Beltran, Himisha

PURPOSE Bone metastases (BM) occur in approximately 30% of patients with metastatic renal cell carcinoma (mRCC) and are associated with poor survival and symptomatic skeletal events (SSEs). Radium-223, an alpha-emitting bone-seeking radioisotope, and cabozantinib, a tyrosine kinase inhibitor, have demonstrated activity in BM. RADICAL (Alliance A031801; ClinicalTrials.gov identifier: NCT04071223 ) evaluated cabozantinib ± radium-223 in mRCC with BM. METHODS This phase II trial enrolled patients with mRCC of any histology with ≥1 BM. Patients were randomly assigned 1:1 to cabozantinib ± radium-223, stratified by osteoclast-targeted therapy (OTT), prior therapy, opioid use, and International mRCC Database Consortium (IMDC) risk. The primary end point was SSE-free survival (SSE-FS). Secondary end points included safety, objective response rate (ORR), progression-free survival, and overall survival (OS). A target of 124 evaluable patients was planned, with a prespecified interim futility analysis at 50% of expected SSE-FS events; the trial would stop if the stratified hazard ratio (sHR) > 1.0. RESULTS The prespecified interim futility analysis was conducted after 90 patients were enrolled and crossed the futility boundary, leading to closure at 98 patients. The final analysis included all 98 patients. Median age was 63 years, 82.7% had clear cell histology, and 79.6% were using an OTT. IMDC risk was favorable (18.4%), intermediate (67.3%), and poor (14.3%). Median follow-up was 13.1 months. Median SSE-FS for cabozantinib with radium-223 versus cabozantinib was 16.7 versus 17.6 months (sHR, 1.46 [90% CI, 0.86 to 2.51]). Median OS was 28.3 versus 19.7 months (sHR, 1.40 [95% CI, 0.70 to 2.79]). ORR was 19.4% versus 25.0% ( P = .78). Grade ≥3 adverse events were similar across arms (69.6% v 75.5%). CONCLUSION Radium-223 did not improve SSE-FS when added to cabozantinib. The combination demonstrated a manageable safety profile.

TPS4616 Background: Osseous metastases (OM) occur in approximately 30% patients with advanced RCC. Despite therapeutic advances, OM are associated with poor survival and risk of symptomatic skeletal events (SSEs). Cabozantinib targets multiple tyrosine kinases, including vascular endothelial growth factor (VEGF) receptors and MET (Mesenchymal-Epithelial Transition factor), which are overexpressed in OM, contributing to cabozantinib’s enhanced bone activity. Radium-223, an alpha-emitting bone-seeking radioisotope, prolongs survival in men with metastatic castration-resistant prostate cancer to the bone. Building on this therapeutic approach targeting OM, our pilot study of radium-223 with VEGF inhibition in RCC with OM has also shown safety, improvement in circulating bone turnover markers, and early efficacy (McKay et al, CCR 2018). To address the unmet need to improve SSE rates and outcomes in RCC and OM, we designed a study investigating cabozantinib with or without radium-223 in patients with RCC with OM (NCT04071223). Methods: This is an open-label, multicenter randomized phase-2 study. Key inclusion criteria include metastatic RCC of any histology with ≥1 OM, at least 1 OM without prior radiation, any number of prior therapies, and Karnofsky performance status ≥ 60%. Use of a bone protecting agent is required unless contraindicated. Patients are randomized 1:1 to cabozantinib with (Arm A) or without (Arm B) radium-223. The starting dose of cabozantinib for Arm A is 40 mg by mouth daily to be escalated to 60 mg daily after cycle 1 (1 cycle = 28 days) if no persistent grade 2 or grade ≥3 toxicity. Radium-223 is administered at a fixed dose of 1.49 microcurie/kg IV every 28 days x 6 doses. The starting dose for cabozantinib in Arm B is 60 mg daily. The primary endpoint is SSE-free survival. Secondary endpoints include safety, progression-free survival, overall survival, time to first SSE, objective response rate, time to subsequent anti-cancer therapies, quality of life (QoL) measures, and correlative analyses including liquid biopsy and tumor tissue analysis. The study is designed to have 85% power to detect an improvement in 6-month SSE-free survival rate from 65% to 78% with one-sided α = 0.05 significance. To ensure 124 evaluable patients, target accrual is 134 (67 per arm). The group-sequential design includes a safety run-in and an interim analysis for futility when 50% of the expected number of events have been observed. The safety run-in, performed in the first 12 patients randomized to combination therapy, did not demonstrate dose limiting toxicities. Final data analysis will occur when 99 events have been observed. The study was activated in July 2020 and accrual is ongoing throughout the National Clinical Trials Network (NCTN). Continued site participation and enrollment are essential to evaluate this therapeutic strategy. Clinical trial information: NCT04071223 .

