Bone metabolism biomarkers in men with advanced prostate cancer (PC) and bone metastases treated with denosumab versus zoledronic acid (ZA)

267

Background: Denosumab, compared with ZA, has recently demonstrated significant benefits in preventing skeletal-related events (SREs) in a double-blind phase 3 study of men with castration-resistant PC and bone metastases (N=1901). This post hoc analysis was performed to determine if key bone metabolism biomarker levels correlated with time-to-first SRE. Methods: Time-to-Grade ≥2 increase in total serum alkaline phosphatase (ALP) was assessed for correlation with time-to-first SRE. Levels of urinary N-telopeptide (uNTX) and serum bone-specific alkaline phosphatase (BSAP) markers were measured at baseline and study week 13, and correlations with time-to-first SRE were assessed. Covariate analyses were performed using a Cox proportional hazards model, stratified by treatment group or (for baseline analyses) with treatment group as the independent variable. Results: Analysis of the relationship between time-to-Grade ≥2 increase in total ALP and time-to-first SRE demonstrated that Grade ≥2 increases in ALP of PC patients were associated with a higher risk of first SRE (hazard ratio [HR] 1.838, 95% confidence interval [CI] 1.559, 2.167; P<0.0001). In dichotomized analyses (< vs ≥ median), a higher level of uNTX and BSAP (at baseline or week 13) was correlated with an increased risk of first SRE (Table). In baseline covariate analyses, treatment benefit for denosumab was maintained after adjusting for either baseline uNTX (HR 0.818, 95% CI 0.703, 0.951; P=0.0091) or BSAP (HR 0.813, 95% CI 0.700, 0.943; P=0.0061). Conclusions: Higher levels of uNTX or BSAP at baseline or week 13 were associated with worse SRE outcomes in men with advanced PC and bone metastases. Denosumab was more efficacious for preventing or delaying SREs compared with ZA, regardless of bone-related biomarker levels. Relationship of covariate to time-to-first SRE Clinical trial information: NCT00321620. [Table: see text]

Impact of crossover and baseline prognostic factors on overall survival (OS) with abiraterone acetate (AA) in the COU-AA-302 final analysis

142

Background: AA + prednisone (P) significantly increased OS, time to opiate use, and was well tolerated at the COU-AA-302 final analysis. Here we further characterize OS benefit adjusting for crossover therapy and for baseline prognostic factors. Methods: Patients (N = 1,088) were randomized 1:1 to receive AA (1 g) + P (5 mg po BID) vs P. Co-primary end points were radiographic progression-free survival and OS. Median time to events with 95% CI was estimated using the Kaplan-Meier method. Stratified log-rank test was used to test the difference in treatment effect. Adjustment for crossover utilized the iterative parameter estimate (IPE) and impact of baseline prognostic factors was examined via the multivariate Cox proportional hazard model. Results: With a median follow-up of 49.2 months and 741 deaths (96% of required), AA + P significantly reduced the risk of death vs P (19%) and prolonged median OS (34.7 vs 30.3 months) (Table). 44% of patients initially receiving P alone subsequently received AA + P as crossover per protocol (17%) or as subsequent therapy (27%). IPE adjustment resulted in a 26% reduction in the risk of death (Table). By multivariate analysis, AA + P treatment led to a 21% reduction in the risk of death; baseline prostate-specific antigen (PSA), lactate dehydrogenase (LDH), hemoglobin, alkaline phosphatase (ALP), bone metastases, and age were significant OS prognostic factors (Table). Conclusions: AA + P yielded a statistically significant improvement in OS. Greater improvement in OS was observed after adjusting for the 44% of patients originally on P who ultimately received AA + P. Adjusting for baseline prognostic factors also demonstrated an AA + P OS benefit. Clinical trial information: NCT00887198. [Table: see text]

Prior and concurrent use of abiraterone and enzalutamide with Ra-223 in an expanded access setting

