Yohann Loriot

5004 Background: We hypothesized resistance to the androgen receptor inhibitor ENZA is due to increases in androgens and can be overcome by combination with the androgen synthesis inhibitor abiraterone (abi). The phase 4 PLATO trial (NCT01995513) is evaluating the safety and efficacy of continued ENZA + abi/prednisone (abi/P) vs PBO + abi/P after PSA progression on ENZA. Methods: In Period (P) 1, men with chemotherapy-naïve mCRPC received ENZA (160 mg); men with no PSA increase from baseline at wk 13 and 21 continued treatment until PSA progression (≥ 25% increase and ≥ 2 ng/mL above nadir). Eligible men were then randomized 1:1 in P2 to ENZA + abi/P (1000 mg/10 mg) or PBO + abi/P. The primary endpoint (EP) was progression-free survival (PFS; radiographic or unequivocal clinical progression, or death on study) in P2, with a prespecified sensitivity analysis of radiographic PFS (rPFS); protected secondary EPs were time to PSA progression (TTPP) and PSA response ≥ 50% in P2. Results: 509 men enrolled in P1. At data cutoff (Oct 7, 2016), 84 were active, 174 discontinued, and 251 were randomized in P2 (ENZA + abi/P, n = 126; PBO + abi/P, n = 125). Median treatment duration in P2 was 5.6 mo for both arms. PFS event by radiographic/clinical/death was 38%/25%/2% for ENZA + abi/P and 55%/18%/1% for PBO + abi/P. Median PFS was 5.7 mo for ENZA + abi/P and 5.6 mo for PBO + abi/P (hazard ratio [HR], 0.83; 95% confidence interval [CI], 0.61, 1.12; P = 0.22). Median TTPP was 2.8 mo for both arms (HR, 0.87; 95% CI, 0.62, 1.24; P = 0.45). PSA response rate was 0.8% for ENZA + abi/P and 2.5% for PBO + abi/P ( P = 0.31). Median rPFS was 10.0 mo for ENZA + abi/P and 7.0 mo for PBO + abi/P (HR, 0.67; 95% CI, 0.47, 0.94; P = 0.02). The most common (≥ 15%) adverse events for ENZA + abi/P vs PBO + abi/P were back pain (21% vs 23%), hypertension (20% vs 7%), nausea (17% vs 9%), and fatigue (14% vs 15%). Conclusions: ENZA + abi/P post PSA progression on ENZA was associated with increased hypertension and nausea and did not result in a statistically significant improvement in composite PFS. The signal seen in rPFS needs further evaluation. Clinical trial information: NCT01995513.

148 Background: Molecular characterization of metastatic castration resistant prostate cancer (mCRPC) is limited by tumor tissue availability. The analysis of circulating tumor cells (CTC) offers an attractive noninvasive surrogate option to analyze molecular alterations. We report whole exome sequencing (WES) of CTCs at the single cell level in mCRPC patients. Methods: Blood samples were drawn from 11 enzalutamide or abiraterone pre-treated mCRPC patients enrolled in the clinical program MOSCATO (NCT02613962). CTC enrichment, immunofluorescent detection and single cell isolation were performed using three methods (ISET filtration, CellSearch and the VyCap puncher system and RosetteSep enrichment) to obtain pools of 1-10 CTCs with distinct epithelial or mesenchymal phenotypes. After Whole Genome Amplification (WGA), WES was performed on the Illumina HiSeq 2000 platform. GATK Haplotype Caller enabled identification of germline polymorphisms from each patient in normal DNA, metastatic sample and CTCs in order to consider WGA induced bias. The detection of sSNV in tumor biopsies and CTCs was assessed with Mutect and IndelGenotyper respectively. Results: 189 WGA of CTC pools were performed. 34 pools of phenotypically different CTCs from 7 patients were selected and sequenced. Mean coverage of 51% was obtained at a sequencing depth of 10X. Allelic drop out was lower for CTC pools containing 5-10 cells. 17/34 (50%) CTC samples had shared sSNV with the paired tumor sample (range 0.35%-68%) Epithelial CTCs had more shared sSNV with metastatic biopsies than CTCs of other phenotypes but shared sSNV were also detected in large non epithelial CTC pointing out a high level of genetic heterogeneity between CTC. Overall, 89 deleterious protein-coding mutations were found only in pools of CTC, including mutations affecting oncogenic drivers such as MAPK1, HSP90AB1 or KDM5B. Conclusions: We present single cell WES of CTCs harboring distinct phenotypes. The detection of shared sSNV between CTC pools and corresponding biopsy could validate the use of CTCs as a liquid biopsy. The finding of sSNV specific to CTCs could offer additional data on tumor heterogeneity.

