Clinical outcomes in men of diverse ethnic backgrounds with metastatic castration-resistant prostate cancer.

BACKGROUND: We have shown previously in multivariable analysis that black men had 19% lower risk of death than white men with metastatic castration-resistant prostate cancer (mCRPC) treated with a docetaxel and prednisone (DP)-based regimen. The primary goal of this analysis was to compare progression-free survival (PFS), biochemical PFS, ≥50% decline in prostate-specific antigen (PSA) from baseline and objective response rate (ORR) in white, black and Asian men with mCRPC treated with a DP-based regimen. PATIENTS AND METHODS: Individual patient data from 8820 mCRPC men randomized on nine phase III trials to a DP-containing regimen were combined. Race used in the analysis was based on self-report. End points were PFS, biochemical PSA, ≥50% decline in PSA from baseline and ORR. The proportional hazards and the logistic regression models were employed to assess the prognostic importance of race in predicting outcomes adjusting for established prognostic factors. RESULTS: Of 8820 patients, 7528 (85%) were white, 500 (6%) were black, 424 were Asian (5%) and 368 (4%) had race unspecified. Median PFS were 8.3 [95% confidence interval (CI) 8.2-8.5], 8.2 (95% CI 7.4-8.8) and 8.3 (95% CI 7.6-8.8) months in white, black and Asian men, respectively. Median PSA PFS were 9.9 (95% CI 9.7-10.4), 8.5 (95% CI 8.0-10.3) and 11.1 (95% CI 9.9-12.5) months in white, black and Asian men, respectively. CONCLUSIONS: We observed no differences in clinical outcomes by race and ethnic groups in men with mCRPC enrolled on these phase III clinical trials with DP.

Serial blood-based analysis of AR-V7 in men with advanced prostate cancer.

BACKGROUND: We previously showed that pretreatment detection of androgen receptor splice variant-7 (AR-V7) in circulating tumor cells (CTCs) from men with castration-resistant prostate cancer is associated with resistance to abiraterone and enzalutamide, but not to taxane chemotherapies. Here, we conducted serial measurements of AR-V7 and evaluated patterns of longitudinal AR-V7 dynamics over the course of multiple sequential therapies. PATIENTS AND METHODS: Metastatic prostate cancer patients treated at Johns Hopkins with AR-directed therapies or taxane chemotherapies underwent serial liquid biopsies for CTC-based AR-V7 analysis at baseline, during therapy, and at progression. We used a CTC enrichment platform followed by multiplexed reverse-transcription polymerase chain reaction analysis to detect full-length androgen receptor and AR-V7 transcripts. Patients selected for inclusion in this report were those who provided ≥4 CTC samples, at least one of which was AR-V7 positive, over the course of ≥2 consecutive therapies. RESULTS: We identified 14 patients who received a total of 37 therapies and contributed 70 CTC samples for AR-V7 analysis during a median follow-up period of 11 months. Three patients remained AR-V7 positive during the entire course of therapy. The remainder underwent transitions in AR-V7 status: there were eight instances of 'conversions' from AR-V7-negative to -positive status (during treatment with first-line androgen deprivation therapy, abiraterone, enzalutamide, and docetaxel), and six instances of 'reversions' from AR-V7-positive to -negative status (during treatment with docetaxel and cabazitaxel). CONCLUSIONS: AR-V7 is a dynamic marker, and transitions in AR-V7 status may reflect selective pressures on the tumor exerted by therapeutic interventions. While 'conversions' to AR-V7-positive status were observed with both AR-directed therapies and taxane chemotherapies, 'reversions' to AR-V7-negative status only occurred during taxane therapies. Serial blood-based AR-V7 testing is feasible in routine clinical practice, and may provide insights into temporal changes in tumor evolution.

Neutrophil-to-lymphocyte ratio as a prognostic biomarker for men with metastatic castration-resistant prostate cancer receiving first-line chemotherapy: data from two randomized phase III trials.

