in the Dunning G tumor. When Linomide treatment was stopped regrowth of the tumors occurred, either in the same animal or on transplantation to new intact hosts, demonstrating that the tumor cells were still viable. Tumor blood vessel density was decreased both after castration and Linomide treatment alone, 40 and 32% respectively. On combination of castration and Linomide a 60% decrease in blood vessel density was found. This was significantly different from either of the two treatments given alone. The enhancement on combining castration and Linomide was confirmed by a further decrease in blood flow, from 19 and 22 to 12 ml. per minute/gm. tissue respectively.

CONCLUSIONS

Linomide, an anti-angiogenic drug, inhibits escape from "castration inhibition".

Phase II study of estramustine, oral etoposide, and vinorelbine in hormone-refractory prostate cancer

Hormone-refractory prostate cancer is characterized by a low response rate following second-line therapy. Encouraging results have been reported in Phase II studies with estramustine associated with vinblastine or etoposide. Vinorelbine is a new semisynthetic vinca alkaloid that has demonstrated activity in prostate cancer. We therefore evaluated the activity of the following schedule: estramustine, 400 mg/m2 orally days 1-42; etoposide, 50 mg/m2 orally days 1-14; and 28-42; vinorelbine, 20 mg/m2 days 1, 8, 28, and 35; cycles being repeated every 8 weeks. Twenty-five patients have been included and are assessable for response and side effects. Patient characteristics were as follows: median age, 71 years (range 55-81); ECOG performance status 0-2; nonosseous disease, 3 cases; bone metastases, 23 cases. Sixty-two cycles have been delivered. Two patients with measurable disease and six patients with bone disease had a partial remission for an overall response rate of 32% (95% confidence interval 15-53%). Seven patients had stabilization of disease and 10 had progression of disease. Median duration of response was 3 months (range 2-5). Prostate-specific antigen in 14 patients (56%) decreased from baseline by at least 50%. Toxicity was manageable. Neutropenia was mild, with only three cases of grade III-IV toxicity. Two patients had severe anemia. The results of this study indicate that the schedule is active and well tolerated in hormone-refractory prostate cancer patients.

The use of prostate-specific antigen as a surrogate end point in the treatment of patients with hormone refractory prostate cancer

Prostate-specific antigen increasingly is being used as a surrogate end point in trials of new agents in patients with hormone refractory prostate cancer. This article reviews data that support this marker as a surrogate end point and the contradictory data reported recently for trials of suramin. These contrasting views may originate in the different mechanisms of actions of the agents studied. These data suggest that a decline in prostate-specific antigen of at least 50% from baseline may be an important predictor of survival for patients receiving cytotoxic therapy.

Evolving strategies of cytotoxic chemotherapy for advanced prostate cancer

Despite the use of cytotoxic chemotherapy for advanced prostate cancer for half a century, its clinical utility in this setting remains undefined. Based on traditional methods of assessment, the list of the most active cytotoxic agents includes cyclophosphamide, doxorubicin, mitoxantrone and cisplatin. With the introduction of more structured methods of assessment, including careful assessment of indices of quality of life and serial measurement of serum prostate-specific antigen (PSA), the role of cytotoxic agents is being re-assessed. In view of the cell cycle characteristics of prostate cancer, there appears to be an emerging role for combination inhibitors of mitosis, including estramustine in combination with the vinca alkaloids, etoposide or paclitaxel.

Immunohistochemical analysis of beta-tubulin isotypes in human prostate carcinoma and benign prostatic hypertrophy

BACKGROUND

beta-tubulin, the intracellular target of several antimicrotubule agents, is encoded by at least six genes and exists as multiple isotypes with tissue-specific expression. Previous in vitro studies indicated that tubulin isotype composition may affect polymerization properties, dynamics, and sensitivity to drugs.

METHODS

To investigate the isotype composition of beta-tubulin in human prostate, tissues were collected from 26 patients after radical prostatectomy and sections were stained with isotype-specific antibodies.

RESULTS

beta IV tubulin is the predominant isotype in benign prostatic hyperplasia (BPH) and adenocarcinoma, showing significantly stronger immunohistochemical expression than beta II and beta III, particularly in Gleason's grade 3 and 4 cancers. Staining for the beta II isotype was invariably weak and often absent in BPH and normal glands. There was a marked increase in beta II isotype stain from BPH to cancer in 77% of the patients, suggesting that the expression of this isotype is related to malignant status.

