Estramustine resistance

Estramustine (EM), a conjugate of nornitrogen mustard and estradiol, is a antimicrotubule drug currently in use for the treatment of advanced prostatic carcinoma. Experimental data are accumulating concerning the antitumor effect of EM in other malignancies, and clinical studies in other malignancies are ongoing. This review summarizes the information available to date concerning the effects of EM and the development of drug resistance. EM depolymerizes microtubules by binding to microtubule-associated proteins (MAPs) as well as tubulin. Because of the radiosensitizing effect of this drug there has been a recent increase in interest concerning estramustine and its clinical use. Recently, it was proposed that EM induces an apoptotic cell death in glioma cells in vitro and in a rat model. EM resistance is distinct from MDR phenotype; it has been used in combination with antimitotic agents which are part of the MDR phenotype. Observations made with estramustine-resistant cell lines show the acquisition of estramustine resistance is a function of multiple adaptation by changes at tubulin expression pattern, and is also associated with changes in tau expression and phosphorylation.

Chemotherapy in advanced prostate cancer

In the United States, prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer death in men. Prostate cancer is a rare disease before age 40; however, the prevalence increases quickly to 80% by the age of 80, and with increasing life expectancy, hormone-refractory prostate cancer (HRPC) will soon represent the most common cancer in the male population in the United States and other Western countries. The evolution of early prostate cancer is variable and extends over many years; some tumors progress slowly or not at all, whereas others may progress more rapidly and be fatal after a few years. A widely held view is that chemotherapy has no role in HRPC because no single agent or combination has been shown to prolong survival in a randomized trial. This concept may be obsolete, as preliminary results for a number of approaches, mostly derived from laboratory observations, show that prostate cancers are not as resistant to chemotherapy as traditionally believed. The population of early "geriatric" HRPC patients is rapidly increasing, posing an even greater challenge to oncologists in coping with this difficult-to-manage patient population. In this article, we analyze the most novel chemotherapeutic combinations for the treatment of HRPC in otherwise healthy elderly men.

Effects of radiotherapy and estramustine on the microvasculature in malignant glioma

Tumour angiogenesis is essential for progression of solid tumours and constitutes an interesting target for therapy. However, impaired tumour blood supply may also be an important obstacle for treatment by radiotherapy and chemotherapy. Estramustine has been shown to increase tumour blood flow and potentiate the effect of radiotherapy in experimental glioma. This study investigated the effects of fractionated radiotherapy and estramustine on angiogenesis in malignant glioma. The intracerebral BT4C rat glioma model was used and the animals were given whole brain radiotherapy 4 Gy x 5 days alone or in combination with estramustine 20 mg kg(-1) i.p. daily. Tumour microvascular density (MVD) was assessed by manual and computerized morphometrical analysis. Expression of vascular endothelial growth factor (VEGF) was studied by in situ hybridization. Radiotherapy decreased MVD to 157 vessels per mm2 compared to 217 vessels per mm2 in controls. Estramustine counteracted this anti-angiogenic effect and potentiated the anti-tumoural effect of radiotherapy. In addition, vessel size increased after estramustine treatment. Five days after completion of radiotherapy the expression of VEGF was increased in the centre of the tumours. In conclusion, fractionated radiotherapy decreases microvascular density in experimental malignant glioma. This effect was abolished by estramustine. The anti-vascular effect of irradiation is important to recognize when combining radiotherapy with cytotoxic drugs.

Novel concept of antisurvival factor (ASF) therapy produces an objective clinical response in four patients with hormone-refractory prostate cancer: case report

BACKGROUND

Osteoblasts and osteoblast-derived survival growth factors, such as insulin-like growth factor I (IGF I), inhibit chemotherapy apoptosis of prostate cancer cells, thereby producing cytotoxic drug-resistant tumor growth, in vitro.

METHODS

We tested a novel therapeutic approach, referred to as antisurvival factor (AFS) therapy, that aimed at reduction of osteoblast-derived IGFs, using dexamethasone (4 mg per os, qD) and growth hormone (GH)-dependent liver-derived IGFs, using a somatostatin-analog (lanreotide, 30 mg, intramuscularly (i.m.), q14D) in combination with triptorelin (3.75 mg, intramuscularly, q28D) to produce a clinical response in 4 patients with progressing hormone-refractory prostate cancer.