253

Background: The aim of this prospective early-access program (EAP) was to monitor acute and long-term safety of Ra-223 CL2. The ALSYMPCA RA-223 phase III trial was completed prior to abiraterone (Abi) and enzalutamide (Enza) approval. Herein we provide experience with RA-223 in relationship to Abi and Enza. Methods: Symptomatic bone metastatic CRPC pts in the US who were ineligible for or had prior docetaxel were enrolled. Treatment included Ra-223 50 kBq/kg IV q4weeks for 6 cycles concomitant with standard of care medications. Analyses were conducted to assess safety and overall survival (OS) in pts with prior and concurrent Abi and Enza. Results: Of 184 treated, 120 (65%) had prior and 35 (19%) pts had concurrent Abi; 59 (32%) had prior and 25 (14%) pts had concurrent Enza. Baseline characteristics were generally balanced in the overall and across prior and concurrent groups. Pts with no concurrent Abi or Enza had a similar OS to the overall group (Abi 16m, Enza 17m, overall 17m). Due to a small number of events (7 Abi, 6 Enza), a median value was not calculated for the concurrent groups. 8 deaths occurred during treatment none were related to RA-223. The rate of Grade 3-5 AEs was similar across concurrent (Abi 37%, Enza 36%) and prior groups (Abi 43%, Enza 42%) vs overall 41%. Most frequently occurring Gr 3-4 events were anemia (Abi 17%, Enza 8%, overall 11%), thrombocytopenia (Abi 6%, overall 3%), and back pain (Enza 8%, overall 4%). Conclusions: In this EAP, Ra-223 concurrently administered with either abiraterone or enzalutamide was safe and well tolerated adding important information on concurrent use of RA-223 and hormonal agents. Clinical trial information: NCT01516762. [Table: see text]

Denosumab for the prevention of skeletal complications in metastatic castration-resistant prostate cancer: comparison of skeletal-related events and symptomatic skeletal events

In this analysis of a phase III trial in patients with castration-resistant prostate cancer and bone metastases, treatment with denosumab reduced the risk of skeletal complications vs zoledronic acid regardless of whether the end point was defined as SSE or SRE. Both SSEs and SREs were associated with development of moderate/severe pain among patients with no/mild pain at baseline.

Background

In a phase III trial in patients with castration-resistant prostate cancer (CRPC) and bone metastases, denosumab was superior to zoledronic acid in reducing skeletal-related events (SREs; radiation to bone, pathologic fracture, surgery to bone, or spinal cord compression). This study reassessed the efficacy of denosumab using symptomatic skeletal events (SSEs) as a prespecified exploratory end point.

Patients and methods

Patients with CRPC, no previous bisphosphonate exposure, and radiographic evidence of bone metastasis were randomized to subcutaneous denosumab 120 mg plus i.v. placebo every 4 weeks (Q4W), or i.v. zoledronic acid 4 mg plus subcutaneous placebo Q4W during the blinded treatment phase. SSEs were defined as radiation to bone, symptomatic pathologic fracture, surgery to bone, or symptomatic spinal cord compression. The relationship between SSE or SRE and time to moderate/severe pain was assessed using the Brief Pain Inventory Short Form.

Results

Treatment with denosumab significantly reduced the risk of developing first SSE [HR, 0.78; 95% confidence interval (CI) 0.66–0.93; P = 0.005] and first and subsequent SSEs (rate ratio, 0.78; 95% CI 0.65–0.92; P = 0.004) compared with zoledronic acid. The treatment differences in the number of patients with SSEs or SREs were similar (n = 48 and n = 45, respectively). Among patients with no/mild pain at baseline, both SSEs and SREs were associated with moderate/severe pain development (P < 0.0001). Fewer patients had skeletal complications, particularly fractures, when defined as SSE versus SRE.

Conclusion

In patients with CRPC and bone metastases, denosumab reduced the risk of skeletal complications versus zoledronic acid regardless of whether the end point was defined as SSE or SRE.

Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10(-8) in some regions of the cosmic string parameter space.

Denosumab or zoledronic acid (ZA) therapy on pain interference and cancer-specific quality of life (CSQoL) in patients with castrate-resistant prostate cancer (CRPC) and bone metastases (BM)

