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5076 Background: LACOG 0415 is a phase II, open-label, clinical trial evaluating ADT-free alternatives for advanced castration sensitive prostate cancer (CSPC). Methods: Patients with locally advanced, high-risk biochemical recurrence or metastatic CSPC were randomized (1:1:1) to receive ADT with abiraterone acetate plus prednisone (ADT+AAP), apalutamide alone (APA), or apalutamide with AAP (APA+AAP). The primary endpoint of the trial was the proportion of patients who achieved PSA≤0.2 ng/mL level at week 25. Patients without disease-progression and with clinical benefit after week 25 were allowed to maintain treatment at the discretion of physicians. Herein, we presented the outcomes of 2 year-overall survival (2y-OS) and time-to-treatment failure (TTF). The time-to-event endpoint was estimated by Kaplan-Meier method and compared by stratified log-rank test. Results: 128 patients were randomized to the ADT+AAP (n = 42), APA (n = 42), and APA+AAP (n = 44) arms. At week 25, PSA≤0.2 ng/mL was observed in 75.6% (95%CI 59.7%-87.6%), 60.0% (95%CI 43.3%-75.1%), and 79.5% (95%CI 63.5%-90.7%) of patients in the ADT+AAP, APA, and APA+AAP arms, respectively. 110 patients continued treatment after week 25. At the 2-year visit, 80 (62.5%) patients remained on the study medication. Median TTF was 24.0 months (95%CI 23.3 - 24.0) with ADT+AAP, 24.0 months (95%CI not estimated) with APA, and 24.0 months (95%CI 13.0-24.0) with APA+AAP. The main reasons for treatment discontinuation were disease progression (n = 8, 6.3%), toxicity (n = 10, 7.8%), death (n = 6, 4.7%), withdrawal (n = 4, 3.1%), and other (n = 19, 14.8%). The estimated proportion of patients who were alive at 2 years (2y-OS rate) was 92.5% (95%CI 84.3-100) with ADT+AAP, 87.9% (95%CI 77.9-97.8) with APA, and 92.7% (95%CI 84.8-100) with APA+AAP (p = 0.5926). 2y-OS was 92.9% (95% CI 85.3 - 96.2) in patients with PSA ≤ 0.2 ng/mL at week 25, while 2y-OS was 85.0% (95% CI 72.9-97.1) in patients with PSA > 0.2 ng/mL at week 25 (p = 0.1250). Conclusions: Patients with advanced CSPC treated with ADT+AAP, APA, or APA+AAP had high rates of PSA response and favorable 2y-OS. PSA ≤ 0.2 ng/mL at week 25 seems to be a surrogate prognostic predictor of OS in advanced CSPC. In the overall sample, patients with PSA ≤ 0.2 ng/mL at week 25 had higher 2y-OS rate than those with PSA > 0.2 ng/mL at week 25 (92.9% vs. 85.0%), however without statistical significance. Clinical trial information: NCT02867020.

64 Background: LACOG0415 is a 3-arm randomized trial evaluating ADT with abiraterone acetate plus prednisone (ADT+AAP), apalutamide alone (APA) or apalutamide with AAP (APA+AAP) for patients with locally-advanced, high-risk biochemical recurrence or metastatic castration-sensitive prostate cancer (ASCO 2020). In this trial, ADT+AAP and APA+AAP achieved the primary endpoint of percentage of patients with PSA ≤ 0.2 ng/mL at week 25. Apalutamide alone showed a high PSA decline > 50% rate, but did not achieve the pre-specified PSA threshold. Here we report patient-reported outcome data using Functional Assessment of Cancer Therapy-Prostate (FACT-P). Methods: HRQoL was measured in the overall population using the FACT-P questionnaire, comprising 5 subscales: physical wellbeing (PWB), functional wellbeing (FWB), emotional wellbeing (EWB), social/family wellbeing (SFWB), and prostate cancer subscale (PCS). Scores for each patient were measured at baseline and every four weeks until week 25. Questionnaire completion was defined as ≥ 1 question answered at an assessment time point. Analysis of HRQoL change from baseline and deterioration included only patients with baseline and ≥ 1 postbaseline score. Differences greater than 10-points in FACT-P total score and differences greater than 3-points in PWB, FWB, EWB, SFWB, and PCS scores were considered clinically significant. The time-to-event endpoint was estimated by Kaplan-Meier method and compared by stratified log-rank test. Results: 128 patients were included in LACOG0415 trial and 122 of them completed the HRQoL assessments (ranging from 95.3% at baseline to 79.7% at week 25). FACT-P and all subscales scores were similar for all three arms at baseline. There were no meaningful differences in FACT-P scores at baseline and at week 25 between the 3 arms. The subscales scores also showed no statistically differences at baseline and at week 25. Time to FACT-P deterioration did not show any statistically difference between three arms ( P=0.3371). Conclusions: ADT free alternatives with APA alone or APA+AAP did not show meaningful differences in HRQoL in patients with advanced castration-sensitive prostate cancer compared to ADT+AAP. The short follow-up period limited the ability to explore differences in HRQoL after 25 weeks. Larger studies with longer follow-up are needed to further evaluate HRQoL with ADT-free strategies. Clinical trial information: NCT02867020. [Table: see text]

