Adjuvant sunitinib in patients with high-risk renal cell carcinoma: safety, therapy management, and patient-reported outcomes in the S-TRAC trial

Background

Adjuvant sunitinib has significantly improved disease-free survival versus placebo in patients with renal cell carcinoma at high risk of recurrence post-nephrectomy (hazard ratio 0.76; 95% confidence interval, 0.59–0.98; two-sided P = 0.03). We report safety, therapy management, and patient-reported outcomes for patients receiving sunitinib and placebo in the S-TRAC trial.

Patients and methods

Patients were stratified by the University of California, Los Angeles Integrated Staging System and Eastern Cooperative Oncology Group performance status score, and randomized (1 : 1) to receive sunitinib (50 mg/day) or placebo. Single dose reductions to 37.5 mg, dose delays, and dose interruptions were used to manage adverse events (AEs). Patients’ health-related quality of life, including key symptoms typically associated with sunitinib, were evaluated with the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30).

Results

Patients maintained treatment for 9.5 (mean, SD 4.4) and 10.3 (mean, SD 3.7) months in the sunitinib and placebo arms, respectively. In the sunitinib arm, key AEs occurred ∼1 month (median) after start of treatment and resolved within ∼3.5 weeks (median). Many (40.6%) AEs leading to permanent discontinuation were grade 1/2, and most (87.2%) resolved or were resolving by 28 days after last treatment. Patients taking sunitinib showed a significantly lower EORTC QLQ-C30 overall health status score versus placebo, although this reduction was not clinically meaningful. Patients reported symptoms typically related to sunitinib treatment with diarrhea and loss of appetite showing clinically meaningful increases.

Conclusions

In S-TRAC, AEs were predictable, manageable, and reversible via dose interruptions, dose reductions, and/or standard supportive medical therapy. Patients on sunitinib did report increased symptoms and reduced HRQoL, but these changes were generally not clinically meaningful, apart from appetite loss and diarrhea, and were expected in the context of known sunitinib effects.

Clinical trial registration

ClinicalTrials.gov, NCT00375674.

Patient experience in the treatment of metastatic castration-resistant prostate cancer: state of the science

Background:

Contemporary therapies for metastatic castration-resistant prostate cancer (mCRPC) have shown survival improvements, which do not account for patient experience and health-related quality of life (HRQoL).

Methods:

This literature review included a search of MEDLINE for randomized clinical trials enrolling ⩾50 patients with mCRPC and reporting on patient-reported outcomes (PROs) since 2010.

Results:

Nineteen of 25 publications describing seven treatment regimens (10 clinical trials and nine associated secondary analyses) met the inclusion criteria and were critically appraised. The most commonly used measures were the Functional Assessment of Cancer Therapy-Prostate (n=5 trials) and Brief Pain Inventory Short Form (n=4 trials) questionnaires. The published data indicated that HRQoL and pain status augmented the clinical efficacy data by providing a better understanding of treatment impact in mCRPC. Abiraterone acetate and prednisone, enzalutamide, radium-223 dichloride and sipuleucel-T offered varying levels of HRQoL benefit and/or pain mitigation versus their respective comparators, whereas three treatments (mitoxantrone, estramustine phosphate and docetaxel, and cabazitaxel) had no meaningful impact on HRQoL or pain. The main limitation of the data were that the PROs utilized were not developed for use in mCRPC patients and hence may not have comprehensively captured symptoms important to this population.

Conclusions:

Recently published randomized clinical trials of new agents for mCRPC have captured elements of the patient experience while on treatment. Further research is required to standardize methods for measuring, quantifying and reporting on HRQoL and pain in patients with mCRPC in the clinical practice setting.

Extended venous thromboembolism prophylaxis in patients undergoing hip fracture surgery – the SAVE-HIP3 study

There is currently limited information available on the benefits and risks of extended thromboprophylaxis after hip fracture surgery. SAVE-HIP3 was a randomised, double-blind study conducted to evaluate the efficacy and safety of extended thromboprophylaxis with the ultra-low molecular-weight heparin semuloparin compared with placebo in patients undergoing hip fracture surgery. After a seven- to ten-day open-label run-in phase with semuloparin (20 mg once daily subcutaneously, initiated post-operatively), patients were randomised to once-daily semuloparin (20 mg subcutaneously) or placebo for 19 to 23 additional days. The primary efficacy endpoint was a composite of any venous thromboembolism (VTE; any deep-vein thrombosis and non-fatal pulmonary embolism) or all-cause death until day 24 of the double-blind period. Safety parameters included major and clinically relevant non-major bleeding, laboratory data, and treatment-emergent adverse events (TEAEs). Extended thromboprophylaxis with semuloparin demonstrated a relative risk reduction of 79% in the rate of any VTE or all-cause death compared with placebo (3.9% vs 18.6%, respectively; odds ratio 0.18 (95% confidence interval 0.07 to 0.45), p < 0.001). Two patients in the semuloparin group and none in the placebo group experienced clinically relevant bleeding. TEAE rates were similar in both groups. In conclusion, the SAVE-HIP3 study results demonstrate that patients undergoing hip fracture surgery benefit from extended thromboprophylaxis.

Cite this article: Bone Joint J 2013;95-B:459–66.

Sunitinib in combination with docetaxel and prednisone in chemotherapy-naive patients with metastatic, castration-resistant prostate cancer: a phase 1/2 clinical trial

BACKGROUND

This phase 1/2 study assessed sunitinib combined with docetaxel (Taxotere) and prednisone in chemotherapy-naive metastatic, castration-resistant prostate cancer (mCRPC) patients.

PATIENTS AND METHODS

To determine the recommended phase 2 dose (RP2D), 25 patients in four dose escalation cohorts received 3-week cycles of sunitinib (2 weeks on, 1 week off), docetaxel and prednisone, preceded by a 4-week sunitinib 50 mg/day lead in. RP2D was evaluated in 55 additional patients. The primary end point was prostate-specific antigen (PSA) response rate.

RESULTS

One phase 1 dose-limiting toxicity occurred (grade 3 hyponatremia). The RP2D was sunitinib 37.5 mg/day, docetaxel 75 mg/m(2) and prednisone 5 mg b.i.d. During phase 2, confirmed PSA responses occurred in 31 patients [56.4% (95% confidence interval 42.3-69.7)]. Median time to PSA progression was 9.8 months. Forty-one patients (75%) were treated >3 months, 12 (22%) completed the study (16 cycles) and 43 (78%) discontinued (36% for disease progression and 27% adverse events). The most frequent treatment-related grade 3/4 adverse events were neutropenia (53%; 15% febrile) and fatigue/asthenia (16%). Among 33 assessable patients, 14 (42.4%) had confirmed partial response. Median progression-free and overall survivals were 12.6 and 21.7 months, respectively.

CONCLUSION

This combination was moderately well tolerated, with promising response rate and survival benefit, justifying further investigation in mCRPC.

