Abstract 1694: Systemic granulocyte-macrophage colony-stimulating factor (GM-CSF) treatment increases T cell receptor diversity in localized and metastatic prostate cancer patients

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is frequently utilized as an adjuvant in cancer immunotherapies, and has known effects as a growth factor. However the extent to which GM-CSF modulates the adaptive immune response, including possible effects on the antigenic repertoire, remains unclear. We used next-generation sequencing of T cell receptor (TCR) beta chain sequences amplified from total RNA from peripheral blood mononuclear cells using consensus primers to assess changes in the circulating antigenic repertoire of prostate cancer patients treated with GM-CSF in multiple clinical trials. Administration of systemic GM-CSF monotherapy to patients with localized prostate cancer prior to planned radical prostatectomy (NCT00305669) results in a significant decline in clonality from the pre-treatment timepoint to the 2-week timepoint on treatment, indicative of increased early repertoire diversity (p=0.039 by Wilcoxon signed rank test). In a separate clinical trial (NCT00064129), the combination of systemic GM-CSF (250 μg/m2/day on days 1-14 of each cycle) with ipilimumab in metastatic castrate-resistant prostate cancer (mCRPC) patients also resulted in a significant decline in clonality from pre-treatment samples to the 2-week timepoint on treatment (p=0.002). In contrast, mCRPC patients who received ipilimumab alone in a separate study (NCT00323882) did not experience a similar decline in clonality after 3 weeks on treatment (p=0.625). In addition, comparison of the dynamics of specific clonotypes between the paired timepoints in the two mCRPC studies demonstrates that while there is no significant difference in the ratios of post-treatment to pre-treatment clonality between studies, patients treated with the combination of iplilimumab and GM-CSF show more repertoire change, with lower Morisita’s distance for all clones found at either timepoint (p=0.023), smaller intraclass correlation coefficient (p=0.028), and a smaller proportion of clonotypes that remain unchanged (defined by +/- 2-fold change for clones found at both timepoints) (p=0.002). These results indicate increased repertoire turnover when GM-CSF is combined with checkpoint inhibition. Hence data from both localized and metastatic prostate cancer, and from monotherapy and combination therapy regimens, supports a role for GM-CSF in inducing early diversification of the TCR repertoire.

Citation Format: David Y. Oh, Li Zhang, Jason Cham, Alan Paciorek, Mark Klinger, Malek Faham, Susan F. Slovin, Lawrence Fong. Systemic granulocyte-macrophage colony-stimulating factor (GM-CSF) treatment increases T cell receptor diversity in localized and metastatic prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1694. doi:10.1158/1538-7445.AM2017-1694

Circulating tumor cells (CTCs) N-terminal androgen receptor expression to identify patients (pts) with castrate resistant prostate cancer (CRPC) who are more sensitive to chemotherapy

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Background: Loss of the retinoblastoma tumor suppressor (RB) function was identified as a major means to develop CRPC; the expression of the androgen receptor (AR) is under stringent RB control; and tumors devoid of RB function are hypersensitive to treatment with chemotherapy. Exploratory analysis evaluated baseline N-terminal AR expression in CTCs in men with chemotherapy-naïve CPRC and correlated to changes in PSA, leading us to inquire if this biomarker may identify pts sensitive to chemotherapy. Methods: In a multicenter phase II randomized trial of approved doses of abiraterone acetate/prednisone (AA-Arm 1) or combination AA and standard doses of cabazitaxel (AA/CBZ-Arm 2). Patients on AA received CBZ upon progression. Baseline CTCs were obtained on all pts and expression of N-terminal AR expression was performed by Epic Sciences. Positive AR N-terminal expression (AR+) was based on the presence of at least 1 CTC or CK- cell with AR N-terminal signal expression above the 3.0 positivity threshold. Serial PSAs were determined at baseline and every 3 weeks with routine labs and imaging every 12 weeks. Results: To date, 42 of 80 pts have been enrolled: 22 pts to AA, and 20 pts to AA/CBZ. Both regimens were well tolerated with 8/42 (19%) pts experiencing treatment-related grade 3 or 4 toxicities. Blood from 35 patients underwent CTC analysis. Seventy-seven percent of pts (27/35) had detectable CTCs; 11 of 35 pts (31%) had AR overexpression. Of the pts with AR+ CTCs, 1/5 pts treated with AA, and 5/6 pts treated with AA/CBZ had a PSA decline > 50% from baseline. Conclusions: Real-time CTC analysis of N-terminal AR expression was feasible and data suggests that this may identify a cohort of pts who may benefit from the combination of CBZ with AA. Further studies are ongoing to evaluate whether cellular heterogeneity and RB expression in CTCs play a role in identifying pts who would benefit from chemotherapy. The trial is coordinated by the Prostate Cancer Clinical Trials Consortium, LLC and funded by Sanofi US Services Inc. and Prostate Cancer Foundation. Clinical trial information: NCT02218606.