BACKGROUND: The neutrophil-to-lymphocyte ratio (NLR), a marker of host inflammation, has been associated with poor outcome in several solid tumors. Here, we investigated associations of the derived NLR (dNLR) and duration of initial androgen deprivation therapy (ADT) with survival of men with metastatic castration-resistant prostate cancer (mCRPC) receiving first-line chemotherapy. PATIENTS AND METHODS: Data from the multinational randomized phase III studies VENICE and TAX327 included a total of 2230 men with mCRPC randomized to receive first-line chemotherapy, and were used as training and validation sets, respectively. Associations of dNLR and duration of initial ADT with overall survival (OS) were evaluated by multivariable Cox regression analysis in the training set stratified for performance status and treatment arm. The model was then tested in the validation set. Subsequently, we investigated the treatment effect of docetaxel on OS in subgroups according to dNLR and duration of initial ADT. RESULTS: In the training set, both dNLR ≥median (2) and duration of initial ADT

Metastasis-free survival is associated with overall survival in men with PSA-recurrent prostate cancer treated with deferred androgen deprivation therapy.

BACKGROUND: Clinical trials in men with biochemically recurrent prostate cancer (BRPC) have been hampered by long survival times, making overall survival (OS) a difficult end point to reach. Intermediate end points are needed in order to conduct such trials within a more feasible time frame. PATIENTS AND METHODS: This is a retrospective analysis of 450 men with BRPC following prostatectomy treated at a single institution between 1981 and 2010, of which 140 developed subsequent metastases. Androgen deprivation therapy (ADT) was deferred until after the development of metastases. Cox regression models were developed to investigate factors influencing OS. RESULTS: Median metastasis-free survival (MFS) was 10.2 years [95% confidence interval (CI) 7.6-14.0 years]; median OS after metastasis was 6.6 years (95%CI 5.8-8.4 years). Multivariable Cox regressions identified four independently prognostic variables for OS: MFS (HR 0.77; 95% CI 0.63-0.94), number of metastases (≤3 versus ≥4; HR 0.50; 95% CI 0.29-0.85), pain (absent versus present; HR 0.43; 95% CI 0.25-0.72), and bisphosphonate use (yes versus no; HR 0.60; 95% CI 0.37-0.98). CONCLUSIONS: MFS emerged as an independent predictor of OS in men with BRPC treated with deferred ADT after the development of metastases. MFS may be a reasonable intermediate end point in future clinical trials. This observation requires prospective validation.

A phase I/IIA study of AGS-PSCA for castration-resistant prostate cancer.

BACKGROUND: This first-in-human phase I/IIA study was designed to evaluate the safety and pharmacokinetics (PKs) of AGS-PSCA a fully human monoclonal antibody directed to prostate stem cell antigen (PSCA) in progressive castration-resistant prostate cancer. PATIENTS AND METHODS: Twenty-nine patients were administered infusions of AGS-PSCA (1-40 mg/kg) every 3 weeks for 12 weeks; 18 final patients received a 40-mg/kg loading dose followed by 20-mg/kg repeat doses. Primary end points were safety and PK. Immunogenicity, antitumor activity and circulating tumor cells were also evaluated. RESULTS: No drug-related serious adverse events were noted. Dose escalation stopped before reaching the maximum tolerated dose as target concentrations were achieved. Drug levels accumulated linearly with dose and the mean terminal half-life was 2-3 weeks across dose levels. The 40-mg/kg loading dose followed by repeated 20-mg/kg doses yielded serum drug concentrations above the projected minimum therapeutic threshold after two to three doses without excessive drug accumulation or toxicity. Significant antitumor effects were not seen. CONCLUSIONS: A 40-mg/kg loading dose followed by 20-mg/kg infusions every 3 weeks is the recommended phase II dose of AGS-PSCA. PSCA is a promising drug target and studies in prostate and other relevant solid tumors are planned.

Identification of endothelin-1 in the pathophysiology of metastatic adenocarcinoma of the prostate.

Prostate cancer is the second most common cause of death from cancer in U.S. men, and advanced, hormone-refractory disease is characterized by painful osteoblastic bone metastases. Endothelin-1, more commonly known as a potent vasoconstrictor, is a normal ejaculate protein that also stimulates osteoblasts. We show here that plasma immunoreactive endothelin concentrations are significantly elevated in men with metastatic prostate cancer and that every human prostate cancer cell line tested produces endothelin-1 messenger RNA and secretes immunoreactive endothelin. Exogenous endothelin-1 is a prostate cancer mitogen in vitro and increases alkaline phosphatase activity in new bone formation, indicating that ectopic endothelin-1 may be a mediator of the osteoblastic response of bone to metastatic prostate cancer.