309 Background: Standard of care (SOC) treatment options for HR-PCa include RT with long-term androgen deprivation (LT-ADT) or RP with selective use of post-operative RT +/- androgen deprivation therapy (ADT). The optimal treatment approach has been assessed in retrospective population-based and multi-center comparisons, which have yielded mixed results with substantial bias. Therefore, we conducted an emulated randomized comparison of RT vs RP in HR-PCa leveraging patients enrolled in RCTs. Methods: We searched Medline for RCTs in HR-PCa with a SOC arm of an RT- or RP-based regimen. Inclusion required similar experimental treatment and contemporaneous enrollment in the same country to reduce bias. This identified 2 trials, NRG/RTOG 0521 (RT+LT-ADT +/- 6 cycles docetaxel [doce]), and CALGB 90203 (RP +/- neoadjuvant 6 cycles doce and ADT). Due to inherent difference in the biochemical recurrence criteria after RT vs RP, we chose inverse probability of treatment weighted (IPTW) cumulative incidence of distant metastasis (DM) as the primary endpoint, considering deaths as competing events. Death after DM was measured to create a harmonized metric of deaths likely attributed to PCa. To assess potential residual selection bias, death without DM to capture non-cancer associated deaths was analyzed. Results: Overall, 1290 patients (RT n=557, RP n=733) were included, with similar median follow-up of 6.4 years. Prior to IPTW, RP patients were significantly younger with lower baseline PSA compared to RT patients. Adjuvant (18%) and salvage therapy (44%) was used in RP cohort. Cumulative incidence of DM was significantly lower in patients who underwent RT compared to RP (8-year DM: 16% vs 23%; p=0.01; subdistribution hazard ratio [sHR] 0.48 [95%CI 0.34-0.69], p<0.001). 8-year rates of death after DM were 10% vs 8% (p=0.72) in the RP and RT patients, respectively. RT patients had significantly greater risk of death without DM (HR 2.09 [1.01-4.34], p=0.048) with early differences measured. On a cross-arm comparison, 8-year cumulative incidence of DM when comparing SOC RT+LT-ADT group versus the doce+ADT+RP group was 18% vs 21%, respectively (sHR 0.75 [0.45-1.24], p=0.26). Conclusions: HR-PCa patients enrolled on RCTs had significantly lower incidence of DM with an RT-based strategy compared to an RP-based approach. Longer follow-up is needed to assess deaths attributed to PCa. Despite the strengths of the comparison (use of cooperative group RCT data, contemporaneous enrollment in the same country, patients fit enough for chemotherapy, and IPTW adjustments) there appears to be residual unmeasured bias, as expected, based on greater early deaths without DM in the RT arm. Utilization of post-operative radiotherapy and ADT+Doce may mitigate differences between RP and SOC RT+LT-ADT.

Indications for and implications of germline genetic testing (GGT) in patients with prostate cancer have expanded over the past decade, particularly related to precision therapies and management. GGT has become the standard of care for many cancers such as breast, ovarian, colorectal, pancreatic, and metastatic prostate cancer, and it is imperative that patients be offered timely and equitable access to testing as it can inform patient-physician shared decision making for management of the current cancer as well as anticipatory guidance for disease progression. Additionally, GGT guides screening for and prevention of secondary malignancies for the patient and cascade testing for at-risk family members. Here, we present data supporting the notion that clinicians should offer all patients with prostate cancer the opportunity to undergo comprehensive GGT for pathogenic germline variants known to be associated with familial cancer and/or known to have implications for treatment and management.

AbstractCurrent US clinical practice guidelines for advanced prostate cancer management contain recommendations based on high‐level evidence from randomized controlled trials; however, these guidelines do not address the nuanced clinical questions that are unanswered by prospective trials but nonetheless encountered in day‐to‐day practice. To address these practical questions, the 2024 US Prostate Cancer Conference (USPCC 2024) was created to generate US‐focused expert clinical decision‐making guidance for circumstances in which level 1 evidence is lacking. At the second annual USPCC meeting (USPCC 2024), a multidisciplinary panel of experts convened to discuss ongoing clinical challenges related to 5 topic areas: biochemical recurrence; metastatic, castration‐sensitive prostate cancer; poly [ADP‐ribose] polymerase inhibitors; prostate‐specific membrane antigen radioligand therapy; and metastatic, castration‐resistant prostate cancer. Through a modified Delphi process, 34 consensus recommendations were developed and are intended to provide clinicians who manage prostate cancer with guidance related to the implementation of novel treatments and technologies. In this report, the authors review the areas of consensus identified by the USPCC 2024 experts and evaluate ongoing unmet needs regarding translational application of the current clinical evidence.

