Flutamide With or Without PROSTVAC in Non-metastatic Castration Resistant (M0) Prostate Cancer

BACKGROUND

Before 2018, there was no standard of care for non-metastatic (M0) castration resistant prostate cancer nmCRPC. Androgen receptor antagonists (ARAs) were commonly used sequentially nmCRPC.

METHODS

This was a multicenter, randomized clinical trial comparing the ARA flutamide+/-PROSTVAC, a pox viral vaccine targeting PSA that includes T-cell co-stimulatory molecules. Eligible men had negative CT and Tc99 bone scans, and rising PSA on ADT. Previous treatment with ARA was a stratification factor. Patients were also evaluated for antigen-specific immune responses using intracellular cytokine staining.

RESULTS

Thirty-three patients randomized to flutamide and 31 to flutamide+vaccine. The median age was 71.8 and 69.8 years, respectively. The median time to treatment failure after a median potential follow-up of 46.7 months was, 4.5 months (range 2-70) for flutamide alone vs. 6.9 months (2.5-40; P = .38) with flutamide+vaccine. Seven patients in each arm had a >50% PSA response. Antigen-specific responses were similar in both arms (58% of patients in flutamide alone and 56% in flutamide+vaccine). The treatments were well tolerated. The most common side effect > grade 2 was injection site reaction seen in 29/31 vaccine patients which were self-limiting.

CONCLUSION

The combination of flutamide+PROSTVAC did not improve outcomes in men with nmCRPC compared with flutamide alone. (ClinicalTrials.gov Identifier: NCT00450463).

Inherited risk for prostate cancer (PCa): Following the natural history of men with high-risk genetics using multiparametric MRI (mpMRI)

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Background: PCa has inherited risk factors including high genetic risk variants such as BRCA1/2, HOXB13, and DNA mismatch repair genes. mpMRI has been shown to be effective for detection and staging of localized PCa. This study follows participants (prts), born biologically male, without a diagnosis of PCa with known germline pathogenic or likely pathogenic variants (PV) in BRCA1/2, MLH1, MSH2, MSH6, PMS2, EPCAM, HOXB13, ATM, NBN, TP53, CHEK2, PALB2, RAD51C/D, BRIP1, or FANCA-FANCM (NCT03805919). Methods: Up to 500 eligible prts 30-75 years old (yo) with a documented germline PV will enroll. Prts undergo biennial clinical exam and mpMRI, and annual PSA monitoring and are followed at 12-month intervals to determine PSA, prostate cancer diagnosis, and/or disease/survival status until death. Indication for prostate biopsy includes clinical or imaging findings. Biopsy specimens undergo molecular analyses. Results: To date, 175 prts have been enrolled: 169 (97%) White, 3 Hispanic (2%), 1 African American (1%), 1 Asian (1%), and 1 biethnic (1%). Median age is 47 yo. The most common monoallelic PV are: 48.6% BRCA2, 25.1% BRCA1, 6.3% CHEK2 and 5.7% MSH2. PVs in ATM, PALB2, HOXB13, PMS2, MLH1, MSH6, BRIP1, EPCAM and RAD51D are ≤4%. One subject carries three distinct PVs ( BRCA2, CHEK2, BRIP1). Indication for biopsy was found in 26.3% of prts with 22/46 (47.8%) with a PIRADS 4 lesion, 6/46 (13.0%) PIRADS 3 lesion, 12/46 (26.1%) elevated PSA (median=2.8 ng/mL) or 6/46 (13.0%) due to clinical discretion. Adenocarcinoma was diagnosed on 13/39 (33.3%) biopsies with median age at diagnosis=59 yo. 9/13 (69%) prts had a PSA <3 ng/ml at diagnosis. Nine prts were diagnosed with ISUP Grade Group (GG) 1, 3 with GG2, and 1 with GG3. Eight prts opted for active surveillance (AS), 2 for radiation therapy (RT), and 3 for prostatectomy (RP). Two prts on AS converted to definitive treatment (one RP and one RT) due to progression in GG on the year 1 AS biopsy. Conclusions: mpMRI screening in men with germline PV can be used for diagnosis and monitoring of PCa and facilitates detection below conventional PSA thresholds in a high genetic risk setting. Access to genetic testing and other variables need to be addressed in underrepresented minorities. Correlative studies, including cfDNA and PBMCs, are ongoing. Clinical trial information: NCT03805919 . [Table: see text]

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

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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]

PSMA PET findings in patients with undetectable PSA more than 3 years after docetaxel for metastatic castration-sensitive prostate cancer (mCSPC)

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Background: Multiple treatment options combined with androgen deprivation therapy (ADT) provide a survival advantage in mCSPC. In this prospective study, mCSPC patients were treated with docetaxel and Prostvac, a therapeutic cancer vaccine. Since initiation of the study, a phase 3 trial of Prostvac did not show independent clinical activity in metastatic castration-resistant prostate cancer. Still, this study offers a chance to evaluate responses to docetaxel-based therapy in mCSPC. More specifically, with FDA approval of prostate-specific membrane antigen (PSMA) PET imaging in just the last year, there is a paucity of data regarding the use of this scan in long-term responders to therapies for mCSPC. Methods: Eligible patients included those with mCSPC and ECOG PS of ≤ 2. As per the CHAARTED regimen, patients started docetaxel within 4 months of initiating ADT with a plan to receive 75mg/m2 for 6 cycles. Patients were randomized to receive Prostvac prior to, concurrent with, or after docetaxel. Restaging was done annually with CT and Tc99 bone scan. The study was powered to evaluate immune responses, which is being reported separately. For this analysis, patients were evaluated as one group. Ten patients are in follow up with continued PSA values of ≤ 0.2 ng/mL and 7/10 were evaluated with 18F-DCFPyL PSMA PET. Results: Seventy-three patients enrolled. Median age was 63 years with a range of 41-86 years. Race distribution was 71.6% White, 20.3% Black, 4.1% other, and 4.1% unknown. Gleason 6, 7, and 8 to 10 was 4.1%, 21.6%, and 68.9% of patients, respectively, with 5.4% being unknown. Median pre-ADT PSA was 34.75 ng/mL. Low-volume disease represented 41.1% of patients and high-volume was 58.9%. After 2 years from the start of ADT, 22% of patients had PSA values of ≤ 0.2 ng/mL. This included 37% of the low-volume group and 12% of the high-volume group. Three years from starting ADT, 14% of patients had PSA values ≤ 0.2 ng/mL (20% of the low-volume group, 9% of the high-volume group). Of the 7 patients who remain in follow-up with PSA values ≤ 0.2 ng/mL and who were evaluated with PSMA PET, median time from start of ADT was 4 years with a range of 3.5-6 years. These patients either had no evidence of disease or minimal residual findings on CT/Tc99 bone scan. Four of the 7 patients still had residual areas of uptake on PSMA PET. Conclusions: Patients treated with docetaxel for mCSPC have the potential for long-term clinical responses. In these long-term responders, despite prolonged PSA response and minimal findings on conventional CT and Tc99 scans, more than half of patients still had findings on PSMA PET imaging. Further studies are required to better understand the clinical implications of these findings and the role of PSMA PET in mCSPC. Clinical trial information: NCT02649855.

Patients with undetectable PSA 2 years after docetaxel for metastatic castration sensitive prostate cancer (mCSPC)

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Background: Patients with mCPSC have multiple treatment options to combine with androgen deprivation therapy (ADT) including docetaxel, abiraterone, enzalutamide and apalutamide, all of which have demonstrated a survival advantage. While oral anti-androgens are administered daily until progression but are less toxic, docetaxel has more upfront side effects. One of the advantages of using docetaxel is that the 6-cycle regimen (over approximately 4 months) potentially affords patients a respite from daily therapies thereafter. Furthermore, docetaxel may be more cost-effective. In this prospective study, mCSPC patients were treated with docetaxel and Prostvac, a therapeutic cancer vaccine. Since this study was initiated, Prostvac did not demonstrate independent clinical activity in a phase 3 trial in metastatic castration resistant prostate cancer. Nonetheless, this study provides an opportunity to evaluate responses to docetaxel-based therapy in mCSPC. Methods: Eligible patients included those with mCSPC and ECOG of ≤ 2. All patients were treated with docetaxel and were planned to receive 75mg/m2 for 6 cycles within 4 months of starting ADT, as per the CHAARTED regimen. Patients were randomized to receive Prostvac prior to, concurrent with or after docetaxel. Patients were restaged annually with CT and Tc99 bone scan. The study was powered to evaluate immunologic responses, which is ongoing. For the purposes of this analysis, all patients were analyzed as one group and long-term PSA responses were evaluated. Results: The study enrolled 73 patients. Age range was 41-86 with a median of 63 years. Race distribution was 71.6% White, 20.3% Black, 4.1% other, and 4.1% unknown. Gleason scores were 6 (4.1%), 7 (21.6%), and 8-10 (68.9%), with 5.4% being unknown. Median pre-ADT PSA was 34.75 ng/mL. Low-volume disease represented 41.1% of patients and high-volume was 58.9%. After 2 years from the start of ADT, 22% of all patients had PSA values of ≤ 0.2 ng/mL. This included 37% of the low-volume group and 12% of the high-volume group. Three years from the start of ADT, 14% of all patients had PSA values ≤ 0.2 ng/mL (20% of the low-volume group, 9% of the high-volume group). Conclusions: These data highlight long-term outcomes of 6 cycles of docetaxel for men with mCSPC. Although there are concerns about the short-term toxicity of docetaxel, there is potential for prolonged stable disease after ̃4 months of chemotherapy that allows these patients to defer additional oral anti-androgen therapy for years in some patients. The proportions of patients presented here are an underestimate of those who could continue to be monitored for slowly rising, but low PSAs, before starting the next line of therapy. Additional research is required to determine the optimal therapeutic sequence for men diagnosed with mCSPC and long-term implications for quality of life and cost-effectiveness. Clinical trial information: NCT02649855.

Clinical and immunologic impact of short-course enzalutamide alone and with immunotherapy in non-metastatic castration sensitive prostate cancer

BACKGROUND

The standard treatment for non-metastatic castration sensitive prostate cancer (nmCSPC) is androgen deprivation therapy (ADT) or surveillance. This study evaluated the potential synergy of immunotherapy and enzalutamide (without ADT) in nmCSPC. In addition, the immunologic impact of enzalutamide was also evaluated in men with normal testosterone.

