Eisenberger, Mario A.

154 Background: Poly ADP-ribose polymerase inhibitors (PARPi) are being studied as a treatment option for men with mCRPC and deficient homologous recombination DNA repair. While the FDA has granted “breakthrough” designation status to olaparib for use in mCRPC patients with either BRCA1/2 or ATM mutations, it is not known if responsiveness to PARPi may be influenced by the mutation type. Because ATM functions as a sensor of DNA damage rather than a mediator of DNA repair, we hypothesized that patients with ATM mutations may not show robust responses to PARPi therapy compared to those with BRCA1/2 mutations. Methods: We conducted a retrospective analysis of mCRPC patients treated with off-label olaparib at Johns Hopkins Hospital and Mayo Clinic Scottsdale who had somatic or germline mutations in BRCA1/ 2 or ATM. The primary endpoint was PSA50 response. Secondary endpoints included overall survival (OS) and radiographic/clinical progression-free survival (PFS). Results: 40 men received olaparib for mCRPC of which 17 had pathogenic mutations (5 ATM-mutant, 12 BRCA1/2-mutant). Eleven (65%) had germline and 6 (35%) had somatic alterations. Five (29%) had Gleason sum ≤7 at diagnosis, 4 (24%) had Gleason sum 8, and 8 (47%) had Gleason sum ≥9. Three (18%) had metastatic disease at diagnosis. Mean age at start of olaparib therapy was 65.6 (range, 52-76) years. Prior chemotherapy was received by 59% of men, and prior abiraterone/enzalutamide by 88% of men. Eleven (65%) had extra-osseous metastases at start of therapy. PSA50 responses were achieved by 10/12 men (83%) with BRCA1/2 mutations and 0/5 men (0%) with ATM mutations (Fisher’s exact test, P= 0.003). Men with BRCA1/2 mutations had a median PFS of 12.3 mo versus 3.3 mo for those with ATM mutations (HR 0.14, 95%CI 0.03-0.60; P= 0.008). There was no difference in OS (HR 0.24, 95%CI 0.03-1.173; P= 0.16). Conclusions: Men with mCRPC harboring mutations in BRCA1/2 appear to have better PSA responses and longer PFS with olaparib compared to men with ATM mutations. ATM-mutant mCRPC patients may require alternative therapies ( e.g. chemotherapy, ATR inhibitors). Larger prospective studies are needed to confirm or refute these preliminary findings.

181 Background: To evaluate whether metformin (Met) a widely-used, nontoxic oral antidiabetic drug with putative anticancer properties leads to improvements in prostate cancer (PC) outcomes in the CHAARTED trial. Methods: In the CHAARTED database where metformin use at baseline was recorded prospectively, we identified patients with metastatic PC who underwent either ADT alone or ADT and docetaxel (D) chemotherapy. Cox proportional hazards models were used to determine the effect of Metformin on outcomes. Results: A total of 788 patients (median age, 63 y) had complete data after randomization. Comparison of ADT+D+Met (n = 39) to ADT+D (n = 357) and ADT+Met (n = 29) to ADT alone (n = 363) revealed similar clinicopathologic characteristics. Cause of death was PC in 13(81%) of ADT+D+Met, 72(85%) ADT+D, 9(82%) ADT+Met and 105(84%) ADT alone groups. See table for PC outcomes and overall survival by metformin use. Cox regression analysis for overall survival stratified by stratification factors at randomization demonstrates Met use was associated with a trend for worse overall survival (HR 1.47 95%CI: [0.95,2.26], p = 0.08) with adjustment for treatment arm and prior local therapy. In contrast, ADT+D use (HR 0.62; 95%CI: [0.47,0.81]) and prior local therapy with surgery or radiation (HR 0.56; 95% CI: [0.38, 0.82]) were associated with improved survival. Conclusions: In this study, baseline metformin did not improve PC outcomes. Partial support and drug supply by Sanofi. Clinical trial information: NCT00309985. [Table: see text]