RESULTS

The patients given ASF therapy exhibited an excellent improvement of clinical performance and a decline of prostate-specific antigen (PSA) within 2 months of ASF therapy. One of them experienced excellent clinical response (normalization of PSA), two experienced good clinical response (decline of PSA of more than 50%), and one experienced stabilization (decline of PSA of less than 50%).

CONCLUSIONS

We conclude that this novel concept of combination therapy, using ASF with hormone ablation, is a promising salvage therapy that should be further assessed with a randomized clinical trial.

Differential uptake of estramustine phosphate metabolites and its correlation with the levels of estramustine binding protein in prostate tumor tissue

Estracyt (EMP) has been used for the treatment of hormone refractory prostate cancer for many years. Recently, new data from combination studies have given rise to new interest in this old drug. Explanations for the synergy found in the clinic are many, but one major factor may be the previous indication that the drug accumulates in the prostate tumor. We have, therefore, examined the level of the four metabolites, estromustine (EoM), estramustine (EaM), estrone, and estradiol in the tumor and serum of 14 patients with T2 and T3 prostate cancer receiving a single i.v. dose of 600 mg of EMP, about 12 h before radical prostatectomy. Because it has been suggested that the uptake into the prostate tumor is due to binding to the estramustine binding protein (EMBP), we have in addition measured the level of EMBP in the prostate tumor tissue. The main serum and tissue metabolite in all patients was EoM followed by EaM, estrone, and estradiol. The levels for EoM ranged from 63.8-162.8 ng/ml in the serum and from 64.8-1209 ng/ml in the prostate tumor, resulting in a mean ratio for serum to tumor of 1:5. The levels for EaM ranged from 8.3-51.4 ng/ml in the serum and 73.9-563.4 ng/ml in the tumor, giving a mean ratio for serum to tumor of 1:13. The levels of EMBP were higher in T3 tumors than in T2 tumors, 54.1 and 40.7 ng/g tissue, respectively. A significant correlation was found between the levels of EaM (r = 0.60) and the levels of EMBP in the tumor. These data demonstrate that 12 h after a single i.v. dose of 600 mg of EMP the levels of the cytotoxic metabolites EoM and EaM are substantially higher in the tumor than in the serum of the same patient and that a correlation exists between the levels of EaM in the tumor and the levels of EMBP. Thus, this supports the hypothesis that the EMBP is responsible for the retention of EoM and EaM in the prostate tumor.

Antiemetic efficacy of prednisolone: a placebo-controlled trial in patients with advanced prostatic cancer treated with estramustine phosphate

The antiemetic effect of prednisolone on nausea/vomiting was investigated in 67 patients with advanced prostatic cancer and a performance status of < or = 2. The study was a double-blind, placebo-controlled, randomized trial with a parallel group design. The objective was to compare the incidence and severity of nausea/vomiting between the two groups. Prednisolone or placebo was given twice daily for 3 weeks with the dose decreased during the third week from 15 mg/day to 10 mg for 3 days and finally to 5 mg/day during the last 4 days. EMP was given as two 140 mg capsules daily for 3 days at the beginning, then as four capsules for 4 days followed by six capsules for 21 days. Areas under curves (AUCs) for nausea and for nausea/vomiting scores were calculated based on the patient's diary notes: nausea (0-3), vomiting (0-6), nausea/vomiting (0-9). Control of emesis in terms of complete, moderate or poor control was registered. Pretreatment characteristics were evenly balanced. The results indicated that no statistical differences between the two groups of patients were present in AUCs for weeks 1-3 or weeks 1-4. We conclude that it was not possible to demonstrate a significant antiemetic efficacy of prednisolone. However, in all but one case the patients in the prednisolone group could be treated for at least 3 weeks without any major incidents of nausea/vomiting.

Relationship of serum testosterone level with proliferating cell nuclear antigen and nm23 protein in human prostatic carcinoma tissue

OBJECTIVE

To elucidate the biological significance of proliferating cell nuclear antigen (PCNA) and nm23 immunoreactivity in prostatic carcinoma (PC) tissue, both expressions were immunohistochemically analyzed, and the results were compared with the change of the serum testosterone (T) level.

