PROMISE Registry: A prostate cancer registry of outcomes and germline mutations for improved survival and treatment effectiveness

TPS274

Background: Recent updates to genetic testing recommendations and approved treatment options for prostate cancer (PCa) patients (pts) have clarified the need for comprehensive genetic registries. Germline DNA damage repair (DDR) defects are present in over 10% of pts who develop metastatic castration-resistant prostate cancer (mCRPC) while 5-10% pts with localized PCa have germline pathogenic variants in DDR genes. NCCN guidelines have recently expanded to address genetic testing to include high risk localized, node positive and metastatic disease, in addition to family cancer history criteria. In May 2020, the FDA approved 2 PARP inhibitors for mCRPC treatment. Genetic registries can address the critical need to identify pts for recently approved targeted treatments, understand real-world effects of targeted therapies, and expand clinical trials examining less common mutations. PROMISE is a prospective genetic registry equipped to meet these needs. Methods: 5000 PCa pts will be screened via the online study portal and at-home germline testing to identify and enroll 500 eligible pts with germline pathogenic variants, likely pathogenic variants, and variants of uncertain significance (VUS) in the genes of interest: ATM, ATR, BARD1, BRCA1, BRCA2, BRIP1, CHEK2, FAM175A, GEN1, HOXB13, MRE11A, MLH1, MSH2, MSH6, PALB2, PMS2, PTEN, RAD51C, RAD51D, TP53 and XRCC2. Additional genes may be added as evidence emerges. Eligible pts must be assigned male at birth and have documented PCa through tissue biopsy, and/or PSA >100ng/dL, and/or radiographic evidence of disease. Pts with or without prior genetic testing, including those with known pathogenic variants, are encouraged to enroll. Exclusion criteria are: inability or unwillingness to provide information for eligibility and incomplete inclusion criteria. Following germline testing, pts will be offered genetic counseling and periodic newsletters with updates on treatments and clinical trials. Every 6 months, eligible pts will complete a patient-reported outcome (PRO) survey (EORTC QLQ-C30) and updated medical records will be obtained for clinical data abstraction. Eligible pts will enter long-term follow-up. The primary endpoint is the creation of a prospective genetic registry of PCa pts. Additional endpoints include: frequency of pathogenic or likely pathogenic germline variants of interest, recruitment of a control group with a VUS in the genes of interest, association between disease characteristics and germline testing results, comparison of PROs between disease subpopulations, longitudinal outcomes, and overall survival. Study duration is 20 years (recruitment: 5 years, follow-up: 15 years). PROMISE is recruiting at 23 US sites. 1829 subjects have enrolled in the screening phase with 189 eligible for long-term follow-up. PROMISE is sponsored and managed by the Prostate Cancer Clinical Trials Consortium. Clinical trial information: NCT04995198 .

Factors related to men’s experience with prostate cancer germline testing

128

Background: Indications for prostate cancer (PCA) germline testing (GT) have greatly expanded, with genetics delivery being implemented in a variety of ways. Here we evaluate factors related to men’s experience with genetic evaluation (GE) in the PCA Genetic Risk, Experience, and Support Study – PROGRESS Registry. Methods: Men took online surveys that covered demographics, PCA history, mode of GE, and measures of patient-reported outcomes (PROs) (satisfaction [Demarco 2004] [Score 6-30; higher=greater satisfaction], decisional conflict [O’Connor 1995] [Score 16-80; higher=greater conflict], attitude re: GT [Marteau 2001] [Score 1-7; higher=perceived benefit], and knowledge of cancer genetics [Erblich 2005] [% correct of 15 questions]). Data were summarized using descriptive statistics. Multiple linear regression modeling assessed relationships between characteristics, mode of GE, and PROs. Significance level was a nominal α = 0.05 (SAS v9.4). Results: PROGRESS reached accrual goal (n=500). Characteristics (among n=414): 87.7% White, 6.0% Asian, 87.7% bachelor’s degree or higher. Among n=422, 46.9% reported PCA diagnosis. Among n=416 who reported genetic results, 27.9% had pathogenic/likely pathogenic variants (P/LPV), 14.7% had VUS, and 9.9% did not know. Mode of GE was delivered: by genetics professional (GP) (24.9% in-person,10.5% phone, 6% telehealth), by doctor (21.1%), from website (20.8%), by genetics lab (5%), and by video (10.8%). Some reported not having pretest discussion (23.7%) or not knowing (8.1%). From multiple regression models, several factors including race, mode of GE, education, and genetic results were related to PROs. Conclusions: Several factors may impact men’s experience with PCA GE, deserving further study into root causes particularly related to diverse populations and genetics care delivery models to support men and their families. [Table: see text]

Phase II, double-blind, randomized study of salvage radiation therapy (SRT) plus enzalutamide or placebo for high-risk PSA-recurrent prostate cancer after radical prostatectomy: The SALV-ENZA Trial

5012

Background: We sought to investigate whether enzalutamide (ENZA) treatment, without androgen deprivation therapy, increases freedom-from-PSA-progression (FFPP) when combined with salvage radiation therapy (SRT) in men with recurrent prostate cancer post-radical prostatectomy (RP). Methods: Men with biochemically recurrent prostate cancer after RP were enrolled into a randomized, double-blind, phase II, placebo-controlled, multicenter study of SRT + placebo vs SRT + ENZA. The randomization (1:1) was stratified by center, surgical margin status (R0 vs R1), PSA prior to salvage treatment (PSA ≥0.5 vs < 0.5 ng/mL), and pathologic Gleason sum (7 vs 8-10) using a minimization algorithm. Following randomization, patients received either placebo or ENZA 160 mg PO once daily for 6 months. Following 2 months of study drug therapy, external beam radiotherapy to 66.6-70.2 Gy was administered to the prostate bed (no pelvic nodes). The primary endpoint was FFPP. The trial design was powered for a HR 0.44 FFPP benefit with intended enrollment of 96 subjects and was closed as planned to enrollment on March 2020 short of that goal. Secondary endpoints were time to local recurrence (LR) within the radiation field, metastasis‐free survival (MFS), and safety as determined by frequency and severity of adverse events (AEs). Results: A total of 86 patients were randomized with a median follow-up of 34 (range 0-52) months. The median pre-SRT PSA was 0.3 (range 0.06-4.6) ng/mL, 56/86 (65%) had extra-prostatic disease (pT3), 39/86 (45%) had Gleason Grade Group 4 or higher and 43/96 (50%) had positive surgical margins. Trial arms were well balanced. FFPP was significantly improved with ENZA vs placebo, for example 2-year FFPP was 87.1% vs 68.1%, respectively, and overall with a HR 0.40 [95% confidence interval (CI), 0.17-0.92, p-value = 0.026]. Subgroup analyses demonstrate differential benefit (p-value of interaction = 0.031) of ENZA in men with pT3 (HR 0.19, 95%CI 0.05-0.67) vs pT2 disease (HR 1.29, 95%CI 0.34-4.81). There were insufficient secondary endpoint events for analysis. The most common adverse events were grade 1-2 fatigue (13% ENZA vs 9%) and urinary frequency (6 % ENZA vs 8%). Conclusions: SRT plus ENZA monotherapy for men with PSA recurrent high-risk prostate cancer following RP is safe and delays PSA progression relative to SRT alone. The impact of ENZA on distant metastasis or survival is unknown at this time. Additional molecular biomarker analyses are being pursued. Clinical trial information: NCT02203695.

Long-term outcomes and genetic predictors of response to metastasis-directed therapy versus observation in oligometastatic castration-sensitive prostate cancer: A pooled analysis of the STOMP and ORIOLE trials

5025

Background: Prospective reports suggest metastasis directed therapy (MDT) in oligometastatic castration sensitive prostate cancer (omCSPC) is associated with improved treatment outcomes. Here we present long term outcomes of the phase II STOMP and ORIOLE trials and assess the ability of a high-risk (HiRi) mutational signature to provide prognostic and predictive information regarding MDT response. Methods: Patients with omCSPC (< 3 lesions) enrolled on STOMP (n = 62) and ORIOLE (n = 54) randomized to MDT or observation were pooled. The primary endpoint was progression-free survival (PFS) defined as either PSA or radiographic progression, initiation of androgen deprivation, or death. Secondary endpoint was radiographic PFS (rPFS) defined as radiographic progression or death. Both were calculated using the Kaplan-Meier method and stratified by treatment group. Next generation sequencing (NGS) was performed to identify a HiRi mutational signature defined as pathogenic mutations within ATM, BRCA1/2, Rb1, or TP53. Cox proportional hazards regressions were fit to calculate hazard ratios (HR) and assess the prognostic and predictive values of HiRi mutational status. Results: Median follow-up was 52.5 months. Median PFS was prolonged with MDT (11.9 months) compared to observation (5.9 months) with a pooled HR of 0.44 (95% CI, 0.29 – 0.66, p-value < 0.001). MDT was associated with PSA decrease in a majority of patients (84%) as compared to the observation group (41%). On NGS, the incidence of a pathogenic mutation in a HiRi gene was 24.3%. HiRi mutation was prognostic for PFS -- in those without a HiRi mutation median PFS was 11.9 months compared to 5.9 months in those with a HiRi mutation (HR of 1.74, p = 0.06). HiRi mutation was also prognostic for rPFS -- those without a high-risk mutation experienced median rPFS of 22.6 months compared to 10.0 months in those with a high-risk mutation (HR 2.62, p < 0.01). Tumors without a HiRi mutation treated with MDT experienced the longest PFS (13.4 months) while those with a HiRi randomized to observation experienced the shortest PFS (2.8 months). Stratifying by both treatment arms and HiRi status appeared to show a differential benefit to MDT, with those with HiRi mutations experiencing a larger relative magnitude of benefit to treatment: (HiRi mutation: HR of 0.05, p < 0.01; no HiRi mutation: HR of 0.42, p = 0.01; p interaction, 0.12) suggesting a HiRi mutational status can provide information regarding differential response to treatment. Conclusions: Long-term outcomes from the only two randomized trials in omCSPC suggest a sustained benefit to MDT over observation. A HiRi mutational signature appears prognostic for outcomes in omCSPC and those with HiRi might have a relatively larger magnitude of response to MDT. Future studies are needed to optimize patient selection. Clinical trial information: NCT02680587.