Suramin, an active drug for prostate cancer: interim observations in a phase I trial.

BACKGROUND: Previous studies indicate that suramin may be an active agent for treatment of solid tumors. The clinical use of suramin is complicated by a broad spectrum of toxic effects and complex pharmacology. Studies have suggested that the dose-limiting neurotoxicity of this agent is closely related to sustained plasma drug concentrations of 350 micrograms/mL or more. PURPOSE: This phase I clinical trial in patients with solid tumors was designed to determine whether plasma concentrations resulting in both antitumor activity and manageable toxicity could be achieved with short, intermittent infusions of suramin. METHODS: Thirty-seven patients, including 33 with metastatic, hormone-refractory prostate cancer, collectively received 43 courses of suramin designed to maintain a plasma concentration range of 200-300, 175-275, or 150-250 micrograms/mL. Patients received a test dose of 200 mg and an initial loading dose of 1000 mg/m2 on day 1 of therapy. Subsequent suramin doses and schedules were individually determined using a strategy of adaptive control with feedback, which used a maximum a posteriori Bayesian algorithm to estimate individual pharmacokinetic parameters. Patients were treated until dose-limiting toxicity or progressive disease developed. RESULTS: Thirty-five of the 37 study patients and 31 of the 33 with prostate cancer were assessable for toxicity and response. Treatment was discontinued in 28 patients because of dose-limiting toxicity consisting of a syndrome of malaise, fatigue, and lethargy; recurrent reduction in creatinine clearance of 50% or more; or axonal neuropathy. Evidence of major antitumor activity was observed in patients with prostate cancer treated at all three plasma drug concentrations. Measurable responses (one complete response and five partial responses) were noted in six of 12 patients with measurable disease. Twenty-four (77%) of 31 patients had a reduction in prostate-specific antigen of 50% or more, and 17 (55%) of 31 had a reduction of 75% or more. Twenty (83%) of 24 patients reported reduction in pain. CONCLUSIONS: Suramin can be safely administered as an intermittent bolus injection by use of adaptive control with feedback to control plasma drug concentrations; toxicity is significant but manageable and reversible. Suramin is active against hormone-refractory prostate cancer. IMPLICATIONS: Future trials should address the role and necessary extent of therapeutic drug monitoring; the optimal plasma drug concentration range and duration of therapy; and the activity of suramin in combination with other agents, in earlier stages of prostate cancer, and in other tumor types.

Gonadotropin hormone-releasing hormone analogues: a new therapeutic approach for prostatic carcinoma.

The introduction of potent analogues of gonadotropin hormone-releasing hormone (GnRH) into clinical practice and their use in patients with metastatic prostatic carcinoma provides an effective alternative to the exogenous administration of pharmacologic doses of estrogens or surgical castration. Their advantages over estrogens are primarily related to a lower incidence of cardiovascular toxicity and gynecomastia. Their choice over orchiectomy is based on cosmetic and psychologic factors since their endocrine effects and clinical benefits are virtually the same. In this review, we describe the current experience with GnRH analogues in the treatment of prostatic carcinoma and discuss their use in the context of other endocrine manipulations. GnRH analogues act on the pituitary and indirectly affect gonadal function, and represent an opportunity for combination with other compounds capable of suppressing or interfering with the effects of circulating and androgens. The availability of several new compounds affecting different aspects of androgen metabolism provides promise for rational drug selection and testing.

Evaluation of prostate-specific antigen as a surrogate marker for response of hormone-refractory prostate cancer to suramin therapy.