METHODS

Patients with rising prostate-specific antigen (PSA) after definitive therapy, normal testosterone and no radiographic metastasis were randomized to enzalutamide for 3 months with/without PROSTVAC for 6 months. Thereafter, patients could be retreated with another 3 month course of enzalutamide when PSA returned to baseline. Immune profiles were evaluated in these patients.

RESULTS

Thirty-eight patients were randomized with a median PSA=4.38 ng/dL and PSA doubling time=4.1 months. No difference was observed between the two groups for PSA growth kinetics, but PSA responses to enzalutamide were noteworthy regardless of PROSTVAC. The median PSA decline after short-course enzalutamide without ADT/testosterone lowering therapy was 99% in both courses. The median time to PSA recovery to baseline after each 84-day course of enzalutamide was also noteworthy because of the duration of response after enzalutamide was discontinued. After the first and second 3 month cycle of enzalutamide, PSA recovery to baseline took a median 224 (range 84-1246) and 189 days (78-400), respectively. The most common adverse events related to the enzalutamide were grade 1 fatigue (71%) and grade 1 breast pain/nipple tenderness (81%). The only grade 3 toxicity was aspartate aminotransferase (AST)/alanine aminotransferase (ALT) elevation in two patients. Enzalutamide was independently associated with immune changes, increasing natural killer cells, naïve-T cells, and decreasing myeloid-derived suppressor cells.

CONCLUSIONS

Three months of enzalutamide without ADT induced substantial PSA control beyond the treatment period and was repeatable, perhaps representing an alternative to intermittent ADT in nmCSPC. In addition, enzalutamide was associated with immune changes that could be relevant as future immune combinations are developed. TRAIL REGISTRATION NUMBER: clinicaltrials.gov (NCT01875250).

Cabozantinib plus docetaxel and prednisone in metastatic castration-resistant prostate cancer

OBJECTIVE

To evaluate the safety and efficacy of cabozantinib combined with docetaxel.

PATIENTS AND METHODS

This was a phase 1/2 multicentre study in patients with metastatic castration-resistant prostate cancer (mCRPC). Docetaxel (75 mg/m² every 3 weeks with daily prednisone 10 mg) was combined with escalating doses of daily cabozantinib (20, 40 and 60 mg). Based on the results of the phase 1 study, the investigation was expanded into a randomized study of docetaxel with prednisone (hereafter 'docetaxel/prednisone') plus the maximum tolerated dose (MTD) of cabozantinib compared with docetaxel/prednisone alone.

RESULTS

A total of 44 men with mCRPC were enrolled in this phase 1/2 trial. An MTD of 40 mg cabozantinib plus docetaxel/prednisone was determined. Dose-limiting toxicities were neutropenic fever and palmar-plantar erythrodysesthesia, and there was one death attributable to a thromboembolic event. In addition, grade 3 or 4 myelosuppression, hypophosphataemia and neuropathy were seen in three or more patients. In the phase 1 study, the median time to progression (TTP) and overall survival (OS) time were 13.6 and 16.3 months, respectively. In the phase 2 study, which was terminated early because of poor accrual, the median TTP and OS favoured the combination (n = 13) compared to docetaxel/prednisone alone (n = 12; 21.0 vs 6.6 months; P = 0.035 and 23.8 vs 15.6 months; P = 0.072, respectively).

CONCLUSION

Despite the limited number of patients in this study, preliminary data suggest that cabozantinib can be safely added to docetaxel/prednisone with possible enhanced efficacy.

Sequential Prostate Magnetic Resonance Imaging in Newly Diagnosed High-risk Prostate Cancer Treated with Neoadjuvant Enzalutamide is Predictive of Therapeutic Response

PURPOSE

For high-risk prostate cancer, standard treatment options include radical prostatectomy (RP) or radiotherapy plus androgen deprivation therapy (ADT). Despite definitive therapy, many patients will have disease recurrence. Imaging has the potential to better define characteristics of response and resistance. In this study, we evaluated prostate multiparametric MRI (mpMRI) before and after neoadjuvant enzalutamide plus ADT.

PATIENTS AND METHODS

Men with localized intermediate- or high-risk prostate cancer underwent a baseline mpMRI and mpMRI-targeted biopsy followed by a second mpMRI after 6 months of enzalutamide and ADT prior to RP. Specimens were sectioned in the same plane as mpMRI using patient-specific 3D-printed molds to permit mpMRI-targeted biopsies to be compared with the same lesion from the RP. Specimens were analyzed for imaging and histologic correlates of response.

RESULTS

Of 39 patients enrolled, 36 completed imaging and RP. Most patients (92%) had high-risk disease. Fifty-eight lesions were detected on baseline mpMRI, of which 40 (69%) remained measurable at 6-month follow-up imaging. Fifty-five of 59 lesions (93%) demonstrated >50% volume reduction on posttreatment mpMRI. Three of 59 lesions (5%) demonstrated growth in size at follow-up imaging, with two lesions increasing more than 3-fold in volume. On whole-mount pathology, 15 patients demonstrated minimal residual disease (MRD) of <0.05 cc or pathologic complete response. Low initial mpMRI relative tumor burden was most predictive of MRD on final pathology.

CONCLUSIONS

Low relative lesion volume at baseline mpMRI was predictive of pathologic response. A subset of patients had limited response. Selection of patients based on these metrics may improve outcomes in high-risk disease.

Evaluating biomarkers in metastatic castration-resistant prostate cancer patients treated with enzalutamide: PSA, circulating tumor cell counts, AR-V7 status and radiographic progression

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Background: Enzalutamideis ahighly effective treatment in metastatic castration resistant prostate cancer (mCRPC). Although Prostate Cancer Working Group (PCWG) guidelines recommend continuing treatment until radiographic/clinical progression (rPD/cPD), many patients discontinue therapy for rising PSA alone. Methods: We conducted an open label, randomized phase 2 trial in mCRPC patients untreated with docetaxel, abiraterone, or enzalutamide, comparing enzalutamide alone or in combination with PROSTVAC, a therapeutic cancer vaccine designed to induce an anti-tumor immune response. The study discontinued accrual after planned interim analysis indicated no difference in progression between the two arms. Patients were followed beyond 1st of 3 confirmed PSA rises until rPD. 49 patients were analyzed for Circulating Tumor Cell (CTC) count and AR-V7 status at 1st PSA rise and at rPD/cPD or last follow up. Results: 57 patients were enrolled with median follow up time of 55.4 mo. 49/57 (86%) patients had rising PSA; median time to 1st PSA rise for all patients was 6.4 mo (95% CI: 3.7-11.0 mo) after starting enzalutamide. 38/57 (67%) patients had progressive disease (majority with rPD; 1/38 (3%) with cPD); median time to progression for all patients was 23.3 mo (95% CI: 16.1-27.8 mo). 5 patients tested positive for AR-V7 within 30 days of rPD. In patients who experienced rPD/cPD, CTCs were detected in 11/24 (46%) samples taken at rPD vs. in only 3/24 (13%) samples taken at rising PSA. CTC counts were higher at rPD compared to samples taken at rising PSA (P = 0.004, Wilcoxon unpaired test). Of the 7 patients still being treated (median time on drug = 4.2 yrs), 2 experienced rising PSA; however none of the patients had detectable CTCs at a median of 30 days from last follow up. Conclusions: These data suggest that a rising PSA may not be a warning of near-term clinically significant disease progression in mCRPC patients treated with enzalutamide, given the 17-month difference between the first rise in PSA and ultimate rPD/cPD seen in this analysis. Further, CTCs and AR-V7 status associate strongly with rPD but not with rising PSA, adding biological rationale to the hypothesis that CTC counts and AR-V7 status are associated with disease progression. Collectively, these data highlight the need to continue to educate patients and providers on PCWG criteria for progression and appropriately-timed utilization of both therapies and diagnostic tests to maximize drug efficacy in mCRPC. Clinical trial information: NCT01867333 .

PSA progression compared to radiographic or clinical progression in metastatic castration-resistant prostate cancer patients treated with enzalutamide

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Background: Enzalutamideis ahighly effective treatment in patients with metastatic castration resistant prostate cancer (mCRPC). Although Prostate Cancer Working Group Guidelines (PCWG) recommend continuing treatment until radiographic progression of disease (rPD) or clinical progression (cPD), many patients discontinue therapy for rising PSA alone. Methods: We conducted an open label, randomized phase 2 clinical trial in mCRPC patients (on testosterone suppression therapy) previously untreated with docetaxel, abiraterone, or enzalutamide, comparing enzalutamide alone or in combination with PROSTVAC, a therapeutic cancer vaccine designed to induce an anti-tumor immune response. The study discontinued accrual after a planned interim analysis indicated no difference in progression between the two arms. Patients were followed beyond PSA progression (first of three confirmed PSA rises, evaluated monthly) until rPD per PCWG (scans done every 3 months per protocol). Results: A total of 57 patients were enrolled with a median follow up time of 55.4 months. Of those, 47 (82%) patients were Caucasian and seven (12%) patients were African American. The median age of patients on enrollment was 67.2 years. 49/57 (86%) patients had PSA progression and the median time to first PSA rise for all 57 patients combined was 6.4 months (95% CI: 3.7-11.0 months) after starting enzalutamide. 38/57 (67%) patients experienced progressive disease (majority with rPD and 1/38 (3%) with cPD), with the median time to progression for all 57 patients of 23.3 months (95% CI: 16.1-27.8 months). Conclusions: Consistent with PCWG recommendations, these data suggest that a rising PSA may not be a warning of near-term clinically significant disease progression in mCRPC patients given the nearly 17-month difference between the first rise in PSA and ultimate rPD or cPD seen in this analysis. These data highlight the need to continue to educate patients and providers on PCWG criteria for progression, which were also used in original trials that led to the FDA approval of enzalutamide, so as not to substantially limit the potential efficacy of mCRPC therapies such as enzalutamide. Clinical trial information: NCT01867333.

Natural history and imaging in men with high genetic risk for developing prostate cancer

Prostate cancer is the most common malignancy and the second leading cause of cancer related deaths in the United States. Established risk factors for prostate cancer incidence include older age, African-American race, and positive family history. Prostate cancer has substantial inherited predisposition and certain genetic variants are associated with increased risk of disease. Screening and imaging should target high-risk populations based on their genetic predisposition.