12

Background: Patients with castration-resistant prostate cancer (CRPC) and bone metastases (BM) may experience debilitating pain that impacts daily functioning and diminishes the quality of life. Previous results from a phase III trial demonstrated superiority of denosumab to ZA in delaying or preventing skeletal-related events (pathological fracture, radiation or surgery to the bone, spinal cord compression) in CRPC patients with BM. In this ad-hoc analysis, we present the results of denosumab or ZA therapy on pain interference (PI) and cancer specific quality of life (CSQoL), focusing on the subgroup of CRPC patients with no/mild pain at baseline. Methods: Men with CRPC and BM (no prior IV bisphosphonate use) were randomized to receive either SC denosumab 120 mg+IV placebo or SC placebo+IV ZA 4mg (adjusted for creatinine clearance) every four weeks. Patients were instructed to take calcium and vitamin D supplements. The Brief Pain Inventory–Short Form (BPI-SF) was used to assess PI. The pre-specified clinically meaningful time of a greater than or equal to two point increase from baseline in PI score (overall, physical, and emotional subdomains) was determined for CRPC patients receiving denosumab or ZA therapy. Patients also completed the Functional Assessment of Cancer Therapy-General (FACT-G) questionnaire at baseline and each monthly visit to determine CSQoL scores. Declining FACT-G scores points to worsening CSQoL, where a greater than or equal to five point decrease is clinically meaningful. Results: Of the 1,901 patients enrolled (n=950, denosumab; n=951, ZA), 1,045 (55%) had no/mild pain at baseline. Compared with ZA, denosumab therapy delayed the time to a greater than or equal to two point increase from baseline in PI for the overall score (HR=0.83 [0.71, 0.98]; P=0.023), physical (HR=0.87 [0.75, 1.02]; P=0.077) and emotional (HR=0.83 [0.71, 0.97]; P=0.020) subdomains. Over a period of 18 months, more ZA-treated patients than denosumab-treated patients experienced a greater than or equal to five point decrease in FACT-G total scores (average relative difference=6.8%, range -9.4 to 14.6%) or worsening of CSQoL. Conclusions: Denosumab therapy significantly delayed the time to worsening of pain interference and maintained a higher overall CSQoL (FACT-G) compared to ZA in CRPC patients with BM. Clinical trial information: NCT00321620.

Optimal testosterone suppression on medical ADT should strive to suppress free testosterone levels to levels similar to orchiectomy: What is that value?

144

Background: The goal of medical androgen deprivation therapy (ADT) for advanced prostate cancer is to provide an equivalency to orchiectomy based upon older assays for serum testosterone (T). Literature shows that based on more modern assays, medical ADT does not always provide optimal total T suppression equivalent to orchiectomy. With the understanding that free, or unbound, T is the biologically and clinically relevant component, the therapeutic goal of ADT should be to decrease free T to levels similar to orchiectomy. Free T has not been well studied in a substantial number of orchiectomized men. The purpose of this study was to examine a subpopulation of orchiectomized men in a clinical trial to determine the level of serum-free T in advanced prostate cancer. Methods: Baseline data was utilized from a double blind, randomized, placebo controlled trial (G300203) to determine the capacity of toremifene 80 mg to prevent bone fractures in men on ADT. This study included 1,389 men from 150 sites in the U.S. and Mexico. Baseline characteristics, including whether men were on medical ADT or status post orchiectomy, were available. Free T levels were assayed at baseline by radioimmunoassay (RIA) (Diagnostic Products Corporation) and are reported for men who underwent orchiectomy. Results: A subpopulation of 114 men underwent orchiectomy. Median age was 76 (range 51 to 90). Median serum free T level was 0.92 pg/ml (min. 0.35 pg/ml and max. 33.95 pg/ml) with a mean level of 1.71 pg/ml ± 2.77. Conclusions: This study is believed to be the largest cohort in which free T levels have been reported in men who underwent orchiectomy. In this cohort, median serum free T is approximately 0.9 pg/ml. This value could be considered to be the optimal testosterone suppression of free T with orchiectomy and represents the goal of medical ADT. At the time this study was performed, RIA was considered to be the standard but has since been shown to underestimate free T levels by 20 to 60%. Currently, equilibrium dialysis coupled with LC-MS/MS is the gold standard, but the results from this analysis provide us with increased understanding of the optimal level of free T in treating advanced prostate cancer. Clinical trial information: NCT00129142.