The ultra-low molecular weight heparin (ULMWH) semuloparin for prevention of venous thromboembolism (VTE) in patients with cancer receiving chemotherapy: SAVE ONCO study

LBA9014

Background: Patients receiving chemotherapy for cancer are at increased risk for VTE; large randomized controlled trials (RCT) are needed to demonstrate benefit of antithrombotic prophylaxis. Semuloparin is a novel ULMWH with high anti-factor Xa and residual anti-factor IIa activities. We performed a multinational RCT to assess the efficacy and safety of semuloparin for VTE prevention in cancer patients receiving chemotherapy (SAVE-ONCO). Methods: This was a double-blind study in patients with metastatic or locally advanced cancer of lung, colon-rectum, stomach, ovary, pancreas, or bladder, initiating a new chemotherapy course. Patients were randomized to receive subcutaneous semuloparin, 20 mg od, or placebo, until change of chemotherapy. The primary efficacy outcome was the composite of any symptomatic deep vein thrombosis (DVT), non fatal pulmonary embolism (PE) and VTE-related death. Clinically relevant bleeding was the main safety outcome. Outcomes were adjudicated by an independent Committee. Results: Of 3,212 randomized patients, 68% had metastatic cancer; the majority had lung (37%) or colon-rectum (29%) cancer. Median treatment duration was ~3.5 months. Twenty of the 1,608 patients treated with semuloparin (1.2%) and 55 of the 1,604 patients treated with placebo (3.4%) had a thromboembolic event, representing a 64% risk reduction in such event rate (hazard ratio [HR]=0.36, 95% confidence interval [CI] 0.21–0.60, p<0.0001, intent-to-treat analysis). Treatment effect was consistent for DVT and PE, with a 59% risk reduction in PE rate (odds ratio 0.41, 95%CI 0.19–0.85). No heterogeneity in the benefit was observed for cancer type or stage. Nineteen of 1,589 patients (1.2%) in the semuloparin and 18 of the 1,583 patients (1.1%) in the placebo group had a major bleeding (HR=1.05, 95%CI 0.55 to 1.99). The rate of clinically relevant bleeding was 2.8% with semuloparin vs 2.0% with placebo (HR=1.40, 95%CI 0.89–2.21). Conclusions: We have demonstrated the benefit of thromboprophylaxis with semuloparin in patients receiving chemotherapy without increase in major bleeding. Such patients should be considered for thromboprophylaxis.

Subsequent treatment with APC8015F and its effect on survival in the control arm of phase III sipuleucel-t studies

139

Background: Sipuleucel-T is an autologous cellular immunotherapy approved for metastatic castrate resistant prostate cancer.

Methods: After disease progression, subjects in the control arms of 3 randomized controlled sipuleucel-T trials were offered 3 infusions of APC8015F, an autologous immunotherapy made from cells cryopreserved at the time of control generation.

Results: Of 249 control subjects, 165 (66.3%) received APC8015F; the median time from randomization to first infusion was 5.2 months (range 1.8 to 33.1), median time from objective disease progression to first APC8015F infusion was 2.2 months (range 0.5 to 14.6), and 145 subjects (87.9%) received all 3 infusions. The frequency of infusional toxicities was increased following APC8015F relative to control infusion, but was slightly lower than following sipuleucel-T. APC8015F-treated subjects (n=155) had improved post-progression survival relative to untreated controls (n=61) (HR=0.52 [95%CI 0.37, 0.73] p=0.0001, log rank test, unadjusted Cox regression); however, APC8015F-treated subjects had more favorable prognostic features than untreated controls. A Cox regression analysis adjusting for baseline PSA and LDH demonstrated that APC8015F therapy remained a predictor of survival in control subjects (HR=0.56 [95%CI 0.40, 0.80]; p=0.001). A Cox regression model adjusting for age, PSA, LDH and post-randomization docetaxel use (yes/no), also showed a significant effect for salvage treatment among control subjects (HR=0.55 [95%CI 0.39, 0.78] p<0.001). Examination of APC8015F product characteristics demonstrated that cumulative CD54 upregulation was associated with survival following first infusion in subjects who progressed and received APC8015F (p=0.03), consistent with previous reports of correlations between sipuleucel-T product parameters and overall survival.

Conclusions: Although confounded with measured and unmeasured factors influencing outcome, these analyses suggest that post-progression treatment with APC8015F may have extended the survival of subjects in the control arms of these studies.

[Table: see text]

Comorbidities predict overall survival (OS) in men with metastatic castrate-resistant prostate cancer (CRPC)

189

Background: Management of prostate cancer in senior adults represents an important challenge as the median age at diagnosis is 68 and comorbidities in patients increase with advancing age. The objective of this analysis was to determine if baseline comorbidities number (CON) prior to initiating frontline chemotherapy impacts OS in men with CRPC.

Methods: Data from a randomized phase III trial of 1,050 men who received docetaxel, prednisone with or without bevacizumab were used in this analysis. Eligible patients had metastatic CRPC with evidence of progressive disease despite castration and anti-androgen withdrawal, ECOG performance status ≤ 2, and adequate bone marrow, hepatic and renal function. Comorbidities on 14 conditions including cardiovascular, hypertension, diabetes, arthritis, thrombosis, AIDS, renal disease, liver disease and peptic ulcer were prospectively collected at baseline from men enrolled on this trial. The proportional hazards model was used to test if CON predicted OS adjusting for treatment arm, age, race, body mass index and predicted survival probability at 24 months using the CALGB nomogram.

Results: In 1,048 men with comorbidity data, the mean CON was 1.5 (s.d.= 1.47, range=0-9) and 73% of men had at least one comorbidity. There was a statistically significant association between CON and risk of death. In multivariable analysis, the hazard ratio (HR) for death for one unit increase in CON was 1.09 (95% CI= 1.04- 1.14, p-value=0.0008).

Conclusions: To our knowledge, this is the first analysis to show that CON is a statistically significant predictor of OS in men with CRPC. These results require prospective validation in phase III trials of men with CRPC.

[Table: see text]

A randomized, double-blind, placebo-controlled phase III trial comparing docetaxel, prednisone, and placebo with docetaxel, prednisone, and bevacizumab in men with metastatic castration-resistant prostate cancer (mCRPC): Survival results of CALGB 90401

LBA4511

Background: The preclinical activity of vascular endothelial growth factor (VEGF) blockade, the inverse relationship of plasma and urine VEGF levels and survival in mCRPC patients (pts), and encouraging phase II data testing estramustine and docetaxel with bevacizumab suggested that VEGF blockade was an appropriate potential strategy in mCRPC. A phase III study testing the effect of adding bevacizumab to standard docetaxel and prednisone therapy administered every 3 weeks in pts with mCRPC was conducted.