100 Background: Two PARP inhibitors (olaparib, rucaparib) are now FDA approved for mCRPC patients with mutations in BRCA1/2, but the relative efficacy of PARP inhibition in BRCA1- vs BRCA2-altered mCRPC is understudied. Methods: We conducted a multi-center retrospective analysis involving 11 academic sites. We collected genomic and clinical data from 123 BRCA1/2-altered mCRPC patients receiving PARP inhibitor treatment. The primary efficacy endpoint was PSA50 response rate (≥50% decline in PSA level). Secondary endpoints were PFS (clinical, radiographic or PSA progression, whichever occurred first) and overall survival (OS). We also captured information on other concurrent genomic alterations. We compared genomic characteristics and clinical outcomes among BRCA1- vs BRCA2-altered mCRPC. Results: A total of 123 patients (13 BRCA1, 110 BRCA2) were included. PARP inhibitors used were olaparib (n = 116), rucaparib (n = 3), talazoparib (n = 2) and veliparib (n = 2). All BRCA1 and 71% of BRCA2 patients had Gleason 8-10 disease. Compared to BRCA2 patients, BRCA1 patients were more likely to have received prior taxane chemotherapy (77% vs 62%). Age, baseline PSA, and prior enzalutamide/abiraterone treatment were similar between groups. PSA50 responses in BRCA1- vs BRCA2-altered patients were 38% vs 65% respectively ( P= 0.06). Median PFS in BRCA1 vs BRCA2 patients was 3.0 mo (95%CI, 0.9–5.1) vs 8.0 mo (95%CI, 5.3–10.6) respectively (HR 0.42, P= 0.01). Similarly, median OS in BRCA1 vs BRCA2 patients was 11.0 mo (95%CI, 9.9–12.1) vs 24.0 mo (95%CI, 18.2–29.8) respectively (HR 0.33, P= 0.005). There were roughly equal proportions of germline mutations (50% vs 45%) and biallelic mutations (31% vs 25%) in the BRCA2 and BRCA1 groups, respectively. There were numerically more TP53 mutations in the BRCA1 vs BRCA2 group (40% vs 29%, P= 0.45), but an equal number of mutations in other key genes ( PTEN, RB1 and AR). Conclusions: PARP inhibitor activity is diminished in BRCA1- vs BRCA2-altered mCRPC. In our cohort, this differential activity was not explained by mutation origin (germline vs somatic) or allelic status (mono- vs biallelic). These findings warrant validation.

5505 Background: ADT combined with AAP, APA, enzalutamide or docetaxel are among the standard treatment options to patients (pts) with hormone sensitive advanced/metastatic prostate cancer (PC). However, treatment-related adverse events (TRAEs) due to ADT impact negatively on the quality of life of these patients. Effective options with fewer TRAEs are required. Methods: LACOG 0415 is a phase II, randomized trial (1:1:1) evaluating the use of AA 1000mg po + prednisone 5mg po BID + ADT versus APA 240mg po alone versus AA 1000mg po + prednisone 5mg po BID + APA 240mg po in patients with advanced PC with non-castrate testosterone levels and indication of ADT (N+ or M+ or biochemical relapse combined with PSA ≥ 20 ng/ml or with PSA≥4 ng/ml and PSA doubling-time < 10 months). Stratification factors: metastatic disease (+/-). Primary endpoint was the percentage of pts who achieved PSA ≤ 0.2 ng/mL at Week 25, we estimated a PSA response rate of 65% in each of the three arms with a null hypothesis of 45%, power of 80% and alfa 5%, using Fleming one-stage method. Secondary endpoints were percentage of pts with ≥ 80% and ≥ 50% decline in PSA at week 25, radiographic progression-free survival (rPFS) and safety. Results: 128 patients were randomized between Oct 2017 and Apr 2019, and 122 pts were evaluable for PSA response. Median age was 69y (range, 53-88); most pts had ECOG PS0-1(99%). 17% of pts had biochemical relapse only, 9% N+ and 74% M+ disease. At week 25 the PSA was ≤ 0.2 ng/mL in 76% of pts in AAP+ADT arm, 59% in APA, and 80% in APA+AAP. All pts had a decline of ≥ 50% in PSA at week 25. 97% had a decline of ≥ 80% in PSA at week 25: 100% of pts in AAP+ADT arm, 95% in APA and 98% in APA+AAP. A total of 3 pts had clinical progressive disease, one in each arm. Two of them also had radiological progression at week 25, 1 pt in AAP+ADT arm and 1 pt in APA. TRAEs rates of any grade were 71% in AAP+ADT arm, 64% in APA, and 65% in APA+AAP. TRAEs rates of Grade≥3 were 12% in AAP+ADT arm, 9% in APA and 16% in APA+AAP. 9 pts (7%) discontinued the treatment before the week 25, 5(4%) of them due to toxicity: 1 pt from AAP+ADT, 2 pts from APA, and 6 pts from APA+AAP. Conclusions: The AAP+ADT and APA+AAP groups showed high effectiveness in terms of PSA response. Radiologic disease control and the decline of ≥ 80% in PSA at week 25 were similar among all treatment arms. APA alone had less toxicity. APA+AAP and APA alone are promising regimens in this setting. No new safety signal was detected in the study. Clinical trial information: NCT02867020 .