BRCAAWAY: A randomized phase 2 trial of abiraterone, olaparib, or abiraterone + olaparib in patients with metastatic castration-resistant prostate cancer (mCRPC) with DNA repair defects

5018

Background: The PARP-inhibitor olaparib is approved for mCRPC patients (pts) with deleterious germline or somatic homologous recombination repair gene mutations (HRRm). PARP1 interacts with androgen signaling, and castration-resistant tumor cells exhibit increased PARP1 activity. Preclinically PARP1-inhibition synergizes with androgen receptor (AR) targeted therapy. BRCAAway is a biomarker selected, randomized, open-label, multicenter phase 2 trial evaluating efficacy of targeting AR vs PARP vs combination in first line mCRPC patients with germline and/or somatic HRRm in BRCA1, BRCA2, or ATM. Methods: Eligible mCRPC pts underwent tumor next generation sequencing and germline testing. Pts with inactivating BRCA1, BRCA2 and/or ATM alterations were randomized 1:1:1 to Arm 1 abiraterone (1000 mg daily) + prednisone (5mg bid) (Abi/pred), Arm 2 olaparib (300 mg bid) or Arm 3 olaparib + Abi/pred. The primary end point is progression-free survival (PFS) analyzed using Kaplan-Meier estimates and Cox regression. Secondary endpoints include measurable disease response rate (RR) by RECIST, PSA-RR, undetectable PSA (≤ 0.2 ng/ml) and toxicity. Arms 1 and 2 pts were allowed to cross over at progression. Pts with other HRRm were treated with olaparib; Arm 4 (ongoing). Results: 161 pts were registered and had NGS testing; 60 pts were randomized to Arms 1-3; to date 59 are evaluable for toxicity and 53 are evaluable for PFS. Baseline median age 67 (range 42-85) years; 54 pts were White, 6 were Black; sites of disease: bone only (n=31), soft tissue only (n=18), bone and soft tissue (n=10); median PSA 14.61 ng/ml (range 0.15-4036.8). Mutational status: BRCA1 only n = 2, BRCA2 only n = 39, ATM only n = 8, and > 1 HRRm n = 11. 34 pts had germline and 26 had somatic mutations. Median (range) follow-up time: 8.3 (0.8, 33.3), 12.2 (2.7, 21.8) and 16.8 (2.9, 41.7) months in Arms 1, 2 and 3. 43 pts had treatment-related adverse events; most common were fatigue (23 pts; 1 Grade (G) 3, 22 G1/2), nausea (17 pts, G1/2), and anemia (9 pts, 2 G3, 7 G1/2). ≥50% PSA decline was 79%, 67%, and 85% of pts in Arms 1, 2, and 3, respectively. Median PSA nadir (ng/mL) (95% CI) Arms 1-3: 2.17 (0.44, 49.27), 3.10 (0.83, 12.01), and 0.50 (0.10, 2.13), respectively. Undetectable PSA, median PFS, and 12-month PFS by Arm are listed in the table. Conclusions: In mCRPC pts with inactivating BRCA1, BRCA2 and/or ATM alterations Abi/pred + olaparib was well tolerated and resulted in longer PFS and better PSA response vs either agent alone. Clinical trial information: NCT03012321. [Table: see text]

Germline BRCA2, ATM and CHEK2 alterations shape somatic mutation landscapes in prostate cancer

148

Background: Prostate cancer (PCa) is a highly heritable malignancy. Germline mutations in homologous recombination repair (HRR) genes, especially in in ATM, BRCA2 and CHEK2, are common in men with PCa, but how these influence somatic mutations is unknown. Characterizing the somatic landscape of tumors from germline HRR-altered PCa patients may provide insights into further therapeutic strategies and identify individuals most likely to benefit from existing therapies. Methods: We retrospectively identified 118 men with germline HRR-altered PCa from Johns Hopkins with available somatic mutation data (g ATM, n = 30; g BRCA2, n = 58; g CHEK2, n = 30). In these patients, somatic NGS analysis were done primarily using prostatic (rather than metastatic) tissues. The proportion of patients in each group with somatic biallelic inactivation was determined. We then compared the somatic mutation landscapes of the 3 groups, focusing on key PCa-relevant genes including AR, TMPRSS2-ERG, PTEN, TP53, BRCA2, ATM, CDK12, APC, FOXA1, AKT1, PIK3CA, and KDM6A among others. Somatic mutation data from primary prostate cancer specimens (n = 3965) found in pooled studies (n = 23) from cBioPortal were included as a reference standard for comparison. Results: Biallelic somatic inactivation was detected in 59% (34/58) of g BRCA2-altered, 47% (14/30) of g ATM-altered, and 0% (0/30) of g CHEK2-altered patients. In all 118 germline HRR-altered individuals, the most common somatic mutations were in BRCA2 (31%), FOXA1 (26%), TMPRSS2-ERG (20%), TP53 (16%), PTEN (15%), and ATM (15%). g BRCA2-altered patients had a higher prevalence of somatic mutations in AR (9% vs 3% in cBioPortal, P < 0.05) and FOXA1 (29% vs 13% in cBioPortal, P > 0.05), suggesting a greater dependency on AR signaling, but a lower prevalence of TMPRSS2-ERG fusions (17% vs 33% in cBioPortal, P < 0.05). g ATM-altered patients had a strikingly low prevalence of somatic TP53 mutations (3% vs 25% in cBioPortal, P < 0.01), indicating mutual exclusivity between these genes. g CHEK2-altered patients had a higher prevalence of somatic CDK12 mutations (10% vs 0% in gATM/gBRCA2 patients, P < 0.05), implying an interaction between CHEK2 and CDK12. No differences were seen between the three groups with respect to alterations in the PI3K/PTEN pathway, WNT pathway, or chromatin-related genes. Conclusions: Biallelic inactivation was frequently observed in PCa patients harboring g ATM and g BRCA2 mutations, but not in those with g CHEK2 mutations. g BRCA2-altered patients were enriched for somatic AR (and FOXA1) mutations and were depleted for TMPRSS2-ERG fusions. g ATM-altered patients were depleted for somatic TP53 mutations, while g CHEK2-altered patients were enriched for somatic CDK12 mutations. Thus, germline mutations appear to impose selective pressures that influence somatic mutation landscapes in PCa.

A systematic review of immune checkpoint inhibitors (ICI) in non-clear cell renal cell cancer (nccRCC) subtypes

353

Background: ICI were approved for advanced RCC treatment either alone or combined with another ICI or a tyrosine kinase inhibitor. While most trial data derive from clear cell (cc) histology, the differential activity of ICI in nccRCC subtypes is not entirely known. The aim of this analysis is to summarize the reported activity of ICI-based therapies in ncc-subtypes or in tumors with sarcomatoid/rhabdoid features. Methods: A systematic literature search following PRISMA guidelines was performed. PubMed, GoogleScholars and ASCO Database were searched for the key-words “renal cell cancer” and “immune check point inhibitors” and equivalents. Publications between July 2016 - July 2021 were considered. All original articles reporting outcomes of ICI in at least 5 patients with an advanced nccRCC were eligible. Case reports, reviews, out of scope publications and articles with no full text available were excluded. Results: This study included a total of 14 publications, mostly case series except one phase II and one phase IIIb/IV trial. The table below summarizes the different histological subtypes included in these studies, more frequently papillary (10-88%), chromophobe (0-34%) and unclassified (4-27.5%) RCC. As for first line (L), ICI monotherapy elicited an overall response ratio (ORR) of 5-26.7%, a median progression free survival (mPFS) of 2.2-4.2 months (m) and a median overall survival (mOS) of 16.3-28.9m. ICI combination therapy associated with a higher ORR of 14.2-33%, a mPFS of 2.4-8.3m and a mOS not reached (NR). In ≥2ndL, ICI alone elicited an ORR of 9.4-22.6%, a mPFS of 3.5-7.1m and a mOS of 11.6m-NR. ICI combination therapy was superior, with a reported ORR of 31-44.4%, a mPFS of 4.3-5.6m and a mOS NR. Overall, ICI therapy elicited a higher ORR in papillary tumors (5-50%). Unclassified RCC response was more variable (0-66.7%). Chromophobe tumors had a lower ORR of 0-20%. ICI therapy outcomes among nccRCC with sarcomatoid/rhabdoid features were of an ORR of 0-42.1%, a mPFS of 2.3-6.9m and a mOS of 25.5m–NR. Nonetheless, outcomes were inferior in ncc comparing to cc tumors. Conclusions: The observed activity of ICI-based therapies was heterogenous among nccRCC subtypes. Combination regimens, papillary subtype and sarcomatoid/rhabdoid features were associated with higher responses. These findings might help treatment decisions and require further validation.[Table: see text]

Virtual genetics board for enhancing knowledge and practice of prostate cancer genetic testing: The ENGAGEMENT study

184

Background: With the increasing indications for germline testing for prostate cancer (PCA), there is a growing need for a spectrum of providers to develop working knowledge and understand considerations of germline testing and genetic counseling. A virtual genetics board was developed to provide case-based discussion of PCA germline testing, standard of care and clinical trial management, hereditary cancer management, and genetic counseling. Methods: A virtual genetics board was launched including experts in GU medical oncology, prostate cancer genetics, radiation oncology, urology, clinical trials, genetic counseling, and molecular oncology. Conferences are held monthly, with cases covering metastatic PCA, high-risk disease, early-stage PCA, or PCA screening. Participants complete a baseline survey of demographic information and cancer genetics knowledge. Post-conference survey includes retaking knowledge questions and feedback on cases and Zoom format. Results: At the time of this report, 57 participants have engaged in the virtual genetics board. Participants include genetic counselors (21%), nurse practitioners (21%), medical oncologists (14%), researchers/scientists (14%), nurses (9%), urologists (5%), radiation oncologists (4%), and other specialties. Practice settings include academic centers (49%), public hospitals (16%), private hospitals (11%), and other settings. The baseline survey was completed by 55 participants, and post-conference survey by 34 participants. Knowledge scores increased regarding cancer inheritance, rates of mutations in metastatic PCA, BRCA2-related cancers, risk of PCA for HOXB13 carriers, and risk for PCA in African American males. Feedback was positive, with over 90% favorable responses on usability of technology, usefulness of case discussions, and relevance to informational needs. Conclusions: Initial results support a virtual genetics board to increase PCA genetic evaluation knowledge. The ENGAGEMENT study is ongoing with monthly live case discussions that are also recorded for on-demand viewing; registration is available at www.prostategenetics.com/engagement.[Table: see text]

PROMISE Registry: A prostate cancer registry of outcomes and germline mutations for improved survival and treatment effectiveness