463 Background: Bone metastases (BMs) are associated with significant morbidity and shorter survival in metastatic renal cell carcinoma (mRCC). Our purpose was to identify prognostic factors for mRCC patients (pts) with BMs. Methods: Data from mRCC pts with BMs, treated at Gustave Roussy between April 1992 and March 2016, were retrospectively collected. Age, sex, ECOG-Performance Status (PS), Memorial Sloan-Kettering Cancer Center (MSKCC) score, histology, number and site of BMs, concomitant metastases (presence and sites), therapy for BMs (radical resection or palliative surgery, radiotherapy, other local and systemic treatments), time to BMs, and outcome were analyzed. Synchronous solitary bone metastasis (SSBM) was defined as a single bone metastasis without concomitant visceral lesions at the initial diagnosis of RCC. Overall survival (OS) was calculated from the date of BMs diagnosis to death or last follow-up using Kaplan-Maier method and modelled with Cox-regression analysis. Results: Three hundred pts were identified. Median time to BMs was 32.4 months (range 0–324 months). In 64 pts (21%), bone was the only metastatic site and 22 of them (7%) had a SSBM; 236 pts (79%) had concomitant metastases in other sites. Median OS was 23.22 months. SSBM pts had better OS then those with concomitant metastases (40 vs. 20 months; p<0.001). At univariate analysis, number of BMs (p<0.0001), spinal column as site of BMs (p<0.005), concomitant metastases (p<0.0001), Fuhrman grade (p<0.001), non-clear cell histology (p<0.003), and MSKCC score (p1) and radical resection are prognostic factors. Additionally, in presence of solitary bone metastasis without other concomitant metastases at the initial diagnosis of RCC, bone surgery should be considered to achieve local tumor control and increase survival.

420 Background: Late relapse in patients with germ cell tumors (GCT) are rare events. As there is no consensus for follow-up (FU) protocols, it is unclear if shorter duration of CT scanning is safe while reducing unnecessary exposure to radiation. Methods: At the completion of their treatment, all patients with Stage I, metastatic good or intermediate prognosis seminoma and non-seminoma (NSGT) underwent physical exam, serum tumor markers and imaging at regular intervals. We retrospectively identified 2 groups of patients with different FU strategies: those with regular CT scan of the chest, abdomen and pelvis for 3 years or less, then followed by abdomino-pelvic ultrasound (Group 1); and those with CT scanning continued beyond 3 years (Group 2). Results: Between December 1997 and March 2016, 203 patients were included: 80 (39.4%) in Group 1 and 123 (60.6%) in Group 2. The mean duration of FU was 6.7 ± 2.4 years in Group 1 and 8.1 ± 2.5 years in Group 2 (p < 0.001). After year 3 the median number of abdomino-pelvic ultrasound in Group 1 was 5 (4-6) and the median number of CT scanning in Group 2 was 6 (5-8). Five (2.4%) relapses were identified: 1 in Group 1 and 4 in Group 2. Relapse was revealed by symptoms in 2 patients with NSGT (1 in each group) who had been lost for FU. Three patients underwent local treatment (2 surgeries for teratoma relapses and 1 radiotherapy for seminoma relapse) and are still disease-free. International prognostic factors score was low and intermediate for the first 2 patients, very low for seminoma relapse and low for teratoma relapses. Conclusions: Patient follow-up by regular abdomino-pelvic ultrasound instead of CT scan appears a feasible alternative after the third year in patients with GCT, with no excess risk of incurable relapses. Prospective validation is required.