TPS404 Background: Androgen deprivation therapy (ADT) combined with abiraterone (AA) or docetaxel are considered the standard of care (SOC) for patients with hormone sensitive (HS) advanced/ metastatic prostate cancer (PC) (STAMPEDE, LATITUDE, CHAARTED). Treatment that could delay disease progression with less toxicities and better quality of life is warrant. Recently, enzalutamide monotherapy showed a 92% PSA response in patients with advanced/ mestatatic prostate cancer without previous hormone therapy. Our study aims to evaluate the efficacy of apalutamide, a second-generation AR inhibitor, monotherapy or in combination with AA vs. SOC in advanced/metastatic HSPC. Methods: This is a phase II, open label, randomized trial evaluating the efficacy of AA 1000mg po qd plus prednisone 5mg po bid and ADT vs. Apalutamide 240mg po alone vs. AA and Apalutamide in patients with advanced or metastatic PC with non-castrate testosterone levels. Main eligible criteria are: 1. Histologically confirmed prostate adenocarcinoma; 2. Hormone naïve patients with indication to ADT in the following settings: Advanced loco-regional disease not amenable to curative local therapy (T3/4 or node positive); Biochemical relapse after primary treatment (surgery or radiotherapy) with PSA >= 4 ng/ml and rising with doubling time less than 10 months or PSA >= 20 ng/ml or N+ or M+; 3. Newly diagnosed metastatic disease; 4. Patient is symptomatic or moderately symptomatic; 5. Non-castration level of testosterone >= 230 ng/dL. The primary endpoint is undetectable PSA levels (below 0.2ng/mL) at week 25. The study aims for 65% of undetectable PSA at week 25 (power of 80% and alfa of 5%) and a total sample size of 126 patients. Secondary endpoints are PSA progression and PSA response (50% and 80%) at week 25, radiographic progression-free survival, safety, health quality of life (FACT-P) and correlation of serum androgen levels with response. As of October 17th, 2017 the study enrolled 1 patient and the recruitment is planned for 12 months in a total of 10 sites in Brazil. This trial is registered at Clinical trial information: NCT02867020.

PURPOSE: To develop a pretreatment prognostic model for survival of patients with progressive metastatic prostate cancer after castration using parameters that are measured during routine clinical management. PATIENTS AND METHODS: Pretreatment clinical and biochemical determinants from 409 patients enrolled onto 19 consecutive therapeutic protocols from June 1989 through January 2000 were evaluated. The factors selected were age, Karnofsky performance status (KPS), hemoglobin (HGB), prostate-specific antigen (PSA), lactate dehydrogenase (LDH), alkaline phosphatase (ALK), and albumin. These factors were combined in an accelerated failure time regression model to produce a nomogram to predict median, 1-year, and 2-year survival. The nomogram was validated internally and externally using data from a multicenter randomized trial of suramin plus hydrocortisone versus hydrocortisone alone. RESULTS: The median survival of the entire group was 15.8 months (range, 0.9 to 77.8 months); 87% have died. In multivariable analysis, KPS, HGB, ALK, albumin, and LDH were significantly associated with survival (P < .05), whereas age and PSA were not. All seven factors were included in the nomogram. When applied to the external validation data set, the nomogram achieved a concordance index of 0.67. Calibration plots suggested that the nomogram was well calibrated for all predictions. CONCLUSION: A nomogram derived from pretreatment parameters that are measured on a routine basis was constructed. It can be used to predict the median, 1-year, and 2-year survival of patients with progressive castrate metastatic disease with reasonable accuracy. The information is useful to assess prognosis, guide treatment selection, and design clinical trials.