TPS191

Background: Recent updates to genetic testing recommendations and approved treatment options for prostate cancer (PCa) patients (pts) have clarified the need for comprehensive genetic registries. Germline DNA damage repair (DDR) defects are present in over 10% of pts who develop metastatic castration-resistant prostate cancer (mCRPC) while 5-10% of pts with localized PCa have germline pathogenic variants in DDR genes. NCCN guidelines have recently expanded to address genetic testing to include high risk localized, node positive and metastatic disease, in addition to family cancer history criteria. In May 2020, the FDA approved 2 PARP inhibitors for mCRPC treatment. Genetic registries can address the critical need to identify pts for recently approved targeted treatments, understand real-world effects of targeted therapies, and expand clinical trials examining less common mutations. PROMISE is a prospective genetic registry equipped to meet these needs. Methods: 5,000 PCa pts will be screened via the online study portal and at-home germline testing to identify and enroll 500 eligible pts with germline pathogenic variants, likely pathogenic variants, and variants of uncertain significance (VUS) in the genes of interest: ATM, ATR, BRCA1, BRCA2, BRIP1, CHEK2, FAM175A, GEN1, HOXB13, MRE11A, MLH1, MSH2, MSH6, NBN, PALB2, PMS2, PTEN, RAD51C, RAD51D, TP53 and XRCC2. Additional genes may be added as evidence emerges. Eligible pts must be assigned male at birth and have documented PCa through tissue biopsy, and/or PSA >100ng/dL, and/or radiographic evidence of disease. Pts with or without prior genetic testing, including those with known pathogenic variants, are encouraged to enroll. Exclusion criteria are: inability or unwillingness to provide information for eligibility and incomplete inclusion criteria. Following germline testing, all pts will be offered genetic counseling and periodic newsletters with updates on treatments and clinical trials. Every 6 months, eligible pts will complete a patient-reported outcome (PRO) survey (EORTC QLQ-C30) and updated medical records will be obtained for clinical data abstraction. Eligible pts will enter long-term follow-up. The primary endpoint is the creation of a prospective genetic registry of PCa pts. Additional endpoints include: frequency of pathogenic or likely pathogenic germline variants of interest, recruitment of a control group with a VUS in the genes of interest, association between disease characteristics and germline testing results, comparison of PROs between disease subpopulations, longitudinal outcomes, and overall survival. Study duration will be 20 years (active recruitment: 5 years, follow-up: 15 years). PROMISE is recruiting at 10 US sites and has 282 subjects enrolled in the screening phase to date. PROMISE is sponsored and managed by the Prostate Cancer Clinical Trials Consortium. Clinical trial information: NCT04995198.

SWOG S1216: A phase III randomized trial comparing androgen deprivation therapy (ADT) plus TAK-700 with ADT plus bicalutamide in patients (pts) with newly diagnosed metastatic hormone-sensitive prostate cancer (mHSPC) (NCT01809691)

5001

Background: Tak is an oral selective nonsteroidal 17, 20-lyase inhibitor that blocks the synthesis of gonadal and adrenal androgens. We evaluated the clinical benefit of Tak with ADT in pts with newly diagnosed mHSPC. Methods: Pts with mHSPC with a Zubrod performance status (PS) of 0-2 and a PSA of ≥ 2 ng/ml were randomized 1:1 to ADT+Tak (300 mg twice daily) or ADT+Bic (50 mg daily). Stratification factors included PS (0-1 vs ≥2), extent of disease (minimal vs extensive), and receipt of ADT prior to registration (yes vs no). The primary endpoint was overall survival (OS). Secondary endpoints were progression free survival (PFS; based on PSA, imaging or clinical progression), PSA at 7 months (≤0.2 vs 0.2 < PSA; ≤-4 vs. > 4 ng/ml) and adverse event (AE) profile. With 2.75 yrs to accrue 1,186 eligible pts and 3 additional yrs of follow-up, we would have 90% power to determine a 33% improvement in OS from 54 to 72 mos (1-sided α = 0.025). A final analysis was pre-specified after 523 deaths using a 1-sided α = 0.022 to account for interim analyses. Results: Between 3/2013 and 7/2017, 1,313 pts were randomized and 1,279 were included in the intention-to-treat (ITT) analysis (32 pts were ineligible and 2 pts withdrew consent). Median age was 68 yrs and 10% of subjects were Black. Median PSA was 30 ng/mL (range 2-6710) and 49% of pts had extensive disease. After a median follow-up of 4.9 yrs, PFS and PSA response were significantly improved with Tak over Bic but no significant improvement in OS was observed (Table). More grade 3/4 AEs occurred in Tak vs. Bic arms (43% vs. 14%), and included hypertension (20% vs. 5%) and fatigue (5% vs. 2%). Five pts in Tak and 1 pt in the Bic arm had grade 5 AE. Conclusions: Despite clinically meaningful improvement in various outcome measures with Tak+ADT over Bic+ADT in this representative population of mHSPC, the improvement in OS did not meet the pre-specified criteria for statistical significance. The median OS of 70 mos in the control arm (standard ADT) was higher than that reported in contemporary phase 3 trials in this setting, and 16 mos higher than originally estimated. This trial sets a new landmark for survival estimates when pts with mHSPC have access to multiple approved subsequent life-prolonging therapies. Funding: NIH/NCI/NCTN grants U10CA180888, U10CA180819, U10CA180820; U10CA180821; and in part by Millennium Pharmaceuticals, Inc. (Takeda Pharmaceutical Company LTD) Clinical trial information: NCT01809691. [Table: see text]

The somatic mutation landscape of germline CHEK2-altered prostate cancer

5084

Background: The intersection between germline and somatic genomics is an evolving field in which germline mutations may predispose to unique patterns of subsequent somatic mutations in cancer. Germline mutations in CHEK2, involved in cell cycle regulation and DNA damage response, are associated with an increased risk of prostate cancer (PCa), while somatic-only CHEK2 alterations in PCa are rare. The association of germline CHEK2 (g CHEK2)-altered PCa with somatic mutations is unknown, and may inform hypotheses about the etiology of these cancers. Methods: Germline DNA sequencing of 1,042 consecutive PCa patients (pts) from the public SignalDB database (www.signaldb.org) was analyzed for prevalence of pathogenic g CHEK2 mutations and was compared to individuals from the general population estimated by the ExAC database (containing 53,105 germline exomes). A separate cohort of 33 PCa pts from Johns Hopkins (JH) with known g CHEK2 mutations and available somatic tumor DNA sequencing (from primary prostatic tissue) was used to assess the association of g CHEK2 mutations with somatic mutations in genes that are recurrently altered in PCa ( TP53, RB1, PTEN, ATM, BRCA1/2, and CDK12); the prevalence of these somatic alterations was compared to those in 333 unselected PCa pts from the TCGA cohort. Somatic biallelic inactivation of CHEK2 was analyzed in a subset of pts. After uncovering a potential link between g CHEK2 and somatic CDK12 mutations, we studied a cohort of 69 pts with somatic CDK12 mutations where germline data were also available. Results: 28 of 1,042 (2.7%) PCa pts from SignalDB had a pathogenic g CHEK2 mutation, compared to a population prevalence (in ExAC) of 1.4% (750 of 53,105) (RR 1.9, 95%CI 1.3–2.8, P< 0.001). Strikingly, only 23.8% of pts from SignalDB with g CHEK2 mutations had biallelic inactivation in the tumor . Furthermore, none of the 33 g CHEK2 pts from the JH cohort had evidence of somatic LOH. There were no differences in mutation prevalences involving TP53, RB1, PTEN, ATM, and BRCA1/2 between g CHEK2-altered and non-altered PCa pts. Unexpectedly, 5 of 33 (15%) g CHEK2-altered pts from the JH cohort had a somatic CDK12 mutation, compared to only 3 of 333 CDK12 mutations (1%) in unselected PCa pts from the TCGA cohort (RR 16.8, 95%CI 4.2–67, P< 0.001). Conversely, 11 of 69 (16%) pts with a somatic CDK12 mutation harbored a pathogenic g CHEK2 mutation, compared to 28 of 1,042 (2.7%) unselected PCa pts from SignalDB (RR 5.9, 95%CI 3.1–11.4, P< 0.001). Conclusions: Prostate cancers from g CHEK2-altered pts are infrequently characterized by biallelic CHEK2 inactivation and may be enriched for somatic CDK12 mutations, suggesting a unique mechanism of carcinogenesis that is different from g BRCA2-altered pts. Conversely, somatic CDK12-mutated cancers may be enriched for g CHEK2 mutations. The co-occurrence of CHEK2 and CDK12 mutations suggests a synergistic role in promoting cancer growth.

COMBAT-CRPC: Concurrent administration of bipolar androgen therapy (BAT) and nivolumab in men with metastatic castration-resistant prostate cancer (mCRPC)

5014

Background: During BAT, intramuscular (IM) testosterone (T) is administered, which results in rapid cycling of serum T levels from supraphysiologic to near-castrate in men with metastatic castration resistant prostate cancer (mCRPC). We previously observed anecdotal clinical responses to immune checkpoint blockade (ICB) in mCRPC patients (pts) previously treated with BAT and hypothesized that that a BAT/ICB combination would be synergistic. Here we report a prospective phase 2 study of men with mCRPC treated with BAT in combination with nivolumab. Methods: This was a multi-center, single arm, open label phase 2 trial (NCT03554317) of men with mCRPC who received T cypionate 400mg IM (BAT) every 28 days and nivolumab 480mg IV every 28 days. LHRH agonist treatment was continued. All pts received BAT as single agent therapy for a 12-week lead-in prior to the addition of nivolumab. Eligible pts were those with asymptomatic mCRPC who had soft tissue disease amenable to biopsy and progressed on at least one prior novel AR targeted therapy. Up to one line of chemotherapy was allowed for the treatment of mCRPC disease. The primary endpoint was confirmed PSA50 response rate. Key secondary endpoints included safety, objective response rate (ORR), and radiographic progression-free survival (rPFS). The trial was designed to detect a 20% absolute increase in PSA50 response rate from the null of 25%. Results: 45 pts were enrolled on study and treated. The confirmed PSA50 response rate was 40.0% (N=18/45, 95% CI: 26-56%, P=0.02 against the 25% null hypothesis). For pts with measureable disease, the ORR was 23.8% (N=10/42). Median rPFS on BAT and nivolumab was estimated at 5.7 months (95% CI: 4.9-7.8 months). 11.1% (N=5/45) of pts were free from radiographic progression for 11 or more months. One patient achieved a complete radiographic response, which is ongoing (>13 months). The majority of adverse events (AE) were Grade <2. The most common AEs were edema (20%), nausea (20%), and back pain (13%). Immune related AE (irAE) were generally mild (Grade <2) with N=2 Grade 3 irAE observed (pericarditis, lipase elevation). Serial biopsies were obtained on trial for translational studies. Conclusions: BAT plus nivolumab was well tolerated without concerning safety signals. The combination met the pre-specified primary endpoint of confirmed PSA50 response in a heavily treated population. Durable responses were observed in a subset of pts. Biomarker analysis is ongoing to identify a molecular signature predictive of response. Clinical trial information: NCT03554317. [Table: see text]