Efficacy and safety of enzalutamide (ENZA) monotherapy in hormone-naive prostate cancer (HNPC)

5001

Background: In locally-advanced prostate cancer, the antiandrogen bicalutamide (Bic) is used to maintain quality of life relative to castration therapy (LHRHa), but efficacy as a monotherapy is limited. ENZA is an oral androgen receptor (AR) inhibitor with higher AR–binding affinity vs Bic, and it prevents nuclear translocation, shows no DNA binding, and induces apoptosis. ENZA was approved in the US after prolonging overall survival in post-docetaxel metastatic castration resistant prostate cancer. This phase 2 study assessed ENZA monotherapy in patients (pts) with HNPC and noncastrate testosterone (T) ≥230 ng/dL. Methods: Pts with any stage HNPC (ECOG PS 0, life expectancy >1 y) requiring hormonal therapy received ENZA 160 mg/d for 25 wks. Primary endpoint was PSA response (≥80% decline at wk 25). Other endpoints were endocrine levels, pharmacokinetics, safety, and metabolic changes (body composition, bone biomarkers, lipids, and glycemic profiles). Results: 67 pts were enrolled. Median age was 73 y; 39% had metastases, 36% and 24% had prior prostatectomy and radiation, respectively. ENZA levels reached steady state after ~4 wks. Mean changes in metabolic outcomes at wk 25 included: –0.24% total body bone mineral density (BMD), –4.15% lean body mass, 6.85% fat body mass, 14.75% bone alkaline phosphatase, 4.55% total cholesterol, 6.48% triglycerides, –1.98% A1c, –0.10% fasting glucose, and 45.06% HOMA-IR. At wk 25, PSA response was 93% (62/67; 95% CI, 86%–99%); median PSA decrease was –99.6%. Mean T and estrogen increased 114% and 72%, respectively; other endocrine increases were observed, the highest was 185% for luteinizing hormone. Most common treatment-emergent AEs were grade 1 and included gynecomastia (36%), fatigue (34%), nipple pain (19%), and hot flush (18%). Five pts had serious AEs (none drug related). Conclusions: ENZA monotherapy achieved a high PSA response rate and marked PSA decline with efficacy similar to castration. In contrast to castration, BMD remained stable and metabolic variables (fat body mass, lipid and glycemic profiles) were not substantially impacted with ENZA monotherapy over the 6 month study period. Endocrine changes and AEs were consistent with potent AR inhibition. Clinical trial information: NCT01302041.

ARN-509 in men with high-risk nonmetastatic castration-resistant prostate cancer (CRPC)

7

Background: ARN-509 is a novel second-generation anti-androgen that binds directly to the ligand-binding domain of the androgen receptor, impairing nuclear translocation and DNA binding. The Phase II portion of a multicenter Phase I/II study is evaluating the activity of ARN-509 in 3 distinct patient populations of men with CRPC (high risk non-metastatic CRPC, metastatic treatment-naïve CRPC, and progressive disease after abiraterone acetate). Preliminary results for the cohort of patients with high-risk non-metastatic CRPC are presented here. Methods: All patients had CRPC, no radiographic evidence of metastases (pelvic lymph nodes <3 cm below the iliac bifurcation were allowed), and high risk for disease progression based on PSA value ≥ 8 ng/mL within 3 months of enrollment and/or PSA doubling time ≤ 10 months. Patients received ARN-509 at the recommended Phase II dose of 240 mg/day, previously established in Phase I (Rathkopf et al, GU ASCO 2012). The primary endpoint was PSA response rate at 12 weeks according to the Prostate Cancer Working Group 2 Criteria. Secondary endpoints included safety, time to PSA progression and 1-year metastasis-free survival. PSA assessments were collected every 4 weeks and tumor scans were performed every 16 weeks. Results: Forty-seven patients were enrolled between November 2011 and May 2012. The median age was 71 years (range 51 to 88) and at baseline, patients presented with ECOG performance status 0 (77%), Gleason Score 8-10 (32%), and median PSA of 10.7 ng/mL. All patients received prior treatment with a LHRH analog with or without a first-generation anti-androgen. At a median treatment duration of 20 weeks, three patients discontinued the study. The most common treatment-related adverse events (AE) were fatigue (30%), diarrhea (28%), nausea (17%), rash (13%), and abdominal pain (11%). The incidence of Grade 3 AEs was 6.4%, and no seizures have been observed to date. The 12-week PSA response was 91% and the time to PSA progression has not been reached. Conclusions: In men with high-risk non-metastatic CRPC, ARN-509 is safe and well tolerated with promising preliminary activity based on high PSA response rates. Clinical trial information: NCT01171898.