e17039 Background: Lewis-Y (LeY) antigen is a blood group related antigen expressed in 75% of OC. hu3S193 is a humanized anti-LeY IgG1 mAb with strong complement and antibody dependent cytotoxicity with clinical benefit shown in a phase II study in pts with platinum-resistant OC and small tumor burden. Improving progression free survival (PFS) in pts who achieve a 2CR is an unmet need. Methods: This phase II study accrued pts with relapsed OC, LeY expression by IHC, and a KPS ≥ 70% who had achieved a 2CR after 5-8 cycles of platinum doublet chemotherapy (chemoRx). Patients received intravenous infusions of hu3S193, 30mg/m2every 2 weeks starting ≤ 8 weeks after the last dose of chemoRx and continuing for 12 doses (24 weeks) or until disease progression or unacceptable toxicity. Primary endpoint was PFS with a sample size calculated to detect a 50% increase in PFS, compared to a historical value of 10.8 months. Secondary objectives were safety and pharmacokinetics (PK). Results: 29 pts were enrolled. Median age: 55 yrs (range 29-67); Median KPS: 90% (range 80-100); LeY expression by IHC (N): strong (20), weak (9); stage at initial diagnosis: I/II (2), III/IV (27); median CA-125 prior to 2CR chemoRx: 104 (range 9-514); chemoRx agents to achieve 2CR: paclitaxel/platin (21), liposomal doxo/carboplatin (8); median cycles of prior chemoRx to achieve a 2CR:6; median doses of hu3S193 delivered: 10 (range 10-12). Evaluable pts: 28 (1 pt did not have 2CR); median PFS: 11.8 months (95% CI: 10.6-13.9) while 3 pts achieved PFS of 25+ months. Grade 4 toxicities observed: none. Most frequent toxicities (any grade/grade 3): Nausea (16/2), Vomiting (15/3), Hypersensitivity (9/0). PK data will be presented. Conclusions: Despite the good tolerance and the longer PFS compared to historical control, this trial did not show a significant improvement with hu3S193 as a consolidative strategy in patients with 2CR in platinum-sensitive OC. Tumor molecular analysis of patients with long PFS may provide insight for future studies. Clinical trial information: NCT01137071.

e15537 Background: PC-RPLND plays an important role in the management of residual masses of advanced NSGCT of the testis. Teratomatous elements in the primary tumor is a risk factor for teratoma in...

465 Background: Prospective studies with sunitinib in mRCC have shown median progression-free survival (mPFS) of 11 months (first line) and 8.3 months (second line). In order to identify patients with LTB with SU, we describe the clinical characteristics of patients with mRCC treated with SU with an mPFS of 15 months or more. Methods: This is a retrospective chart review of patients with mRCC treated with SU in two hospitals, Alexander Fleming Institute Buenos Aires in Argentina and Hospital Israelita Albert Einstein in Sao Paulo, Brazil. Inclusion criteria included patients treated with SU who had a PFS of at least 15 months. Results: Between September 1995 and August 2009, 29 cases were identified. Patient demographics were: median age of 56 years, 65% male, 96% with previous nephrectomy, Eastern Cooperative Oncology Group performance status (PS) of either 0 (52%) or 1 (48%), 93% had clear cell histology, 69% received prior systemic therapy, and 78% had ≤ 2 metastatic sites (mostly in the lungs, liver and bone). Patients were started on SU 50 mg 4 weeks on treatment/2 weeks off treatment (4/2) (n=26) or 37.5 mg 6 weeks continuous dosing (n=3). For those patients starting on 4/2, dose reduction was necessary in 59% of the patients to maintain SU therapy. Median duration of therapy was 23.7 months. During treatment, 24 patients (83%) developed hypertension. Response rates were as follows: complete response 7% (n=2), partial response 38% (n=11), stable disease 52% (n=15); data missing for one patient. Conclusions: LTB is seen in patients who are young, have good performance status, and either 1 or 2 metastatic sites. Dose reductions are common in order to maintain treatment while benefiting from SU. Treatment with SU as either first- or second-line therapy did not appear to influence outcome. Hypertension is a common finding and serves as a predictive marker during treatment, but study limitations preclude the identification of pre-treatment predictive factors.

5078 Background: Lewis-Y (LeY) antigen is a blood group related antigen expressed in 75% of OC. hu3S193 is a humanized anti-LeY IgG1 mAb with strong complement dependent cytotoxicity and excellent ...

4609 Background: Continuous androgen deprivation (AD) is a standard therapy for systemic PC. Rapid cyclic AD and androgen repletion (AR) after a 1 month induction with castration was shown to be fe...