Methods: 1050 pts with chemotherapy naïve, mCRPC with evidence of progressive disease despite castrate testosterone levels and anti-androgen withdrawal, ECOG performance status ≤ 2, and adequate bone marrow, hepatic and renal function were eligible. Pts were prospectively randomized with equal probability to receive docetaxel (D:75 mg/m2 IV over 1 hour q 21 days), plus prednisone (P) 5 mg po BID with either bevacizumab (B:15 mg/kg given intravenously q 3 weeks following D) or placebo. All patients received dexamethasone 8 mg PO 12, 3 and 1 hour prior to D. Randomization was stratified by predicted 24 mo survival probability, age and history of prior arterial thrombotic event. The primary endpoint was overall survival (OS). The trial was designed with 86% power to detect a 21% decrease in the hazard rate of death (equivalent to an increase in median OS from 19 months to 24 months) assuming a two-sided significance level of 0.05. The primary analysis was based on the stratified log-rank statistic adjusted for the stratification factors following observation of 748 deaths.

Results: See Table .

Conclusions: Despite an improvement in PFS, measurable disease response and post-therapy PSA decline, the addition of bevacizumab to docetaxel and prednisone did not improve OS in men with mCRPC, and was associated with greater morbidity and mortality. The median OS of pts treated with standard DP (21.5 m) was longer than previously reported (19 m).

[Table: see text]

[Table: see text]

Development of risk groups in metastatic castration-resistant prostate cancer (mCRPC) to facilitate the identification of active chemotherapy regimens

5137

Background: Our aim was to develop and validate clinically applicable predictive factors for a >30% PSA decline 3 months following chemotherapy initiation, and to assess the performance of a risk-group based classification in predicting PSA declines and overall survival (OS) in men receiving chemotherapy for mCRPC. Methods: In TAX327, 1006 men with mCRPC were randomized to receive docetaxel (D) in two schedules, or mitoxantrone (M), each with prednisone: 989 provided data on PSA decline at 3 months. Predictive factors for a >30% 3-month decline in PSA levels were identified using multivariate logistic regression in D treated men (n = 656) and validated in M treated men (n = 333). Risk factors were combined to form risk groups to predict PSA declines, OS, tumor, and pain responses. Prostate Cancer Working Group (PCWG2) disease states were evaluated for these outcomes in docetaxel treated men. Results: In multivariate analysis, four independent risk factors predicted for absence of >30% decline in 3-month PSA: significant baseline pain (OR 0.63 p = 0.02), visceral metastases (OR 0.66, p = 0.03), anemia (hemoglobin <13 g/dl, OR 0.72 p = 0.07), and bone scan progression at baseline (OR 0.60 p = 0.009). Predictive accuracy was moderate with a concordance index (c-index) of 0.61. Risk groups (good, intermediate, poor) were developed with median OS of 25.7 (95% CI 23.3–28.6), 18.7 (17.3–19.7), and 12.8 (11.5–14.6) months, respectively (p < 0.0001), and >30% PSA decline in 78, 66, and 58 percent of men (p < 0.001). In the validation M cohort, similar trends for PSA declines and OS were noted across risk groups (OS 22.5, 16.0, 11.8 mo, p < 0.001). PCWG2 subtypes (node only, bone metastatic, and visceral disease), were also highly prognostic and predictive but did not predict OS as well as the TAX327 risk groups (c-index 0.56). Conclusions: Risk groups have been identified and internally validated that predict PSA decline and OS in men with mCRPC. This classification may facilitate evaluation of new regimens of systemic therapy that warrant definitive testing in comparison to docetaxel and prednisone in phase III trials. Prospective validation of these risk groups is needed.

[Table: see text]

Phase I study of PTK787/ZK222584 (PTK/ZK) and RAD001 for patients with advanced solid tumors and dose expansion in renal cell carcinoma patients

5039

Background: PTK/ZK is an orally active tyrosine kinase inhibitor that blocks all known VEGF receptors. RAD001 is an orally active macrolide which selectively inhibits mTOR. Combination therapy with VEGFR and mTOR inhibition may have additive efficacy in several tumor types, particularly renal cell carcinoma (RCC). Materials and Methods: A phase I/II study of PTK/ZK and RAD001 was performed in patients with advanced solid tumors to determine the maximum tolerated dose (MTD), safety and tolerability. Patients were given escalating daily doses of PTK/ZK in combination with RAD001 (see table ) in 28-day cycles. Patients were assessed for adverse events every 2 weeks and tumor response every 2 cycles. A dose expansion cohort of 20 patients with metastatic RCC is ongoing to further evaluate safety and preliminary efficacy. Results: To date, 27 patients have received a total of 136 cycles. The dose escalation phase included 14 patients and 3 dose levels; dose-limiting toxicities included grade 3 diarrhea and hypertriglyceridemia (14%); asthenia, fatigue and mucositis (7%). Pharmacokinetic studies are pending. A MTD of PTK/ZK 1,000 mg and RAD001 5 mg daily was determined and studied in an expanded cohort of RCC patients. Prior therapy with a VEGF inhibitor was allowed. To date, 13 evaluable RCC patients demonstrate 2 (15%) partial responses and 8 (62%) with stable disease > 3 months; median TTP is 6 months. Conclusions: PTK/ZK and RAD001 combination is well-tolerated and demonstrates clinical activity in patients with RCC despite prior exposure to VEGF inhibition. An MTD of 1,000 mg daily of PTK/ZK and 5 mg daily of RAD001 is the recommended dose for Phase II/III testing.

[Table: see text]

No significant financial relationships to disclose.

Sunitinib therapy for patients (pts) with metastatic renal cell carcinoma (mRCC): Updated results of two phase II trials and prognostic factor analysis for survival

5095

Background: Two single-arm phase 2 trials reported a 42% objective response rate (ORR) with sunitinib as second-line therapy in mRCC pts (JAMA 2006;295:2516–24). Efficacy results were updated and an analysis of prognostic factors for survival was performed on pooled data. Methods: Eligibility criteria and treatment plan were nearly identical for both trials. Pts with mRCC who failed =1 prior cytokine-based therapy received sunitinib in repeated 6-week cycles of 50 mg/day orally for 4 weeks, followed by 2 weeks off treatment. Response was assessed by investigators according to RECIST. Pretreatment clinical and biochemical features were examined for prognostic factors by univariate and multivariate analysis (p<0.05 significance level was used in the backward stepwise selection procedure). Results: Updated efficacy data for 168 evaluable pts showed an ORR of 45% (95% CI: 39%, 54%), median progression-free survival (PFS) of 8.4 months (95% CI: 7.9, 10.7), and median overall survival (OS) of 22.3 months (95% CI: 14.8, 36.0). Twenty pts remain on treatment with sunitinib with the longest pt on the drug for >3.5 years with partial response for >3 years. The median duration of response was 11.6 months (95% CI: 9.9, 15.2), and included 1 pt with a complete response for >2 years. The proportion of pts alive at 2 years is 48%. Final prognostic factors for survival in the multivariate model were ECOG PS 0 vs. =1 (p=0.0034); time interval from diagnosis to sunitinib treatment =1 yr vs. <1 yr (p=0.0002); hemoglobin =13 vs. <13 g/dL for males and =11.5 vs. <11.5 g/dL for females (p=0.0002). Conclusions: Median survival is nearly 2 years, which compares favorably to the historical experience (12.7 months) in second-line therapy with other agents (JCO 2004;22:454–63). The influence of sunitinib therapy on patient survival is being investigated in a randomized phase 3 trial compared to interferon-a in first-line therapy for mRCC. Further study of prognostic factors to sunitinib therapy is warranted in the first-line setting.