Enzalutamide monotherapy: Phase II study results in patients with hormone-naive prostate cancer

18

Background: Enzalutamide (ENZA) is an oral androgen receptor inhibitor that has been approved in the US and shown to increase overall survival by 4.8 months over a placebo (HR, 0.63) in patients with metastatic castration resistant prostate cancer (CRPC) previously treated with docetaxel (Scher et al, N Engl J Med 2012;367:1187). Compared with bicalutamide in nonclinical studies, enzalutamide had higher androgen receptor–binding affinity, prevented nuclear translocation, showed no DNA binding, and induced apoptosis (Tran et al, Science 2009;324:787). In contrast to previous phase II and III studies that exclusively enrolled patients with CRPC receiving androgen deprivation therapy (ie, testosterone (T) levels ≤50 ng/dL), this phase II study assessed the efficacy and safety of ENZA monotherapy in patients who had never received hormone therapy; presenting with non-castrate T levels (≥230 ng/dL). Methods: This was a 25-wk, open-label, single-arm study of patients with hormone-naïve, histologically confirmed prostate cancer (all stages) requiring hormonal treatment, an ECOG PS score of 0, and a life expectancy >1 y. All patients received ENZA 160 mg/d without concomitment castration. Primary endpoint was PSA response (>80% decrease at wk 25). Secondary endpoints included changes in endocrine levels and safety/tolerability. Results: Among 67 men enrolled, the median (range) age was 73 (48, 86) y; 39% had metastases; 36% and 24% had undergone prostatectomy or radiotherapy before study entry. The PSA response rate (>80% PSA decline at wk 25) was 93%, with a median (range) decrease of −99% (−100, −57) at wk 25. Serum T and estrogen levels increased by a median (range) of 113% (−32, 300) and 58% (−49, 321) at wk 25, respectively, compared with baseline. 82% of men reported drug-related AEs (mostly Grade 1 or 2). Most frequent treatment-emergent AEs included gynaecomastia (36%), fatigue (34%), and hot flush (18%). 7% of men experienced SAEs; none were drug-related. Conclusions: ENZA monotherapy (160 mg) was associated with significant PSA response in nearly all men with hormone-naïve prostate cancer. Endocrine level changes and most common AEs (gynecomastica, fatigue and hot flush) were consistent with potent AR inhibition. Clinical trial information: NCT01302041.

Updated interim analysis (IA) of COU-AA-302, a randomized phase III study of abiraterone acetate (AA) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) without prior chemotherapy

5

Background: AA, a specific inhibitor of CYP17, blocks androgen biosynthesis and improves overall survival (OS) in mCRPC post-docetaxel (Lancet Oncol 2012;13:983-92). This pre-specified updated IA (55% total OS events) extends previous IA for COU-AA-302 evaluating clinical benefit of AA vs prednisone (P) in mildly symptomatic or asymptomatic pts with progressive mCRPC without prior chemotherapy. Methods: 1088 pts were stratified by Eastern Cooperative Oncology Group performance status (ECOG-PS, 0 vs 1) and randomized 1:1 to AA 1000 mg + P 5 mg po BID vs Placebo + P. Co-primary endpoints: radiographic progression-free survival (rPFS) and OS. Median time with 95% CI was estimated using the Kaplan-Meier method. The O’Brien-Fleming Lan-DeMets α-spending function was used for OS. Results: At 55% IA, OS, rPFS and secondary endpoints all favored the AA arm (Table). Median follow-up = 27.1 mos. A post hoc sensitivity multivariate analysis for OS using known prognostic factors supported primary results (HR 0.74, P = 0.0017). Grade 3/4 AEs (AA, P) (%): hypertension 4.2 vs 3.1; hypokalemia 2.6 vs 1.9; ALT↑ 5.5 vs 0.7; AST↑ 3.1 vs 0.9. Conclusions: In updated IA of COU-AA-302, improvement in rPFS (risk reduction 47%) remained statistically significant. Risk of death decreased by 21% but did not reach pre-specified efficacy boundary. Median OS for AA (35.3 mos) is the longest reported for this mCRPC population. Secondary endpoints were clinically and statistically significant; safety profile despite longer exposure remains favorable. Targeting extragonadal androgen synthesis reduces morbidity associated with disease progression in mCRPC pts without prior chemotherapy. Clinical trial information: NCT00887198. [Table: see text]

Efficacy and safety of zoledronic acid in men with castration-sensitive prostate cancer and bone metastases: Results of CALGB 90202 (Alliance)