Next-generation sequencing (NGS) of tissue and cell free DNA (cfDNA) to identify somatic and germline alterations in advanced prostate cancer

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Background: With the goal of accelerating enrollment onto appropriate clinical trials, we performed prospective genomic characterization of pts with advanced prostate cancer. Given the long natural history and osseous disease predominance, we also analyzed plasma cfDNA to assess the feasibility of identifying targetable alterations in pts for whom adequate tumor tissue was unavailable. Methods: 1038 tumors from 896 pts along with matched normal DNA were analyzed with a capture-based NGS assay (MSK-IMPACT) targeting 341–468 genes. In 5/2015, the protocol was amended to allow pts to opt-in for a formal germline analysis of 76 genes associated with heritable cancer risk. In select pts, plasma cfDNA was collected and analyzed using the same assay. Results: Between 2/2014 and 2/2017, 576 primary tumors and 462 metastases were sequenced. The most notable finding was the high frequency of known or likely pathogenic germline and somatic mutations in genes that regulate DNA damage response (DDR). In the subset with both tumor and germline analysis, 28.84% (169/586) had a DDR mutation identified compared to only 10.65% (33/310) of pts with somatic only analysis. In the subset with tumor and germline analysis, 9.39% (55/586) had somatic only DDR mutations and 16.38% (96/586) had germline only DDR mutations, including 8 pts with two germline mutations. 3.07% (18/586) had co-occurring somatic and germline DDR mutations, with only 0.68% (4/586) involving the same DDR gene (all BRCA2). Prostate cancer had the highest tissue failure rate among the overall MSK-IMPACT solid tumor cohort, and bone biopsy-derived tissue was successfully sequenced in only 42% of pts. Profiling of cfDNA did identify somatic DDR or AR mutations in 12.5% (4/32) of pts without adequate tumor for analysis. Conclusions: This prospective genomic profiling effort identified frequent somatic and germline DDR mutations that may guide PARPi or platinum therapy. Both somatic and germline analyses were required to identify all pts with likely pathogenic DDR alterations. NGS-based cfDNA analysis is feasible in advanced prostate cancer and may identify mutations missed by tumor only sequencing.

A phase II trial of abiraterone acetate (AA) without prednisone in castration resistant prostate cancer (CRPC)