PURPOSE: We evaluated the surrogate role of serum prostate-specific antigen (PSA) using prospectively collected information from patients with hormone-refractory prostate cancer (HRPC) treated with suramin. MATERIALS AND METHODS: Data from 103 patients were analyzed using survival analysis, exploratory analysis, and regression analysis. RESULTS: There was a significant survival difference between groups of patients with a PSA decrease of < or = 0% or greater than 0% (P = .018). There were no significant overall survival differences between groups of patients with PSA decreases less than 50% or > or = 50% and less than 75% or > or = 75%. Tree-based modeling did not define a specific threshold percentage PSA change as a response criterion. For a response of 1-year survival, sensitivity increased (0.91 v 0.69), but specificity decreased (0.37 v 0.62), with a 75% versus 50% PSA decrease used as classification criterion. Differences between the area under the receiver-operating curves (ROCs) with 50% and 75% PSA decreases as threshold values were small. For a response of 1-year survival, attributable proportions were 0.38 and 0.68, respectively, with 50% and 75% PSA decreases as threshold values. When pretreatment variables were assessed by Cox proportional hazards model, hemoglobin level was the most significant predictor of survival. When percentage PSA change was included in the model, hemoglobin level remained the most significant factor, but percentage PSA change was also a weak, but statistically significant, factor. PSA was a weak, but statistically significant, predictor of survival in Cox proportional hazards model with PSA as a time-variant covariate. CONCLUSION: Reduction in PSA level has weak prognostic significance with respect to survival in HRPC patients, but, currently, PSA reduction cannot be used as a reliable response criterion to evaluate treatment efficacy in individual patients. Prospective, randomized studies, including prospective measurement of other indices related to symptomatic clinical benefits, are required.

Development and validation of a pharmacokinetically based fixed dosing scheme for suramin.

PURPOSE: We used population pharmacokinetic-parameter estimates and designed a fixed dosing schedule to maintain plasma suramin concentrations between 100 and 300 micrograms/mL and then evaluated its performance. MATERIALS AND METHODS: On day 1, patients received a 200-mg test dose and 1,000-mg/m2 loading dose. On days 2, 3, 4, and 5, patients received 1-hour infusions of 400, 300, 250, and 200 mg/m2, respectively. Subsequent 1-hour infusions of 275 mg/m2 were given on days 8, 11, 15, 19, 22, 29, 36, 43, 50, 57, 67, and 78. Therapy was discontinued for dose-limiting toxicity (DLT) or progressive disease (PD). Patients were to be removed from the fixed dosing schedule if, after day 5, three consecutive peak plasma suramin concentrations were greater than 300 micrograms/mL. RESULTS: Forty-two patients, including 40 with hormone-refractory prostate cancer (HRPC), received 700 infusions. Forty patients were assessable for toxicity; 38 were assessable for response. Two patients with preexisting pulmonary disease died early of respiratory insufficiency. Treatment was discontinued in five patients due to DLT and in seven due to PD. No patient had treatment discontinued due to repeated peak plasma suramin concentrations > or = 300 micrograms/mL. The fixed dosing schedule was precise, unbiased, and well tolerated. DLT consisted of grade 4 nephrotoxicity (n = 2), neurotoxicity (n = 2), and corticosteroid-induced psychosis (n = 1). Three patients, who received all 18 doses of suramin per protocol, developed severe, but not dose-limiting, malaise, fatigue, and lethargy. Twenty-four of 36 assessable patients with elevated serum prostate-specific antigen (PSA) levels had a > or = 50% reduction, lasting more than 4 weeks, and 18 had a > or = 75% reduction, lasting more than 4 weeks. Twelve of 23 (52%) symptomatic HRPC patients noted a subjective improvement in pain. There were no measurable responses in four patients with measurable disease. The estimated median survival time in 38 assessable patients with HRPC was 18.8 months. The estimated median time to progression in 35 patients, for whom data were available, was 10.1 months. CONCLUSION: This easily implemented schedule allowed suramin to be administered safely as an intermittent bolus injection. Toxicity was manageable and reversible.

A reevaluation of nonhormonal cytotoxic chemotherapy in the treatment of prostatic carcinoma.