Clinical efficacy of abiraterone and enzalutamide metastatic castration sensitive prostate cancer patients who progressed rapidly on docetaxel with a genomic analysis

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Background: Docetaxel has become a standard of care for mCSPC. Enzalutamide and abiraterone have been proven to improve survival in metastatic castration-resistant prostate cancer (mCRPC) patients. Little is known about patients who have been treated with docetaxel for mCSPC and subsequent therapeutic responses. This retrospective analysis is to evaluate the response duration of abiraterone and enzalutamide in patients who previously received docetaxel for mCSPC but developed mCRPC within 12 months. Methods: Clinical Trial NCT02649855 enrolled patients with newly diagnosed mCSPC who were treated with standard androgen deprivation therapy (ADT) and docetaxel (75 mg/m2 every 3 weeks for 6 cycles) sequenced with immunotherapy (PROSTVAC) from February 2016 to present. Patients who had progression (based on consecutive PSA rises or imaging) within 1 year of completing docetaxel and went on to subsequent abiraterone/enzalutamide were evaluated. (Note these are different PSA progression criteria than used in CHAARTED, Sweeney, NEJM, 2015). A PCR-based NGS panel (OncoMine Comprehensive Assay v3) will evaluate available tissue from these patients. Results: Of the 46 patients evaluated regardless of immunotherapy sequence, 15 (33%) went on subsequent therapy after progression on docetaxel for mCSPC, with 12 patients starting abiraterone/enzalutamide (7 with high volume disease and 5 with low volume disease). The median age was 62 (41-83) years. 6/12 patients (50%) initiated enzalutamide and 6/12 patients (50%) initiated abiraterone. The median duration of treatment for both was 7.43 (1.53 – 16.0) months, the median time to prostate-specific antigen (PSA) progression was 2 (0 – 11) months; the median duration of PSA decline was 2 months in patients with both high and low volume disease. Of note, 3/12 (25%) of patients did not have PSA response, all of them had high volume disease. Conclusions: These data from a small cohort suggest that patients who have progression within 12 months of completing docetaxel for mCSPC have limited subsequent benefit from enzalutamide or abiraterone. Additional studies are required to determine optimal timing and treatment sequence for patients with mCSPC who rapidly develop mCRPC. Clinical trial information: NCT02649855.

A phase I and randomized phase II study of cabozantinib plus docetaxel and prednisone (C+DP) versus docetaxel and prednisone (DP) alone in metastatic castrate-resistant prostate cancer (mCRPC)

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Background: A phase I study of Cabozantinib (C) in combination with docetaxel (D) and prednisone (P) in patients (pts) with mCRPC determined that 40 mg daily was the maximum tolerated dose of C in combination with D and P (C+DP). We report a pooled analysis of the phase I and randomized phase II study comparing C+DP to DP alone. Methods: Eligible pts had mCRPC without prior chemotherapy in the castrate setting. All pts received a fixed dose of D (75 mg/m2IV day one of each 21 day cycle) and P (5 mg PO twice daily), and in the C+DP group, C at three escalating dose levels: 20 mg, 40 mg, or 60 mg in the phase I cohort (all PO daily) and 40 mg daily in the phase II cohort. Results: A total of 32 pts received C+DP (19 pts in phase I and 13 pts in the phase II cohort). 12 pts received DP alone. Baseline characteristics for C+DP vs DP included median age 69 (45 – 84) vs 69 (50-83) and median PSA 74.8 ng/ml (0.01-4093.7) vs 309.5 ng/ml (94.6 – 2649) respectively. Clinical trial information: NCT01683994. 18/32 C+DP pts had previous enzalutamide or abiraterone, with a median PFS of 13.6 months (95% CI: 5.2 – 21.0). 23/32 pts (72%) treated with C+DP required dose reduction or discontinuation of C, and 10/32 (31%) required C discontinuation. 2/32 patients (6%) in the C+DP group died on protocol, possibly related to study drug (sudden death NOS/venous thromboembolism). Grade 4 adverse events (AEs) in the C+DP group included: neutropenia (28%), leukopenia (6%), pulmonary embolism (3%), and mucositis (3%) and in DP: hyperglycemia (8%). Grade 3 AEs (>10%) in C+DP included: neutropenia (31%), febrile neutropenia (16%), leukopenia (13%), hypophosphatemia (13%) and in DP: anemia (17%). Conclusions: In pts with mCRPC, C+DP is associated with a greater PFS and PSA responses compared to DP alone. Toxicities with the combination were manageable. Further study is required to better define the potential benefits of C+DP in mCRPC.[Table: see text]

Efficacy of abiraterone and enzalutamide in patients who had disease progression within twelve months of completing docetaxel for metastatic castration sensitive prostate cancer

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Background: Docetaxel is a standard of care for mCSPC. Enzalutamide and abiraterone have been proven to improve survival in metastatic castration-resistant prostate cancer (mCRPC) patients. Little is known about patients who have been treated with docetaxel for mCSPC and subsequent therapeutic responses. This retrospective analysis is to evaluate the response duration of abiraterone and enzalutamide in patients who previously received docetaxel for mCSPC but developed mCRPC within 12 months. Methods: Clinical Trial NCT02649855 enrolled patients with newly diagnosed mCSPC who were treated with standard androgen deprivation therapy (ADT) and docetaxel (75 mg/m2 every 3 weeks for 6 cycles) sequenced with immunotherapy (PROSTVAC) from February 2016 to present. Patients who had progression (based on consecutive PSA rises or imaging) within 1 year of completing docetaxel and went on to subsequent abiraterone/enzalutamide were evaluated. (Note these are different PSA progression criteria than used in CHAARTED, Sweeney, NEJM, 2015). Results: Of the 46 patients evaluated regardless of immunotherapy sequence, 15 (33%) went on subsequent therapy after progression on docetaxel for mCSPC, with 12 patients starting abiraterone/enzalutamide (6 each with high and low volume disease). The median age was 62 (41-83) years. 7/12 patients (58.3%) initiated enzalutamide and 5/12 patients (41.7%) initiated abiraterone. The median duration of treatment for both was 7.12 (1.53–16.0) months, the median time to prostate-specific antigen (PSA) progression was 5.54 (0–15.83) months; 5/12 (41.7%) of patients did not have PSA response. Of note, patients with low volume disease had a median treatment duration of 5.88 months, 3 of them did not have PSA response. Conclusions: These data from a small cohort suggest that patients who have progression within 12 months of completing docetaxel for mCSPC have limited subsequent benefit from enzalutamide or abiraterone. Additional studies are required to determine optimal timing and treatment sequence for patients with mCSPC who rapidly develop mCRPC. Clinical trial information: NCT02649855.

A comparison of prostate cancer bone metastases on 18F-Sodium Fluoride and Prostate Specific Membrane Antigen (18F-PSMA) PET/CT: Discordant uptake in the same lesion

Purpose

Prostate-Specific Membrane Antigen (PSMA) PET/CT has been introduced as a sensitive method for characterizing metastatic prostate cancer. The purpose of this study is to compare the spatial concordance of ¹⁸F-NaF PET/CT and ¹⁸F-PSMA-targeted PET/CT within prostate cancer bone metastases.

Methods

Prostate cancer patients with known bone metastases underwent PSMA-targeted PET/CT (¹⁸F-DCFBC or ¹⁸F-DCFPyL) and ¹⁸F-NaF PET/CT. In pelvic and spinal lesions detected by both radiotracers, regions-of-interest (ROIs) derived by various thresholds of uptake intensity were compared for spatial colocalization. Overlap volume was correlated with uptake characteristics and disease status.

Results

The study included 149 lesions in 19 patients. Qualitatively, lesions exhibited a heterogeneous range of spatial concordance between PSMA and NaF uptake from completely matched to completely discordant. Quantitatively, overlap volume decreased as a function of tracer intensity. and disease status, where lesions from patients with castration-sensitive disease showed higher spatial concordance while lesions from patients with castration-resistant disease demonstrated more frequent spatial discordance.

Conclusion

As metastatic prostate cancer progresses from castration-sensitive to castration-resistant, greater discordance is observed between NaF PET and PSMA PET uptake. This may indicate a possible phenotypic shift to tumor growth that is more independent of bone remodeling via osteoblastic formation.

Activity of durvalumab plus olaparib in metastatic castration-resistant prostate cancer in men with and without DNA damage repair mutations

Background

Checkpoint inhibitors have not been effective for prostate cancer as single agents. Durvalumab is a human IgG1-K monoclonal antibody that targets programmed death ligand 1 and is approved by the U.S. Food and Drug Administration for locally advanced or metastatic urothelial cancer and locally advanced, unresectable stage 3 non-small cell lung cancer. Olaparib, a poly (ADP-ribose) polymerase inhibitor, has demonstrated an improvement in median progression-free survival (PFS) in select patients with metastatic castration-resistant prostate cancer (mCRPC). Data from other trials suggest there may be improved activity in men with DNA damage repair (DDR) mutations treated with checkpoint inhibitors. This trial evaluated durvalumab and olaparib in patients with mCRPC with and without somatic or germline DDR mutations.

Methods

Eligible patients had received prior enzalutamide and/or abiraterone. Patients received durvalumab 1500 mg i.v. every 28 days and olaparib 300 mg tablets p.o. every 12 h until disease progression or unacceptable toxicity. All patients had biopsies of metastatic lesions with an evaluation for both germline and somatic mutations.

Results

Seventeen patients received durvalumab and olaparib. Nausea was the only nonhematologic grade 3 or 4 toxicity occurring in > 1 patient (2/17). No patients were taken off trial for toxicity. Median radiographic progression-free survival (rPFS) for all patients is 16.1 months (95% CI: 4.5–16.1 months) with a 12-month rPFS of 51.5% (95% CI: 25.7–72.3%). Activity is seen in patients with alterations in DDR genes, with a median rPFS of 16.1 months (95% CI: 7.8–18.1 months). Nine of 17 (53%) patients had a radiographic and/or PSA response. Patients with fewer peripheral myeloid-derived suppressor cells and with alterations in DDR genes were more likely to respond. Early changes in circulating tumor cell counts and in both innate and adaptive immune characteristics were associated with response.