METHODS

The paraffin-embedded materials obtained from 49 untreated PC and 16 hormonally refractory PC (hr-PC) were used. Of the 49 untreated PC, 35 received luteinizing hormone-releasing hormone (LH-RH) analogue treatment, while 14 received a cisplatin-based chemotherapy. The immunohistochemistry of PCNA and nm23 protein was performed using an anti-PCNA monoclonal antibody (PC-10) and an antihuman nm23 polyclonal antibody (OA-11-890), respectively. The serum T level was measured by means of radioimmunoassay.

RESULTS

In both untreated PC and hr-PC, the immunoreactivity of nm23 protein significantly correlated with the PCNA expression. Both PCNA expression and nm23 protein immunoreactivity were higher in poorly differentiated PC than those observed in well-differentiated PC, while no significant difference in the serum T level was observed between poorly and well-differentiated PCs. On the other hand, both PCNA expression and nm23 protein immunoreactivity were significantly higher in hr-PC than those observed in untreated PC, whereas the serum T level was significantly lower in hr-PC. In 35 PCs treated with LH-RH analogue, no significant difference in both PCNA expression and nm23 protein immunoreactivity was found between those specimens obtained before and at 3 months after the treatment, while a significant reduction of the serum T level was noted at 3 months after the treatment. Similarly, in 14 PCs treated with a cisplatin-based chemotherapy, the same change of PCNA expression and nm23 protein immunoreactivity as observed in LH-RH analogue treatment was found, while no significant difference of the serum T level was found.

CONCLUSIONS

These findings appear to indicate that (1) nm23 protein immunoreactivity is interrelated with cellular proliferation in PC tissue and (2) alteration of the serum T level during a short period was not enough to explain the essential change of cellular proliferation of PC tissue, but might reflect other aspects of tumor growth such as apoptosis.

Cellular changes in prostatic carcinoma after treatment with orchidectomy, estramustine phosphate and medroxyprogesterone acetate

Thirty-three patients with prostatic carcinoma were treated with either estramustine phosphate, orchidectomy or high dose medroxyprogesterone acetate. Therapy response was evaluated by cytological examination of fine needle aspiration biopsies performed before and after 6 weeks treatment. At follow-up, 11 of 14 patients treated with estramustine phosphate had regressive and/or degenerative changes, in 2 patients there were no prostatic carcinoma cells in the smears and in one there was a marked reduction of the number of tumour cells. In 7 of 10 patients treated with orchidectomy there was a marked reduction of the percentage of malignant cells while smears from 3 patients were unchanged. In the 8 patients treated with high dose medroxyprogesterone acetate the cell patterns were unmodified compared with before treatment. We conclude that, in contrast to the lack of effect of treatment with medroxyprogesterone acetate, treatment with orchidectomy and especially estramustine phosphate caused morphologic cellular changes in prostatic carcinoma.

Estramustine phosphate versus placebo as second line treatment after orchiectomy in patients with metastatic prostate cancer: DAPROCA study 9002. Danish Prostatic Cancer Group

PURPOSE

We compared the effect of 560 mg. estramustine phosphate daily to placebo as a supplement to standard palliative therapy in patients with progressive disease after bilateral orchiectomy as first line therapy for metastatic prostate cancer.

MATERIALS AND METHODS

In a double-blind multicenter study 131 patients with progressing metastatic hormone refractory prostate cancer were randomized to receive 280 mg. estramustine phosphate 2 times daily versus placebo. End points were clinical progression and death. Adverse events, decrease in prostate specific antigen (PSA) and subjective response were also assessed.

RESULTS

Adverse events were common in both groups but breast tenderness/gynecomastia and diarrhea were more frequent among patients in the estramustine phosphate group. Subjective responses were few (9 of 50 estramustine phosphate and 4 of 57 placebo cases, p = 0.15). Median observation time for survival was 43 months and 124 patients died. Median time to subjective progression and median overall survival did not differ significantly between the 2 groups at 4.6 and 9.4 months in the estramustine phosphate group versus 5.0 and 6.1 months in the placebo group. Of 61 patients in the estramustine phosphate group 29 achieved a reduction in PSA of more than 25% at 1 month of followup compared to only 3 of 68 receiving placebo. A decrease in PSA after 1 month correlated significantly with survival.