154 Background: Interactions between metastatic prostate cancer cells, osteoblasts, osteoclasts, and other participants in bone metabolism are complex and result in pathologic bone physiology. Ra-223, a targeted alpha therapy, accumulates at sites of bone metastases and prolongs survival. Ra-223 and docetaxel (D), acting through different mechanisms of action, may have beneficial effects on bone pathophysiology and tumor microenvironment. Prior data suggest treatment with Ra-223 results in favorable alterations in bone biomarkers that are associated with survival. Methods: 53 patients with progressing CRPC and ≥ 2 bone metastases were randomized 2:1 to Ra-223 (55 kBq/kg q6wk × 5) + D (60 mg/m² q3wk × 10) versus D (75 mg/m² q3wk with step-down option to 60 mg/m²). Bone resorption (CTX-1, ICTP) and formation (P1NP, bALP) markers, tALP, and PSA were analyzed at wk 19 (after 3 Ra-223 injections) and 3 wk after end of treatment (EOT). Results: Mean % change at wk 19 and EOT are shown (Table). tALP, bALP, P1NP, and PSA declined early during treatment, reaching an average of > 30% decline from baseline by wk 19 in both arms. Mean % declines were greater in the Ra-223 + D versus the D-alone arm at wk 19 and EOT. Bone resorption markers CTX-1 and ICTP showed little decline at wk 19. Conclusions: Ra-223 + D patients had greater % decline in tALP and in bone formation markers bALP and P1NP. Due to small patient numbers and preliminary data, further analysis and correlation with clinical outcomes in a larger study is warranted. Clinical trial information: NCT01106352. [Table: see text]

5075 Background: Radium-223 (Ra-223), an α emitter, and docetaxel (D), a chemotherapy, prolong overall survival (OS) in metastatic castration-resistant prostate cancer (CRPC) patients (pts). This study examined safety and efficacy of Ra-223 + D v D alone. Preliminary phase IIa prostate-specific antigen (PSA) and alkaline phosphatase (ALP) data were previously reported (Morris et al. ASCO 2015). All pts have been randomized and have completed treatment. Methods: D-eligible pts with progressing CRPC and ≥ 2 bone metastases were randomized 2:1 to Ra-223 (50 kBq/kg q 6 wk × 5) + D (60 mg/m² q 3 wk × 10) v D (75 mg/m² q 3 wk × 10; step-down option to 60 mg/m²). Primary end point was safety; exploratory efficacy end points were PSA and ALP changes, progression-free survival (PFS), and OS. Results: 53 pts (36 Ra-223 + D; 17 D) were randomized; 33 Ra-223 + D and 13 D pts were treated. For pts in the Ra-223 + D arm, 25 (76%) had all 6 Ra-223 injections, and 20 (61%) had all 10 D cycles. For the D-alone pts, 5 (38%) received all 10 cycles (3 received 75 mg/m², and 2 stepped down to 60 mg/m²). Pts in Ra-223 + D arm had a lower percentage of grade 3/4 treatment-emergent adverse events during treatment (Ra-223 + D, 49%; D, 62%); no Ra-223 + D and 2 (15%) D pts had febrile neutropenia; no pts had clinically significant thrombocytopenia in either arm. Ra-223 + D had longer time to all measures of progression and longer PFS (Table). Waterfall plots of PSA and ALP will be presented. Two Ra-223 + D pts and one D pt died of disease progression during 9-mo follow-up. Conclusions: Ra-223 + D was well tolerated. Ra-223 + D treated pts had longer times to progression and fewer adverse events v pts in D arm. Further studies of Ra-223 + D are planned. Clinical trial information: NCT01106352.