No significant financial relationships to disclose.

Phase II trial of sunitinib in bevacizumab-refractory metastatic renal cell carcinoma (mRCC): Updated results and analysis of circulating biomarkers

5035

Background: Sunitinib malate is an oral, multitargeted tyrosine kinase inhibitor with antiangiogenic and antitumor activity. This study evaluated the safety and activity of sunitinib in mRCC patients (pts) previously treated with the VEGF-neutralizing antibody, bevacizumab. Levels of angiogenic biomarkers, including plasma VEGF and soluble VEGFR-3 (sVEGFR-3), were assessed for predictive significance with clinical response. Methods: Pts were required to have mRCC with disease progression following bevacizumab- based therapy, measurable disease, ECOG performance status 0 or 1, and adequate organ function. Pts were treated with sunitinib 50 mg daily in 6-week cycles (4 weeks on, followed by 2 weeks off). The primary endpoint was objective response according to RECIST. Plasma VEGF and sVEGFR-3 levels were measured in pre-treatment samples and at multiple timepoints on study. Results: A total of 61 pts were enrolled. The objective partial response rate was 23% (95% CI: 13%, 36%); 35 pts (57%) demonstrated stable disease. The median duration of response was 36 weeks (95% CI: 26, NA) and progression-free survival was 30 weeks (95% CI: 18, 34). Plasma VEGF levels increased from baseline (3-fold mean elevation), while plasma sVEGFR-3 levels decreased from baseline (40% mean reduction). Pre-treatment VEGF levels were significantly higher in pts (n=34) with <10 weeks between cessation of bevacizumab and start of sunitinib (p<0.001); ELISA specificity suggests that detected VEGF is not bevacizumab-bound. Pre-treatment sVEGFR-3 levels were significantly lower at baseline in responding pts vs. non-responding pts (p<0.0318). A greater reduction in sVEGFR-3 levels was seen in responding pts vs. non-responding pts (p<0.10). Pretreatment VEGF and VEGF fold-changes did not differ according to clinical response. Conclusions: Sunitinib has significant antitumor activity in bevacizumab-refractory mRCC pts, suggesting absence of cross-resistance between bevacizumab and sunitinib. Biomarkers including plasma VEGF and sVEGFR-3 may have predictive potential in sunitinib-treated patients.

No significant financial relationships to disclose.

Systemic strategies for prostate cancer

Systemic therapy beyond hormonal therapy for advanced prostate cancer includes chemotherapy, antiangiogenic therapy, signal transduction inhibitors, immunomodulatory therapy, and other experimental therapeutics. This review will discuss the state of systemic therapy for advanced prostate cancer in 2007, with an emphasis on therapy in the neoadjuvant, adjuvant, and metastatic setting. As chemotherapy gains greater acceptance in the urologic oncology community for use in men with hormone-refractory disease, evaluating the role of systemic therapy in earlier disease states is essential given the success in other solid tumors for advancing cure rates. Current randomized phase III trials worldwide are addressing these questions in each disease state, and are anticipated to change the landscape of prostate cancer management for years to come. In this discussion, we will emphasize those agents that are currently being evaluated in phase II and III trials, with an emphasis on those trials that are likely to impact the standard of care in the near future. The collection of tumor or surrogate tissue is emphasized to define biomarkers that may predict for sensitivity to these systemic therapies.

Timing and patterns of recurrences and deaths from prostate cancer following adjuvant pelvic radiotherapy for pathologic stage T3/4 adenocarcinoma of the prostate

To determine the timing and patterns of late recurrence after radical prostatectomy (RP) alone or RP plus adjuvant radiotherapy (RT). Between 1970 and 1983, 159 patients underwent RP for newly diagnosed adenocarcinoma of the prostate and were found to have positive surgical margins, extracapsular extension and/or seminal vesicle invasion. Of these, 46 received adjuvant RT and 113 did not. The RT group generally received 45-50 Gy to the whole pelvis, then a boost to the prostate bed (total dose of 55-65 Gy). In the RP group, 62% received neoadjuvant/adjuvant androgen deprivation vs 17% in the RT group. Patients were analyzed with respect to timing and patterns of failure. Only one patient was lost to follow-up. The median follow-up for surviving patients was nearly 20 years. The median time to failure in the surgery group was 7.5 vs 14.7 years in the RT group (P=0.1). Late recurrences were less common in the surgery group than the RT group (9 and 1% at 10 and 15 years, respectively vs 17 and 9%). In contrast to recurrences, nearly half of deaths from prostate cancer occurred more than 10 years after treatment. Deaths from prostate cancer represented 55% of all deaths in these patients. Recurrences beyond 10 years after RP in this group of patients were relatively uncommon. Despite its long natural history, death from prostate cancer was the most common cause of mortality in this population with locally advanced tumors, reflecting the need for more effective therapy.

Phase I/II trial of the prostate-specific membrane antigen (PSMA)-targeted immunoconjugate MLN2704 in patients (pts) with progressive metastatic castration resistant prostate cancer (CRPC)

4500

Background: MLN2704 is an immunoconjugate that utilizes the PSMA-targeted monoclonal antibody MLN591 to deliver the maytansinoid antimicrotubule agent DM1 directly to prostate cancer cells. This multicenter trial was designed to determine the tolerability, optimal dosing schedule and efficacy of MLN2704 in pts with progressive metastatic CRPC. Methods: Pts aged ≥18 yrs with progressive metastatic CRPC received MLN2704 i.v. over 2.5 hr q1wk, q2wks or q3wks for 12 wks, with additional doses permitted in responders. Doses within a given schedule were escalated in 40% increments in the absence of excessive dose-limiting toxicity (DLT). Results: 61 pts have been treated. The most common adverse events (AEs) were nausea, fatigue, and schedule-dependent neurotoxicity. The only DLT was gr 3 hepatic transaminitis in 1/6 pts at 330 mg/m2 q2wks; the only gr 4 AE was transient neutropenia, in 2 pts (330 mg/m2 q2wks and q3wks). Declines in PSA were most frequent at 330 mg/m2 q2wks ( table ), including 49–88% PSA declines in 4/6 pts. However, given the frequency of grade 2–3 peripheral neuropathy an additional cohort is being treated with 330mg/m2 on days 1 and 15 of a 6-wk cycle. Initial results with this 6-wk schedule indicate PSA declines with a lower incidence of gr 2–3 toxicities, particularly neuropathy. Conclusions: Accrual to the dose-escalation phase is complete. Dose-dependent antitumor effects were seen. Peripheral neuropathy has limited continuous dosing at higher dose levels prompting a schedule change. Accrual to the 6-wk schedule is continuing.