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Background: AA blocks CYP17 and suppresses adrenal androgens and glucocorticoids. Given the risk of mineralocorticoid excess (ME), AA is administered with corticosteroids. In this phase II multicenter, single-arm study, we assess the safety of AA without steroids in CRPC. The primary objective is to determine the proportion of men requiring prednisone to manage ME. Methods: Eligible patients had CRPC with controlled blood pressure (BP) ( < 140/90 on ≤3 agents) and a normal or ≥3.5 mmol/L potassium. Patients initially received AA (1000 mg daily) alone. Patients who developed a BP ≥ 140/90 were treated with anti-hypertensives (HTN) and/or a mineralocorticoid antagonist (MA) prior to steroids. Hypokalemia was treated with supplementation or a MA. Patients with persistent or severe ME were initiated on prednisone (5 mg twice daily). To assess response to steroids, prednisone was added to AA at PSA progression. Therapy was continued until radiographic progression, toxicity, or withdrawal. Results: 60 patients were enrolled of whom 51 (83%) had metastases 16 (27%) received prior chemotherapy, 6 (10%) enzalutamide, and 4 (7%) ketoconazole. Grade (G) 3-4 adverse events (AEs) of interest included HTN (G3 n = 8, 13%; G4 n = 1, 2%), hypokalemia (G3 n = 4, 7%; G4 n = 0), fatigue (G3 n = 1, 2%; G4 n = 0). There was no G ≥3 edema. 9 patients (15%) initiated prednisone for toxicity: HTN (n = 3, 5%), hypokalemia (n = 4, 7%), fatigue (n = 2, 3%). Baseline PSA was 15.4 ng/mL. Time to nadir PSA was 2.5 months (IQR 1.4, 6.3) and median nadir PSA was 2.1 ng/mL. 67% of patients (n = 40) experienced a ≥50% PSA decline and 35% (n = 21) experienced a ≥90% decline. 19 patients (32%) initiated prednisone for PSA progression. Median time to prednisone initiation in patients with PSA progression was 6.1 months (IQR 4.9, 11.7); 5 patients (8.3%) had a PSA decline and 1 achieved a ≥50% decline. Levels of corticosteroids will be reported. Conclusions: In CRPC, AA without steroids is feasible, however clinically significant AEs, particularly HTN, can occur in a minority of patients. HTN and hypokalemia can be treated with anti-HTN agents or potassium without steroids in the majority. Use of AA without prednisone needs to be balanced with the potential risk of toxicity. Clinical trial information: NCT02025010.

The Role of Therapeutic Layering in Optimizing Treatment for Patients With Castration-resistant Prostate Cancer (Prostate Cancer Radiographic Assessments for Detection of Advanced Recurrence II)

OBJECTIVE

To offer recommendations on identification of disease progression, treatment management strategies, and suggestions on timing of initiating and discontinuing specific castration-resistant prostate cancer (CRPC) treatments.

MATERIALS AND METHODS

The Prostate Cancer Radiographic Assessments for Detection of Advanced Recurrence II Working Group convened to provide guidance on sequencing, combination, or layering of approved treatments for metastatic CRPC based on available data and clinical experience.

RESULTS

A consensus was developed to address important questions on management of patients with metastatic CRPC.

CONCLUSION

In the absence of large-scale clinical trials, the Working Group recommends that patients may best be managed with a layered approach of approved therapies with unique or complimentary mechanisms of action.

A phase II study combining ipilimumab and degarelix with or without radical prostatectomy (RP) in men with newly diagnosed metastatic noncastration prostate cancer (mNCPC) or biochemically recurrent (BR) NCPC

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Background: Androgen deprivation therapy (ADT) does not completely eliminate disease in mNCPC or BRPC. We explored a multimodality treatment (tx) approach combining ADT with ipilimumab (ipi) with the aim of achieving no evidence of disease or complete elimination of disease, given the potential for cure seen with immunotherapy. Methods: Cohort A (Coh A) enrolled men with ≤ 10 bone metastases treated with induction of degarelix (deg) and ipi prior to RP and subsequent ipi q3 weeks x 3 and 8 months (mos) total of deg. Cohort B (Coh B) opened later and enrolled men with BRNCPC after RP with a doubling time ≤ 12 mos, and received ipi q3 weeks x 4 and 8 mos of deg. The primary endpoint was an undetectable PSA (<0.05) at 12 and 20 mos with non-castrate testosterone. Results: 16 pts (7 Coh A; 9 Coh B) were treated. No Coh A pts experienced immune related toxicities (irAE) that delayed surgery. 4/7 (57%) Coh A pts came off study for irAE, 1 (14%) for insurance reasons, and 2 (29%) completed all protocol requirements. In Coh B 6/9 (67%) pts have completed tx and entered follow-up. Conclusions: A combined modality approach with ipi 10mg/kg, ADT, and RP in mNCPC was associated with limiting toxicities, however 3mg/kg was better tolerated and more feasible in a BRNCPC cohort. One pt in Coh A (14%) had an undetectable PSA with testosterone recovery while evaluation of efficacy for Coh B is ongoing. The role for RP and other immunotherapeutic approaches in NCPC remain viable interests to the field. Clinical trial information: NCT02020070. [Table: see text]