27

Background: Zoledronic acid (ZA) decreases risk of skeletal-related events (SREs) in men with castration-resistant prostate cancer (CRPC) and bone metastases. This phase III study evaluated efficacy and safety of earlier treatment with ZA in men with castration-sensitive metastatic prostate cancer. Methods: CALGB 90202 was a randomized, double-blinded, placebo-controlled phase III trial in men with castration-sensitive prostate cancer and bone metastases who had initiated androgen deprivation therapy within six months of study entry. Subjects were randomized 1:1 in blinded manner to receive ZA (4 mg intravenously every 4 weeks) or placebo (P). After progression to CRPC, all patients crossed over to open-label ZA. The primary endpoint was time to first SRE. Target sample size was 680. Time to SRE was defined as interval between date of randomization and date of first SRE (radiation to bone, or clinical fracture, or surgery to bone, or death due to prostate cancer). With 470 SRE events, the log-rank test has 88% power to detect a 23% decrease in hazard rate of SRE event assuming a one-sided type I error rate of 0.05. The study was discontinued prematurely after the corporate supporter withdrew study drug supply. Primary analysis was based on the stratified log-rank statistic adjusting on the stratification factors following observation of 284 SREs (60% of total events). Results: Between June 2004 and April 2012, 645 patients were randomly assigned to ZA or P. Median time to first SRE was 32.5 months in the ZA group and 29.8 months in the P group (hazard ratio (HR) 0.96 [0.76-1.22]; stratified log-rank P=0.74). A total of 271 deaths were observed; median follow-up time for surviving patients was 24.4 months (20.6, 28.3). Overall survival was similar between groups (HR= 0.89 [0.70-1.14]; stratified P=0.34). Rates of grade 3 or higher adverse events were similar between groups (15% vs. 12% in ZA and P). Conclusions: In men with castration-sensitive prostate cancer and bone metastases, early treatment with zoledronic acid was not associated with lower risk for SREs or death. Early termination limited statistical power of the study. Clinical trial information: NCT00079001.

Interim analysis (IA) results of COU-AA-302, a randomized, phase III study of abiraterone acetate (AA) in chemotherapy-naive patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

LBA4518

Background: AA is an androgen biosynthesis inhibitor that inhibits CYP17 and improves overall survival (OS) in post-docetaxel mCRPC. The primary objective of COU-AA-302 was to compare clinical benefit of AA + prednisone (P) vs placebo (PL) + P in chemo-naive, asymptomatic/mildly symptomatic mCRPC pts. Methods: 1088 pts (151 centers; 12 countries) were randomized 1:1 to AA (1 g) + P (5 mg BID) or PL + P. Co-primary endpoints: radiographic progression-free survival (rPFS) and OS. Median times estimated using K-M method including LR statistic for inference. The Lan-DeMets α-spending function was used for OS. Results:The Independent Data Monitoring Committee concluded that the OS, rPFS and secondary endpoints (Table) all favored the AA arm and unanimously recommended unblinding the study and crossing pts from PL to AA at IA (43% of total events). Median follow up = 22.2 mos. Grade 3/4 AEs (AA + P, PL + P) (%): hypertension 3.9 vs 3.0; hypokalemia 2.4 vs 1.9; ALT↑ 5.4 vs 0.7; AST↑ 3.0 vs 0.9. Conclusions:AA + P produced a statistically significant improvement in rPFS and a strong trend for increased OS at this IA. AA resulted in clinically and statistically significant effects on all secondary endpoints. IA results confirmed the acceptable tolerability/safety profile of AA. This is the first randomized trial to demonstrate both OS and rPFS benefits in chemo-naive mCRPC and that inhibition of persistent extragonadal androgen synthesis significantly delays initiation of cytotoxic chemo. While median OS (AA arm) has not been reached, median PL arm OS (27.2 mos) is the longest measured in any phase III mCRPC study. [Table: see text]

Interim analysis (IA) results of COU-AA-302, a randomized, phase III study of abiraterone acetate in chemotherapy-naive patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

LBA4518

The full, final text of this abstract will be available at abstract.asco.org at 12:01 AM (EDT) on Saturday, June 2, 2012, and in the Annual Meeting Proceedings online supplement to the June 20, 2012, issue of Journal of Clinical Oncology. Onsite at the Meeting, this abstract will be printed in the Saturday edition of ASCO Daily News.