Conclusions

Durvalumab plus olaparib has acceptable toxicity, and the combination demonstrates efficacy, particularly in men with DDR abnormalities.

Trial registration

ClinicalTrials.gov identifier: NCT02484404.

Electronic supplementary material

The online version of this article (10.1186/s40425-018-0463-2) contains supplementary material, which is available to authorized users.

A Prospective Comparison of 18F-Sodium Fluoride PET/CT and PSMA-Targeted 18F-DCFBC PET/CT in Metastatic Prostate Cancer

The purpose of this study was to compare the diagnostic performance of ¹⁸F-DCFBC PET/CT, a first-generation ¹⁸F-labeled prostate-specific membrane antigen (PSMA)-targeted agent, and ¹⁸F-NaF PET/CT, a sensitive marker of osteoblastic activity, in a prospective cohort of patients with metastatic prostate cancer. Methods: Twenty-eight prostate cancer patients with metastatic disease on conventional imaging prospectively received up to 4 PET/CT scans. All patients completed baseline ¹⁸F-DCFBC PET/CT and ¹⁸F-NaF PET/CT scans, and 23 patients completed follow-up imaging, with a median follow-up interval of 5.7 mo (range, 4.2-12.6 mo). Lesion detection was compared across the 2 PET/CT agents at each time point. Detection and SUV characteristics of each PET/CT agent were compared with serum prostate-specific antigen (PSA) levels and treatment status at the time of baseline imaging using nonparametric statistical testing (Spearman correlation, Wilcoxon rank). Results: Twenty-six patients had metastatic disease detected on ¹⁸F-NaF or ¹⁸F-DCFBC at baseline, and 2 patients were negative on both scans. Three patients demonstrated soft tissue-only disease. Of 241 lesions detected at baseline, 56 were soft-tissue lesions identified by ¹⁸F-DCFBC only and 185 bone lesions detected on ¹⁸F-NaF or ¹⁸F-DCFBC. ¹⁸F-NaF detected significantly more bone lesions than ¹⁸F-DCFBC (P < 0.001). Correlation of PSA with patient-level SUV metrics was strong in ¹⁸F-DCFBC (ρ > 0.5, P < 0.01) and poor in ¹⁸F-NaF (ρ < 0.3, P > 0.1). When PSA levels were combined with treatment status, patients with below-median levels of PSA (<2 ng/mL) on androgen deprivation therapy (n = 11) demonstrated more lesions on ¹⁸F-NaF than ¹⁸F-DCFBC (P = 0.02). In PSA greater than 2 ng/mL, patients on androgen deprivation therapy (n = 8) showed equal to or more lesions on ¹⁸F-DCFBC than on ¹⁸F-NaF. Conclusion: The utility of PSMA-targeting imaging in metastatic prostate cancer appears to depend on patient disease course and treatment status. Compared with ¹⁸F-NaF PET/CT, ¹⁸F-DCFBC PET/CT detected significantly fewer bone lesions in the setting of early or metastatic castrate-sensitive disease on treatment. However, in advanced metastatic castrate-resistant prostate cancer, ¹⁸F-DCFBC PET/CT shows good concordance with NaF PET/CT.

Immunotherapy for biochemically recurrent prostate cancer

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Background: Annually about 30-50,000 men are diagnosed with biochemically recurrent prostate cancer (BCRpc), defined by a rising PSA after radical prostatectomy (RP) or definitive radiation therapy (RT) with negative conventional imaging (CT and bone scan). Standard treatments include salvage therapies, androgen deprivation or surveillance. The role of immunotherapy in BCRpc is undefined. Methods: This study evaluates PROSTVAC, a pox-viral based therapeutic cancer vaccine targeting PSA, in BCRpc. Key eligibility criteria include PSA > 0.8 after RP or > 2.0 after RT with a maximum PSA of 30, PSA doubling time (DT): 5-15 months; testosterone > 100, negative CT and bone scan. Patients (pts) are randomized to vaccine for 6 months or 6 months surveillance followed by 6 months of vaccine. In a post hoc analysis delayed PSA declines were characterized as a confirmed PSA decline after an intra-study apex PSA (ISAP) defined by a peak PSA affirmed by a contiguous PSA within 10% (to exclude lab variations). 80 pts will be enrolled at NCI, Dana-Farber Cancer Institute and Memorial Sloan Kettering Cancer Center. Results: Of the 26 pts enrolled thus far, 22 have been followed for > 9 months after vaccine and are evaluable. On-study median values were age 66.8 years (54-78), PSA 2.67 ng/ml (0.83-28.5), PSA DT 7.5 months (5.1-14.9). 8 pts (38%) had delayed PSA declines after ISAP (-12% to -99%). Of 13 pts on surveillance for 6 months, only one pt had a similar decline lasting only 56 days. Conclusions: Preliminary data from this study suggests that PROSTVAC may be associated with delayed, but sustained PSA declines in BCRpc which are rarely seen in surveillance alone. Additional data will be acquired from this study, but this provides rationale to develop immunotherapy combinations in BCRpc. Clinical trial information: NCT02649439. [Table: see text]

A phase 2 study of olaparib and durvalumab in metastatic castrate-resistant prostate cancer (mCRPC) in an unselected population

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Background: Data suggests 25-30% of sporadic mCRPC has defects in DNA repair pathways which may confer sensitivity to PARP inhibition (PARPi). Immune checkpoint blockade may increase the proportion of patients that respond to PARPi. We hypothesize that increased DNA damage by olaparib (O) will complement anti-tumor activity of immune checkpoint blocking antibody, durvalumab (D), in mCRPC (NCT02484404). Methods: Single arm pilot study with accrual of 25 patients (pts) with mCRPC and disease that is amenable to biopsy. Prior treatment with enzalutamide and/or abiraterone is required. D is given at 1500 mg iv q28 days + O 300 mg tablets po q12 hours. The primary endpoint is PFS. Core biopsies undergo mutational analysis. Results: In the first 17 pts, median age is 66 (range 45-79 years), median baseline PSA is 79.67 ng/mL [3.93-2356 ng/mL]). Median Gleason score is 8. 6 patients have bone only disease and 11 patients have bone and soft tissue/visceral disease. Median number of cycles is 7 (2-17). Grade 3/4 adverse events include anemia 4/17 (24%), lymphopenia 2/17 (12%), infection 2/17 (12%), thrombocytopenia, leukopenia, neutropenia, nausea, vomiting, UTI, hypertension, hearing impairment, fatigue, syncope, oral mucositis, muscle weakness, and muscle cramps [1/17 each, (6%)]. 8/17 pts (47%) had PSA responses >50%. 6 of these pts had mutations in the DNA damage repair pathways (DNAdr). 2/17 pts (11%) had PSA responses >30% with no known mutations in DNAdr. 4 pts had a PR. The 12 month PFS is 51.5% (95% CI: 25.7-72.3%). Conclusions: Preliminary data shows D+O is well tolerated with activity in an unselected population. Accrual is ongoing with biomarker analysis. Clinical trial information: NCT02484404.

Abstract LB-059: Neoadjuvant immunotherapy with androgen deprivation therapy (ADT) prior to radiation in prostate cancer: Impact on multiparametric prostate MRI and immune responses

Background: There is increasing interest in using combination immunotherapy in the neoadjuvant setting in prostate cancer, however, endpoints for such studies remain elusive. We have conducted a clinical trial evaluating immunotherapy with ADT in patients with high risk prostate cancer. Patients were assessed for immune responses and changes in endorectal (er) MRI which can be used to assess intraprostatic tumors. Methods: Treatment-naïve high-risk (Gleason 8-10, PSA&gt;20, or stage T3) prostate cancer patients (pts) were randomized to standard ADT+Radiation + an immunotherapy targeting MUC1 (tecemotide, aka L-BLP25) in this trial (NCT01496131). ADT consisted of gonadotropin-releasing hormone therapy. Immunotherapy included low dose (300 mg/m2, maximum 600 mg) pre-treatment cyclophosphamide for regulatory T-cell depletion. erMRI was done at baseline and after 2 months of immunotherapy including multiparametric MRI evaluation of apparent diffusion coefficient (ADC) maps from diffusion-weighted MRI. Monthly peripheral blood assessments analyzed immune cell subsets using flow cytometry and intracellular cytokine (ICC) staining for MUC-1 specific responses.

Results: 28 pts with high risk prostate cancer were enrolled (n=14/arm). As expected, PSA declined in all pts 2 months after ADT. erMRI after 2 months of treatment suggested greater improvements in ADC values in pts receiving immunotherapy+ADT vs. ADT alone. Improved ADC on MRI indicates increased intratumoral diffusion and has been associated with decreased tumor density. The improvements in ADC were seen when one dominant tumor per patient was evaluated (p=0.17) but were more pronounced when up to 3 lesions were evaluated per pt (n=44 lesions; p=0.031). Compared to baseline, there were trends to increases in CTLA4+ CD8+ T-cells consistent with immune activation and decreases in myeloid derived suppressor cells (MDSCs) in pts receiving immunotherapy+ADT coinciding with the erMRI changes. These immune findings were not seen in the ADT alone group. 3 of 14 pts had MUC1 specific immune response by ICC. 2 of these patients had the greatest changes in ADC noted on erMRI over a 2-year period.

Conclusions: Based on assessments by erMRI, pts who received ADT+immunotherapy had greater improvements in ADC than pts receiving ADT alone. Given that ADC improvements are associated with decreased tumor density, this suggests a possible greater anti-tumor effect of the ADT-immunotherapy combination vs. ADT alone. These findings were associated with trends to increased activated CD8+ T-cells and decreased MDSCs in pts receiving immunotherapy+ADT, with 3/14 pts having MUC1 specific immune responses. Further studies are required to confirm the potential to use ADC on erMRI as a potential (bio)marker of anti-tumor effect of immune combinations including ADT.