The palliative role of nonhormonal cytotoxic chemotherapy in the treatment of endocrine-resistant prostatic carcinoma has not been established. Conventional means of quantifying tumor response are most frequently not applicable in this disease because of the lack of measurable objective parameters to allow for a reliable estimation of antitumor effects. While this problem is not unique to prostatic carcinoma, this review illustrates its magnitude in this disease. Only approximately 5% of patients studied fulfill the various criteria for complete response (CR), partial response (PR), or both, while the vast majority of patients reported as responders are actually in the stable disease category. Stable disease is highly questionable as an indicator of antitumor response and should not be used as a criterion for response in conventional phase II studies unless it is convincingly demonstrated that it occurs as a result of treatment. A study design that may allow a more reliable assessment of the value of the stable disease category is described in the text. More effective means for assessing tumor responses and better instruments to measure aspects of quality of life are needed. Review of several prospective randomized clinical trials showed that no treatment program tested during the last decade resulted in a survival advantage when compared with a concurrently treated control group. Furthermore, in two such trials, four different single chemotherapeutic agents widely used in the treatment of this disease (cyclophosphamide, 5-fluorouracil, estramustine phosphate, and streptozocin) either alone or in combination, did not produce any prolongation of survival when compared to a no chemotherapy (standard treatment) control arm. Survival curves for endocrine-resistant patients fall within a relatively narrow and possibly predictable range that may be used as an additional endpoint in conjunction with response (CRs and PRs only) in phase II trials. More definitive evidence of therapeutic efficacy in this disease should derive from phase III trials using survival as one of the major endpoints. Because of the poor results observed with chemotherapy thus far, we suggest that the appropriate control arm for phase III testing in endocrine-resistant patients continues to be a no chemotherapy control arm consisting of a best symptomatic care or a uniformly applied second-line endocrine manipulation.

Androgen deprivation and four courses of fixed-schedule suramin treatment in patients with newly diagnosed metastatic prostate cancer: A Southwest Oncology Group Study.

PURPOSE: To assess the feasibility of administering a combination of suramin and hydrocortisone in addition to androgen deprivation in a cooperative group setting; to assess the feasibility of treatment with multiple courses of suramin; and to assess progression-free and overall survival in patients with newly diagnosed metastatic prostate cancer who underwent such treatment. PATIENTS AND METHODS: Patients with newly diagnosed metastatic prostate cancer who had adequate hematologic, hepatic, renal, neurologic, and coagulation parameters were treated by combined androgen deprivation and suramin plus hydrocortisone. Suramin was administered on a 78-day fixed dosing schedule (one cycle), and suramin treatment cycles were repeated every 6 months for a total of four cycles. The statistical design was developed on the basis of the feasibility of administering suramin, as judged by the number of patients who developed neurotoxicity of grade 3 or higher or by treatment interruption of 4 weeks or longer due to any persistent suramin-related toxicity. RESULTS: Of the 62 patients enrolled onto the study between August 1994 and January 1997, 59 were eligible and assessable for toxicity on the first cycle. Thirty-two (54%) of 59 patients received a second cycle, 13 (22%) of 59 patients received a third cycle, and only five patients (8%) received a fourth cycle. During the first cycle, 27 patients were removed from the study: 17 because of toxicity, five because of disease progression, two who had died, and three because of other reasons. There was one therapy-related death. Grade 4 toxicities were noted in 11 and three patients during first and second courses, respectively. Neurotoxicity of grade 3 or higher was observed in nine and seven patients during the first and second cycles, respectively. Fifteen patients had treatment interruptions of 4 weeks or longer. Overall, only 54% (95% confidence interval, 41% to 67%) of the patients demonstrated acceptable limits of toxicity. CONCLUSION: Suramin plus hydrocortisone and androgen deprivation has limited applicability in the treatment of patients with newly diagnosed metastatic prostate cancer.

Suramin: development of a population pharmacokinetic model and its use with intermittent short infusions to control plasma drug concentration in patients with prostate cancer.