CONCLUSIONS

The beta II tubulin isotype is a potential marker for prostate adenocarcinoma. The possibility that tumor beta-tubulin isotype composition may effect the response to antimicrotubule drug therapy in prostate cancer and other tumors merit investigation.

Epirubicin combined with estramustine phosphate in hormone-resistant prostate cancer: a phase II study

Twenty-four assessable patients with hormone-resistant prostate cancer (HRPC) were to receive daily doses of oral estramustine phosphate (EMP), 10 mg kg(-1), and intravenous epirubicin (EPR) infusions, 100 mg m(-2), every third week up to a cumulative dose of 500 mg m(-2). Biochemical response [> or = 50% reduction in pretreatment serum prostate-specific antigen (PSA) after three cycles of > or = 3 weeks' duration] was demonstrated in 13 of 24 patients included (54%). No objective response (WHO criteria) was observed, although seven of nine evaluable patients achieved a > or = 50% serum PSA reduction. Subjective improvement (pain score, performance status) occurred in 7 of 24 patients, whereas nine patients progressed subjectively. There was no correlation between subjective and biochemical response. Biochemical progression (> or = 50% increase of nadir PSA) occurred after a median of 12 weeks. All but two patients were alive after a median follow-up time of 8.7 months for surviving patients (range 3.3-13.2). Eight patients experienced grade 3/4 leucopenia, with no indication of cumulative myelosuppression. Cardiovascular toxicity was experienced by four patients. Two patients developed angioedema twice, in one patient requiring hospitalization at the intensive ward. Based on this limited series, the combination of EPR and EMP in patients with HRPC is tolerable and appears to be effective in terms of significant PSA reduction. The results warrant further investigations of the two drugs and, in particular, of the clinical significance of > or = 50% PSA decrease in patients with HRPC.

A phase II trial of deferoxamine in patients with hormone-refractory metastatic prostate cancer

The management of hormone-refractory metastatic prostate cancer remains a therapeutic dilemma. We report the results of a phase II trial with deferoxamine administrated at a dose of 50 mg/kg (maximum dose 5 g) administered intravenously over 8 hr daily, repeated for 5 days at 4-week intervals for 2 courses. Fourteen patients with advanced hormone-refractory prostate cancer were treated and 28 courses were delivered. Essentially no toxicity was observed. Using combined clinical and prostate-specific antigen (PSA) criteria. 13 of 14 patients had disease progression. However, 9 of 14 patients had stable measurable or evaluable disease and progressed solely based on PSA criteria. Deferoxamine in this dose and schedule has no activity in hormone-refractory prostate cancer. Further investigation of the effect of deferoxamine on PSA production/expression is warranted.

Formation of topoisomerase II alpha complexes with nascent DNA is related to VM-26-induced cytotoxicity

Several clinically active anticancer drugs are known to interfere with DNA topoisomerase II activity. However, the importance of the individual alpha (170 kDa) and beta (180 kDa) isozymes as targets of topoisomerase II-active drugs is not clear. To address this question, human CCRF-CEM leukemia cells were incubated with bromodeoxyuridine, and either the nascent DNA or bulk DNA not undergoing replication was purified by immunoprecipitation with an anti-bromodeoxyuridine antibody. The topoisomerase II isozymes that coprecipitated with either the nascent DNA or bulk DNA were analyzed by Western blotting. The alpha isozyme formed complexes with nascent DNA in cells pretreated with either VM-26 or mitoxantrone, while the beta isozyme was only bound to bulk DNA. At moderately cytotoxic concentrations, VM-26 enhanced the binding of topoisomerase II alpha to nascent DNA at least 5.2-fold compared to bulk DNA. However, in VM-26 resistant CEM/VM-1 cells incubated with equitoxic concentrations of VM-26, topoisomerase II alpha complex formation with nascent DNA was decreased at least 5.5-fold compared to bulk DNA. Drug-induced binding of topoisomerase II beta with bulk DNA in CEM/VM-1 cells did not correlate with cytotoxicity. Collectively, these results indicate that the formation of VM-26 stabilized complexes of topoisomerase II alpha with nascent DNA are critical to the development of cytotoxicity, and that resistance of CEM/VM-1 cells to VM-26 is related to impaired formation of these complexes. The results also provide indirect evidence that topoisomerase II alpha is involved in DNA, replication.