Effect of denosumab on prolonging bone-metastasis free survival (BMFS) in men with nonmetastatic castrate-resistant prostate cancer (CRPC) presenting with aggressive PSA kinetics

4510

Background: Denosumab, an anti-RANK-ligand monoclonal antibody, has been shown to prolong BMFS by a median 4.2 months and with a 15% risk reduction vs. placebo in men with non-metastatic CRPC and baseline PSA value ≥ 8.0 ng/mL and/or PSA doubling time (PSADT) ≤10.0 months. To determine the efficacy of denosumab in men at greatest risk for bone metastases, we evaluated BMFS in a subset of men with PSADT ≤6 months (previously reported in Smith MR, et al: J Clin Oncol. 23:2918-2925, 2005). Methods: 1,432 men with non-metastatic CRPC (baseline medians: PSA: 12.3 ng/mL, PSADT: 5.1 months, ADT duration: 47.1 months) were randomized 1:1 to receive monthly subcutaneous denosumab 120 mg or placebo. The first patient enrolled February 2006; primary analysis cut-off was July 2010, when >660 men had developed bone metastasis or died. The primary endpoint was BMFS (time to first bone metastasis or death from any cause). BMFS results are presented for men with baseline PSADT ≤6 months. Results: Median BMFS in the placebo group of men with PSADT ≤6 months was 6.5 months shorter than for the placebo group in the full population (18.7 months vs. 25.2 months), indicating that these men are at particularly high risk. In this group of men with PSADT ≤6 months, denosumab prolonged BMFS by a median of 7.2 months and with a 23% reduction in risk compared with placebo (Table). Conclusions: Patients with shortened PSADT are at higher risk of developing bone metastasis and denosumab is markedly effective at prolonging BMFS in this subset of patients. [Table: see text]

Cabozantinib (XL184) in chemotherapy-pretreated metastatic castration resistant prostate cancer (mCRPC): Results from a phase II nonrandomized expansion cohort (NRE)

4513

Background: Cabozantinib (cabo) inhibits MET and VEGFR2. High rates of bone scan resolution, pain relief and overall disease control, independent of PSA changes, were previously reported in a phase II study in mCRPC patients (pts). This is a NRE cohort in docetaxel (D)-pretreated pts with a novel primary endpoint of bone scan response based on computer-aided quantitative assessment of bone scan lesion area (BSLA) and a double-reader, independent, blinded review (Nucl Med Commun, in press). Methods: D-pretreated (≥225 mg/m2) CRPC pts with bone metastasis were required to have progressed in soft-tissue or bone within 6 months of last dose of D. Pts received 100 mg cabo qd. Tumor response was assessed q6 wks. Bone scan response (BSR) was defined by a ≥30% decline in BSLA. Pain intensity (worst pain over the past 24 hrs; BPI scale 0-10) and interference with sleep and daily activity were prospectively assessed using an IVR system. Analgesic use was collected by diary. Bone turnover markers and CTCs were assessed. Results: 93 D-pretreated pts were enrolled (89 evaluable with ≥6 wks f/u). Median age was 67, 46% received cabazitaxel and/or abiraterone, 32% had visceral disease, 51% had fatigue, and 18% had anemia. 44% had worst pain ≥4 of which 95% were taking narcotics. Median CTC count was 49 and 80% had ≥5. Median f/u was 125 days (range, 23-305). Of 85 pts evaluable for BSR, 51 (60%) had a PR, 24 (28%) SD, 5 (6%) PD and 5 (6%) d/c’d prior to f/u scan. 21/30 pts (70%) had reduction of measurable disease.16/33 pts (49%) with BPI ≥4 and ≥12 wks f/u had pain reduction durable for ≥6 wks; 46% had decreased narcotic use, including 27% who discontinued use. Sleep and daily activity were improved in pts with pain relief. Among pts with elevated serum levels, 74%, 67% and 47% had declines on treatment of ≥30% in CTx, NTx and bALP, respectively. In 59 pts with CTCs ≥5, 92% had a decrease of ≥30% and 39% converted to <5 CTCs at weeks 6 or 12. 12% discontinued cabo due to AEs. Most common Gr 3/4 AEs were fatigue (19%), nausea (10%) and anemia (10%). Conclusions: Cabo treatment resulted in high rates of bone scan response, durable pain relief, and reductions in bone turnover markers and CTCs in D-pre-treated CRPC pts with bone metastases.