Interim results of aasur: A single arm, multi-center phase 2 trial of apalutamide (A) + abiraterone acetate + prednisone (AA+P) + leuprolide with stereotactic ultra-hypofractionated radiation (UHRT) in very high risk (VHR), node negative (N0) prostate cancer (PCa)

5012

Background: Standard of care in VHR PCa is radiation therapy (RT) with 18-36 months (mos) of androgen-deprivation therapy (ADT). With this regimen, chronic ADT toxicity is significant and biochemical recurrence (BCR) frequent. We sought to improve tumor control and minimize toxicity with intensified short course ADT with dual androgen receptor signaling inhibitors (ARSI) and UHRT. Methods: 64 patients (pts) with VHR, N0 PCa were enrolled from 4 centers. VHR PCa was defined as Gleason score (GS) 9-10, >4 cores of GS 8 disease, or 2 high-risk features (including rT3/T4 disease). Treatment (tx) involved 6 mos of A, AA+P, and leuprolide with prostate/seminal vesicle-directed RT (7.5-8 Gy x 5 fractions). The primary endpoint was BCR defined as nadir PSA + 2ng/mL. Biochemical recurrence-free survival (bRFS) is reported herein. Our hypothesized reduction in BCR from 25% to 10% at 3 years (yrs) required 53 pts to provide a power of 0.84 and an alpha of 0.03. Undetectable PSA was defined as <0.10 ng/mL. Non-castrate testosterone (T) was a post-tx value >150 ng/mL. All analyses were intention-to-treat. Toxicity and health-related quality of life measures were evaluated using CTCAEv4.0 and the EPIC-26 questionnaire. Results: Baseline characteristics are summarized in the Table; 63 of 64 pts completed protocol tx. Median time to nadir PSA from tx start was 2 mos (range, 1-9); 63 of 64 pts (98.4%) achieved an undetectable nadir PSA. Median time to post-tx, non-castrate T was 6.5 mos (range, 2.5-25.5). Median follow-up (f/u) for pts without BCR was 30 mos (range, 15-44). Seven pts had BCR; 2-yr bRFS was 95.0% (95% CI, 89.7-100); 3-yr bRFS was 89.7% (95 CI, 81.0-99.3). For the 57 pts without BCR, 56 (98.2%) had T > 150ng/mL at last f/u; median PSA at last f/u was 0.10 ng/mL (IQR, <0.10-0.30); of these, 40 (70.2%) pts had PSAs ≤ 0.20 ng/mL with 24 (42.1%) undetectable. Fifteen pts experienced transient Grade 3 toxicities: 12 (18.8%) with hypertension and 3 with rash (4.7%). EPIC-26 scores for a subset of pts (n=21) at baseline and 12 mos showed no significant decline in urinary or bowel domains; declines in sexual (-11.9) and hormone (-5.7) domains met significance. Conclusions: Compared to historic controls with the long course ADT, AASUR demonstrated impressive 3-yr bRFS, rapid T recovery, and limited toxicities; the safety profile of this regimen was consistent with the known AE profile of the ARSI and RT. This regimen warrants further, randomized evaluation. Funded by Janssen Pharmaceuticals. Managed by the Prostate Cancer Clinical Trials Consortium. Clinical trial information: NCT02772588. [Table: see text]

Comparative effectiveness of systemic treatments for metastatic castration-sensitive prostate cancer: A parametric survival network meta-analysis of randomized controlled trials

5532

Background: Treatment decision-making for metastatic castration-sensitive prostate cancer (mCSPC) is complicated by the unclear comparative effectiveness and widely varying costs of competing strategies. Objective: To compare the effectiveness and safety of systemic treatments for mCSPC. Methods: We searched bibliographic databases, regulatory documents, and trial registries for randomized controlled trials testing active drugs added to androgen deprivation therapy (ADT) for mCSPC. We used Cochrane risk-of-bias tool (version 2) to assess trial quality and Bayesian network meta-analysis (NMA) to estimate the relative effects of competing treatments. In addition to combing published time-invariant hazard ratios (HRs), we reconstructed survival data from Kaplan Meier curves to enable parametric survival NMA that allows time-varying HR. Results: Seven trials with 7,236 patients were included comparing six treatments (Table). Risk of bias is a concern for trials with open label (N=4), missing data (N=3), or unprespecified analysis (N=3). Ordered from the most to the least effective, treatments significantly improving overall survival (OS) include abiraterone acetate, apalutamide, and docetaxel; treatments significantly improving radiographic progression-free survival (rPFS) include enzalutamide, abiraterone, apalutamide, and docetaxel. (see HRs in Table) Allowing time-varying HR produced similar treatment rankings. Serious adverse events (SAE) were substantially increased for docetaxel (odds ratio [OR] 104.17, 95% credible interval [CI] 24.85-1012.32) and slightly increased for abiraterone (OR 1.42, 95% CI 1.11-1.83). Conclusions: Abiraterone provided the largest OS benefit with slightly increased risk of SAE. Apalutamide offered comparable OS benefit with abiraterone without increasing SAE risk. Although enzalutamide delayed rPFS to the greatest extent, longer follow-up is needed to examine its OS benefit. [Table: see text]

A phase II randomized trial of RAdium-223 dichloride and SABR versus SABR for oligomEtastatic prostate caNcerS (RAVENS)

TPS5586

Background: Metastasis directed therapy (MDT) is able to prolong progression free survival (PFS) and forestall initiation of androgen deprivation therapy (ADT) in men with hormone-sensitive, oligometastatic prostate cancer (HSOPCa) compared to observation. While MDT appears to be effective in HSOPCa, a large percentage of men will have disease recurrence. Patterns of failure demonstrate patients tend to recur in the bone following MDT, raising the question of sub-clinically-apparent osseous disease. Radium-223 dichloride is a radiopharmaceutical with structural similarity to calcium, allowing it to be taken up by bone where it emits alpha particles, and therefore might have utility in the treatment of micrometastatic osseous disease. Therefore, the primary goal of the phase II RAVENS trial is to evaluate the efficacy of Stereotactic ablative radiation (SABR) + radium-223 dichloride in prolonging PFS in men with HSOPCa. Methods: Patients with HSOPCa and 3 or less metastases with at least 1 bone metastasis (by conventional imaging) will be randomized 1:1 to SABR alone vs. SABR + radium-223 dichloride. Eligibility criteria include PSA doubling time of < 15 months and ECOG performance status of < 2. Patients cannot be on ADT and must have normal testosterone levels at the time of randomization. Patients randomized to the combination arm will receive six doses of Radium-223 dichloride at four week intervals. A sample size using a 1:1 randomization scheme of 30 patients per arm will provide 80% power to detect an increase of median PFS from 10 months to 20 months with type I error = 0.1, using a one-sided log-rank test. To account for 5% early drop out, we will randomize a total of 64 patients (32 per arm). The primary end point is PFS with a primary hypothesis that SABR + radium-223 dichloride will increase median PFS from 10 months in the SABR arm to 20 months in the SABR + radium-223 dichloride arm. Progression is a composite endpoint including PSA progression per Prostate Cancer Working Group 2 (PCWG2), symptomatic progression, radiologic progression per RECIST 1.1 criteria, initiation of ADT, or death due to any cause. Secondary clinical endpoints include toxicity and quality of life assessments, local control at 12 months, locoregional progression, time to distant progression, time to new metastasis, and duration of response. Biological correlates will be evaluated including changes in circulating tumor cells following therapy, deep sequencing of circulating tumor DNA, and T-cell repertoire profiling before and after therapy. Clinical trial information: NCT04037358 .

RESTORE: A single-arm, open-label phase II trial of bipolar androgen therapy (BAT) in men with metastatic castration resistant prostate cancer (mCRPC)—A comparison of post-abiraterone (Abi) versus post-enzalutamide (Enza) patients (Pts)

5576

Background: A paradoxical inhibition of cell growth has been observed in both androgen-sensitive and castration resistant prostate cancer cell lines following the addition of high-dose testosterone.We have conducted several clinical trials investigating a mode of supraphysiologic testosterone therapy termed, BAT, in which testosterone levels are rapidly driven to the supraphysiologic range followed by a return to near-castrate levels over 28-day treatment cycles with favorable results. We previously reported the efficacy of BAT in mCRPC pts that were progressing on enza. In this study, we compared the effect of BAT in mCRPC pts whose last therapy was abi vs. enza. In addition, we examined the benefit of abi or enza rechallenge after progression on BAT. Methods: 59 mCRPC pts (n = 29 post abi; n = 30 post enza) were enrolled and received at lease one dose of BAT monotherapy, 400mg intramuscularly every 28 days. After clinical or radiographic progression on BAT, pts were rechallenged with the AR targeted therapy to which they were most recently resistant. The co-primary endpoints were a 50% decline in PSA from baseline (PSA50) for BAT and for enza/abi rechallenge. Results: 5/29 (17.2%) of post-abi pts compared to 9/30 (30%) in the post enza group achieved a PSA50 response (P = 0.36). Post BAT rechallenge with abi (n = 19) or enza (n = 22) resulted in a PSA50 response rate of 15.8% (n = 3) and 68.2% (n = 15), respectively (P = 0.001). The total duration of benefit (i.e. PFS on BAT + PFS on rechallenge = “PFS2”) was significantly longer in the post enza vs. post-abi patients (Median PFS2: 12.75 vs. 8.125 months; P = 0.04. Lastly, AR-V7 negative (n = 42) pts has a significantly longer median PFS2 compared to AR-V7 positive (n = 10) pts. (10.3 vs. 7.1 months, P = 0.005). Conclusions: Our data suggest that BAT may be more effective at resensitizing mCRPC to direct AR antagonists (i.e. enza) compared to abi. Detection of AR-V7 portended a worse outcome on BAT/rechallenge. Further clinical study is warranted. Clinical trial information: NCT02090114 . [Table: see text]

TRANSFORMER: Bipolar androgen therapy (BAT) versus enzalutamide (E) for castration-resistant metastatic prostate cancer (mCRPC)