[Table: see text]

[Table: see text]

Pharmacokinetics (PK) and efficacy of sunitinib in patients with metastatic renal cell carcinoma (mRCC)

4531

Background: Sunitinib malate (SU11248) is an oral, multi-targeted tyrosine kinase inhibitor of VEGFR, PDGFR, KIT, FLT3, and RET. Clinical studies have demonstrated efficacy of sunitinib in patients with multiple tumor types including two phase II studies in mRCC, where second-line monotherapy with sunitinib showed a response rate of greater than 40% by RECIST, with an additional ≥25% of pts exhibiting prolonged stable disease. A population PK analysis was performed to assess the exposure-response relationship between PK and tumor volume changes, clinical response, and time to tumor progression (TTP) in these two mRCC studies. Methods: In these two studies, 169 patients with mRCC were treated with sunitinib 50 mg/day for 4 weeks, followed by a 2-week off period (Schedule 4/2). Response to treatment was assessed by measuring tumor volume. Clinical response was assessed using RECIST and TTP using logistic regression and Kaplan-Meier survival analysis. A previously described population PK model of sunitinib and its primary active metabolite SU12662 was updated using additional data from three trials, including the two RCC trials. Using the model and trough plasma concentrations, steady-state AUCs of sunitinib plus SU12662 were estimated for each mRCC patient and tested as a predictor of response. Results: PK profiles were evaluable for 149 patients in the two mRCC trials. Plasma clearance (CL) decreased by an average of 28% in mRCC patients relative to healthy volunteers. Covariates, such as gender, age, and ECOG score also affected CL, however all of these changes were less than the estimated inter-individual variability in CL of 43%. Improved clinical response and longer TTPs were associated with greater AUCs. Within 12 weeks of treatment, mean tumor volume decreased by 24–32% in each trial. Conclusions: Individual patient exposures to sunitinib and SU12662 can be predicted with sparse concentration measurements using population PK analysis, and an exposure-response relationship is evident in mRCC. Dose adjustment is not warranted based upon any evaluated covariate. Over the first 12 weeks of treatment at 50 mg daily on Schedule 4/2, increased exposure was associated with improved clinical response and decreased tumor volumes.

[Table: see text]

Phase I/II study of docetaxel and atrasentan in men with metastatic hormone-refractory prostate cancer (HRPC)

14504

Background: Docetaxel is first-line standard treatment for metastatic HRPC. New combinations with targeted therapies may improve clinical responses. . Atrasentan is an endothelin receptor A (ETA) inhibitor with an IC50 in the pM range. Clinical studies suggest atrasentan delays time to disease progression, bone turnover markers and PSA kinetics. Methods: We conducted a Phase I/II trial of docetaxel and atrasentan to define the maximum tolerated dose (MTD), dose limiting toxicity (DLT), pharmacokinetics (PK) and treatment response of this regimen. Patients were treated with docetaxel IV every 3 weeks at doses ranging from 60 to 75 mg/m2. Atrasentan was given orally at 10 mg daily starting on Day 3 and continuously thereafter. Initially, we defined DLT as grade IV neutropenia, but subsequently amended the protocol to redefine DLT as grade IV neutropenia lasting ≥ 7 days. Plasma PK evaluations were conducted for each drug when administered alone (Cycle 1 Day 1, 21) and together (Cycle 2 Day 1). Serial samples were evaluated by LC-MS and data were modeled using a standard, two-stage approach. Results: 18 patients were enrolled over 3 dose levels (9 at 60 mg/m2; 6 at 70 mg/m2 and 3 at 75 mg/m2) in the phase I portion and to date 9 more patients have been enrolled in a dose expansion cohort at a docetaxel dose of 70 mg/m2. Patient demographics include median age 69, PSA level 87.3 ng/ml, hemoglobin 12.7 g/dl, and KPS 90%. DLT, initially any grade IV neutropenia, was seen at every dose level, however no grade IV neutropenia has lasted ≥ 7 days and no MTD has been defined to date. Drug-related grade III/IV toxicities included only neutropenia (42%); grade I-II toxicities included fatigue, peripheral edema, and nausea. To date, 5 of 15 evaluable patients who have been treated with 70–75 mg/m2 of docetaxel and 10 mg of atrasentan demonstrate a sustained PSA response. Preliminary PK data in 11 patients show a mean docetaxel terminal half-life of 46 hr and systemic clearance of 55 L/hr. The median difference in systemic clearance between the cycles was 18% with values increasing in 67% of subjects. Conclusions: The combination of docetaxel and atrasentan appears to be well tolerated to date. The study is ongoing to more accurately determine safety, response and potential pharmacokinetic interactions.

[Table: see text]

LBH589, a novel histone deacetylase inhibitor (HDACi), treatment of patients with cutaneous T-cell lymphoma (CTCL). Changes in skin gene expression profiles related to clinical response following therapy

7501

Background: LBH589 is a novel histone deacetylase inhibitor in Phase I trials. Since other HDACi have induced disease regression in CTCL, we evaluated the activity of LBH589 and resulting changes in gene expression of LBH589 in CTCL patients (pts). Methods: Pts with advanced-stage CTCL, who had progressed following prior systemic therapy were entered into the DLT dose level 30mg M,W,F cohort (n = 1) or the subsequent MTD dose level 20mg M,W, F weekly (n = 10). LBH589 was continued until disease progression or unacceptable toxicity. The first three pts had 3mm punch biopsies from CTCL-involved skin lesions at 0, 4, 8 and 24h after administration, which were subjected to gene expression profiling using Affymetrix U133 plus 2.0 GeneChips with 47,000 probesets. Results: Eleven pts with CTCL have been entered to date. Two of the pts attained a complete response (CR), 3 attained a partial response (PR), 2 achieved stable disease (SD) with ongoing improvement, and 4 progressed on treatment (PD). Of particular interest, 2 pts who were initially SD required discontinuation because of toxicities (Grade III diarrhea at week 4, Grade II fatigue at week 12). Both had ongoing improvement in their disease achieving a CR and PR, respectively 3 months later. Of the 5 responding pts, one with a CR (discontinued after 10 doses due to Grade III diarrhea) progressed at 8m. Microarray data on the first 3 pts (2CR and 1PD) demonstrated distinct gene expression response profiles between the 3 pts. Surprisingly, the pt with PD showed the greatest transcriptional response with more than 16,000 genes activated or repressed over the 24 hr time course. Of these responsive genes, close to 60% were activated while 40% were repressed. In contrast, less than 1000 genes showed a 2-fold change in expression in the 2 pts with a CR with greater than 85% of the genes being repressed. Conclusions: LBH589 induce CR’s in CTCL pts. Regression of disease can occur some weeks after discontinuation of therapy. Preliminary microarray analysis of tumor samples indicated that LBH589 mediates changes in gene expression in vivo with an unexpected observed inverse relationship between the number of genes altered and clinical outcome.