Prognostic stratification of post-docetaxel metastatic castration resistant prostate cancer (mCRPC) from a phase III randomized trial

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Background: A prognostic model for mCRPC post docetaxel is necessary to guide therapy. We retrospectively analyzed a phase III trial enrolling progressive mCRPC following docetaxel to construct a prognostic model. Additionally, we studied the impact of neutrophil-lymphocyte ratio (NLR), a potential marker for inflammatory and immune state. Methods: A phase III trial (SUN-1120) comparing prednisone combined with sunitinib (N=584) or placebo (N=289) for mCRPC following docetaxel-based chemotherapy was evaluated. The treatment arms were combined for analysis, since no statistical difference was observed in the primary endpoint of overall survival (OS). A logarithmic transformation was applied to non-normal factors. The Kaplan-Meier method was used for OS estimation. To identify an optimal prognostic model for survival, we used a Cox proportional hazards regression methods with forward stepwise selection, stratifying for ECOG PS, progression type (PSA or radiographic) and treatment group. A risk score was calculated and patients were categorized into risk groups to assess model performance. Results: Data from patients without missing data (n=806) were used to construct an optimal model. The factors used in the model that remained individually significant in multivariate analysis were: log-LDH (HR 2.77 [95% CI=2.23, 3.44], p<0.001), hemoglobin (0.81 [0.76, 0.87], p<0.001), log-NLR (1.63 [1.38, 1.92], p<0.001), >1 organ involved (1.53 [1.24, 1.88], p<0.001), log-alkaline phosphatase (1.14 [1.01, 1.30], p=0.041) and log-PSA (1.07 [1.00, 1.13], p=0.036). No clear cutpoints were identified; thus, these prognostic factors were used to group patients into 3 equally sized risk categories. Low, medium and high risk patients (n=268-270 per group) had median (95% CI) OS estimates of 23.7 (21.4-not reached), 13.5 (11.6-15.8) and 7.3 (6.3-8.4) months, respectively. Conclusions: A prognostic risk model with readily available variables significantly discriminated between outcomes in post-docetaxel mCRPC and may provide valuable information in future studies. High NLR was associated with an independent poor prognostic impact, and warrants prospective validation.

Investigator-sponsored trial of efficacy and tolerability of cabozantinib (cabo) at lower dose: A dose-finding study in men with castration-resistant prostate cancer (CRPC) and bone metastases

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Background: Cabo (XL184) is an oral inhibitor of MET and VEGFR2. In a randomized discontinuation trial of cabo 100mg daily, 76% of men with CRPC and bone metastases had partial or complete resolution of bone scan lesions as early as week (wk) 6. However, treatment was limited by adverse events (AEs), with dose reductions in 51% of patients (pts), and discontinuations in 10%. The current study was designed to determine the efficacy and tolerability of cabo at lower starting doses. Methods: An adaptive response scheme was used to determine the lowest active daily cabo dose among dose levels +1 (60mg), 0 (40mg), and -1 (20mg). The primary endpoint was wk 6 bone scan response (BSR) assessed with an automated FDA 510(k) approved computer-aided detection system. A ≥30% decrease in total bone scan lesion area (BSLA) was defined as a response. The first cohort was treated at dose level 0. The number of responses (≥8 vs. <8 among 11 evaluable pts) was used to select the dose level (-1 vs. +1) for the second cohort. Based on the observed BSR rate in the second cohort of 11 pts, a dose was selected for expansion to treat 13 more pts. Results: The study completed planned enrollment of 36 pts. Median age was 66; 44% were docetaxel-pretreated. Among 12 pts enrolled at dose level 0, there were 10 BSRs at wk 6 including 1 complete response (CR), and 1 pt with stable disease (SD). The median decrease in BSLA was 62%. Ten pts evaluated at wk 12 included 9 BSRs (3 CRs), and 1 sustained SD. Among 11 pts then treated at dose level -1, 10 pts were evaluable at wk 6: 1 BSR, 5 SD, and 4 had progressive disease. No pts in the 2 cohorts required dose reduction or treatment interruption at 12 wks; 1 pt discontinued due to grade 3 AEs (anorexia, fatigue). 6/12 pts with ≥6 months follow-up remain on study. 5/5 pts enrolled at 40mg with CTCs ≥5 per 7.5mL converted to <5. Thirteen pts accrued to the expansion cohort at 40mg daily had confirmed high BSR rate. Conclusions: Cabo 40mg daily achieves a high BSR rate in men with CRPC and bone metastases, and is associated with better tolerability than previously reported for cabo 100mg daily.