Targeting reciprocal feedback inhibition: Apalutamide and everolimus in patients with metastatic castration-resistant prostate cancer (mCRPC)

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Background: Studies in xenograft CRPC and PTEN-deficient prostate cancer models have shown synergistic anti-tumor activity of next-generation anti-androgens such as apalutamide when combined with PI3K/mTOR inhibitors such as everolimus. (Carver B et al., Cancer Cell 2011) The primary hypothesis of this study was that the combination of apalutamide with everolimus would overcome resistance to prior hormonal therapy with abiraterone acetate and prednisone (AAP). Methods: The primary endpoint in mCRPC patients with prior AAP was to evaluate the safety, pharmacokinetics (PK), and recommended phase 2 dose (RP2D) of fixed dose apalutamide 240 mg po qd when combined with everolimus 5 mg po qd (cohort 1, n = 3) and everolimus 10 mg po qd (cohort 2, n = 6). The plan was to expand to treat 40 patients at the RP2D. Results: Nine patients were enrolled in phase 1. The PK for the combination was consistent with historical data of either drug given as monotherapy. The most common treatment related adverse events were < = grade 2 fatigue (67%), diarrhea (56%), and anorexia (56%). In cohort 2, 1 patient had a DLT of grade 3 rash. The median time on treatment was 17 weeks (range 7-51+). The best response was SD in all 9 patients. Patients came off study for: progression (n = 3), investigator choice (n = 3) and toxicity unrelated to treatment (n = 2). Seven patients had detectable CTCs at baseline (EPIC Sciences). One patient had a rise in CTC number that then converted to undetectable and remained on study 37 weeks. One out of 6 evaluable patients had PTEN loss in tissue at baseline (MSK IMPACT) and remained on study 12 weeks. One patient with prior AAP and enzalutamide exposure has remained on study 51+ weeks with a > 50% decline in PSA (PTEN pending). Conclusions: Although the combination of apalutamide and everolimus was safe and well tolerated, the treatment response was similar to historical data of AAP followed by apalutamide alone. (Rathkopf D et al., ASCO 2014) We elected to close this study before expansion in favor of evaluating novel AR/PI3K pathway combinations in patients who have not yet been exposed to AAP. Drug provided by Janssen and Novartis. Trial support: PCF and MSK Experimental Therapeutics Center. Clinical trial information: NCT02106507.

Seizure rates in enzalutamide (ENZ)-treated men with metastatic castration-resistant prostate cancer (mCRPC) at increased risk of seizure: UPWARD study

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Background: ENZ is an androgen receptor inhibitor that improved survival in studies of men with mCRPC. Seizure is a risk of ENZ treatment, and patients (pts) with seizure risk factors were excluded in prior studies. In the TRUVEN report (data on file), pts with mCRPC and potential seizure risk factors, but no ENZ exposure, had a seizure rate of 2.8/100 pt-years. The UPWARD study assessed the seizure risk in ENZ-treated pts with mCRPC who had potential seizure risk factors. Methods: This was a global, multicenter, single-arm, open-label safety study. Enrolled pts had ≥ 1 baseline potential seizure risk factor, including medications lowering seizure threshold, stroke, or prior seizure history. Evaluable pts had ≥ 3 months (ms) of treatment with ENZ or ≥ 1 confirmed seizure in a 4-m treatment period. Exclusion criteria included seizure within the past 12 ms and receipt of anti-epileptic medication. Pts received ENZ (160 mg/day). The primary end point was the proportion of evaluable pts with ≥ 1 confirmed seizure during the 4-m treatment period. Results: A total of423 pts received ENZ; 366 were evaluable. Baseline seizure risk factors were medications lowering seizure threshold (n = 242), brain injury (n = 112), and cerebrovascular accident/transient ischemic attack history (n = 94). Four (1.1%) evaluable pts had ≥ 1 confirmed seizure within 4 ms of ENZ initiation. Four (1.1%) pts had a first seizure after 4 ms. The rate of confirmed seizure was 2.6/100 pt-years. 357 pts (84.4%) experienced ≥ 1 treatment-emergent adverse event (TEAE); 141 (33.3%) had ≥ 1 serious TEAE and 29 (6.9%) had ≥ 1 drug-related serious AE. 38 (9.0%) deaths were reported during treatment/within 30 days of discontinuation; four deaths were considered possibly drug related (cerebral hemorrhage, mCRPC progression, sudden cardiac death, and general deterioration). Conclusions: The incidence of confirmed seizures in the UPWARD study is similar to pts with mCRPC and similar risk factors but no ENZ exposure in the TRUVEN report. ENZ was generally well tolerated, and TEAE data are consistent with its known safety profile. These results suggest that ENZ did not increase the risk of seizures in the UPWARD study. Clinical trial information: NCT01977651.