Symptomatic improvement associated with combined estramustine and vinblastine chemotherapy for metastatic prostate cancer

We evaluated the effectiveness of combination chemotherapy using estramustine and velban for metastatic prostate cancer. Patients with progressive metasatatic prostate cancer and rising prostate-specific antigen (PSA) values were evaluated between 1992 and 1994. All treatment was given on an outpatient basis. Vinblastine, 4 mg/m2 i.v., was given weekly for 6 weeks with a 2-week rest period. Estramustine, 10 mg/kg orally, was given in three divided doses for 6 weeks with a 2-week rest period between cycles. Of 15 patients, six (40%) had a response, in which a 25% decrease in PSA was associated with subjective improvement. There were no complete responses. Five partial responders had less pain. Median duration of response or time to progression was 9 months. Survival was 11.7 months for responders, 13.2 months for nonresponders. The combination of estramustine and velban is an effective therapy in progressive metastatic prostate cancer as measured by a decrease in PSA and improvement of symptoms.

New approaches to adjuvant therapy for patients with adverse histopathologic findings following radical prostatectomy

Some men affected with clinically localized prostate carcinoma suffer life-threatening recurrence, despite previous treatment with surgery or radiation therapy, underscoring the need for new, effective, systemic adjuvant treatment approaches. Recent molecular mechanism-based prostate cancer drug discovery efforts have identified several candidate targets for systemic prostate cancer adjuvant therapy; however, traditional cancer treatment development algorithms may not be appropriate for many of the new treatment strategies. To best exploit the clinical potential of these molecular treatment strategies, novel translational research strategies are required to support hypothesis-driven clinical research and development.

Hormonal and Chemotherapeutic Systemic Therapy for Metastatic Prostate Cancer

BACKGROUND: Prostate cancer is the most frequently diagnosed cancer and the second leading cause of cancer death in men in the United States. It is estimated that over 300,000 men will have been diagnosed with prostate cancer in 1996, and more than 40,000 will have died of this disease. METHODS: The authors combined their experience with a review of the literature on management of this disease to examine the effectiveness of treatments for both localized and metastatic prostate cancer. RESULTS: Surgery and radiation therapy are potentially curative modalities for cancer still limited to the gland. Androgen ablation therapy results in stabilization or regression of metastatic disease in most instances but is not curative. Some new approaches are described for patients with hormone-refractory prostate cancer. CONCLUSIONS: Newer tumor-biology-based combinations are promising in the treatment of hormone-refractory prostate cancer, but their effect on patient survival needs to be evaluated in larger clinical trials.

Inhibition of prostate cancer growth by 9-aminocamptothecin and estramustine

OBJECTIVES

Hormone-refractory prostate cancer continues to be associated with a very poor prognosis. Agents that interact with the nuclear matrix have been demonstrated to have activity against hormone-refractory prostate cancer. It was the aim of this study to assess the activity of estramustine, an estradiol-nitrogen mustard conjugate, and 9-aminocamptothecin (9-AC), a topoisomerase I inhibitor, in a preclinical model of hormone-refractory prostate cancer.

METHODS

We used the Dunning rat prostatic adenocarcinoma model to demonstrate that the combination of estramustine and 9-AC interacts at the level of the nuclear matrix to inhibit the growth of prostate cancer cells.

RESULTS

We demonstrate that the combination of these two agents at pharmacologically achievable doses are cytotoxic to rat and human prostate cancer cells in vitro and in vivo in the rat.

CONCLUSIONS

The combination of the two drugs was significantly more cytotoxic than either drug alone. We have instituted a Phase II clinical trial in patients with hormone-refractory prostate cancer using 9-AC based on these preclinical findings.

High-dose chemotherapy with peripheral blood stem-cell transplantation for hormone-refractory advanced carcinoma of the prostate: experience of two cases

Two patients with hormone-refractory advanced prostate cancer were treated with high-dose chemotherapy and peripheral blood stem-cell transplantation. A satisfactory number of stem cells were collected by appropriately timed leukapheresis in these patients. The stem-cell samples collected from the first patient were positive for prostate-specific antigen messenger ribonucleic acid expression; such expression was not detected in the samples from the second patient. The first patient has remained in complete remission as of December 1995. The second patient died of the disease.