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Phase I dose escalation, pharmacokinetic, and biomarker study of imatinib mesylate plus capecitabine in advanced solid tumor malignancies

3093

Background: Preclinical data have suggested at least additive antitumor effects when imatinib (I) and 5-FU are combined. The goals of this study were to determine the maximal tolerated dose for the combination of I and capecitabine (C) in solid tumor patients (pts), as well as to describe non-dose limiting toxicities (non-DLT), pharmacokinetics (PK), and pharmacodynamics (PDGFR inhibition in granulation tissue). Methods: 24 pts (12 M, 12 F) with solid tumor malignancies received C plus I using a 21 day (d) cycle. C was dosed BID for 14/21 d. I was dosed QD x 21d. Results: 24 of 24 pts were fully evaluable for toxicity and efficacy. 6 pts were treated at dose level 1 (C 1000 mg/m2 BID, I 300 mg QD). The only dose limiting toxicity (DLT) at dose level 1 was grade (gr) 3 diarrhea in 1 patient; however 5 of 6 pts required dose reductions in a subsequent cycle. Therefore, the next 18 pts were treated at dose level -1 (C 750 mg/m2 BID and I 300 mg QD). One DLT (gr 3 fatigue) was seen at dose level -1. Non-DLT gr ¾ toxicities at any point at dose level -1 were gr 4 anemia (n=1) and gr 3 lymphopenia (n=6). Toxicities requiring dose reductions at any point on dose level -1 occurred in 7/18 patients. Gr ½ toxicities found in > 10% of all patients at any point in the trial were anemia (46%), leukopenia (17%), neutropenia (21%), lymphopenia (29%), thrombocytopenia (29%), nausea (71%), anorexia (41%), edema (42%), diarrhea (38%), hand foot syndrome (33%), vomiting (33%), headache (25%), insomnia (25%), skin rash (25%), constipation (21%), stomatitis (17%), lightheadedness (13%), fatigue (13%), numbness/tingling (13%), taste change (13%), and elevated transaminases (13%). 1 pt with carcinoid tumor had a partial response. 1 pt with non-small cell lung cancer had a minor response, and 5/21 pts had stable disease as their best response. 1 pt had stable disease for 8 months and another pt was stable for 6 months. Conculsions: On a 21 d cycle, the recommended phase 2 dose of C plus I is C 750 mg/m2 BID for 14 d, and I 300 mg QD.

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Public health impact of PSA doubling time after radical prostatectomy on prostate cancer specific and overall survival

4568

Background: Among patients treated with radical prostatectomy (RP) with a PSA recurrence, we previously found men with a PSA doubling time (PSADT) <3 months were at increased risk of prostate cancer death, though these men constituted a small subset of patients. We sought to determine the actual and predicted number of prostate cancer deaths stratified by PSADT. Methods: We retrospectively studied 379 men treated with RP between 1982 and 2000 with a PSA recurrence. We calculated the actual and 15-year actuarial number of prostate cancer deaths in each of the following PSADT categories: <3, 3.0–8.9, 9.0–14.9, and ≥15.0 months. Results: Median follow-up after PSA recurrence was 7 years. During this time, there were 76 prostate cancer deaths; the majority (51%) were among men with a PSADT of 3.0–8.9 months. Though men with a PSADT <3 months were at the greatest risk of death, this group accounted for only 20% (n=15) of all prostate cancer deaths. Using actuarial 15-year estimates of prostate cancer specific survival, 50% of all prostate cancer deaths were among men with a PSADT of 3.0–8.9 months while men with a PSADT <3 months accounted for only 13% of prostate cancer deaths. Using actuarial 15-year estimates of all-cause and prostate cancer specific mortality, among men with a PSADT <15 months, prostate cancer was estimated to be the cause of death in 94% (145/155). Only among men with a PSADT >15 months was the risk of competing causes of mortality high enough such that the majority of deaths were not attributed to prostate cancer. Conclusions: Among a select cohort of men treated with RP who experienced a PSA recurrence, prostate cancer was estimated to account for 75% of all deaths. Though men with a PSADT <3 months were at the greatest risk, the majority of deaths occurred among men with a PSADT of 3.0–8.9 months. Efforts to reduce prostate cancer mortality should focus on men with intermediate PSADT times (3.0–15.0 months) as they represent the greatest public health concern among men with PSA recurrence following RP.

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No significant financial relationships to disclose.

Efficacy and safety of sunitinib malate (SU11248) in bevacizumab-refractory metastatic renal cell carcinoma (mRCC)

4522

Background: Sunitinib malate (SU11248) is an oral, multitargeted tyrosine kinase inhibitor of the vascular endothelial growth factor receptor (VEGFR) family, platelet-derived growth factor receptor (PDGFR) and other related receptors. It has demonstrated anti-tumor activity in cytokine-refractory mRCC patients (pts). The activity of sunitinib in pts refractory to VEGF binding agents such as bevacizumab, however, has not been evaluated. It was hypothesized that tumor resistance to bevacizumab may be driven, in part, through pathways sensitive to inhibition by sunitinib. A phase II study evaluating the activity of sunitinib in bevacizumab-refractory mRCC was thus conducted. Methods: Pts with mRCC who demonstrated RECIST-defined disease progression within 3 months after bevacizumab-based therapy were treated with sunitinib (50 mg daily, 4 weeks of a 6-week cycle). Additional eligibility included measurable disease, clear cell histology, ≤ 2 prior systemic regimens, prior nephrectomy, performance status 0 or 1 and adequate organ function. The primary endpoint was objective response by RECIST criteria. A single-stage design was employed to test the null hypothesis that the true response rate is ≤ 5% versus the alternative hypothesis that the true response rate is ≥ 15%. Results: Accrual of 60 patients has been completed. Baseline characteristics include a median age of 59 years; 92% of pts had ≥ 2 metastatic sites and 23% had prior radiotherapy. Thirty-two of 60 pts enrolled are evaluable for response; 28 pts are too early for assessment. Twenty-six pts (81%) demonstrated some degree of tumor shrinkage, including, 4 pts (13%; 95% CI 4%, 29%) demonstrating an objective partial response. The most common treatment-related adverse events (AEs) included fatigue, diarrhea, dysgeusia, and nausea. Serious treatment-related AEs included fatigue, diarrhea, nausea and one fatal cerebral hemorrhage; 3 pts withdrew due to an AE. Conclusions: Sunitinib has substantial antitumor activity in bevacizumab-refractory mRCC pts, suggesting that sunitinib may inhibit signaling pathways involved in bevacizumab resistance. The precise mechanisms of response to sunitinib in bevacizumab-refractory tumors will require additional studies.