5517

Background: Rapid cycling between high and low testosterone (T) (i.e BAT) produces tumor response in mCRPC, and may overcome resistance to newer AR therapies. Here we report a randomized study comparing BAT to E in men with mCRPC progressing on abiraterone (A). Methods: In this phase 2 trial, men received either T cypionate 400mg IM (BAT) once every 28 days or daily oral E 160mg. Primary endpoint was clinical/radiographic PFS; crossover was permitted at progression. Secondary endpoints were OS, PSA progression to primary and crossover therapy, PSA and objective responses (OR), time to PSA progression from randomization through crossover (PFS2), quality of life (QoL), and AEs. Results: 195 men were randomized (94 to BAT, 101 to E). Results are presented in table. Although diametrically opposed therapies, median PFS and PSA response in the intent-to-treat (ITT) population was not significantly different between BAT and E. OR and OS favored BAT. For those who received BAT and then crossed over to E the PSA50 response was 77.8% and time to PSA progression was 10.9 mo compared to 25.3% and 3.8 mo for those receiving E immediately after A. The sequence of treatment had a significant effect on median PSF2 which was 28.2 mo for men receiving BAT→E vs. 19.6 m for E→BAT. For men who crossed over from BAT to E, OS was 37.3 mo vs. 28.6 months for those receiving E without crossover. AEs were primarily grade 1-2 in the BAT arm and included fatigue, generalized pain, and lower extremity edema. BAT improved QoL (fatigue, physical functioning, sexual function) vs. E. Conclusions: BAT could be safely administered to asymptomatic men with mCRPC. BAT produced a comparable PFS to E in A-refractory mCRPC pts. However, PSA50 and OR after crossover, as well as PFS2, were significantly improved in men who received BAT→E versus E→BAT. OS in men receiving BAT→E was 37.3 mo, exceeding historical expectations. These results support the hypothesis that treatment with BAT is safe, has efficacy and can restore sensitivity to antiandrogens. Clinical trial information: NCT02286921 . [Table: see text]

Treatment response comparisons between ATM and BRCA2 germline carriers for mCRPC

63

Background: Over 10% of men with metastatic prostate cancer (PC) have germline DNA damage response gene alterations; most studies have reported BRCA2 alone or an aggregate of BRCA1, BRCA2 and ATM. Emerging data suggest ATM mutations have distinct effects and warrant individual gene evaluation. We hypothesize that, compared to patients (pts) carrying germline BRCA2 mutations (g BRCA2mut), pts carrying germline ATM mutations (g ATMmut) may have different treatment response to androgen-receptor-targeted agents, docetaxel, platinum therapy and PARP inhibitors (PARPi). Methods: This is an international, multicenter, retrospective case-control study of pts with PC who underwent clinical germline genetic testing between 2014-2019. We identified pts with g ATMmut and matched pts with g BRCA2mut by stage at diagnosis and year of testing. IRB-approved medical records review, χ² and log rank tests were performed. Results: 39 g ATMmut cases and 39 matched g BRCA2mut cases were identified for total of 78. A third (13/39) of pts in each cohort had metastases at diagnosis. Of those diagnosed with localized stage, 81% (21/26) of gATMmut and 73% (19/26) of g BRCA2mut developed metastasis (median times to metastasis 69 vs 49 months, respectively (p=0.1)). Pts in g ATMmut and g BRCA2mut cohorts had similar age, Gleason grade, and PSA at diagnosis. We did not observe a difference in PSA50 response rates to abiraterone, enzalutamide, docetaxel, or carboplatin for mCRPC (Table). g BRCA2mut pts were more likely to respond to PARPi for mCRPC; where available, somatic loss of heterozygosity (LOH) data will be reported at final presentation. Conclusions: While response to standard therapies appears similar between g ATMmut and g BRCA2mut cohorts, response to PARPi in g ATMmut appears to be attenuated compared to g BRCA2mut. More studies are needed and pts with g ATMmut warrant prioritization for novel treatment strategies.[Table: see text]

A phase II randomized trial of Observation versus stereotactic ablative RadiatIon for OLigometastatic prostate CancEr (ORIOLE)

116

Background: Mounting evidence supports metastatic ablation for oligometastatic prostate cancer (OMPC). Importantly, biomarkers to determine patients who benefit most from complete ablation are unknown. We hypothesize that stereotactic ablative radiation (SABR) will improve oncologic outcomes in men with OMPC. Methods: In this phase II randomized trial, men with recurrent hormone-sensitive OMPC (1-3 radiation fields) were stratified by primary management (radiotherapy vs surgery), PSA doubling time, and prior androgen deprivation therapy and randomized 2:1 to SABR or observation (OBS). The primary endpoint was progression at 6 months by PSA (≥ 25% increase and ≥ nadir + 2 ng/mL), conventional imaging (RECIST 1.1 criteria or new lesion on bone scan), or symptomatic decline. Tissue, liquid and imaging correlatives were analyzed as biomarkers. Results: From 5/2016-3/2018, 54 patients were randomized. Progression at six months occurred in 19% of SABR patients and 61% of observation patients [p=0.005]. SABR improved median PFS (not reached vs 5.8 months, HR 0.30, p = 0.0023). Total consolidation of PSMA radiotracer-avid disease decreased the risk of new lesions at six months (16% vs 63%, p = 0.006). No toxicity ≥ grade 3 was observed. T-cell receptor sequencing identified increased clonotypic expansion (p = 0.03) following SABR and correlation between baseline clonality and progression with SABR only. Analysis of circulating tumor DNA (ctDNA) and germline mutations identified a mutation profile that was associated with benefit from SABR. Conclusions: SABR for OMPC improves outcomes and is enhanced by total consolidation of disease identified by PSMA-targeted PET. SABR induces a systemic immune response, and baseline immune phenotype and tumor mutation status may predict the benefit from SABR. These results underline the importance of prospective randomized investigation of the oligometastatic state with integrated imaging and biological correlates. Clinical trial information: NCT02680587.

Evaluation of the patient-reported outcomes common terminology criteria for adverse events (PRO-CTCAE) with abiraterone acetate plus prednisone (AAP), degarelix (D), or the combination in men with biochemically recurrent prostate cancer (BCRPC)

5080

Background: Patient-reported symptoms using the PRO-CTCAE provide insights into the patient experience with care. Earlier use of AAP (an androgen biosynthesis inhibitor plus prednisone) with androgen deprivation therapy in castration sensitive disease may lead to increased symptoms. We previously reported a randomized phase 2 trial of intermittent AAP, D, or AAP+D in BCRPC (NCT01751451) and now share the PRO-CTCAE results. Methods: Men were randomized 1:1:1 to AAP, D, or AAP+D for 8 months, then entered follow up with PSA, testosterone, and safety monitoring. PRO-CTCAE was elicited from patients monthly for hot flashes (HF), fatigue, arthralgias, myalgias, anxiety, depression, sexual function, plus overall QOL. Changes from baseline to end of treatment were compared between groups. AUCs were calculated for each item as a measure of symptom severity over time. Results: 110 men were included. Compliance with PRO-CTCAE reporting from baseline to EOT was 93%. HF did not differ between AAP+D and D, but were increased relative to AAP (all p < 0.05). These differences were consistent when HF were measured as an AUC (all p < 0.01). Fatigue severity did not differ between groups however men receiving AAP reported a small worsening in activity interference from fatigue as compared to AAP+D (p < 0.05). Overall QOL scores were high and did not differ with AAP+D relative to AAP or D. Conclusions: Collection of PRO-CTCAE was feasible and did not demonstrate differences in fatigue, HF, or QOL between AAP+D and D. Comparisons of PRO-CTCAE to matched clinician-reported AEs, and changes in PRO-CTCAE with testosterone recovery during follow up are planned. Clinical trial information: NCT01751451.

A phase I dose escalation study of PCUR-101 in men with metastatic castration-resistant prostate cancer (mCRPC)

e16517

Background: The combination of PCUR-101 (a synthetic form of the plant-derived medicinal agent, plumbagin) and surgical castration caused regression of androgen dependent tumors in mice. These promising pre-clinical results led to this first-in-human study of PCUR-101 in combination with androgen deprivation therapy (ADT) in men with metastatic, castrate resistant PCa (mCRPC). Methods: The goal of this phase I multicenter trial was to determine the safety profile, maximum tolerated dose (MTD), recommended phase II dose, clinical activity, and pharmacokinetic (PK) parameters of PCUR-101. A 3 + 3 dose escalation design was employed. Patients (pts) in cohorts of 3 were treated with escalating doses of PCUR-101 (50 mg – 200 mg) orally once daily continuously. Cycles were 28 days. Exploratory correlates of IL-6 and urine polyamines were also included. Results: 12 pts (median age 75 [range 63-86]) with mCRPC on ADT were treated in the dose escalation cohorts. No DLTs were observed during treatment and the MTD was not reached. The most frequent adverse events (AEs) included diarrhea (11 pts; all grade 1 or 2), nausea (7 pts; all grade 1 or 2), vomiting (4 pts; all grade 1 or 2) and constipation (3 pts; all grade 1 or 2). No objective responses were observed but 1 pt had PSA decrease by > 50%. Pts remained on study treatment for a median of 10 weeks (range 3-32 weeks). 5 pts, with stable disease, remain on active treatment. PK data could not be fully evaluated due to issues with the PK assay. Analyses of IL-6 and putrescine levels in pt samples indicate that, as compared to no treatment, PCUR-101 treatment in each cycle was associated with decreases in their levels. Reasons for treatment discontinuation included disease progression (n = 4), adverse event (n = 1; nausea and vomiting), subject withdrawal (n = 1), and investigator or sponsor decision (n = 1). After treating 12 pts, the sponsor decided to stop the trial in order to reformulate the study drug to allow for higher dosing and to redevelop the PK assay. Conclusions: At the doses evaluated, PCUR-101 combined with ADT was seen to be safe and may prolong disease stability in men with mCRPC. A second phase I study is planned using a new drug formulation and PK assay. Clinical trial information: NCT03137758.