The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of prostate carcinoma

Prostate cancer is the most commonly diagnosed malignancy and second leading cause of cancer death among men in the United States. In recent years, several new agents, including cancer immunotherapies, have been approved or are currently being investigated in late-stage clinical trials for the management of advanced prostate cancer. Therefore, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel, including physicians, nurses, and patient advocates, to develop consensus recommendations for the clinical application of immunotherapy for prostate cancer patients. To do so, a systematic literature search was performed to identify high-impact papers from 2006 until 2014 and was further supplemented with literature provided by the panel. Results from the consensus panel voting and discussion as well as the literature review were used to rate supporting evidence and generate recommendations for the use of immunotherapy in prostate cancer patients. Sipuleucel-T, an autologous dendritic cell vaccine, is the first and currently only immunotherapeutic agent approved for the clinical management of metastatic castrate resistant prostate cancer (mCRPC). The consensus panel utilized this model to discuss immunotherapy in the treatment of prostate cancer, issues related to patient selection, monitoring of patients during and post treatment, and sequence/combination with other anti-cancer treatments. Potential immunotherapies emerging from late-stage clinical trials are also discussed. As immunotherapy evolves as a therapeutic option for the treatment of prostate cancer, these recommendations will be updated accordingly.

A Randomized Phase II Trial of Short-Course Androgen Deprivation Therapy With or Without Bevacizumab for Patients With Recurrent Prostate Cancer After Definitive Local Therapy

PURPOSE

Patients with recurrent prostate cancer after local treatment make up a heterogeneous population for whom androgen deprivation therapy (ADT) is the usual treatment. The purpose of this randomized phase II trial was to investigate the efficacy and toxicity of short-course ADT with or without bevacizumab in men with hormone-sensitive prostate cancer.

PATIENTS AND METHODS

Eligible patients had an increasing prostate-specific antigen (PSA) of ≤ 50 ng/mL and PSA doubling time of less than 18 months. Patients had either no metastases or low burden, asymptomatic metastases (lymph nodes < 3 cm and five or fewer bone metastases). Patients were randomly assigned 2:1 to a luteinizing hormone-releasing hormone agonist, bicalutamide and bevacizumab or ADT alone, for 6 months. The primary end point was PSA relapse-free survival (RFS). Relapse was defined as a PSA of more than 0.2 ng/mL for prostatectomy patients or PSA of more than 2.0 ng/mL for primary radiation therapy patients.

RESULTS

Sixty-six patients received ADT + bevacizumab and 36 received ADT alone. Patients receiving ADT + bevacizumab had a statistically significant improvement in RFS compared with patients treated with ADT alone (13.3 months for ADT + bevacizumab v 10.2 months for ADT alone; hazard ratio, 0.47; 95% CI, 0.29 to 0.77; log-rank P = .002). Hypertension was the most common adverse event in patients receiving ADT + bevacizumab (36%).