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Finasteride and bicalutamide as primary hormonal therapy in patients with advanced adenocarcinoma of the prostate

BACKGROUND

Medical or surgical castration is effective in advanced prostate cancer but with profound side-effects, particularly on sexual function. Effective, less toxic therapies are needed. This study examined whether the addition of finasteride to high-dose bicalutamide enhanced disease control, as measured by additional decreases in serum prostate-specific antigen (PSA).

PATIENTS AND METHODS

Forty-one patients with advanced prostate cancer received bicalutamide (150 mg/day). Finasteride (5 mg/day) was added at first PSA nadir. Serum PSA was measured every 2 weeks until disease progression. Questionnaires were administered to assess sexual function.

RESULTS

Median follow-up is 3.9 years. At the first PSA nadir, median decrease in PSA from baseline was 96.5%. Thirty of 41 patients (73%) achieved a second PSA nadir and median decrease of 98.5% from baseline. Median time to each nadir was 3.7 and 5.8 weeks, respectively. Median time to treatment failure was 21.3 months. Toxicities were minor, including gynecomastia. Seventeen of 29 (59%) and 12 of 24 (50%) men had normal sex drive at baseline and at second PSA nadir, respectively. One-third of men had spontaneous erection at both time points.

CONCLUSION

Finasteride provides additional intracellular androgen blockade when added to bicalutamide. Duration of control is comparable to castration, with preserved sexual function in some patients.

Neoadjuvant docetaxel followed by radical prostatectomy in patients with high-risk localized prostate cancer: a preliminary report

Effective treatment options for high-risk localized prostate cancer are limited. Patients at high risk for recurrence include those with biopsy Gleason scores of 8 to 10, prostate specific antigen (PSA) levels > 20 ng/mL, and clinical stage T3 disease. Docetaxel chemotherapy is active in hormone-refractory prostate cancer, either combined with estramustine or used as a single agent. To determine if systemic therapy can improve the outcome of radical prostatectomy in men with high-risk localized prostate cancer, we are undertaking a pilot phase II clinical trial of weekly docetaxel at 36 mg/m(2) for up to 6 months, followed by surgery. Patients are monitored with weekly visits, monthly digital rectal examinations, PSA measurement, and testosterone tests, and endorectal magnetic resonance imaging done at baseline, after two cycles, and again after six cycles. To date, 15 patients have been enrolled, and 70 cycles of chemotherapy have been administered. Toxicity has been mostly grade 1 in intensity, and fatigue has been the most common grade 2 toxicity reported. The primary endpoint of the trial is measurement of pathologic complete response rate, for which data are not yet available. Recruitment to the trial is ongoing.

Prognostic significance of plasma vascular endothelial growth factor levels in patients with hormone-refractory prostate cancer treated on Cancer and Leukemia Group B 9480

PURPOSE

Plasma vascular endothelial growth factor (VEGF) levels are significantly elevated in patients with hormone-refractory prostate cancer (HRPC) compared with patients with localized disease and have been associated with disease progression in other cancer patient populations. Therefore, we measured VEGF levels in plasma prospectively collected from patients enrolled in Cancer and Leukemia Group B 9480, an intergroup study of suramin in patients with HRPC, to determine whether these levels had prognostic significance.

EXPERIMENTAL DESIGN

Pretreatment plasma was collected from patients with HRPC enrolled in Cancer and Leukemia Group B 9480. In a subset of samples representative of the entire cohort, plasma VEGF levels were determined in duplicate using a Quantiglo chemiluminescent ELISA kit (R&D Systems, Minneapolis, MN). Statistical analyses were performed to determine the correlation between pretreatment plasma VEGF levels and time of overall survival. The proportional hazards model was used to assess the prognostic significance of various cut points in multivariate models.

RESULTS

Plasma VEGF levels in this population ranged from 4-885 pg/ml, with a median level of 83 pg/ml. As a continuous variable, plasma VEGF levels inversely correlated with survival time (P = 0.002). Using various exploratory cut points, plasma VEGF levels appeared to correlate with survival. In multivariate models in which other prognostic factors (serum prostate-specific antigen, alkaline phosphatase, evidence of measurable disease, and hemoglobin) were included, plasma VEGF levels were significant at various cut points tested.

CONCLUSION

Although these data are exploratory and need to be confirmed in an independent data set, they suggest that VEGF may have clinical significance in patients with HRPC.

Activity of the herbal combination, PC-SPES, in the treatment of patients with androgen-independent prostate cancer

OBJECTIVES

To retrospectively evaluate the response to treatment with PC-SPES, an herbal supplement, because patients with androgen-independent prostate cancer have limited treatment options.

METHODS

A retrospective analysis was performed of patients with prostate cancer progression despite androgen ablation therapy who were treated with PC-SPES (3 capsules twice daily). We explored potential predictors of response.

RESULTS

Twenty-three patients with androgen-independent prostate cancer were treated. The median age was 70 years. Eighteen patients had received prior secondary hormonal treatment and 10 prior chemotherapy. With a median follow-up of 8 months, 20 (87%; 95% confidence interval 66% to 97%) of 23 patients experienced a post-therapy decline in prostate-specific antigen (PSA). The median decline in PSA among these patients was 40% (range 1% to 88%). Of 23 patients, 12 (52%; 95% confidence interval 31% to 73%) had a greater than 50% decline in PSA. The median duration of the PSA response was 2.5 months (range 1 to 9+); the median time from the start of therapy to PSA progression was 6 months (range 2 to 12). Seven patients died of progressive prostate cancer. Toxicity was mild and included nipple tenderness, nausea, and diarrhea. One patient with a known history of coronary artery disease developed angina. In univariate analyses, older patients and those with a longer duration of initial androgen ablation therapy were more likely to respond to PC-SPES.

CONCLUSIONS

PC-SPES is a well-tolerated and active treatment for androgen-independent prostate cancer. Additional testing is necessary to identify the active components of PC-SPES and its role in the treatment of patients with androgen-independent prostate cancer.

Rational basis for Trk inhibition therapy for prostate cancer

BACKGROUND

Prostatic cancer cells are lethal because they acquire the ability to activate survival pathways that do not require androgenic stimulation. As a rational approach to developing effective therapy for these devastating cells, specific signal transduction pathways uniquely required for the survival of these nonandrogen-dependent prostate cancer cells must be identified. Previous studies suggested that the neurotrophin/trk signal transduction axis may regulate such unique survival pathways. In the present study, the changes in expression of the neurotrophins (NGF, BDNF, and NT-3) and their cognate receptors (i.e., trk and p75NTR) during the progression of normal prostatic epithelial cells to malignancy were documented. Additionally, the consequences of inhibiting these trk signaling pathways on the in vitro survival of prostate cancer cells was tested.