485 Background: PD-L1 is involved in immune regulation and is prognostic in many tumor types. The aim of this study was to assess PD-L1 expression in orchiectomy and metastases (mets) from GCT and to assess for an association with outcome. Methods: Immunohistochemistry (IHC) on whole sections from archival formalin-fixed paraffin-embedded tissue from Dana-Farber Cancer Institute (DFCI) and Gustave Roussy (IGR) was performed using anti-PD-L1 antibody E1L3N. Stained slides were scored semi-quantitatively and assessed independently. At DFCI, PD-L1 was scored as percent of positive tumor cells (TC) and extent of positive immune cell (IC) infiltrate; at IGR, a cut-off of 5% defined positive TC and IC. PD-L1 status was assessed by site, histology and chemotherapy (CT) status. PD-L1 status was correlated with clinical outcome. Most samples at DFCI were pre-CT (74.2%) whereas most at IGR were post-CT (85.4%). Results: IHC from 171 patients with GCT (89 DFCI, 82 IGR) from 1987-2014 was reviewed. The DFCI cohort included 69 orchiectomy, 15 mets and 5 unknown origin with 28 total deaths; the IGR cohort included 26 lung mets, 36 mediastinal or retroperitoneal lymph node mets and 20 primary mediastinal tumors. DFCI had 38 seminoma (S), 50 nonseminoma (NS) and 1 unknown; at IGR, 13 S and 69 NS. In both cohorts, PD-L1 staining in IC was higher in S (DFCI 33/38 moderate (mod)-high (86.8%); IGR 12/13 positive (92.3%)) vs. NS (DFCI 26/50 mod-high (52.0%); IGR 35/68 positive (51.5%)) (DFCI p = 0.003; IGR p = 0.006). At DFCI, 5 samples had PD-L1 positive TC (2 mixed GCT, 2 pure choriocarcinomas (CC) and 1 S); at IGR, 14 had positive TC (all NS, including 11 pure CC). More PD-L1 positive TC were CC than other GCT types (DFCI p = 0.003; IGR p < 0.001). In 36 S orchiectomy samples at DFCI, 0/4 that scored none-mild died and 2/31 (6.5%) that scored mod-high died (p = 1.00); in 30 NS orchiectomy samples, 4/9 (44.4%) that scored none-mild died and 2/16 (12.5%) that scored mod-high died (p = 0.14). Conclusions: Higher PD-L1 status in orchiectomy is not associated with GCT survival. PD-L1 positive TC may serve as a histological marker for CC among NS. Higher PD-L1 expression on IC in S and on TC in CC may point to immunotherapy as a therapeutic option in these tumors.

527 Background: Currently both E and A are standard treatments for patients (pts) with mRCC after failure of first line therapy (1L)with VEGF-targeted therapy. There is no comparative study reported so far, and this study aims to evaluate these 2 drugs in a large center. Methods: Patient characteristics, safety and outcome data from all mRCC pts who received E or A as 2L at Gustave Roussy from April 2007 to May 2015 have been compared. Progression-free Survival (PFS) and Overall Survival (OS) were assessed by the Kaplan-Meier method and compared with the log-rank test. Results: 81 pts were treated with E and 45 pts with A. The table shows patient characteristics. The 2 groups were similar. The most common 1L was sunitinib (79% in E group and 82.2% in A group). Median follow up was 29 mo (95%CI 26 – 31), 26 mo for A and 33 mo for E (p=0.046). Median OS was 21.5 mo for E and 14.9 mo for A (p = 0.23). Median PFS was 5.3 and 7.7 mo for E and A respectively (p = 0.39). Disease control rate was 69% and 73% (p=0.31) and partial response was achieved in 4% and in 24% of pts (p=0.002), respectively in E and A cohort. At time of analysis E is ongoing in 3 pts (4%) and A in 9 pts (20%) (p=0.008). Third-line therapy (3L) was administrated in 62% of pts after E and in 33% after A (p=0.003). The most common 3L after E is A (48%) and vice versa the most common after A is E (71%). Median PFS of 3L after E is 9.1 mo (12.1 mo for A and 8 mo when 3L is not A (p=0.17)). Median PFS of 3L after A is 7.8 mo (95%CI 4-12). Conclusions: No statistically significant difference for PFS and OS were observed. Nevertheless, A showed more PR than E, while more pts received 3L after E. A remains very active in 3L. [Table: see text]