137 Background: Prior work from SWOG 9346 revealed that PSA ≤ 0.2 ng/dL at 7 months (mo) is prognostic for longer OS with ADT alone. We sought to evaluate if this optimal decline remained predictive of better OS when D was added to ADT for initial mHSPC treatment. Methods: We performed a landmark survival analysis at 7 mo using the E3805 database (NCT00309985). Inclusion required at least 7 mo of followup and PSA levels at 7 mo from ADT initiation. Survival was defined from ADT start or randomization to death. SWOG 9346 PSA nadirs of ≤ 0.2, > 0.2-4 and > 4 were used as classifiers. Results: 719 patients were eligible for analysis: 358 treated with ADT plus D and 361 with ADT alone. Median follow-up was 23.1 mo. On multivariable analysis (MVA), achieving a PSA ≤ 0.2 at 7 mo was more likely if the patient received D and had lower volume disease, prior local therapy, and lower baseline PSAs (all p ≤ 0.01). Across all patients, median OS was significantly longer if PSA at 7 mo reached ≤ 0.2 compared to > 4 (p < 0.0001) (Table). On MVA, PSA ≤ 0.2 at 7 mo and low volume disease were prognostic of longer OS (all p < 0.01). On ADT, 28.8% achieved a PSA ≤ 0.2 at 7 mo vs. 45.3% on ADT+D. Patients on ADT alone who achieved a PSA nadir ≤ 0.2 had the best survival. These patients were more likely to have low volume disease (56.7%) compared to the ADT + D pts (46.3%). Conclusions: Achieving PSA ≤ 0.2 at 7 mo remains prognostic for longer OS with ADT for mHSPC, whether administered alone or with D. Adding D to ADT increased the likelihood of a lower PSA and improved survival. Partial support and drug supply by Sanofi. Clinical trial information: NCT00309985. [Table: see text]

136 Background: Patients with a low burden of metastatic disease and who relapse after localized therapy with curative intent have a longer overall survival. It is unclear whether these patients benefit from early docetaxel (D). Methods: Patients in GETUG-AFU15 (N = 385, median follow-up 84 mo) and CHAARTED (N = 790, median follow up 54 mo) were randomized to ADT alone or ADT + D and outcomes described using the same definition of high volume (HV) and low volume (LV) disease. (HV: visceral metastases and/or 4 or more bone metastases with at least one outside the axis) and whether the patients had prior local therapy or not. Results: Table 1 details across both studies that de novo HV group treated with ADT alone has the shortest overall survival and D has a consistent effect in improving OS. In contrast, in both studies patients with LV disease had a much longer OS with no evidence that D improved OS. Conclusions: There was no apparent survival benefit in CHAARTED and GETUG-15 studies with D for LV whether patients had prior local treatment or not. Across both studies, early D had a consistent effect and improved OS in HV pts especially those with no prior local therapy. Partial Support and drug supply by Sanofi. Clinical trial information: NCT00104715, NCT00309985. [Table: see text]

LBA2 Background: Docetaxel (D) improves OS of men with mPrCa who have progressed on androgen deprivation therapy (ADT). We aimed to assess the benefit of upfront chemohormonal therapy for metastatic PrCa. Methods: 1:1 randomization to ADT alone or ADT + D dosed 75mg/m2 every 3 weeks for 6 cycles within 4 month (mos) of starting ADT. Stratification factors: high volume (HV) vs. low volume (LV) disease (HV: visceral metastases and/or 4 or more bone metastases); anti-androgen use beyond 30 days; Age ≥70 vs. < 70 years; ECOG PS 0-1 vs. 2; Prior adjuvant ADT > 12 vs. ≤ 12 mos; FDA approved drug for delaying skeletal related events. Key eligibility criteria: suitable organ and neurological function for D; adjuvant ADT ≤ 24 mos and no progression within 12 mos of adjuvant ADT. OS was the primary endpoint and the study was powered to assess for a 33.3% improvement in median OS (80% power and 1-sided alpha=2.5%). Projected median OS for ADT alone: HV-33 mos; LV-67 mos. Results: 790 men were accrued from 7/28/06 to 11/21/2012: ADT N=393; ADT + D: N=397; balanced for demographic, stratification and disease factors. Median age: 63 years (range: 36 to 91); 98% ECOG PS 0 or 1; 89% Caucasian; 24% prior radiotherapy, 24% prior prostatectomy; HV 64% on ADT and 67% on ADT + D. Data released after 4th interim analysis in Sept 2013 when O’Brien Fleming upper boundary was crossed with 53.1% information. This report reflects 1/16/2014 data with median follow-up of 29 mos with 137 deaths on ADT alone vs. 104 deaths on ADT+D. ADT+D: Grade (G) 3/4 Neutropenic fever: 4%/2%; G3 neuropathy: 1% sensory, 1% motor; 1 death due to treatment (no deaths due to treatment on ADT). Efficacy data is in the table below. After disease progression, 123 pts on ADT alone and 45 pts on ADT + D received docetaxel. Conclusions: ADT + D improves OS over ADT alone in men with HV mPrCa. Longer follow-up is needed for men with LV mPrCa. Clinical trial information: NCT00309985. [Table: see text]