Baseline genomic and circulating tumor cell (CTC) correlative data from very high-risk (VHR), localized, node-negative prostate cancer patients

e16563

Background: Few data exist on CTC frequency and number, genetic landscape, and tumor mutational burden (TMB) in VHR, node negative, localized prostate cancer (PCa). Methods: We are conducting a single-arm phase 2 trial of ultra-hypofractionated radiation (RT) with 6 months of abiraterone, apalutamide and leuprolide in VHR PCa, defined as: Gleason (Gl) 9-10 or 2 high risk features (including radiographic (r) T3/T4 disease) or > 4 cores of Gl8. We report baseline correlatives in the first 38 screened patients (pts). CTCs were isolated using a non-selection based platform (EPIC Sciences). Additional analyses were conducted using MSK IMPACT, a next generation sequencing assay. Results: Median PSA was 14.8 ng/mL (IQR, 7.7-28.1); Gl7 was present in 5% (n = 2), Gl8 in 32% (n = 12), Gl9 in 61% (n = 23) and Gl10 in 2% (n = 1) of pts; on MR, 42% of pts were rT2 (n = 16), 39% had rT3a disease (n = 15) and 18% had rT3b disease (n = 7). CTC data were available on 31 pts; 74% (n = 23) had ≥1 detectable CTC (range, 0.8-14.6 cells per mL); 29% (n = 9) had CK+ clusters (range, 0.8-7.1 clusters per mL). IMPACT was available for 20 pts: KMT2D/C mutations were present in 25% (n = 4), TP53 missense mutations in 20% (n = 4), FOXA1 mutations in 20% (n = 4), PTEN truncating or missense mutations in 15% (n = 3), SPOP missense mutations in 15% (n = 3), PIK3CA activating mutations in 15% (n = 3), APC deletions in 15% (n = 3); 85% (17/20) had alterations in one of these genes. No clinically significant germline mutations were present. Median TMB was 2.63 mutations/mB (range, 0.87-60.56); the TMB-highest pt had an in-frame deletion in MSH2. Among IMPACTed pts with normalized testosterone post-protocol treatment (n = 16), there was a trend towards an association with SPOP/FOXA1 mutations and undetectable ( < 0.05 ng/mL) PSA; 5/6 pts with mutations had undetectable PSA (83.3%) vs 3/10 without (30%) (p = 0.12). The trial is managed by the PCCTC and funded by Janssen. Conclusions: The genetic profile and TMB of VHR, localized PCa resembles non-castrate, metastatic disease. The frequency of detectable CTCs is high with implications for post-treatment surveillance. SPOP/FOXA1 mutations may predict initial response to RT with total androgen blockade. Clinical trial information: NCT02772588.

Overcoming resistance to antiandrogens with a TGF-β RI inhibitor in preclinical mouse model of PCa

288

Background: Epithelial-mesenchymal transition (EMT) is a significant contributor to PCa metastatic progression and therapeutic resistance in patients treated with the androgen receptor (AR) directed therapies. We previously demonstrated that aberrant TGF-β signaling accelerates prostate tumor progression in the TRAMP mouse model of tumorigenesis via selective effects on EMT. Methods: We hypothesize that the combination of the TGF-β receptor inhibitor, galunisertib (G), and enzalutamide (E) will perturb the interactive signaling between TGF-β and AR signaling affecting the phenotypic landscape of EMT. This perturbation may be exploited in our mouse model, towards enhanced anti-tumor efficacy in advanced castration-resistant PCa (CRPC). We treated 2-week old mice for two weeks with the G (75mg/kg) and/or E (30mg/kg) in combination and as single agents. Results: Treatment with G alone or in combination with E resulted in a significant reduction in prostate tumor weight without affecting total body weight. Immunohistochemical (IHC) and Western blot analysis showed that, while treatment with the G alone led to increased apoptosis and decreased cell proliferation, combination of G and E had significantly higher efficacy in inducing apoptosis and inhibiting cell proliferation than either E or G alone. As expected treatment with the G decreased the levels of nuclear Smad4 protein; the combination of G and E further decreased nuclear Smad4 expression. Furthermore the combination of G and E reversed phenotypic EMT to MET (mesenchymal-epithelial-transition), as assessed by the increase in E-cadherin among the prostate tumor cell populations. IHC and Western blot analysis also revealed that the combined treatment of G and E led to a significant decrease in nuclear AR levels compared to E-only-treated or vehicle-control tumors. Conclusions: These results provide significant insights as to the therapeutic impact of G to effectively impair the TGF-β signaling and overcome resistance of PCa patients to E by reversing EMT to potentially sensitize tumors to the antiandrogen effect. This study has major translational relevance; the combination of G and E may lead to synergistic anti-tumor impact in patients with CRPC.

Phase II study of bipolar androgen therapy (BAT) in men with metastatic castration-resistant prostate cancer (mCRPC) and progression on enzalutamide (enza)

5017

Background: Androgen receptor (AR) overexpression is a common adaptive resistance mechanism in mCRPC. High dose testosterone in this setting may induce tumor responses and restore normal AR expression. To evaluate BAT, we enrolled men with mCRPC progressing on enza to assess (1) responses to BAT and (2) enza re-challenge after BAT. Methods: Eligible men had minimally symptomatic mCRPC with progression on enza. Subjects received testosterone cypionate 400mg IM every 28d and continued gonadal suppression, until progression. Subjects were evaluated with PSAs each cycle, and CT/bone scans every 3 cycles. Upon progression on BAT, men were re-challenged with enza. The co-primary endpoints were > 50% PSA responses (PSA50) to BAT and PSA50 to enza re-challenge. The null hypothesis was a PSA50 rate of 5% for both endpoints, with alternative hypotheses of 20% to BAT and 25% to enza. 30 subjects were required for 90% and 83% power, respectively, with overall type 1 error of 0.1. Secondary endpoints were safety, objective response, progression-free survival (PFS), and effect on circulating tumor cell-based AR and AR-V7 expression. Results: 30 eligible subjects were accrued (2014-2016). No dose limiting toxicities were seen. 2 subjects had transient pain flares after BAT initiation. Common grade 1-2 adverse events (AE) were musculoskeletal pain (40%), increased hemoglobin (37%), breast tenderness (17%) and rash (17%). 3 Grade 3-4 AE potentially attributable to BAT occurred (pulmonary embolism, NSTEMI, and urinary obstruction). 9/30 men (30% [95% CI: 17-48%]) achieved a PSA50 to BAT. 5/14 men (36%) with measurable disease had an objective response by RECIST 1.1. The median clinical/radiographic PFS on BAT was 8.6 months. 21 subjects proceeded to enza re-challenge, yielding 15 PSA50 responses (54% by intention to treat [95% CI: 34-69%]), with a PFS of 4.8 months. 1/3 AR-V7+ subjects responded to BAT, and all had decreased AR-V7/AR ratios (2 converted to AR-V7-) after 3 cycles. Conclusions: The study met its primary endpoints, demonstrating preliminary efficacy of BAT in men with progressive mCRPC after enza. A randomized study comparing BAT to enza in mCRPC is ongoing. Clinical trial information: NCT02090114.

A phase II randomized trial of observation versus stereotactic ablative radiation for oligometastatic prostate cancer (ORIOLE)

TPS5094

Background: ORIOLE is a randomized, non-blinded Phase II interventional study evaluating the safety and efficacy of SBRT in biochemically recurrent, oligometastatic, hormone-sensitive prostate cancer at 3 centers in the US. Patients will be stratified by clinical characteristics and randomized 2:1 to SBRT or observation. The primary clinical endpoint is progression at 6 months defined by PSA increase, radiologic or clinical evidence, ADT initiation, or death from any cause. Secondary endpoints include local control at 6 months, SBRT-associated toxicity and quality of life, and ADT-free survival. Imaging and laboratory correlates will characterize, in isolation, the effects of SBRT on oligometastatic disease. Methods: Eligible patients are hormone-sensitive, have undergone prior definitive treatment and recurred with 1-3 asymptomatic bone or soft tissue metastases diagnosed within 6 months, PSA doubling time (PSADT) < 15 months, ECOG performance status ≤ 2, and normal organ and marrow function. Minimization will be used to balance assignment by primary intervention, prior ADT, and PSADT. Accrual of 54 patients provides 85% power to detect a decrease in progression rate from 80% to 40% with type I error = 0.05 using one-sided Fisher’s exact test. Hazard ratios and Kaplan-Meier estimates of progression free survival, ADT free survival, and time to locoregional and distant progression will be calculated based on intention-to-treat. Local control will be assessed using RECIST 1.1 criteria. Withdrawal prior to 6 months will be counted as progression. Adverse events will be summarized and quality of life pre- and post-SBRT will be measured by Brief Pain Inventory. The investigational targeted imaging agent 18F-DCFPyL will be compared to bone scan and CT for identifying oligometastases before SBRT and monitoring disease response following SBRT. Biological alterations induced by SBRT will be investigated using circulating tumor cell analysis, deep sequencing of circulating tumor DNA, and T-cell repertoire profiling. A hereditary cancer assay will inform efforts to advance personalized screening and therapy. Clinical trial information: NCT02680587.

PSA doubling time (PSADT) and proximal PSA value predict metastasis-free survival (MFS) in men with biochemically recurrent prostate cancer (BRPC) after radical prostatectomy (RP)

5075

Background: We previously reported a relationship between PSADT and MFS in BRPC post RP (Pound 1999; Freedland 2007; Antonarakis 2012). In men with PSADT<12 months, who are at high risk of lethal PCa, we sought to identify a PSA cutpoint (proximal PSA; PP) that indicates the imminent emergence of metastasis (M+). In this report we combined Center for Prostate Disease Research and Johns Hopkins (CPDR/JHU) databases to investigate the association of the PP value on MFS in men with BRPC and PSADT <12 mos. Methods: In the CPDR/JHU RP database (31,296), 513 men with BCR (>0.2ng/ml) with PSADT <12 mos who received no adjuvant/salvage ADT/RT were prospectively followed until radiological evidence of M+ are included in this analysis. All patients were evaluated yearly with >1 PSA and scans at regular intervals until M+. Associations with MFS were compared using logrank test and Cox regression. The PP is the most recent value >6 months prior to M+/censor. Results: M+ occurred in 218 of 513 patients with BRPC (median follow up 9 years). Risk of M+ increased successively for PSADT 6.0-7.5, 4.5-6, 3.0-4.5, and <3.0 months, adjusted for pT stage and Gleason score. PP ≥10ng/ml significantly increased risk of M+ in pts with PSADT <12 mos, regardless of PSADT subgroup, hazard ratio=2.95, p<.0001. Median MFS was 4.0 years at PP >10ng/ml vs 20 years at PP <10ng/ml. Table 1 shows median MFS and 3, 5, and 7 year MFS rates in subgroups with PSADT <3 and 3.01-6 months representing the highest risk groups. Conclusions: In men with PSADT<12 months, PSADT subgroups <7.5 months and PP >10ng/ml are independent predictors of MFS, adjusted for pT stage and Gleason score. PP ≥10ng/ml further define risk of M+ in BRPC with PSADT<12 months. These data can assist physicians in patient counseling and clinical trial design. [Table: see text]

Risk factors for metastatic prostate cancer: A sentinel event case series

235

Background: After 25 years of declines in late stage prostate cancer (PCa), evidence is mounting that an increasing fraction of men may present with metastatic disease, well after they might have been treated with local therapy. Identification of modifiable risk factors may allow for systems-level interventions to reduce delayed diagnoses. Methods: We performed an in-depth case series analysis of 15 patients who presented with metastatic disease at Johns Hopkins Sidney Kimmel Comprehensive Cancer Center using root cause analysis, a tool commonly employed to understand the root cause of dangerous adverse events. Results: Key factors in late diagnosis include lack of insurance, lack of routine PSA testing, comorbidities, reluctance of patients to follow up actionable PSA as well as aggressive disease. Three patients had aggressive disease that would likely not have been discovered at an early stage regardless screening. However, analysis of the remaining 12 patients illuminated how health system factors led to missing important diagnostic information might have led to diagnosis of PCa at an earlier stage. Conclusions: These cases emphasize the need for systems-based approaches to early diagnosis of prostate cancer, which may prevent men from missing the opportunity to cure prostate cancer at an early stage. These results show how one might target PCa screening recommendations to more fully reflect key risk factors such as race and family history.