CONCLUSIONS

Although this study did not prove estramustine phosphate to be superior to placebo in terms of protocol end points, it generates the hypothesis that prolonged survival may be achieved with estramustine phosphate treatment in a subgroup of patients and that this may be predicted by a decrease in PSA after 1 month of therapy.

[Effect of estramustine phosphate on hormone refractory prostate cancer]

Clinical effects of estramustine phosphate (EMT) on hormone refractory prostate cancer were studied. Prostate cancer relapsed in 70 of the 259 patients with stage C and D diseases who had initially responded to endocrine therapy. After cancer relapse, endocrine therapy was changed to oral administration of EMT in 21 patients, while initial endocrine therapy was continued in 14 and additional radiation therapy was given in 35. A partial response or no change was observed in 11 of the 21 patients (52%) given EMT therapy, the mean duration of the response being 14.2 months. The 21 patients given EMT therapy survived significantly longer than the 14 patients with continued on endocrine therapy, and those responding to EMT therapy tended to have a better survival than those unresponsive. Side effects of EMT included loss of appetite in 2 patients and edema of the lower limb in 1, but they were not severe enough to require discontinuation of the drug. EMT may be a useful drug for patients with advanced prostate cancer with relapse after endocrine therapy.

Combined hormono/chemotherapy as primary treatment for metastatic prostate cancer: a randomized, multicenter study of orchiectomy alone versus orchiectomy plus estramustine phosphate. The Dutch Estracyt Study Group

OBJECTIVES

Based on the theory that hormone-resistant cells are present in all metastatic patients, early administration of chemotherapy appears to be logical and its use is supported by experimental studies. Therefore, trials with combined hormonal and cytotoxic treatment as primary therapy should be conducted. In the present trial, the efficacy and tolerance of estramustine phosphate (EMP) as a chemotherapeutic agent in addition to hormonal treatment (orchiectomy) was studied in patients with metastatic and nonmetastatic prostate cancer not previously treated. EMP was chosen because it produces few serious adverse reactions and no cumulative toxicity.

METHODS

Four hundred nineteen patients were included in a 1.5-year period starting in January 1989. Patients with locally advanced prostate cancer or with bone metastases were randomized to orchiectomy (O) or orchiectomy followed by EMP (O + E), given until progression.

RESULTS

Analysis of the total group showed no significant difference in time to progression between the treatment groups. Because the course of the disease is different in patients with either T4 tumor only or with lymph node metastases only (M0) as compared with patients with bone metastases (M1) and because the number of progressions in the M0 patients was low, corresponding analyses were performed for these subgroups as well. In the M1 patients, there was a tendency for a longer time to progression in the O + E group than in the O group, but there was no indication of a difference between the groups with regard to survival. In the M0 patients, there was no indication of any difference in results between the treatments. Multivariate analysis of prognostic factors showed pain, alkaline phosphatase, metastasis status, and tumor stage to be significant factors. There was a relation between age and drug treatment in that a significant beneficial effect of EMP in terms of prolonged progression-free interval as well as survival was evident in younger patients (aged less than 73 years) with metastatic disease. Tumor stage was also of importance for the drug effect; T0 to T3 patients who received EMP survived longer than those who were treated with orchiectomy only. The most common adverse reaction was nausea in the O + E group, which led to discontinuation of the drug in 7 patients. Cardiovascular problems are not uncommon in this age group, and there was a higher incidence of cardiovascular events, predominantly cardiac failure, in the O + E group, leading to treatment interruption in 16 patients.

CONCLUSIONS

Our results indicate that future studies of hormono/chemotherapy should focus on younger patients with bone metastases.

Unique synergism or antagonism of combinations of chemotherapeutic and hormonal agents in human prostate cancer cell lines

OBJECTIVE

To evaluate combinations of anti-tumour agents in tissue cultures using three established cell lines derived from patients with prostate cancer to obtain potential candidates for therapeutic testing in patients with prostate cancer.

MATERIALS AND METHODS

Seventeen anti-tumour agents were tested for synergism or antagonism in combination studies in DU 145, PC 3 and LnCaP cell lines. After determining the dose required for 50% inhibition of growth in each, combinations were screened using the median-effect plot and combination-index isobolograms.