PURPOSE: This study aimed to (1) develop a population pharmacokinetic model for suramin; (2) use Bayesian methods to assess suramin pharmacokinetics in individual patients; (3) use individual patients' pharmacokinetic parameter estimates to individualize suramin dose and schedule and maintain plasma suramin concentrations within predetermined target ranges; and (4) assess the feasibility of outpatient administration of suramin by intermittent, short infusions. METHODS: Plasma suramin concentrations were measured by high-performance liquid chromatography (HPLC), and compartmental pharmacokinetic models were fit using a Bayesian algorithm. Population pharmacokinetic models were developed using an iterative two-stage approach. Estimates of each patient's central-compartment volume were used to calculate suramin dosage. Simulation of that patient's suramin clearance was used to predict the time of his next dose. Using this approach, plasma suramin concentration was maintained at between 200 and 300, 175 and 275, 150 and 250, or 100 and 200 microgram/mL in four sequential patient cohorts. The ability of two- and three-compartment, open, linear models to fit the pharmacokinetic data was compared. Population pharmacokinetic parameters were estimated, using both two- and three-compartment structural models in 69 hormone-refractory prostate cancer patients. RESULTS: Target plasma suramin concentrations in individual patients were rapidly achieved. Concentrations were maintained within desired ranges for > or = 85% of treatment duration in all cohorts. A three-compartment, open, linear model described suramin pharmacokinetics better than did a two-compartment, open, linear model. Population pharmacokinetic estimates generated for two- and three-compartment pharmacokinetic models demonstrated modest interpatient pharmacokinetic variability and the long terminal half-life of suramin. CONCLUSION: Suramin can be administered by intermittent short infusion. Adaptive-control-with-feedback dosing facilitated precise control of plasma suramin concentrations and allowed a number of different concentration ranges to be studied. This approach is expensive and labor-intensive. Although we have demonstrated the ability to control drug exposure, simpler dosing schedules require critical evaluation. Population pharmacokinetic parameters generated in men with hormone-refractory prostate cancer will facilitate rational design of such schedules.

Phase I and clinical evaluation of a pharmacologically guided regimen of suramin in patients with hormone-refractory prostate cancer.

PURPOSE: This phase I study was designed with the following objectives: (1) to describe the overall and dose-limiting toxicity (DLT) of suramin administered by intermittent short intravenous infusions until DLT or disease progression; (2) to determine the ability of an adaptive control with feedback (ACF) dosing strategy to maintain suramin plasma concentrations within a preselected range; (3) to develop a population model of suramin pharmacokinetics; and (4) to identify preliminary evidence of antitumor activity. PATIENTS AND METHODS: Seventy-three patients with advanced, incurable, solid tumors (including 69 with hormone-refractory prostate cancer) received an initial 5- to 7-day daily loading treatment followed by intermittent infusions individually determined by ACF using a Bayesian algorithm and relying on population models of suramin pharmacokinetics. Treatment was given to three cohorts of patients based on target plasma suramin concentration ranges (peak, 30 minutes postsuramin, and trough on morning of the treatment day), as follows: cohort 1, 175 to 300 micrograms/mL (27 patients); cohort 2, 150 to 250 micrograms/mL (23 patients); and cohort 3, 100 to 200 micrograms/mL (23 patients). All patients were to receive suramin until DLT or disease progression. RESULTS: The DLT was most commonly seen in cohort 1 and included a syndrome of malaise and fatigue, associated with weight loss, anorexia, and changes in taste. Other reversible toxicities were neurologic, renal, cutaneous, edema, lymphopenia and anemia, ophthalmologic, and alopecia. Forty of 67 assessable patients (60%) had a 50% reduction and 25 of 67 (37%) a 75% reduction in prostate-specific antigen (PSA) levels that lasted more than 4 weeks, seven of 18 (40%) had measurable responses, and 18 of 37 (49%) demonstrated major pain improvement. The overall times to disease progression and survival were 170 and 492 days, respectively. CONCLUSION: We have characterized all toxicities with suramin in a pharmacologically guided phase I study designed to maintain plasma suramin concentrations of 100 to 300 micrograms/mL (cohorts 1 to 3). The incidence of grade 3 to 4 neurologic abnormalities was relatively low, particularly in cohorts 2 and 3 (100 to 250 micrograms/mL). Evidence of significant and durable antitumor activity was seen in all three cohorts.

A Phase I clinical and pharmacological evaluation of sodium phenylbutyrate on an 120-h infusion schedule.