CONCLUSION

ADT combined with bevacizumab resulted in an improved RFS for patients with hormone-sensitive prostate cancer. Long-term follow-up is needed to determine whether some patients have a durable PSA response and are able to remain off ADT for prolonged periods. Our data provide rationale for combining vascular endothelial growth factor-targeting therapy with ADT in hormone-sensitive prostate cancer.

Biomarkers for immunotherapy in genitourinary malignancies

Immunotherapy for genitourinary malignancies such as prostate, renal, and bladder cancers has experienced a resurgence since the development of 3 novel strategies: the autologous cellular product therapy, Sipuleucel-T for prostate cancer, the checkpoint inhibitors, anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4), anti-programmed cell death ligand 1 (anti-PD1), and anti-programmed cell death ligand 1), respectively. These agents have led to strikingly durable responses in several of these solid tumors, but their efficacy has been inconsistent. Why all solid tumors are not equal in their response to these therapies is unclear. More importantly, changes in humoral or cellular responses which may reflect changes in a tumor's biology have been limited due to differences in immune monitoring and lack of consistency in established reliable immunologic endpoints. How to design immunologic end points that reflect a meaningful effect on the cancer remains a challenge for clinical trial development. The issues faced by clinical investigators and the current state of immune monitoring are discussed.

Trial Design and Objectives for Castration-Resistant Prostate Cancer: Updated Recommendations From the Prostate Cancer Clinical Trials Working Group 3

PURPOSE

Evolving treatments, disease phenotypes, and biology, together with a changing drug development environment, have created the need to revise castration-resistant prostate cancer (CRPC) clinical trial recommendations to succeed those from prior Prostate Cancer Clinical Trials Working Groups.

METHODS

An international expert committee of prostate cancer clinical investigators (the Prostate Cancer Clinical Trials Working Group 3 [PCWG3]) was reconvened and expanded and met in 2012-2015 to formulate updated criteria on the basis of emerging trial data and validation studies of the Prostate Cancer Clinical Trials Working Group 2 recommendations.

RESULTS

PCWG3 recommends that baseline patient assessment include tumor histology, detailed records of prior systemic treatments and responses, and a detailed reporting of disease subtypes based on an anatomic pattern of metastatic spread. New recommendations for trial outcome measures include the time to event end point of symptomatic skeletal events, as well as time to first metastasis and time to progression for trials in the nonmetastatic CRPC state. PCWG3 introduces the concept of no longer clinically benefiting to underscore the distinction between first evidence of progression and the clinical need to terminate or change treatment, and the importance of documenting progression in existing lesions as distinct from the development of new lesions. Serial biologic profiling using tumor samples from biopsies, blood-based diagnostics, and/or imaging is also recommended to gain insight into mechanisms of resistance and to identify predictive biomarkers of sensitivity for use in prospective trials.

CONCLUSION

PCWG3 moves drug development closer to unmet needs in clinical practice by focusing on disease manifestations most likely to affect prognosis adversely for therapeutics tested in both nonmetastatic and metastatic CRPC populations. Consultation with regulatory authorities is recommended if a trial is intended to seek support for drug approval.

Immunotherapeutic approaches in prostate cancer: combinations and clinical integration

Despite multiple immunologic approaches with peptide, protein, and DNA vaccines, no single therapy has induced complete remission or maintained durability of response in patients with castration-resistant prostate cancer (CRPC). Historically, immunotherapy has had limited effect on solid tumors with the exception of melanoma and renal cell carcinomas, which have been deemed as immunologic cancers given their potential for remissions either spontaneously or after removal of the primary lesion. There is considerable excitement about using an immunotherapy in combination with biologic agents such as checkpoint inhibitors, cytokines, other vaccines, or chemotherapy. Sipuleucel-T represents one of several novel immunologic therapeutic approaches to treat prostate cancer in addition to other solid tumors. It is the first in its class of autologous cellular therapies to demonstrate safety and an overall survival benefit in patients with asymptomatic or minimally symptomatic CRPC and represents a unique treatment method that may be further enhanced with other agents. Although sipuleucel-T can be used as a foundation on which to build and enhance future immunologic clinical trials, other exciting strategies are in development that may be easily integrated into the algorithm of current care.