182 Background: In PREVAIL, enzalutamide (ENZA) significantly improved OS (hazard ratio [HR] 0.71; P < 0.0001) and rPFS (HR 0.19; P < 0.0001) compared with placebo in chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC). Using data from the final analysis at 439 rPFS events we showed a strong correlation between investigator and central review. Here we report sensitivity analyses (SAs) from the final analysis of investigator-assessed rPFS and the association between investigator-assessed rPFS and OS. Methods: The coprimary endpoint of rPFS was defined as time from randomization to the earliest objective evidence of centrally assessed radiographic progression, defined by PCWG2 guidelines for bone disease and RECIST v1.1 for soft-tissue disease, or death within 168 days of treatment discontinuation. Bone progression was captured using a validated bone scan data capture assay. Four SAs were performed on investigator-assessed rPFS to evaluate the impact of: (1) progression in bone, (2) clinical progression, (3) a required confirmatory scan for soft-tissue disease progression, and (4) all deaths, regardless of length of time after study drug discontinuation. Associations of investigator-assessed rPFS and OS were calculated using Pearson’s correlation coefficient, Spearman’s rho, and Spearman’s rho estimated through the Clayton copula. Results: Treatment effects remained significant with each SA, with HRs of (1) 0.21 (95% confidence interval [CI] 0.18, 0.27), (2) 0.21 (95% CI 0.17, 0.26), (3) 0.23 (95% CI 0.19, 0.30), and (4) 0.23 (95% CI 0.19, 0.30) (P < 0.0001 for each). Results of rPFS and OS associations are presented in the table below. Conclusions: SAs of rPFS in PREVAIL demonstrated a robust and consistent treatment benefit with ENZA. We observed a modest association between rPFS and OS. However, some unaccounted factors, such as post-protocol treatment, could have reduced the strength of the association of rPFS and OS in the placebo arm. Clinical trial information: NCT01212991. [Table: see text]

437 Background: Local treatment of BM in mRCC pts comprises different approaches including thermal ablation techniques as well as radiofrequency ablation (RFA) and cryotherapy. We report our experience for the treatment of BM of mRCC pts using thermal ablation. Methods: The medical records of all pts with mRCC submitted to thermal ablation of BM from Feb 2008 to Oct 2013 were retrospectively analyzed. Intention of treatment was recorded in 3 categories: complete treatment of all BM in pts with oligometastatic disease or prevention of skeletal related events (SRE) risk and/or pain relief in pts with multimetastatic disease. The local control rate and prognostic factors for local failure (LF) were analyzed including patient characteristics, extension of disease, BM characteristics and type of treatment. Results: 22 pts with BM of mRCC were treated by thermal ablation techniques, with 32 procedures (3 pts had >=3 BM treated). Histology of primary tumor was clear cell in 20 and chromophobe carcinoma in 2 pts. At time of BM treatment, Heng prognostic score was good, intermediate and poor in 36, 59 and 5% of pts. Median age was 67 yrs (48-85). A majority of men were treated (16/22=73%). In 34%, pts had BM synchronous with the primary. BM presented cortical bone erosion in 69% and neurological structures in the vicinity in 50%. Intention of treatment was complete control of BM in 43% and prevention of risk of SRE and/or pain relief in 57% of pts. Cryotherapy was performed in 72% and RF in 28% of cases. Concomitant cimentoplasty and arterial embolization was performed in 70% and 30% respectively. Pain relief was achieved in 81% of pts. LF occurred in 19% of pts (n=6) (95% CI: 4-33%). The median follow-up was 13.4 months (95% CI: 11-21). Median OS was not reached. 86% of pts are still alive at 12 months. The unfavorable prognostic factors for LF were BM size >50 mm (p=0.035) and neurological structures in the vicinity (p=0.0083). Conclusions: Thermal ablation techniques are treatment options that should be considered in the curative and palliative treatment of BM in pts with mRCC. When indications are carefully discussed, these techniques have the potential to achieve good local control and acceptable survival.