PURPOSE: Sodium phenylbutyrate (PB) demonstrates potent differentiating capacity in multiple hematopoietic and solid tumor cell lines. We conducted a Phase I and pharmacokinetic study of PB by continuous infusion to characterize the maximum tolerated dose, toxicities, pharmacokinetics, and antitumor effects in patients with refractory solid tumors. PATIENTS AND METHODS: Patients were treated with a 120-h PB infusion every 21 days. The dose was escalated from 150 to 515 mg/kg/day. Pharmacokinetics were performed during and after the first infusion period using a validated high-performance liquid chromatographic assay and single compartmental pharmacokinetic model for PB and its principal metabolite, phenylacetate. RESULTS: A total of 24 patients were enrolled on study, with hormone refractory prostate cancer being the predominant tumor type. All patients were evaluable for toxicity and response. A total of 89 cycles were administered. The dose-limiting toxicity (DLT) was neuro-cortical, exemplified by excessive somnolence and confusion and accompanied by clinically significant hypokalemia, hyponatremia, and hyperuricemia. One patient at 515 mg/kg/day and another at 345 mg/kg/day experienced this DLT. Toxicity resolved < or =12 h of discontinuing the infusion. Other toxicities were mild, including fatigue and nausea. The maximum tolerated dose was 410 mg/kg/day for 5 days. Pharmacokinetics demonstrated that plasma clearance of PB increased in a continuous fashion beginning 24 h into the infusion. In individuals whose V(max) for drug elimination was less than their drug-dosing rate, the active metabolite phenylacetate accumulated progressively. Plasma PB concentrations (at 410 mg/kg/day) remained above the targeted therapeutic threshold of 500 micromol/liter required for in vitro activity. CONCLUSION: The DLT in this Phase I study for infusional PB given for 5 days every 21 days is neuro-cortical in nature. The recommended Phase II dose is 410 mg/kg/day for 120 h.

Evaluation of biomarkers of survival response in hormone-refractory prostate cancer patients treated with suramin.

Hormone-refractory prostate cancer (HRPC) patients often have nonmeasurable disease. In such patients, predictive biomarkers other than tumor response may be required to compare therapeutic effects. We examined the predictive value for survival of various clinical and laboratory parameters, including prostate-specific antigen (PSA), in HRPC patients treated with suramin. Data from 103 HRPC patients were analyzed using various survival analyses, the likelihood ratio approach, and logistic regression analyses. When pretreatment factors, percentage decrease in PSA at 4 weeks from start of treatment (deltaPSA), and updated survival data were fit by a multivariate Cox proportional hazards model, acid phosphatase, lactate dehydrogenase, and deltaPSA were significant, with risk ratios close to 1. There was a decrease in likelihood ratio with increasing APSA. A logistic regression model was developed to predict the probability of <1 year of survival from the start of treatment. Hemoglobin and deltaPSA were found to be significant variables. However, in view of the complexities involving the relationship between PSA expression and prostate cancer growth and possible selective effect of treatment on PSA, further prospective testing is necessary. Therefore, deltaPSA cannot necessarily be used as a biomarker for survival response in individual patients during the evaluation of the therapeutic response of HRPC to new antineoplastic drugs.

National Cancer Institute study of luteinizing hormone-releasing hormone plus flutamide versus luteinizing hormone-releasing hormone plus placebo.

A randomized, double-blind trial in patients with disseminated, previously untreated prostate cancer (stage D2) was designed to test the hypothesis that maximal androgen blockade improves the effectiveness of the treatment of prostatic cancer. Six hundred three men received leuprolide in combination with either placebo or flutamide, and were followed for a minimum of 5 years. The 303 patients randomly assigned to receive leuprolide and flutamide had a longer progression-free survival and an increase in the median length of survival compared with the 300 patients receiving leuprolide plus placebo. Differences between the treatments were particularly evident for men with minimal disease and good performance status.

Prostate cancer treatment strategies based on tumor-specific biological principles: future directions.