RESULTS

Estramustine (the primary product of dephosphorylation of estramustine phosphate) showed strong synergism in all three cell lines with hydroxyflutamide, the non-immunosuppressive cyclosporin analogue PSC 833, and Liarozole. In the hormone-sensitive cell line LnCaP alone, synergism was also observed with vinblastine, paclitaxel, docetaxel, bicalutamide, ketoconazole and all-trans-retinoic acid. Other synergistic combinations of two agents were: Liarozole plus docetaxel in LnCaP, PSC 833 plus bicalutamide in DU 145 and PC 3, dexamethasone plus docetaxel in LnCaP, and finasteride plus hydroxyflutamide. Synergistic combinations of three agents were: estramustine plus PSC 833 and Liarozole and schedule-dependent combinations of estramustine, PSC 833, and all-trans-retinoic acid.

CONCLUSION

Some of the synergistic combinations have shown clinical effects in patients with hormone-refractory prostate cancer. Based on these findings, new combinations, e.g. estramustine with either PSC 833 or Liarozole, need to be clinically evaluated.

A transient increase in serum procollagen 1 carboxyterminal peptide following effective treatment in prostate cancer patients with bone metastases

Procollagen 1 carboxyterminal peptide (P1CP) is thought to be an indicator of new bone formation. The present report demonstrates that effective endocrine therapy induced an initial increase followed by a delayed decrease in serum levels of P1CP and alkaline phosphatase in spite of an immediate decrease in serum PSA and PAP and improvement of clinical symptoms in prostate cancer patients with bone metastases. The transient increase in P1CP and alkaline phosphatase is a healing reaction and is followed by apparent improvement. Short-term effects of endocrine therapy on prostate cancer patients with bone metastases should be comprehensively evaluated based upon the entire spectrum of clinical and laboratory findings including serial changes of serum prostate markers and bone markers as well.

New therapeutic agents for hormone-refractory prostate cancer

The identification of active chemotherapeutic agents for use in the treatment of advanced hormone-refractory prostate cancer remains a priority of clinical research. An estimated 317,100 new cases will be diagnosed in 1996. This increased diagnosis of disease can be directly attributed to the widespread use of screening serum prostate-specific antigen. However, this has not been associated with a reduction in mortality; more than 41,000 men in the United States are expected to die of the disease this year. The natural history of hormone-resistant disease has remained unaltered, with patients having a median survival of only approximately 12 months. Use of surrogate endpoints, such as a reduction in prostate-specific antigen or improvement in pain, may be appropriate for the evaluation of novel agents or combinations. A number of promising new approaches have been recently tested and brought to trial, including combined antimicrotubular therapy, camptothecins, and matrix metalloproteinase inhibitors. It is only through the development of these and other novel compounds that we can hope to affect the natural course of prostate cancer.

Targeting microtubule-associated proteins in glioblastoma: a new strategy for selective therapy

BACKGROUND

This report presents a summary of preclinical data concerning the use of estramustine, an antimicrotubule agent against human glioblastoma cells. The strategy for the investigation of estramustine is predicated on the unique affinity of this agent for microtubule-associated proteins (MAPs).

METHODS

A series of laboratory investigations were used to demonstrate antiproliferative effects (MTT assay, colony forming assay, thymidine incorporation), cell cycle synchronization (flow cytometry), intracellular localization of binding sites (immunocytochemistry, electron microscopy), and activity in subcutaneous xenografts of human glioblastoma.

RESULTS

Estramustine has potent in vitro activity against human glioblastoma cells and can enhance the cytotoxic effects of ionizing radiation. Estramustine-binding protein was abundantly expressed in glioblastoma cells and may contribute to the selective effects of estramustine on neoplastic cells. This agent has activity against subcutaneous xenografts of human glioblastoma. Synthesized novel estrogen carbamates also can inhibit proliferation of glioblastoma cells.

CONCLUSIONS

Cytoskeletal elements (MAPs) of glioblastoma cells may provide a useful target for therapy with agents like estramustine because of the potent antimitotic effects of this agent and its affinity to a protein that is expressed in glioma cells. These observations have stimulated a search for other estrone carbamates with antimitotic activity that exceeds more conventional antimicrotubule agents.