METHODS

Immmunocytochemistry, RT-PCR, and ELISA assays were used to characterize the changes in the neurotrophin ligands (i.e., NGF, BDNF, and NT-3) and their cognate high-affinity (i.e., trk A, B, and C) and low-affinity neurotrophin (i.e., p75 NTR) receptors in normal vs. malignant human prostatic tissues. CEP-751 is an indolocarbazole compound specifically designed to inhibit the initiation of these neurotrophin/trk signal transductions. The consequence of CEP-751 inhibition of trk signaling for in vitro clonogenic survival of a series of human prostatic cancer lines was also tested.

RESULTS

These studies demonstrated that normal prostatic tissue from patients without prostate cancer contains substantial levels of nerve growth factor (NGF), which is produced in a paracrine manner by stromal cells. These stromal cells lack both trk and p75NTR receptors. In contrast, normal prostatic epithelial cells from patients without prostate cancer do not secrete detectable levels of neurotrophins, but do express trk A and p75 NTR. While the NGF/trkA/p75 NTR axis is present in the normal prostate, normal prostatic epithelial cells do not depend on this axis for their survival. In contrast, malignant prostate epithelial cells directly secrete a series of neurotrophins (i.e., NGF, BDNF, and/or NT-3) and express at least one if not more of the trk receptor proteins (i.e., trk A, B, and/or C), while no longer expressing the p75NTR receptors. In addition, inhibition of autocrine trk signaling via CEP-751 treatment induces the apoptotic death of these malignant cells.

CONCLUSIONS

Prostate carcinogenesis involves molecular changes leading to the paracrine and/or autocrine production of a series of neurotrophins. This is coupled to the ectopic expression of trk B and trk C, as well as to the continued expression of trk A, and the loss of expression of p75NTR receptors. These changes result in the acquisition by malignant prostate cells of a unique requirement for trk signaling pathways for survival. Based on these findings, trk inhibition is a novel, rational approach for prostate cancer therapy.

Sustained in vivo regression of Dunning H rat prostate cancers treated with combinations of androgen ablation and Trk tyrosine kinase inhibitors, CEP-751 (KT-6587) or CEP-701 (KT-5555)

The indolocarbazole analogue CEP-751 is a potent and selective tyrosine kinase inhibitor of the neurotrophin-specific trk receptors that has demonstrated antitumor activity in nine different models of prostate cancer growth in vivo. In the slow-growing, androgen-sensitive Dunning H prostate cancers, which express trk receptors, CEP-751 induced transient regressions independent of effects on cell cycle. Because androgen ablation is the most commonly used treatment for prostate cancer, we examined whether the combination treatment of CEP-751 with castration would lead to better antitumor efficacy than either treatment alone. For a 60-day period, H tumor-bearing rats received treatment with either castration, CEP-751 (10 mg/kg once a day s.c. for 5 days every 2 weeks), a combination of both, or vehicle. Castration caused tumor regression, followed by tumor regrowth in 4-6 weeks, whereas intermittent CEP-751 treatments resulted in tumor regressions during each treatment, which were followed by a period of regrowth between intermittent drug treatment cycles. Overall, both monotherapies significantly inhibited tumor growth compared with the vehicle-treated control group. However, the combination of castration and concomitant CEP-751 produced the most dramatic results: sigificantly greater tumor regression than either therapy alone, with no signs of regrowth. A related experiment using an orally administered CEP-751 analogue (CEP-701), as the trk inhibitor, and a gonadotrophin-releasing hormone agonist, Leuprolide, to induce androgen ablation demonstrated similar results, indicating that these effects could be generalized to other forms of androgen ablation and other trk inhibitors within this class. In addition, when CEP-701 was given sequentially to rats bearing H tumors, which were progressing in the presence of continuous androgen ablation induced by Leuprolide, regression of the androgen-independent tumors occurred. In summary, these data demonstrate that CEP-751 or CEP-701, when combined with surgically or chemically induced androgen ablation, offer better antitumor efficacy than either monotherapy and suggest that each therapy produces prostate cancer cell death through complementary mechanisms.

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.

Mutational analysis of the TrkA gene in prostate cancer

BACKGROUND

TrkA, the high affinity, tyrosine kinase receptor for nerve growth factor (NGF) has been implicated as an oncogene in several neoplasms. In prostate cancer, inhibitors of the NGF/TrkA signal pathway results in tumor growth inhibition. In contrast, inhibition of this trk pathway in the normal prostate produces no effect. One explanation for this difference between normal and malignant prostate is that TrkA is mutated in prostate cancer, changing its function. To test this possibility human primary prostate cancers were screened for evidence of mutations in the TrkA gene to identify how this gene might be activated in prostate cancer.

METHODS

Single-strand conformation polymorphism was used to screen genomic DNA, isolated from 42 human primary prostate cancers. In samples in which an aberrant banding pattern was identified, the screen was repeated using both the tumor DNA and DNA isolated from normal tissue of the same patients. Genetic changes were confirmed by direct sequencing of the aberrantly migrating bands.

RESULTS

Although somatic mutations were not identified in any of the exons screened, four polymorphisms were detected in three different exons. Some of these polymorphisms occurred in the majority of the patients screened, but their frequencies were similar when compared with DNA isolated from a control group.

CONCLUSIONS

Genetic mutations of TrkA do not seem to play a significant role in activation of this pathway in prostate cancer. However, the absence of mutations in otherwise genetically unstable prostate tumor DNA suggests that intact NGF/TrkA pathways may be important in prostate cancer development.

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.

Membrane association of the myristoylated alanine-rich C kinase substrate (MARCKS) protein appears to involve myristate-dependent binding in the absence of a myristoyl protein receptor

The myristoylated alanine-rich C kinase substrate, or MARCKS protein, has been implicated in several cellular processes, yet its physiological function remains unknown. We have studied the molecular basis of its membrane association in a cell-free system in order to help elucidate its regulation and function. First, we showed that the MARCKS protein incorporated [3H]myristate when its mRNA was translated in vitro in reticulocyte lysates. The myristoylated protein bound rapidly to freshly fractionated cell membranes, while a nonmyristoylated mutant associated to a much lesser extent (< 15% of wild type). To determine whether this binding was due to a specific cytoplasmic-face protein "receptor," as is seen with pp60v-src, we pretreated the membranes in several ways. Prior treatment of membranes with heat (100 degrees C for 3 min) or trypsin did not affect subsequent MARCKS binding. Binding was markedly decreased in 50 mM EDTA, 0.5 M NaCl, or 1.0% Triton X-100; it was restored to normal after removal of the NaCl and EDTA but was still decreased after removal of the Triton X-100. These findings argued against the existence of a protein receptor for the MARCKS protein on cellular membranes. Finally, MARCKS protein phosphorylated in vitro with protein kinase C bound to the cell membranes to the same extent as the nonphosphorylated protein; this binding was also unaffected by an excess of a synthetic peptide corresponding to the phosphorylation site domain of the protein. We conclude that, at least in this in vitro system, the membrane association of the MARCKS protein is primarily dependent on the amino-terminal myristate moiety and does not appear to involve a specific cytoplasmic-face protein receptor.