Citation Format: Ravi A. Madan, Baris Turkbey, Lauren M. Lepone, Renee N. Donahue, Italia Grenga, Samuel Samuel Borofsky, Peter A. Pinto, Deborah Citrin, Aradhana Kaushal, Andra Krauze, Sheri McMahon, Myrna Rauchhorst, Anna Couvillon, Martin H. Falk, S Peter Eggleton, Stephen C. Greco, Peter L. Choyke, William L. Dahut, Jeffrey Schlom, James L. Gulley. Neoadjuvant immunotherapy with androgen deprivation therapy (ADT) prior to radiation in prostate cancer: Impact on multiparametric prostate MRI and immune responses [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 LB-059. doi:10.1158/1538-7445.AM2017-LB-059

Combination of PDL-1 and PARP inhibition in an unselected population with metastatic castrate-resistant prostate cancer (mCRPC)

5026

Background: About 30% of sporadic mCRPC has defects in DNA repair pathways which may confer sensitivity to PARP inhibition. There is limited data about PDL1 inhibition in mCRPC. We hypothesize increased DNA damage by olaparib (O) will complement anti-tumor activity of immune checkpoint blocking antibody, durvalumab (D), in mCRPC:NCT02484404. Methods: Single arm pilot study with accrual of 25 patients (pts) with mCRPC and biopsiable disease. Prior treatment with enzalutamide and/or abiraterone is required. D is given at 1500 mg iv q28 days + O 300 mg po q12 h. Primary endpoint is PFS. Pretreatment and on-study core biopsies undergo mutational analysis. Results: 10 pts have enrolled (median age 65 yr [range 51-79], median baseline PSA: 85.78 [22.17-809.9 ng/mL]). 7 pts have GS ≥ 8. Grade 3/4 adverse events include anemia 2/7 (29%), thrombocytopenia, lymphopenia, neutropenia, nausea, fatigue, UTI, and lung infection [1/7 each, (14%)]. 5/7 pts (71%) on-study >2 months (mos) have PSA declines > 50%. Median PFS is 7.8 mos (95% CI: 1.8 mos-undefined). Conclusions: Preliminary data shows D+O is well tolerated with activity in an unselected population. Accrual is ongoing with biomarker analysis. Clinical trial information: NCT02484404. [Table: see text]

Changes in multiparametric prostate MRI and immune subsets in patients (Pts) receiving neoadjuvant immunotherapy and androgen deprivation therapy (ADT) prior to radiation

30

Background: Endorectal(er) MRI is an emerging tool in assessing intraprostatic tumors. Immunotherapy development in prostate cancer has been limited due to the lack of intermediate (bio)markers of response. Methods: Untreatedpts with high-risk prostate cancer were randomized in a trial (NCT01496131) of standard ADT+Radiation + an immunotherapy targeting MUC1 (tecemotide, aka L-BLP25). Pts had erMRI at baseline and after 2 months of ADT+/- biweekly immunotherapy. Low dose (300 mg/m2, maximum 600 mg) cyclophosphamide for regulatory T-cell depletion preceded first immunotherapy. Multiparametric MRI included evaluation of apparent diffusion coefficient (ADC) maps from diffusion-weighted MRI. Monthly peripheral blood assessments utilized flow cytometry to evaluate immune cell subsets. This analysis focuses on the 2 month neoadjuvant period of ADT+/-immunotherapy before radiation. Results: 28 pts (n = 14/arm) with high risk prostate cancer (Gleason 8-10, PSA > 20, or stage T3) were enrolled. PSA declined in all pts 2 months after ADT. erMRI findings at 2 months indicated greater improvements in ADC values in pts receiving immunotherapy+ADT vs. ADT alone. Improved ADC on MRI suggests improvements in intratumoral diffusion and has been associated with decreased tumor density. This relative improvement between the groups occurred both per patient (p = 0.16) and per lesion (p = 0.031). Relative to baseline, pts receiving immunotherapy+ADT had increases in CTLA4+ CD8+ T-cells consistent with immune activation (p = 0.0134) and decreases in myeloid derived suppressor cells (MDSCs; p = 0.0353) during the neoadjuvant period corresponding to the erMRI changes. These immune findings were not seen in the ADT alone group. Conclusions: Pts who received immunotherapy+ADT for 2 months had greater improvements in ADC values on erMRI, consistent with decreased tumor density, relative to pts receiving ADT alone. Corresponding increases in activated CD8+ T-cells and decreases in MDSCs were seen in pts receiving vaccine+ADT. These preliminary findings suggest that ADC on MRI may be useful in assessing immunologic impact. Further study is warranted. Clinical trial information: NCT01496131.

A phase II study of the anti-programmed death ligand-1 antibody durvalumab (D; MEDI4736) in combination with PARP inhibitor, olaparib (O), in metastatic castration-resistant prostate cancer (mCRPC)

162

Background: Recent data suggests 25-30% of sporadic mCRPC has defects in DNA repair pathways which may confer sensitivity to PARP inhibition. Immune checkpoint blockade is a promising avenue in mCRPC treatment. We hypothesize that increased DNA damage by O will complement anti-tumor activity of immune checkpoint inhibitor, D, in mCRPC (NCT02484404). Methods: Eligible pts have mCRPC with adequate end organ function and biopsiable disease (bone or soft tissue). Prior treatment with enzalutamide and/or abiraterone is required. D is administered at 1500 mg iv q28 days with O at 300 mg po q12 h. Primary endpoint is PFS. Secondary endpoints include PSA responses, safety and ORR. Single arm pilot study with a total accrual of 25 pts. On-study core biopsies undergo mutational analysis. Results: 6 pts have enrolled (median age 67 yr [range 60-79], median ECOG PS 1 [1-2]). Median baseline PSA: 258.1 (54.1-809.9 ng/mL). 4 pts have Gleason score (GS) > 8 and 2 pts have GS of 7. Grade 3/4 adverse events include anemia 2/6 (33%), thrombocytopenia, lymphopenia, nausea, febrile neutropenia, aspiration pneumonia [1 each, (17%)]. Conclusions: Exploiting synergy of D+O is a treatment option for heavily pre-treated pts. Preliminary data shows D+O is tolerable and active in mCRPC pts without germline BRCA mutation. Paired tumor biopsies and blood samples including ctDNA are being collected. Accrual is ongoing. Clinical trial information: NCT02484404. [Table: see text]

Phase II trial of docetaxel, bevacizumab, lenalidomide and prednisone in patients with metastatic castration-resistant prostate cancer

OBJECTIVE

To determine the safety and clinical efficacy of two anti-angiogenic agents, bevacizumab and lenalidomide, with docetaxel and prednisone.

PATIENTS AND METHODS

Eligible patients with metastatic castration-resistant prostate cancer enrolled in this open-label, phase II study of lenalidomide with bevacizumab (15 mg/kg), docetaxel (75 mg/m(2) ) and prednisone (10 mg daily). Docetaxel and bevacizumab were administered on day 1 of a 3-week treatment cycle. To establish safety, lenalidomide dosing in this combination was escalated in a conventional 3 + 3 design (15, 20 and 25 mg daily for 2 weeks followed by 1 week off). Patients received supportive measures including prophylactic pegfilgrastim and enoxaparin. The primary endpoints were safety and clinical efficacy.

RESULTS

A total of 63 patients enrolled in this trial. Toxicities were manageable with most common adverse events (AEs) being haematological, and were ascertained by weekly blood counts. Twenty-nine patients (46%) had grade 4 neutropenia, 20 (32%) had grade 3 anaemia and seven (11%) had grade 3 thrombocytopenia. Despite frequent neutropenia, serious infections were rare. Other common non-haematological grade 3 AEs included fatigue (10%) and diarrhoea (10%). Grade 2 AEs in >10% of patients included anorexia, weight loss, constipation, osteonecrosis of the jaw, rash and dyspnoea. Of 61 evaluable patients, 57 (93%), 55 (90%) and 33 (54%) had PSA declines of >30, >50 and >90%, respectively. Of the 29 evaluable patients, 24 (86%) had a confirmed radiographic partial response. The median times to progression and overall survival were 18.2 and 24.6 months, respectively.

CONCLUSIONS

With appropriate supportive measures, combination angiogenesis inhibition can be safely administered and potentially provide clinical benefit. These hypothesis-generating data would require randomized trials to confirm the findings.

Clinical and immunologic impact of short course enzalutamide without androgen deprivation therapy for biochemically recurrent prostate cancer

214

Background: Enzalutamide (enz) is FDA approved for advanced prostate cancer, but studies are evaluating enz in earlier stages of disease. We have conducted a clinical trial (NCT01875250) of enz ± a therapeutic vaccine in biochemically recurrent prostate cancer. Methods: Eligible patients (pts) had a PSA between 2.0-20.0 ng/ml, no metastatic disease and normal testosterone (T). Treatment for all pts included enz 160 mg daily for 84 days (D), but no T lowering therapy was permitted. This analysis evaluated all pts for the impact of enz on PSA and T regardless of randomization. Pts treated with Enz alone were evaluated for immune responses.The impact of the vaccine will be evaluated after protocol-defined requisite follow-up. Results: Median age for all pts (n = 34) was 66 years (range: 52-87), with a median on-study baseline PSA of 4.55 ng/ml (2.02-19.43). Common adverse events included fatigue and breast tenderness, but no pts discontinued enz for toxicity. The median PSA decline was 99% (range: 52% to > 99%) with 11/34 pts having undetectable nadirs. Median time to first PSA rise after 84 D course of enz was 29 D (13-70) and median recovery to baseline PSA in 25 evaluable pts was 190 D (84-469). T increased above normal limits in 18/34 pts (median Tmax = 802 ng/dl). Immune analysis (n = 12) indicated enz alone increased naïve T-cells and NK cells, and decreased several subsets of myeloid derived suppressor cells with a highly suppressive phenotype. Conclusions: The preliminary findings from this study suggest that short-course enz is well tolerated, leads to prolonged PSA suppression and enhanced immune responses in patients with biochemically recurrent prostate cancer. These immune studies provide the rationale for the use of enz in combination with immunotherapeutics in this and other malignancies. Clinical trial information: NCT01875250.