Estramustine in malignant glioma

Estramustine, a carbamate ester combining 17 beta-estradiol and nornitrogen mustard, has primarily been employed in the treatment of advanced prostatic carcinoma. However, a significant amount of preclinical investigation has been directed toward estramustine's activity against human malignant glioma. These studies have demonstrated that estramustine has potent antiproliferative effects against malignant glioma both in vitro and in vivo. Similar antimitotic effects also have been demonstrated for other carbamate esters. Estramustine does not impair proliferation of nonneoplastic astrocytes at concentrations that inhibit glioma cells. Although the reasons for this selective activity remain to be determined, it has been shown that malignant gliomas expresses an estramustine-specific binding site, estramustine-binding protein, more than brain tissue. In the clinical situation, an uptake and accumulation of estramustine in human glioma tissue have been demonstrated. Estramustine has been shown to enhance the cytotoxic effects of irradiation in relatively radioresistant glioma cells both in cell culture and in a rat glioma model. Estramustine has been regarded as mainly an anti-mitotic drug but recently other effects such as inhibition of DNA synthesis, induction of apoptosis, and membrane alterations have been shown. This report summarizes the preclinical observations concerning the effects of estramustine and related compounds on human malignant gliomas. These findings form the basis for proposing further laboratory and clinical investigation regarding estramustine and human malignant gliomas.

Effect of concomitant administration of clodronate and estramustine phosphate on their bioavailability in patients with metastasized prostate cancer

Estramustine phosphate is generally used as a second-line treatment in patients with advanced prostate cancer. The bone metastases due to the cancer are often treated simultaneously with clodronate in order to relieve the bone pain. Therefore, the interaction of clodronate (800 mg orally four times daily) and estramustine phosphate (280 mg orally twice daily) on their bioavailability was studied in twelve patients with prostate carcinoma and bone metastases. The drugs were first given separately, each to six patients, for five days, and then concomitantly for the same period. The bioavailabilities of the drugs were calculated on the last day of each treatment period. When clodronate was given alone, its concentrations in serum and AUC for one dose interval (6 hr) did not differ from those obtained with the drug given concomitantly with estramustine phosphate, nor did the combination of estramustine phosphate change the excretion of clodronate in urine. The serum concentrations of estramustine phosphate were elevated by about 80% when the drug was given together with clodronate. The AUC for one dose interval (12 hr) was also significantly higher for estramustine phosphate with clodronate than without clodronate. The urinary excretion of estrone, a major metabolite of estramustine phosphate, was also significantly higher after the admission with clodronate. The results suggest that clodronate increases the oral bioavailability of estramustine phosphate.

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.

Salvage immunotherapy with subcutaneous recombinant interleukin 2 (rIL-2) and alpha-interferon (A-IFN) for stage D3 prostate carcinoma failing second-line hormonal treatment

Immunotherapy with subcutaneous rIL-2 and alpha IFN was administered to stage D3 prostate cancer patients after failure of secondary treatment with oral estramustine phosphate. Of a total of 15 patients, 2 are in partial response, with estramustine maintained after 44+ and 36+ weeks, respectively. Response to estramustine was observed initially in 7 of 13 patients, with a median duration of 12 weeks (range 8-20). No response to estramustine was observed in the remaining 6 patients. After the failure of estramustine, 13 patients were treated with immunotherapy. After the first cycle, progression of disease no therapy was given to those patients. A reduction of PSA levels was observed during the first cycle in 2 patients (15.3%); levels subsequently increased during the second cycle of treatment. A partial response was observed in 4 patients (30.7%), with a reduction of PSA levels in 3. The duration of response was 28 and 32 weeks in 2 patients who survived after failure for 18 and 21 weeks, respectively. Two patients are still alive, with continued partial response at 62+ and 42+ weeks. Side effects were represented mainly by a flu-like syndrome, associated with fever and nausea in all patients. The serum concentration of IL-10 was measured in 8 patients under study and in 11 matched controls. Levels higher than mean + 2D of controls before, during, or after immunotherapy were correlated with treatment failure, whereas levels below 6 ng/ml were encountered among the patients who showed a clinical response and a reduction of PSA during treatment. Within the limitations of this pilot study, it appears difficult to distinguish between a spontaneously slowly progressing disease and a true response to therapy.