Immune evaluation study of sipuleucel-T (Sip-T) in African-American and European-American men with castration-resistant prostate cancer

206

Background: Sipuleucel-T (Sip-T) is an autologous cellular immunotherapy indicated for asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC) patients and targets the prostate antigen, prostatic acid phosphatase (PAP). In Phase 3 trials of Sip-T, there was a suggestion that AA men treated with Sip-T had enhanced OS benefit compared to the general population. This study was designed to evaluate the peripheral immune parameters in African American (AA) and European American (EA) prostate cancer patients receiving Sip-T treatment. Methods: Peripheral blood mononuclear cell and serum samples were evaluated for T- and B cell responses in 10 AA and 20 EA men with mCRPC. Antigen-specific T cell response was measured by IFN-γ Elispots, antigen-specific IgG and IgM responses to PA2024, PAP, PSMA, and PSA by ELISA, cytokine and chemokine levels by luminex and immune cell phenotyping by flow cytometry in the PBMC at baseline, 6-, and 10-week time points after completion of Sip-T treatment. Results: IFN-γ EliSpots were ≥ 2-fold higher when stimulated with PA2024 and PAP antigens in AA compared to EA patients post treatment. Humoral immune responses (IgM) to PA2024 and PAP was ≥ 100-fold higher at 6 and 10 weeks after completion of the 3rd infusion in both groups, however, there were no appreciable differences in antibody levels between AA and EA patients. Interestingly, there were ≥ 2-fold higher IgM titers for non-targeted PSA and PSMA at 6 and 10 weeks post treatment compared to baseline levels in both groups suggesting epitope spreading. Humoral responses (IgM) to PAP, PSA and PSMA at baseline were higher in AA patients compared to EA patients. The Th1 and Th2 cytokine and chemokine profiles showed no difference between AA and EA men except for inflammatory chemokine IL-8 which gradually decreased at 6 and 10 weeks from the baseline in AA patients compared to the transient decreases in EA patients. Conclusions: Our preliminary results are suggestive of slightly increased IFN-γ EliSpot responses in AA patients compared to EA patients. Both, AA and EA showed potent IgM antibody response to PA2024 and PAP antigens post treatment compared to the baseline levels. Clinical trial information: NCT01727154.

A phase II study of muscadine grape skin extract in men with biochemically recurrent prostate cancer

248

Background: Pulverized muscadine grape ( Vitis rotundifolia) skin (MPX) is a potential therapeutic option for men with biochemically recurrent (BCR) prostate cancer (PCa) wishing to defer androgen deprivation therapy. MPX demonstrated antitumor effects in PCa through antioxidant activity of its principal polyphenol components, ellagic acid, quercetin, and resveratrol. A Phase I trial demonstrated safety of MPX in doses up to 4000 mg/day. Methods: This is a 12-month, multi-center, placebo-controlled, two-dose, double-blinded trial of MPX (manufactured by Muscadine Naturals Inc. in Warsaw, NC) in 125 men with BCR PCa. Participants were stratified by baseline PSADT and Gleason score, with no restrictions for PSADT and no upper limit PSA value. Patients were randomly assigned 2:2:1 to receive 4000 mg (8 capsules) of MPX, 500 mg (1 capsule) of MPX plus 7 capsules of placebo, or 8 capsules of placebo. PSA levels were obtained every 3 months The trial was powered to detect a statistically significant between-group difference of around 6 months (low dose) and 12 months (high dose) in PSADT relative to placebo. Results: The intention to treat (ITT) population included 116 patients, of which 97% were treated for up to 6 and 58% were treated for up to 12 months. This ITT population was 79% white, with median age 68 years, 47% with Gleason score ≤ 6 or 3+4, and 12% with ECOG status of 1. Median PSADT in the ITT population lengthened from 7.5 months at baseline (range 1.4 to 74.6) to 9.8 months after treatment (range 2.3 to 151.5) (p < 0.001). There was no significant treatment difference in PSADT between the control and the treatment groups (p = 0.84). Eighteen percent (21/116) of men had a post-baseline PSADT of more than 200% of baseline. No clinically significant toxicities were seen. Conclusions: These data suggest that both 500 and 4000 mg of MPX are safe. The lengthening PSADT in patients treated with MPX is not significantly greater than that provided by placebo. A subgroup analysis of patients more likely to benefit (those with the AA genotype of MnSOD) is ongoing. Clinical trial information: NCT01317199.

Bipolar androgen therapy (BAT) in men with hormone sensitive (HS) prostate cancer (PC)

236

Background: We documented a paradoxical anti-tumor effect when castration-resistant prostate cancer patients were treated with intermittent, high-dose testosterone (i.e. BAT) [PMID: 25568070]. Since the adaptive increase in androgen receptor expression that follows chronic androgen deprivation therapy (ADT) may underlie this effect, we tested whether men with HS PC would also respond to BAT if given following a 6-month ADT lead-in. Methods: Men with asymptomatic HS PC and low metastatic burden (N = 20) (no visceral disease, ≤ 10 bone metastases, no lymph nodes > 5 cm short axis diameter) or non-metastatic biochemically recurrent disease (N = 13) were enrolled. Following 6-months of ADT, those with a PSA < 4 ng/ml went on to receive 2 cycles of BAT. A cycle of BAT was defined as intramuscular testosterone (T) cypionate or enanthate 400 mg on Days (D) 1, 29 and 57 followed by ADT alone D 85-169. ADT was continued throughout the study to allow for rapid cycling from near castrate to supraphysiologic range T following T injections. The primary endpoint was the percent of patients with a PSA < 4 ng/ml after 2 cycles of BAT, with the study designed to reject a null rate of 40% at a one-sided alpha = 0.1. Secondary endpoints included quality of life (QOL) as measured by the SF-36, FACT-P, IIEF and IPSS surveys. Results: Twenty-nine of 33 patients received BAT following the ADT lead-in (1 withdrew consent, 3 had PSA > 4 ng/ml). The primary endpoint was met, with 17/29 men (59%, lower bound 90% confidence interval = 45%) having a PSA < 4 ng/ml after 2 cycles of BAT. Ten patients receiving BAT had RECIST evaluable disease, and 8 (80%) objective responses were observed (4 complete; 4 partial). Three patients progressed per RECIST criteria and 3 had unconfirmed progression on bone scan. Men treated with 6-months of ADT had improved QOL after the first cycle of BAT. The median improvement in SF-36, FACT-P, and IIEF total scores were 3.2 (range, -20 to 48; P = 0.21), 3.5 (range, -30 to 50; P = 0.04), and 10 (range, -4 to 59; P < 0.001) points, respectively. There was no change in total IPSS score (median change 0 [range, -9 to 8; P = 0.87]). Conclusions: BAT demonstrated preliminary efficacy in men with HS PC following 6-months of ADT. BAT may improve QOL in men that have received ADT. Clinical trial information: NCT01750398.

Risk of prostate cancer in African-American men: Evidence of mixed effects of dietary quercetin by serum vitamin D status

BACKGROUND

African-American (AA) men experience higher rates of prostate cancer (PCa) and vitamin D (vitD) deficiency than white men. VitD is promoted for PCa prevention, but there is conflicting data on the association between vitD and PCa. We examined the association between serum vitD and dietary quercetin and their interaction with PCa risk in AA men.

METHODS

Participants included 90 AA men with PCa undergoing treatment at Howard University Hospital (HUH) and 62 controls participating in HUH's free PCa screening program. We measured serum 25-hydroxy vitD [25(OH)D] and used the 98.2 item Block Brief 2000 Food Frequency Questionnaires to measure dietary intake of quercetin and other nutrients. Case and control groups were compared using a two-sample t-test for continuous risk factors and a Fisher exact test for categorical factors. Associations between risk factors and PCa risk were examined via age-adjusted logistic regression models.

RESULTS

Interaction effects of dietary quercetin and serum vitD on PCa status were observed. AA men (age 40-70) with normal levels of serum vitD (>30 ng/ml) had a 71% lower risk of PCa compared to AA men with vitD deficiency (OR = 0.29, 95%CI: 0.08-1.03; P = 0.055). In individuals with vitD deficiency, increased dietary quercetin showed a tendency toward lower risk of PCa (OR = 0.91, 95%CI: 0.82-1.00; P = 0.054, age-adjusted) while men with normal vitD were at elevated risk (OR = 1.23, 95%CI: 1.04-1.45).

CONCLUSION

These findings suggest that AA men who are at a higher risk of PCa may benefit more from vitD intake, and supplementation with dietary quercetin may increase the risk of PCa in AA men with normal vitD levels. Further studies with larger populations are needed to better understand the impact of the interaction between sera vitD levels and supplementation with quercetin on PCa in AA men.

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

BACKGROUND

We previously showed that pretreatment detection of androgen receptor splice variant-7 (AR-V7) in circulating tumor cells (CTCs) from men with castration-resistant prostate cancer is associated with resistance to abiraterone and enzalutamide, but not to taxane chemotherapies. Here, we conducted serial measurements of AR-V7 and evaluated patterns of longitudinal AR-V7 dynamics over the course of multiple sequential therapies.