Phase II study of the oral cyclophosphamide and oral etoposide combination in hormone-refractory prostate carcinoma patients

BACKGROUND

Hormonotherapy temporarily controls symptoms in 80% of patients with metastatic prostate carcinoma. Once progression occurs, no consensus exists on further therapy. Oral etoposide (VP-16) has shown clinical efficacy in advanced small cell lung carcinoma, breast cancer, germ cell tumors, and lymphomas, A synergistic effect between etoposide and alkylating agents such as estramustine was recently reported. We began a prospective Phase II study of an oral combination of cyclophosphamide (CPM) and VP-16 in patients with hormone-refractory [correction of refactory] prostate carcinoma (HRPC).

METHODS

Patients were orally treated with CPM (100 mg/day) and VP-16 (50 mg/day) for 14 days every 28 days. Therapy continued until there was evidence of disease progression.

RESULTS

From November, 1992, to February, 1995, 20 patients with HRPC were entered into the study. Patients were eligible if they had an ECOG performance status (PS) of 0 to 2. All of the patients presented with bone metastasis, and 70% presented with bone pain. Seventy-five percent had failed at least two hormonal manipulations. The mean duration of treatment was 5 months (range 2-12). Performance status improved in 26% of the patients, and bone pain was relieved in 71%. An objective response was defined as a decrease of 50% or more in the prostate-specific antigen (PSA) level. One patient demonstrated a complete response, and six patients had partial responses assessed by PSA plasma levels (objective response rate: 35%). The mean duration of response was 8 +/- 6 months (range: 2-24). Median survival was 11 months. Toxicities were minimal.

CONCLUSIONS

The combination of oral CPM and VP-16 may be an active and well tolerated regimen for patients with HRPC.

Treatment of Androgen-Independent Prostate Cancer

Androgen-ablative therapy for metastatic prostate cancer is effective for 60%-80% of men, but its effects are always finite and the majority of men develop androgen-independent disease within two years. Although current therapies for androgen-independent disease have not been shown to impact on survival, recent clinical and laboratory insights offer hope for effective therapy. For instance, recent data indicate that androgen-independent disease may still be dependent on hormonal stimulation, suggesting that hormonally based therapies may provide continued benefit. Chemotherapy, especially with estramustine and etoposide, seems to be an effective combination for a majority of patients. Treatment with suramin had been hampered by its side effects, but new dosing schedules are effectively circumventing toxicity. Radioisotopes such as strontium 89 have been shown to provide effective palliation for a majority of androgen-independent patients. Overall, these and other emerging efforts may be the foundation for therapies that offer hope for a significant survival benefit.

Therapy for hormone-resistant prostate cancer: no longer a myth

In conclusion, there have been impressive efforts to identify new cellular targets for the treatment of hormone-refractory disease. It appears that in some cases, survival may be extended; however, further prospective trials are necessary to confirm these observations.

Phase II study of topotecan in metastatic hormone-refractory prostate cancer

Systemic chemotherapy with currently available agents has not improved survival for patients with hormone refractory prostate cancer (HRPC), consequently, the evaluation of new agents is warranted. Topotecan is a specific inhibitor of topoisomerase I with broad antitumor activity in preclinical studies. The purpose of this phase II trial was to determine the objective response rate of topotecan administered as a 30 minute infusion for five consecutive days in men with metastatic HRPC. Thirty-four evaluable patients were treated with topotecan 1.1-1.5 mg/m2 as a 30 minute infusion daily for five days, repeated every three weeks until disease progression or unacceptable toxicity. Response was assessed with a combination of standard solid tumor response criteria and the serum prostate specific antigen (PSA) for patients with bidimensionally measurable disease, and by serial measurements of the PSA in patients with bone only (evaluable) disease. One of 13 patients (7.6%) with measurable soft tissue disease had a PR in nodal sites. Of 21 patients with only osseous metastases, 1 (4.7%) had improvement in bone scan. Six of the 34 evaluable patients (17.6%) had the serum PSA decrease by > or = 50% and 2 (5.8%) had PSA decreases of > or = 75%. Toxicity was chiefly hematologic with 66% of patients experiencing Grade 3 or 4 granulocytopenia. Thirty-nine percent of cycles required a delay to allow for hematologic recovery and ten patients required red cell transfusions. Non-hematologic toxicity, mainly nausea and alopecia, was mild. Topotecan administered at this dose and schedule has limited activity in patients with HRPC. Further trials of topo I inhibition in HRPC should utilize alternative schedules of topotecan (e.g., prolonged infusion) or other camptothecin analogs with more potent topo I inhibitory activity.