An analysis of sodium 18f-fluoride PET/CT and prostate specific antigen (PSA) changes in men with metastatic castration resistant prostate cancer (mCRPC)

203

Background: Recently there has been growing evidence that 18F-Fluoride PET/CT has increased sensitivity relative to technetium-99m diphosphonate (Tc-99m MDP) bone scan for evaluating metastatic bone disease. This analysis studied changes in 18F-Fluoride PET/CT and evaluated associations with PSA changes for mCRPC patients (pts) on enzalutamide (enz). Methods: As part of a randomized phase II study evaluating enz with or without vaccine therapy, men with mCRPC electively underwent 18F-Fluoride PET/CT at 3 month (mos) intervals [NCT01867333]. At these points serum PSA was collected. Data was taken on max SUV and volume of presumed cancerous lesions and a variable, ΣSUV*Volume, was calculated which was defined as the sum of the products of SUV max and volume of cancerous lesions. Results: At the time of our analysis, 19 pts had PSA and PET/CT data for at least 2 time points within 1 year of initiating therapy. The median baseline PSA was 19.6 ng/ml (0.76-587). All pts had predominantly bone disease with 10 having small volume lymphadenopathy. Only 1/19 pts progressed by PSA Working Group criteria. An analysis found that 18/19 pts (95%) had an association between changes in PSA and ΣSUV*Volume. Of these 18 pts, 13 had a major ( > 50%) and 1 had a minor ( > 30%) PSA response and all 14 had an accompanying decrease in ΣSUV*Volume. For 11/14 pts with PSA responses, the change in ΣSUV*Volume paralleled the change in PSA at all time points, while for 3 pts an associated change between ΣSUV*Volume and PSA was delayed by 3 mos. 4/14 pts had short term responses lasting only 3 mos followed by PSA increases. For these 4 pts the changes in ΣSUV*Volume paralleled PSA changes, decreasing at 3 mos and increasing thereafter. Finally 4/18 patients had no PSA response to therapy. All 4 pts had increases in ΣSUV*Volume which paralleled rising PSA values. Conclusions: Preliminary data from a small cohort suggests that findings on 18F-Fluoride PET/CT are associated with PSA changes. This represents a substantial difference from standard Tc-99m MDP and further suggests that 18F-Fluoride PET/CT may provide a more sensitive analysis of bone disease. Additional data from this and other studies are required.

Comparison of survival of African-American (AA) patients (pts) in docetaxel (D)-based combination therapies in metastatic castrate-resistant prostate cancer (mCRPC)

272

Background: AA pts experience greater prostate cancer (PC) incidence and mortality compared to Caucasian (C) pts but are underrepresented in clinical trials (CTs). Greater representation of AAs is required to explore differences in clinical benefit in advanced disease where recent data has reaffirmed the role of D. Methods: In a retrospective analysis, baseline characteristics, Gleason score (GS), ECOG PS, number of cycles (cys), maximum prostate-specific antigen (PSA) declines, radiographic responses, overall survival (OS) and progression-free survival (PFS) were captured in 2 recent D based CTs. Results: Of 136 pts, 28 (21%) self-identified as Black or AA. Median age of AA pts is 66 (50-78 yrs). Median GS is 8 (5-10). Median ECOG PS is 1 (0-2). 15 pts have bone and soft tissue disease; 13 pts have bone only disease. Median number of cys is 28.5 (1-63). Of 27 evaluable pts, 26 had PSA declines (-26 to -99%). Radiographic responses include 11 (39%) partial responses and 16 (57%) pts with stable disease. Median OS for AAs is 29.0 months (mos) (95% CI: 20.9-34.7 mos); median PFS is 21.5 mos (95% CI: 13.7-28.9 mos). Median OS for all non-AA pts is 24.8 mos (95% CI: 21.8-29.5 mos); median PFS is 16.1 mos (95% CI: 14.1-20.1 mos). The VEGF-634G > C SNP, associated with a more aggressive phenotype of PC, was evaluated in 54 pts. No evidence was found that genotype frequency varies between C and AA pts. Conclusions: In this analysis, AA pts did not have inferior OS (29 mos) or PFS (21.5 mos) outcomes compared to non-AA pts (24.8, 16.1 mos). Further analysis from larger studies is required to determine differential benefits of D for AA pts compared to non-AA pts. Clinical trial information: NCT00089609, NCT00942578.

Abstract CT222: Ferumoxytol enhanced MRI for lymph node staging in genitourinary cancers

Background: Conventional imaging has limited accuracy in genitourinary (GU) cancer staging. This study examines the utility of ferumoxytol enhanced MRI in lymph node (LN) staging of GU cancers.

Methods: This ongoing IRB-approved phase II clinical trial enrolls patients with prostate cancer, renal cell carcinoma, or bladder cancer at high risk for LN metastases. Patients undergo baseline T2 and T2* weighted MRI scans followed by injection of 7.5mg/Kg ferumoxytol. Repeat scans are acquired at 24hr and 48hr post-injection. The criterion for positive LNs was preservation of hyper-intense signal indicating failure to take up ferumoxytol. Validation was by histopathology when available or on clinical grounds, for which LNs that changed size on routine imaging were considered true positives.

Results: To date, 13 patients have completed the study. Of 11 prostate cancer patients, one was studied pre-operatively while 10 had suspected therapy failure. Median age and PSA were 65yrs (36-75) and 5.6ng/mL (0.3-201). The other 2 patients had renal cell carcinoma and bladder cancer. Overall, 20 LNs were identified with mean size 1.9cm (0.7-3.8) long axis by 1.3cm (0.6-2.6) short axis. There were 14 true positive LNs, 1 false positive, 1 false negative, and 4 nodes pending validation. Validation was by histopathology for 7 LNs, with 2 nodes pending biopsy, and clinical grounds for 13 LNs, with 2 inconclusive nodes awaiting further validation. Ferumoxytol correctly identified LN status in 9 of 10 patients with validated nodes (Table 1).

Conclusions: Ferumoxytol enhanced MRI shows promise in detecting malignant LNs &gt;6mm in GU cancer patients. Since the method involves a conventional MRI unit with off-label use of an FDA-approved agent, it could be widely available. However, further validation is necessary before routine use.

Table 1: Preliminary results for LN staging in GU cancer patients using ferumoxytol enhanced MRI

SubjectStudy ArmGenderAge (yr)PSA at study initiation (ng/mL)LN numberLN locationsize/long axis (cm)size/short axis (cm)Ferumoxytol positive? 1 = yes, 0 = noResult1prostate cancerM6325.061R ext iliac3.02.61TP2L ext iliac1.30.81TP2prostate cancerM6573.961L RP1.61.41TP2L int iliac3.81.91TP3prostate cancerM6410.491R ext iliac3.00.91pending2L ext iliac1.91.10pending4prostate cancerM742.061L RP1.71.51TP5prostate cancerM642.891R ext iliac1.61.11TP6prostate cancerM650.281L int iliac1.50.81TP7prostate cancerM752.871R int iliac0.70.71TP8prostate cancerM6427.911R common iliac1.71.71inconclusive9prostate cancerM72201.21L RP2.31.70FN10prostate cancerM736.771L int iliac1.51.01TP11prostate cancerM361.351R femoral0.80.81FP2L ext iliac1.51.01inconclusive3R perirectal0.80.61TP12renal cell carcinomaF41N/A1aortocaval2.82.21TP2R RP3.62.31TP3R int iliac2.01.51TP13bladder cancerM59N/A1aortocaval1.51.01TPRP = retroperitoneal, TP = true positive, FN = false negative, FP = false positive, ext = external, int = internal

Citation Format: Anna M. Brown, Sandeep Sankineni, Marcelino Bernardo, Dagane Daar, Juanita Weaver, Yolanda McKinney, Anna Couvillon, James L. Gulley, Bradford J. Wood, Peter A. Pinto, William L. Dahut, Ravi Amrit Madan, Peter L. Choyke, Baris Turkbey. Ferumoxytol enhanced MRI for lymph node staging in genitourinary cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT222. doi:10.1158/1538-7445.AM2015-CT222

Cabozantinib (C) plus docetaxel (D) and prednisone (P) in metastatic castrate-resistant prostate cancer (mCRPC)

235

Background: Docetaxel (D) improves overall survival in metastatic castrate-resistant prostate cancer (mCRPC), but benefits remain short-lived. Clinical data suggests patients (pts) with mCRPC treated with anti-androgen therapy like abiraterone (AA) or enzalutamide (ENZA) have decreased responses to subsequent therapy due to cross-resistance in the androgen pathway targeted by D, AA, or ENZA(van Soest et al, Eur J Cancer 49:18, 2013). Combining D with other agents, like cabozantinib (C), could target different cellular signaling pathways potentially minimizing tumor resistance. Methods: D naive pts receive 75 mg/m2 IV on day 1 of a 21 day cycle, and prednisone (P) 5 mg po q12 hours with C at 3 dose levels: 20, 40, or 60 mg po daily until maximum tolerated dose (MTD) is defined. In phase 2, pts who have progressed on AA or ENZA, enroll on a randomized 2 arm cohort comparing D plus C to D alone. Results: 20 pts have been accrued; 4 at 20 mg C, 8 at 40 mg C, and 7 at 60 mg C. On phase 2, 1 pt is randomized to D alone. Median age is 68 (44-84 yrs). Median baseline PSA is 94.7 (0.01-754.1 ng/mL). Gleason score is 9 (7-10). Median cycles is 9.5 (1-33). 8 pts have bone only disease, 12 pts have bone and soft tissue disease. Common grade 2 and grade 3 adverse events possibly related to C: hand/foot syndrome (4/16), oral mucositis (4/16), hypophosphatemia (4/16), and fatigue (3/16). The MTD of C is 40 mg daily with D. 15 pts were previously treated with AA or ENZA. In 13 patients previously treated with AA, median PFS has not been reached, with a median potential follow up of 12.4 months. Six month PFS is 77.8% and 9 month PFS is 60.5%. Conclusions: D plus P may have limited benefits after disease progression on AA as seen in 3 retrospective analyses demonstrating a median PFS survival of 4.6 months or less (Mezynski J, et al. Ann Oncol 23;11, 2012) (Aggarwal R, et al. Clin Genitourin Cancer 12;5, 2014) (Schweizer MT, et al. Eur Urol 66;4, 2014). PFS results seen in this trial compare favorably to previously published data of treatment with D after AA in mCRPC, suggesting the addition of C to D may help overcome acquired resistance. Further randomized trials will determine if C in combination with D will enhance clinical outcomes. Clinical trial information: NCT01683994.