A phase I/IIa trial of prostate specific membrane antigen (PSMA) positron emission tomography (PET) imaging with 89Zr-Df-IAB2M in metastatic prostate cancer (PCa)

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Background: There is a pressing need for improved imaging biomarkers to identify disease distribution and response in both localized and advanced prostate cancer patients. PSMA-directed imaging is undergoing analytic and clinical validation for these contexts of use. IAB2M is an anti-PSMA recombinant minibody (Mb) derived from huJ591. We have previously reported on 28 pts imaged with IAB2M(Pandit-Taskar et al, SNM 2015). Here we report the lesion targeting and uptake (SUV) of the Mb and correlation with pathology of biopsied lesions on the full complement of the 38 pts examined in this trial. Methods: 38 pts with progressive metastatic PCa received escalating amounts of the Mb (16 pts at 10mg, 16 pts at 20mg, 6 pts at 50mg) in a phase I/IIa trial. All pts underwent standard imaging (SI) using CT, bone scintigraphy (BS), FDG PET, followed by imaging with 5 mCi of IAB2M. Whole body PET/CT scans were performed and evaluated for lesion targeting and SUVmax. Biopsy (bx) locations were selected by a consensus panel prioritized on the basis of: IAB2M & FDG positivity, IAB2M & FDG mismatch, and CT or BS positivity & any PET mismatch. Results: A total of 556 lesions (410 bone, 146 soft tissue) in 38 pts were detected by SI or IAB2M. In bone, IAB2M detected 344 lesions (83.9%), CT 209 (51%), BS 211 (51.5%), and FDG 109 (26.6%). For soft tissue, IAB2M detected 119 (81.5%), CT 83 (56.8%), and FDG 79 (54.1%). The SUV for bone lesions ranged from 2.1-60.4 for 10mg Mb, 1.7- 33 in 20mg Mb, and 2.3-17.5 in 50mg Mb. For soft tissue lesions, SUV range was 3.1-45.4, 2.1-20, and 1.9-13.8 respectively. 28 bxs (13 bone, 15 soft tissue) were obtained from 27 pts; 27 bxs were evaluable (1 was non-diagnostic). 20/27 (74.1%) bxs were pos for PCa; 20/24 (83.3%) IAB2M pos lesions were path pos and 3/3 (100%) IAB2M neg lesions were neg on path. All imaging and path correlated (true pos + true neg) in 23/27 (85.2%) bxs. Conclusions: PET imaging with IAB2M has demonstrated higher lesion detection when compared with SI. IAB2M’s high concordance with path suggests pos findings represent bx confirmed PCa. Further studies to examine biochemically recurrent prostate cancer are planned. Clinical trial information: NCT01923727.

Genomic characterization of primary and metastatic prostate cancer (PC) using a targeted next-generation sequencing assay

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Background: Genomic alterations in PC have been described across the disease continuum, creating opportunities for selective clinical trial enrollment of patients (pts) with high-risk or metastatic disease based on their tumor profile. MSK-IMPACT is an exon capture-based sequencing assay performed in a CLIA-certified laboratory that targets 410 cancer-associated genes, many of which are potential drug targets. We assessed mutations and copy number alterations (CNAs) in primary and metastatic samples from untreated, hormone-treated and castration resistant pts. Methods: PC pts were enrolled on an IRB-approved protocol for tumor genomic profiling. Fixed tumor and matched germline samples were subjected to DNA sequencing analysis using MSK-IMPACT for the identification of somatic mutations and CNAs. Results: 315 samples from 271 pts were successfully sequenced (Table). Overall success rate was 80% (67% for bone). 14 tumors were pathologically classified as neuroendocrine or had neuroendocrine features. 23% of patients had tumor somatic alterations in DNA repair genes (BRCA2, BRCA1, ATM, FANCA and CDK12). Additional alterations were observed in PI3K, MAPK and Wnt-βCatenin pathway genes. Common alterations in the metastatic tumors include TP53 deletion/mutation (42%), AR amplification/mutation (38%), PTEN deletion/mutation (27%), RB1 deletion/mutation (20%), BRCA2 deletion/mutation (11%), FOXA1 mutation (11%) and SPOP mutation (4%). Among metastatic samples, tumors from pts with castration-resistant disease had higher CNA burden when compared to tumors from non-castration-resistant pts (0.31 vs. 0.19 fraction genome altered, p < 0.05, unpaired t-test), as well as higher rates of AR amplification/mutation (49% vs. 3%, p < 0.01, Fisher’s exact test). Conclusions: Genomic profiling of primary and metastatic prostate tumors is feasible with the clinical MSK-IMPACT sequencing assay and has identified actionable alterations in > 40% of patients. This is allowing for selective trial enrollment and further investigation of PC genomics. [Table: see text]