Prostate cancer represents a heterogeneous disease entity with varying degrees of behavior, aggressiveness, patterns of metastasis, and response to therapy. Progressive metastatic prostate cancer is associated with a formidable array of morbidity that ultimately contributes to death of the patient. Thus far, there has been no convincing evidence to support routine use of non-hormonal chemotherapeutic agents or combinations over symptomatic treatment only. Furthermore, no single compound or combination has shown a dramatic improvement in conventional quality of life parameters over symptomatic treatment only. Androgen ablation remains the primary systemic therapeutic modality for this disease, yet the intense delineation of mechanisms involved in tumor cell metastasis has lead to new therapeutic strategies, ranging from cytotoxic to cytostatic, including immunomodulators. Among those strategies currently being studied are granulocyte-macrophage colony-stimulating factor-transduced prostate cancer vaccines, differentiation therapy, gene therapy, inducers of apoptosis, antimetastatic agents, angiogenesis inhibitors, radiation therapy (local and systemic), and systemic approaches targeted at prostate cancer morbidity. The difficult issue is which agents should be developed and how should we best assess the response using standard and newly identified endpoints. Certainly, the future of advanced prostate cancer therapy will undergo dramatic changes as a result of the continued interaction between the laboratory and the clinic.

Interleukin-6: a candidate mediator of human prostate cancer morbidity.

OBJECTIVES: Interleukin-6 (IL-6) is evaluated as a candidate mediator of morbidity in patients with metastatic adenocarcinoma of the prostate. METHODS: IL-6 concentration is measured by enzyme-linked immunoadsorbent assay (ELISA) in the ejaculate plasma of healthy men, in primary culture of prostate epithelial cells, in human prostate cancer cell line cultures and SCID mouse xenografts, and in the plasma of 73 men with metastatic adenocarcinoma of the prostate. RESULTS: High levels of IL-6 secretion are found in the normal human ejaculate, in prostate epithelial primary culture, and in three of four anaplastic, androgen-independent human prostate cancer cell lines tested. In contrast, the hormone-responsive and PSA-secreting cell lines and the hormone-independent line PPC-1 do not secrete detectable levels of IL-6 by ELISA: The acquisition of a p53 mutation in LNCaP-GW and PPC-1 is not sufficient to confer the phenotype of high IL-6 secretion. Seventy-three men with well-characterized, advanced, hormone refractory prostate cancer prior to suramin therapy are tested for incidence of abnormal circulating levels of IL-6. Plasma IL-6 levels have a bimodal distribution, with the upper quartile of patients having abnormal levels from 9 to 61 pg/mL. A direct comparison of the high and low serum IL-6 groups show that elevated IL-6 levels are strongly correlated with objective measures of morbidity: decreased hematocrit, hemoglobin, and serum cholesterol, and increased white blood cell count and serum lactate dehydrogenase levels all in the absence of clinical infection. CONCLUSIONS: These data show that IL-6 is a prostate exocrine gene product, a candidate mediator of prostate cancer morbidity, and a candidate marker of disease activity for prospective clinical testing.

Assessment of hormone refractory prostate cancer.

OBJECTIVES: To define guidelines for the assessment of treatment in patients with hormone-refractory prostate cancer (HRPC). METHODS: In the light of modern research, and taking new treatment options into account, the Committee essays to specify different categories of patients entering clinical trials, and to define response criteria and those endpoints that are relevant in phase III studies and in short-term follow-up. RESULTS: HRPC comprises a range of disease states with varying responsiveness to therapy and length of survival. Patients with progression as evaluated by increasing prostate-specific antigen (PSA) values alone have a more favorable prognosis than those presenting with increasing tumor spread. In the assessment of these patients, the modes of previous therapy and the kind of tumor progression must be taken into account. The benefit of treatment of HRPC is often modest. While duration of survival remains the main and ultimate endpoint, the means of measuring short-term responsiveness to therapy are limited. A minority of patients have measurable tumor lesions. Decrease of PSA or other biochemical tumor markers may indicate depression of the tumor activity, but is not always associated with prolongation of survival. A variety of new treatments in HRPC are being investigated. They affect measurable tumor parameters in different ways. CONCLUSIONS: When a new agent is to be tested, it is important to measure all possible parameters before deciding which particular ones are appropriate for future investigations of this agent. In symptomatic patients, evaluation of subjective parameters, for example, relief of pain or improvement of performance status, is often the most reliable measure of treatment effect. However, these parameters should be clearly defined.