Association of NaF PET/CT findings with PSA and alkaline phosphatase in untreated castration-sensitive prostate cancer

122

Background: NaF PET/CT is an emerging imaging technique with potentially high sensitivity in detecting bone metastasis (mets), however, its role in castration-‐sensitive prostate cancer (CSPC) is undefined and it remains unclear which CSPC patients should have NaF PET/CT. Methods: We retrospectively reviewed NaF PET/CT scans done on 45 patients with untreated, high risk CSPC with the goal of determining which disease features were associated with positive findings. Two blinded radiologists reviewed each scan and determined by consensus if findings were negative for metastasis (0% liklihood of mets), possible (50%), probable (75%), or consistent with mets (90%). Prostate specific antigen (PSA) and alkaline phosphatase (AP) values were then evaluated at time of NaF scan when available. Results: Of the 45 patients 2 were Gleason 6, 5 were Gleason 7, 36 were Gleason 8 to 10, 2 unknown. When grouped by findings on NaF PET/CT, there were no substantial differences seen between median PSA or AP values. When patients with both PSA and AP values > median were evaluated, there was no clear association with NaF PET/CT findings. Conclusions: Preliminary findings from this small retrospective analysis suggest that there may be limited associations between PSA and/or AP with findings on NaF PET/CT scan in untreated patients with CSPC. Further analysis in larger cohorts of pts is required. [Table: see text]

Ferumoxytol enhanced MRI for lymph node staging in prostate cancer

208

Background: Conventional imaging methods of lymph node staging in prostate cancer are limited. The goal of this study is to determine the utility of ferumoxytol enhanced MRI in lymph node (LN) staging. Methods: This ongoing IRB-approved clinical trial enrolls prostate cancer patients at high risk for LN metastases. Patients first undergo baseline T2 and T2* weighted MRI scans followed by 7.5mg/Kg ferumoxytol injection. Repeat scans are acquired at 24 hr and 48 hr post-injection. The criterion for positive LNs was hyperintense signal indicating failure to take up ferumoxytol. Validation was determined on clinical grounds or by histopathology when available. Results: To date, 11 patients have completed the study. One patient was examined pre-operatively while the other 10 had suspected therapy failure. Median age and PSA were 65 yrs (36-75) and 5.6ng/dL (0.3-201). Of 16 LNs with median size 1.6 x 1.1cm, 10 were true positives, one was false positive and one was false negative with 4 nodes pending validation. The LN status was correctly identified in 8 of 11 patients [Table]. Conclusions: Ferumoxytol enhanced MRI shows promise in detecting malignant LNs with diameter >6mm in prostate cancer paients. This method is performed in a conventional MRI unit with off-label use of an FDA-approved agent and thus could be widely available. However, further validation is necessary before routine use. Clinical trial information: NCT02141490. [Table: see text]

A safety study of trebananib (AMG 386) and abiraterone in metastatic castration-resistant prostate cancer

218

Background: Trebananib is an angiopoietin1/2 antagonist peptibody. Androgens stimulate expression of VEGF via activation of hypoxia inducible factor-a (HIFa). Androgen deprivation therapy (ADT) is associated with lower HIF1a gene expression in prostate cancer tissue. Dual targeting of the androgen and angiogenic axis represents a potential synergistic anti-angiogenic therapeutic approach in metastatic castration resistant prostate cancer (mCRPC). In this preliminary safety study we hypothesize that trebananib in combination with abiraterone will have a favorable tolerability and efficacy profile. Methods: Patients with mCRPC were treated with abiraterone 1000mg daily and prednisone 5 mg twice daily. Trebananib was administered intravenously every week, in escalating doses from 15mg/kg to 30mg/kg on days 1, 8, 15, and 22 every 28-days. Results: A total of 9 patients were enrolled. Three of nine patients had prior chemotherapy. The median age was 63.8 (63-71yrs). No dose limiting toxicities were observed. The most common grade ≥ 2 toxicities included limb edema (3/9), hyperglycemia (1/9), gastrointestinal (2/9), fatigue (2/9), hypertension (1/9), confusion (1/9), weight gain (1/9) and insomnia (2/9). 5/9 of patients had an overall PSA decline of >30%. 8/9 patients were evaluable for response. Prior chemotherapy patients were on study for 1 and 3 months. No prior chemotherapy patients were treated for 1, 6, 9, 10, 10, and 17 months. Conclusions: Trebananib in combination with abiraterone is well tolerated and displayed an acceptable safety profile in patients with mCRPC. Based on this safety data a randomized phase II study randomizing chemotherapy-naïve mCRPC patients to either abiraterone/prednisone plus AMG 386 at 30mg/kg or abiraterone/prednisone is currently accruing at the NCI. Clinical trial information: NCIT01553188.

A phase I study of the multikinase inhibitor cabozantinib (C) plus docetaxel (D) and prednisone (P) in metastatic castrate-resistant prostate cancer (mCRPC)

108

Background: Cabozantinib (C) is a multikinase inhibitor of c-Met, vascular endothelial growth factor receptor two and RET. C has shown activity in metastatic castrate resistant prostate cancer (mCRPC), with resolution of bone lesions on bone scan (BS), regression of soft tissue/visceral disease (STD), reductions in circulating tumor cells and bone biomarkers. Combining docetaxel (D) with other agents, without overlapping toxicities, can target different cellular signaling pathways necessary for tumor survival. Methods: Patients (pts), with no prior D for CRPC, receive a fixed dose of D (75 mg/m2 IV day one of each 21 day cycle) and prednisone (P) (5 mg po q12 hours) with C at three escalating dose levels: 20 mg, 40 mg, or 60 mg (all po daily). Using a standard three-plus-three design, three to six pts are treated at each dose level until the maximum tolerated dose (MTD) has been defined. Results: Thirteen pts have been accrued; four on dose level one, six on dose level two, and three on dose level three. Median age 69 (45 to 84). Four pts have an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of zero and nine pts have a PS of one. Median Gleason score is nine (7 to 10). Median on-study prostate-specific antigen (PSA) is 129.2 ng/mL (0.01-508.5 ng/mL). Median cycles is six (1 to 17). Grade 1 adverse events (AEs), possibly related to C; dysgeusia (4/12), oral mucositis (4/12), increased ALT (3/12), and epistaxis (3/12). Grade 2 AEs; nausea (2/12), hand/foot syndrome (2/12), fatigue (2/12), dysgeusia (2/12), oral mucositis (2/12), hypophosphatemia (2/12), and anemia (2/12). Grade 3 AE is hypophosphatemia (2/12). Grade 4 AE is neutropenia (1/12). MTD of C is 60 mg. Of nine evaluable pts, six have bone only disease. Of these six, three pts have PSA declines of less than 30% with improvement on BS (two pts) or stable BS (one pt). The other three pts have PSA declines of greater than 30% and bone scan improvement. Three pts have STD and bone disease; one patient had a PSA decline of greater than 30% with improvement on BS and SD by CT scan. One patient had an increase in PSA of less than 30% with improvement on BS and CT. The third pt had PD by CT and an increase in PSA equal to 30%. PFS probability at six months is 90.0% and is 67.5% at eight months and beyond. Conclusions: The addition of C to D and P, has an acceptable toxicity profile. CT scan and BS improvements did not correlate with PSA declines in all pts. An expansion cohort will combine D plus P with C at the MTD (60 mg) to determine clinical benefit. Clinical trial information: NCT01683994.

Use of supportive measures to improve outcome and decrease toxicity in docetaxel-based antiangiogenesis combinations in metastatic castrate resistant prostate cancer (mCRPC)

e16017

Background: We have completed accrual of 63 patients (pts) to our study combining lenalidomide (L), with bevacizumab (B), docetaxel (D), and prednisone (P) (ART-P) in mCRPC. Due to the lack of improved survival and the increased toxicity of anti-angiogenic docetaxel combinations in the MAINSAIL and CALGB 90401 trials, we attempted to compare and contrast our studies with these failed phase III trials. Methods: Among the first 52 pts on ART-P, 3 received L 15 mg daily, 3 received 20 mg daily, and the others received 25 mg daily for 14 days of every 21−day cycle (C). We then enrolled 11 pts at L 15 mg. All pts received D 75 mg/m2 and B 15 mg/kg on day 1 with P 10 mg and enoxaparin daily. Pegfilgrastim was given on day 2. Patients on CALGB 90401 received D 75 mg/m2 and B 15 mg/kg on day 1, with P 10 mg. On MAINSAIL, pts received D 75 mg/m2, L 25 mg daily for 14 days of every 21−day cycle with daily P. Patients on CALGB 90401 and MAINSAIL did not receive enoxaparin or pegfilgrastim prophylactically. Results: The median number of Cs on ART-P is 18 (1-52). Median PFS is 19.1 months. Twenty-seven pts had a PR, and one pt with measurable disease had a CR. Two patients (3%) had deep vein thromboses. Of 1,334 Cs given, 14 cycles were complicated by febrile neutropenia (FN) (1%). There were no treatment related deaths. In comparison, median number of Cs in MAINSAIL L+DP arm was 6, with a PFS of 45 weeks and an OS of 77 weeks. Thirty-four pts (6.5%) developed pulmonary emboli and there were 2 deaths due to toxicity in the experimental arm. Nearly 12% of Cs were complicated by FN. In the experimental arm of CALGB 90401 trial, median OS was 22.6 months with median PFS of 9.9 months. The median number of Cs were 8 and 19 pts developed thrombosis/emboli (3.6%). In addition, 37 patients developed FN and treatment related deaths were reported at 4%. Conclusions: The use of supportive care allowed longer treatment duration with the ART-P combination as compared to D+L (MAINSAIL) and D+B (CALGB 90401), potentiating a longer PFS, RR and possibly OS with an improved safety profile. This data demonstrates the potential importance of supportive measures and is hypothesis generating for future combination studies. Clinical trial information: NCT00942578.