Immunotherapy in metastatic prostate cancer

INTRODUCTION

Prostate cancer remains a challenge as a target for immunological approaches. The approval of the first cell-based immune therapy, Sipuleucel-T for prostate cancer introduced prostate cancer as a solid tumor with the potential to be influenced by the immune system.

METHODS

We reviewed articles on immunological management of prostate cancer and challenges that lie ahead for such strategies.

RESULTS

Treatments have focused on the identification of novel cell surface antigens thought to be unique to prostate cancer. These include vaccines against carbohydrate and blood group antigens, xenogeneic and naked DNA vaccines, and pox viruses used as prime-boost or checkpoint inhibitors. No single vaccine construct to date has resulted in a dramatic antitumor effect. The checkpoint inhibitor, anti-CTLA-4 has resulted in several long-term remissions, but phase III trials have not demonstrated an antitumor effect or survival benefit.

CONCLUSIONS

Multiple clinical trials suggest that prostate cancer may not be optimally treated by single agent immune therapies and that combination with biologic agents, chemotherapies, or radiation may offer some enhancement of benefit.

Everolimus combined with gefitinib in patients with metastatic castration-resistant prostate cancer: Phase 1/2 results and signaling pathway implications

BACKGROUND

The effects of mammalian target of rapamycin (mTOR) inhibition are limited by feedback reactivation of receptor tyrosine kinase signaling in phosphatase and tensin homolog-null tumors. Thus, this study tested the combination of mTOR inhibition (everolimus) and epidermal growth factor receptor inhibition (gefitinib) in castration-resistant prostate cancer (CRPC).

METHODS

In phase 1, 12 patients (10 with CRPC and 2 with glioblastoma) received daily gefitinib (250 mg) with weekly everolimus (30, 50, or 70 mg). In phase 2, 27 CRPC patients received gefitinib with everolimus (70 mg).

RESULTS

Phase 1 revealed no pharmacokinetic interactions and no dose-limiting toxicities. In phase 2, 18 of 27 patients (67%) discontinued treatment before the 12-week evaluation because of progression as evidenced by prostate-specific antigen (PSA) levels (n = 6) or imaging (n = 5) or because of a grade 2 or higher toxicity (n = 7). Thirteen of the 37 CRPC patients (35%) exhibited a rapidly rising PSA level after they had begun treatment, and this declined upon discontinuation. Fluorodeoxyglucose positron emission tomography 24 to 72 hours after the initiation of treatment showed a decrease in the standardized uptake value consistent with mTOR inhibition in 27 of the 33 evaluable patients (82%); there was a corresponding rise in PSA in 20 of these 27 patients (74%).

CONCLUSIONS

The combination of gefitinib and everolimus did not result in significant antitumor activity. The induction of PSA in tumors treated with mTOR inhibitors was consistent with preclinical data showing that phosphoinositide 3-kinase (PI3K) pathway signaling feedback inhibits the androgen receptor (AR). This clinical evidence of relief of feedback inhibition promoting enhanced AR activity supports future studies combining PI3K pathway inhibitors and second-generation AR inhibitors in CRPC.