PATIENTS AND METHODS

Metastatic prostate cancer patients treated at Johns Hopkins with AR-directed therapies or taxane chemotherapies underwent serial liquid biopsies for CTC-based AR-V7 analysis at baseline, during therapy, and at progression. We used a CTC enrichment platform followed by multiplexed reverse-transcription polymerase chain reaction analysis to detect full-length androgen receptor and AR-V7 transcripts. Patients selected for inclusion in this report were those who provided ≥4 CTC samples, at least one of which was AR-V7 positive, over the course of ≥2 consecutive therapies.

RESULTS

We identified 14 patients who received a total of 37 therapies and contributed 70 CTC samples for AR-V7 analysis during a median follow-up period of 11 months. Three patients remained AR-V7 positive during the entire course of therapy. The remainder underwent transitions in AR-V7 status: there were eight instances of 'conversions' from AR-V7-negative to -positive status (during treatment with first-line androgen deprivation therapy, abiraterone, enzalutamide, and docetaxel), and six instances of 'reversions' from AR-V7-positive to -negative status (during treatment with docetaxel and cabazitaxel).

CONCLUSIONS

AR-V7 is a dynamic marker, and transitions in AR-V7 status may reflect selective pressures on the tumor exerted by therapeutic interventions. While 'conversions' to AR-V7-positive status were observed with both AR-directed therapies and taxane chemotherapies, 'reversions' to AR-V7-negative status only occurred during taxane therapies. Serial blood-based AR-V7 testing is feasible in routine clinical practice, and may provide insights into temporal changes in tumor evolution.

AR splice variant 7 (AR-V7) and response to taxanes in men with metastatic castration-resistant prostate cancer (mCRPC)

138

Background: AR-V7 is a truncated form of AR that lacks the ligand-binding domain but remains constitutively active. We previously showed that detection of AR-V7 from circulating tumor cells (CTCs) in men with mCRPC was associated with primary resistance to enzalutamide and abiraterone. Here, we hypothesized that AR-V7[+] patients would retain sensitivity to taxane chemotherapy. Methods: We used a qRT-PCR assay to interrogate CTCs for AR-V7 mRNA in prospectively enrolled patients with mCRPC starting docetaxel or cabazitaxel. We sought associations between AR-V7 status and PSA response rates (the primary endpoint), PSA progression-free survival (PSA-PFS), and clinical/radiographic progression-free survival (PFS). Multivariable regressions were performed to determine the independent effect of AR-V7 status on clinical outcomes. 36 taxane-treated men were required to produce a 2-sided 95% CI for the difference in PSA response rates (between AR-V7[+] and AR-V7[–] men) with an upper bound of 60%, assuming that 30% of men would be AR-V7[+]. Results: 37 taxane-treated patients were enrolled, and 17 (45.9%) had detectable AR-V7 in CTCs. PSA responses were achieved in both AR-V7[+] and AR-V7[–] men (41% vs 65%, P=0.19). Median PSA-PFS was comparable in AR-V7[+] and AR-V7[–] men (4.5 vs 6.2 mo, HR 1.72, P=0.32). Likewise, median PFS was comparable in AR-V7[+] and AR-V7[–] men (5.1 vs 6.9 mo, HR 2.65, P=0.11). After incorporating data from our prior study in 62 abi/enza-treated patients, it was observed that clinical outcomes in AR-V7[+] men were superior with taxanes than with abi/enza, while outcomes did not differ by treatment type in AR-V7[–] men. For example, in AR-V7[+] men, PSA responses were higher in taxane-treated versus abi/enza-treated men (41% vs 0%, P<0.001), and median PSA-PFS and PFS were longer in taxane-treated men (HR for PSA-PFS = 0.19, P=0.001; HR for PFS = 0.21, P=0.003). Conclusions: Detection of AR-V7 in CTCs from men with mCRPC is not associated with primary resistance to taxane chemotherapy, and such patients may retain sensitivity to taxanes. Further, in AR-V7[+] men, taxanes appear to be more efficacious than abi/enza. AR-V7 may represent a treatment-selection marker in mCRPC.

A phase I trial of muscadine grape skin in men with biochemically recurrent prostate cancer

263

Background: New therapies are being explored as an alternative to observation in men with biochemically recurrent prostate cancer (BRPC). Muscadine Grape Skin (MPX) is comprised of ellagic acid, quercetin, and resveratrol and demonstrates preclinical activity against prostate cancer cells in vitro. Here we summarize data from a phase I dose finding trial. Methods: This phase I study assigned non-metastatic BRPC patients to increasing doses of MPX (Muscadine Naturals) in cohorts of two patients, with six patients at the highest dose, using a modified continual reassessment method. Dose selection is based on preclinical data showing the equivalent of 500 to 4,000 mg of MPX to be safe in mouse models. Our primary end point was to determine the recommended phase II dosing. We calculated changes in prostate-specific antigen (PSA) doubling time (PSADT) from at least three measurements prior to trial initiation and PSA measurements on study. Results: The cohort (n=14, 71% white, 29% black) had a median follow-up of 14.7 (6.9 to 20.7) months, median age 61, median Gleason seven, and median PSA of 5.1 ng/mL (0.2 to 153.4). Four patients had possibly related gastrointestinal symptoms, including grade 1 flatulence, grade 1 soft stools, and grade 1 burping. No other related adverse events were reported and one patient reported improvement of chronic constipation. Two of 14 patients came off study for metastatic disease. Median within-patient PSADT increased from 9.4 to 12.3 months with a PSADT difference of 3.9 months. Conclusions: These data suggest that 4,000 mg of MPX is safe, and exploratory review of change in PSADT suggests there is enough data to proceed to a phase II trial. Both low dose (500 mg) and high dose (4,000 mg) MPX are being further investigated in a multicenter, placebo-controlled, dose evaluating phase II trial. Clinical trial information: NCT01317199.

The effect of PSA frequency and duration on PSA doubling time (PSADT) calculations in men with biochemically recurrent prostate cancer (BRPC) after definitive local therapy

4559

Background: The prognostic nature of PSADT in men with BRPC makes it an attractive intermediate endpoint for assessing novel therapies in these patients. Although a number of investigational agents appear to favorably modulate PSADT, slowing in PSADT has also been observed in placebo-treated men. We aimed to determine whether PSADT calculations could be influenced by the frequency and duration of PSA measurements. Methods: We performed a retrospective analysis of men with BRPC who chose to defer hormonal therapy. Eligible men were those with PSA values ≥0.2 ng/mL and at least 6 values taken on average 3 mo apart, and whose local prostate cancer therapy was completed ≥1 year prior. To examine the influence of PSA frequency and duration on PSADT, we calculated median PSADT using different subsets of available PSA values (e.g. each vs every other; and first 3 vs. remaining PSA values). Results: After a median follow-up of 58 mo (range, 6-185 mo), 213 men with BRPC had ≥6 PSA values and 127 men had ≥9 PSA values for analysis. Men (77% white, 23% black/other) had a median age of 61 y with Gleason score distribution as follows (≤6: 30%; 7: 40%; ≥8: 18%; NOS: 12%). For men with ≥6 data points: PSADT calculated using earlier values ranged from 13.2 to 16.6 mo, compared to 16.6 to 17.8 mo, respectively, for the remaining values (within-patient change range: 0.6-1.2 mo). For men with ≥9 data points: PSADT calculated using earlier values ranged from 15.3 to 19.9 mo compared to 22.1 to 22.3 mo, respectively, for the remaining values (within-patient change range: 3.5 to 4.5 mo). When we examined the frequency of PSADT by using every other value, we found little difference (22.3 vs 22.1 mo). Conclusions: These data show that PSADT appears to increase even in the absence of therapy, and may be influenced by duration of PSA follow up. This finding explains PSADT slowing on placebo arms and calls into question the utility of PSADT as a surrogate endpoint. Placebo-controlled trials and the use of standard clinical endpoints are recommended to screen novel agents in men with BRPC to mitigate bias because of natural PSADT variability.

First-in-human study of AMG 900, an oral pan-Aurora kinase inhibitor, in adult patients (pts) with advanced solid tumors

3009

Background: Aurora kinases A, B, and, C play essential roles in regulating cell division. Overexpression of aurora A and B in human tumors is associated with high proliferation rates and poor prognosis. AMG 900 is an investigational, orally administered, highly selective inhibitor of aurora A, B, and C that demonstrated activity in drug-resistant cell lines and human tumor xenografts. This study evaluated the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of AMG 900. Methods: Key eligibility criteria: ≥ 18 years old, advanced solid tumors, measurable disease, ECOG ≤ 2, and adequate organ function. AMG 900 was administered orally daily for 4 consecutive days (D) every 2 weeks (Q2W). In the dose-escalation phase, the starting dose was 1 mg and was escalated by 100% in subsequent cohorts (1 pt/cohort) until dose limiting toxicity (DLT) or grade 2 (G2) AMG 900-related toxicity occurred in the first 28 D. Dose escalation continued in a standard 3+3 design at ≤ 25% if DLT occurred or ≤ 50% if G2 related toxicity occurred. The maximum tolerated dose (MTD) was determined without prophylactic G-CSF support. Results: As of OCT 2011, 19 pts (1 pt at 1, 2, 4, and 8 mg; 3 pts at 16 mg; and 6 pts at 24 and 30 mg) had received ≥ 1 dose of AMG 900. Demographics were 58% women, median age 60 (32-77) years, and ECOG 0/1, 63%/37%. There were 4 DLTs: G4 neutropenia > 7 days at 24 mg (n=1) and 30 mg (n=1); G4 neutropenia > 7 days + G4 thrombocytopenia at 30 mg (n=1); and febrile neutropenia (FN) at 30 mg (n=1). MTD without G-CSF support was 24 mg. 89% of pts had treatment-related adverse events (AEs). G≥3 treatment-related AEs were neutropenia, 8 (42%); leukopenia, 4 (21%); anemia, 2 (11%); thrombocytopenia, 1 (5%); and FN, 1 (5%). Preliminary PK showed no obvious departures from dose-proportionality with a half-life of ~16 h. Tumor-response data were available for 17 pts: stable disease, 13 pts (range 0.4 to 43.7 wks); progressive disease, 4 pts. One pt (16 mg cohort) with recurrent ovarian cancer had 16% tumor shrinkage and 45% decrease in CA-125 (SD > 6 months). Conclusions: AMG 900 administered at 24 mg daily for 4D Q2W is the recommended dose for phase 2 trials. Dose escalation is now ongoing to determine the MTD with prophylactic G-CSF.