A phase I study of cabozantinib (Cabo) plus docetaxel (D) and prednisone (P) in metastatic castrate resistant prostate cancer (mCRPC)

TPS5095

Background: In mCRPC, two randomized trials demonstrated an overall survival (OS) benefit with the chemotherapeutic agent D. However, the survival improvement is modest and new strategies are needed to enhance clinical response. D-based combinations have been evaluated as one alternative strategy. Cabo targets multiple tyrosine kinases including c-Met, vascular endothelial growth factor receptor 2 (VEGFR2) and RET. Cabo has shown activity in mCRPC, with resolution of bone lesions on bone scan, regression of soft tissue/visceral disease, and reductions in circulating tumor cells and bone biomarkers (Smith, et al, J Clin Oncol 30, 2012 [suppl; abstr 4513]). We hypothesize the addition of Cabo to D and P, in patients (pts) with mCRPC, will have an acceptable toxicity profile and could lead to improved survival by targeting different cellular pathways simultaneously. This combination therapy may represent a safe and effective strategy to improve the outcome of mCRPC pts treated with D-based chemotherapy. Methods: This is a phase I trial to determine the safety profile and the recommended phase II dose of Cabo in combination with D and P. Pts receive a fixed dose of D (75 mg/m2 IV day 1 of each 21 day cycle) and P (5 mg po q12 hours) in combination with Cabo at three escalating doses: dose level 1 is 20 mg, level 2 is 40 mg, and level 3 is 60 mg (all po qdaily). Using a standard 3 + 3 design, three patients will initially be treated at each dose level until the maximum tolerated dose (MTD) has been defined. An expansion cohort will then be enrolled at the MTD. The accrual ceiling for the study, including both the dose escalation and the expansion phases, is set at 24 pts. Secondary objectives include assessments of pharmacokinetics of each agent, evaluation of antitumor activity of the combination therapy, and assessment of changes in molecular biomarkers for receptor tyrosine kinase and angiogenesis pathways, as well as biomarkers for bone metabolism. Restaging with bone and CT scan will be undertaken every 3 cycles. Enrollment at dose level 1 has been completed without dose-limiting toxicity. Accrual is ongoing at the second dose level. Clinical trial information: NCT01683994.

A randomized phase II clinical trial of enzalutamide in combination with the therapeutic cancer vaccine, PSA tricom, in metastatic, castration resistant prostate cancer

TPS5104

Background: There is a strong rationale to combine therapeutic cancer vaccines with hormonal abrogation in prostate cancer. Androgen abrogation augments T-cell trafficking to prostate, decreases immune tolerance, increases production of naïve thymic T-cells, enhances cytotoxic T-cell repertoire. PSA TRICOM (PROSTVAC) is a therapeutic, viral-vector based, off-the-shelf, cancer vaccine of PSA & 3 co-stimulatory molecules in phase III testing. This was developed at the NCI in collaboration with Bavarian Nordic Immunotherapeutics. It has demonstrated safety and survival benefit in a randomized phase 2 trial of metastatic castrate resistant prostate cancer (mCRPC). Enzalutamide is a modern androgen receptor inhibitor (ARI) approved for the treatment of mCRPC. Data from the clinical trials with these therapies suggest good individual tolerability without any overlapping toxicities. Analysis of previous trials suggests that vaccines may enhance clinical outcomes with ARI. These data form the scientific basis for a combination approach of a cancer vaccine with ARI to control tumor progression in mCRPC. Methods: A randomized, phase 2, open-label clinical trial at the NCI will enroll 72 chemo-naïve, minimally symptomatic patients with mCRPC. They will be randomized (1:1) to enzalutamide (160 mg daily) alone, or enzalutamide with PSA TRICOM for treatment until radiographic progression. PSA-TRICOM will be administered in a core phase (with day 1, 15 and 29 then 4 additional monthly boosts) followed by continued boosts every 3 months. The primary end point will evaluate time to progression in each arm with secondary endpoints including overall survival and systemic immune responses (lymphocyte subsets, regulatory T-cells, regulatory T-cell function, cytokines, naïve thymic emigrants). If a therapeutic cancer vaccine can enhance the clinical efficacy of a hormonal agent such as enzalutamide, it may help define a new role for vaccines as an adjuvant to standard therapies. We will also evaluate this combination in a second trial in non-metastatic, castration-sensitive patients where this combination may yield its greatest clinical impact.

Feasibility of continuing docetaxel-based therapy in patients with metastatic castrate-resistant prostate cancer (mCRPC) that experience hypersensitivity reactions (HSR)

132

Background: Patients that receive docetaxel are observed closely for HSRs. Severe HSRs have been reported in patients premedicated with corticosteroids. The rate of allergic reactions reported in the TAX 327 trial (n=332) was 8% (any grade) and 1% (grade 3/4). In TAX 327 treatment was stopped after a total of 10 cycles of docetaxel. A recent trial conducted at the NCI has included patients treated with docetaxel-based therapy until radiographic progression with no cap on total dose or cycle number. Most patients have had significantly more than 10 cycles (median greater than 16 with a range of 1 to 48; however, some cycles did not include docetaxel). Given the increased incidence of HSR to docetaxel on our protocols, we developed guidelines for the clinical management of HSRs to docetaxel. Methods: We reviewed the literature on taxane HSRs and developed a 4-step clinical management guideline for the prevention and treatment of HSRs to docetaxel. Our guidelines utilize increasing amounts of H1/H2 antihistamines, corticosteroids, slower infusion rates of docetaxel, and/or decreasing concentrations of docetaxel. Results: From August 2009 to present, 63 mCRPC patients have been treated with docetaxel-based therapy. Twenty-three patients (37%) have experienced a HSR to docetaxel. HSRs initially occurred at cycle 1 (17%), cycle 2 (48%), cycle 3 (17%), cycle 4 (n=2), cycle 14 (n=1), cycle 16 (n=1). All patients were re-challenged with docetaxel using our 4-step clinical management guideline approach. Ten patients continued docetaxel without further HSRs. The remaining 13 patients continued to experience HSRs but were able to safely complete each infusion of docetaxel. No patients required discontinuation of therapy. Of the 23 patients with HSRs, 21 received more than 10 cycles of therapy with a median of 17 and a range of 1 to 38. Conclusions: Patients with mCRPC disease that is taxane sensitive and who experience HSR to docetaxel can continue to receive docetaxel safely. Most of these patients demonstrated a continued PSA, clinical, and radiographic response to therapy.

Use of supportive measures to improve outcome and decrease toxicity in docetaxel-based antiangiogenesis combinations

128

Background: We have recently completed accrual of 63 patients (pts) to our study combining lenalidomide (L), with bevacizumab (B), docetaxel (D), and prednisone (P) (ART-P). Due to the lack of improved survival and the increased toxicity of anti-angiogenic docetaxel combinations in the MAINSAIL and CALGB 90410 trials we attempted to contrast and compare our studies with the failed phase III trials. Methods: Among the first 52 pts on the ART-P, 3 received L 15 mg daily, 3 had 20 mg daily, and the rest had 25 mg daily for 14 days of every 21−day cycle (C). We later enrolled 11 more pts at L 15 mg. All pts received D 75 mg/m2 and B 15 mg/kg on day 1 with P 10 mg and enoxaparin daily throughout each C. Pegfilgrastim was given on day 2. Patients on CALGB 90410 received D 75 mg/m2 and B 15 mg/kg on day 1 with P 10 mg and on MAINSAIL received D 75 mg/m2, L 25 mg daily for 14 days of every 21−day cycle with daily P. Patients on CALGB 90410 and MAINSAIL did not receive enoxaparin or pegfilgrastim prophylactically. Results: Median number of Cs in ART-P was 16 (3−38). PFS was 22 months and median OS has not been reached. Pts with measurable disease had 1 CR and 25 PR (86.7% RR). Two patients (3%) had deep vein thromboses. Of 1,219 cycles given, 14 cycles were complicated by febrile neutropenia (FN) (1.1%). There were no treatment related deaths. In comparison, median number of Cs in MAINSAIL L+DP arm was 6, with a PFS of 45 weeks and an OS of 77 weeks. Thirty-four pts (6.5%) developed pulmonary emboli and there were 2 deaths due to toxicity in the experimental arm. Nearly 12% of Cs were complicated by FN. In the experimental arm of CALGB 90410 trial, median OS was 22.6 months with median PFS of 9.9 months. Median number of Cs was 8, and 19 pts developed thromboses/emboli (3.6%). In addition, 7% of patients developed FN and treatment related deaths were reported at 4%. Conclusions: The use of supportive care allows the ART-P combination to be given for more cycles than were given in MAINSAIL and CALGB 90401 potentiating a longer PFS, RR and possibly OS with an improved toxicity profile. This data demonstrates the potential importance of supportive measures and is hypothesis generating for future combination studies. Clinical trial information: NCT00942578.

Randomized phase II clinical trial to assess MUC1 specific immune response to L-BLP25 vaccine in addition to standard therapy in newly diagnosed high-risk prostate cancer

TPS4701

Background: In high-risk prostate cancer, radiation therapy (RT) + androgen deprivation therapy (ADT) improve survival. Nonetheless, 10-year disease specific mortality is about 25%. L-BLP25 is a cancer vaccine containing the BLP25 lipopeptide that targets MUC1 tumor antigen. It may enhance immune targeting of cells that express MUC1 (e.g. prostate cancer). In murine models, RT synergizes with vaccine-induced anti-cancer immunity (augments T-cell mediated cancer cytolysis, up-regulates cellular Fas and co-stimulatory/adhesion molecules). ADT augments T-cell trafficking to prostate. Immune response to combining the three (L-BLP25 + RT + ADT) is not known. The current trial intends to study this immune response to L-BLP25 + RT + ADT and compare it to RT+ADT alone. Using ELISPOT, endo-rectal MRI and serial prostate biopsies, this trial was designed to correlate systemic immune response with changes in tumor imaging and/or tumor microenvironment after treatment with L-BLP25. This trial may provide insight into immune response biomarkers that are most appropriate in this setting. Methods: A randomized (1:1), open-label, phase II trial of 42 pts is planned. Eligibility: Adult males with newly diagnosed high-risk prostate cancer (T3 or Gleason ≥ 8 or seminal vesicle involvement or N1 or PSA>20) and HLA-A2/A3 positivity (to allow for ELISPOT analysis). The vaccine arm will receive RT + 2-year ADT + L-BLP25. Standard arm will receive RT + 2-year ADT. L-BLP25 vaccine schedule: biweekly X 5 starting with neo-adjuvant ADT, then 6 weekly X 4 starting with RT. A single 300mg/m2 cyclophosphamide infusion (decreases suppressor T-cells) will be given 3 days before L-BLP25 to enhance immune response in the vaccine arm. The impact of L-BLP25 + RT+ADT on MUC-1-specific systemic immune response will be determined using interval peripheral blood ELISPOT assays. Endo-rectal coil MRI will be done before and after treatment to study prostate signal changes for correlative and predictive analysis. MRI-UltraSound guided lesion-targeted serial prostate biopsies will be obtained to assess immune response in tumor microenvironment. Two pts have been enrolled.