Abstract Purpose: Mutations in hematopoietic progenitor cells accumulate with age leading to clonal expansion, termed clonal hematopoiesis (CH). CH in the general population is associated with hematopoietic neoplasms and reduced overall survival (OS), predominantly through cardiovascular adverse events (CVAE). Because androgen receptor pathway inhibitors (ARPI) used in metastatic castration-resistant prostate cancer (mCRPC) are also associated with CVAEs and because CH negatively impacted survival in an advanced solid tumor cohort, we hypothesized that CH in mCRPC may be associated with increased CVAEs and inferior survival. Experimental Design: A targeted DNA sequencing panel captured common CH mutations in pretreatment blood samples from 957 patients enrolled in Alliance A031201: a randomized trial of enzalutamide ± abiraterone/prednisone in the first-line mCRPC setting. The primary outcome was the impact of CH on OS; the secondary outcomes were progression-free survival (PFS) and CVAEs. Results: Baseline comorbidities were similar by CH status. No differences in OS/progression-free survival were detected regardless of treatment arm or the variant allele frequency threshold used to define CH [primary: 2% (normal-CH, N-CH); exploratory: 0.5% (low-CH) and 10% (high-CH, H-CH)]. Patients with H-CH (7.2%) and TET2-mutated N-CH (6.0%) had greater odds of any CVAE (14.5% vs. 4.0%; P = 0.0004 and 12.3% vs. 4.2%; P = 0.010, respectively). More major CVAEs were observed in patients with H-CH (5.8% vs. 1.9%; P = 0.042) and N-CH (3.4% vs. 1.8%; P = 0.147). Conclusions: CH did not affect survival in patients with mCRPC treated with ARPIs in A031201. H-CH and TET2-mutated CH were associated with more CVAEs. These findings inform the risk/benefit discussion about ARPIs in mCRPC.

TPS5118 Background: Novel androgen receptor pathway inhibitors (ARPIs) improve overall survival (OS) in patients (pts) with metastatic hormone-sensitive prostate cancer (mHSPC) in conjunction with testosterone suppression (TS) relative to TS alone. However, the duration of treatment required to derive clinical benefit is unclear, as is whether continuous treatment is requisite for optimal cancer outcomes. Favorable PSA declines have been associated with prolonged OS in clinical trials testing TS + ARPIs. We thus designed this single-arm Phase 2 trial to test the hypothesis that pts who achieve exceptional response to upfront TS + ARPI can suspend treatment, allowing for T recovery and improvement in quality of life while maintaining favorable clinical outcomes. Methods: Eligible pts had mHSPC by conventional imaging with PSA ≥ 5 ng/ml and T ≥ 150 ng/dl (or not known to have been hypogonadal) prior to starting treatment, have been receiving TS for 540-750 days and ARPI for ≥ 360 days, and have achieved PSA < 0.2 ng/ml (stable or falling for 3 consecutive measurements) with castrate T <50 ng/dl at the time of enrollment. Intermittent ADT for biochemical recurrence prior to mHSPC diagnosis, prior local therapy, prior radiation to metastatic sites, and up to 6 cycles of docetaxel in mHSPC are permitted. Pts who underwent surgical castration, received ARPI prior to mHSPC diagnosis, or are receiving experimental treatment for mHSPC or participating in a clinical trial that does not allow for TS or ARPI interruption are excluded. After enrollment, pts discontinue both TS and ARPI and are followed with PSA and T levels every 3 months, conventional CT/MRI and bone scan at least every 6 months, and FACT-P questionnaire for patient-reported outcomes every 6 months. Treatment re-initiation triggers are PSA increase to ≥ 5 ng/ml, radiographic change (progressive disease per modified RECIST 1.1 on CT/MRI or unconfirmed progressive disease per PCWG3 on bone scan), or symptoms attributable to prostate cancer. Subsequent management is per physician discretion. The primary endpoint is remaining treatment-free with eugonadal T (> 150 mg/dl) 18 months after the start of treatment interruption, with 75 pts to be enrolled to differentiate 18-month treatment free rates of 0.30 (null hypothesis) and 0.45 (alternative hypothesis). Secondary endpoints include time to eugonadal T, duration off treatment, and changes in patient-reported outcomes. Exploratory endpoints include radiographic progression-free survival, time to next treatment, OS, and correlation of tissue- and blood-based biomarkers with clinical endpoints. The study was activated in July 2022 and accrual is ongoing throughout the NCTN. Support: U10CA180821, U10CA180882, UG1CA189823, https://acknowledgments.alliancefound.org , Veracyte Inc. Clinical trial information: NCT05241860 .

5074 Background: PC commonly expresses PSMA and has dose-responsive radiosensitivity. 177Lu-based radioligands usually use an empiric dosing regimen. This 1st dose-escalation study of 177Lu-PSMA-617 employed a dose-dense fractionation schedule intended to allow delivery of higher total doses to overcome radioresistance due to repopulation. Here, we report mature results of the study. Methods: Progressive mCRPC following > 1 potent ARPI (e.g., abi/enza) and chemo (or unfit/refuse taxane) without limit of # prior therapies provided adequate organ function and ECOG PS 0-2. Treatment: single cycle of fractionated dose 177Lu-PSMA-617 on D1 and D15. In Ph I dose-escalation, patients (pts) received one cycle of 7.4 - 22 GBq followed by Simon 2-stage Ph II at 22.2 GBq. PSMA expression was not required for treatment, but pre- and post-treatment 68Ga-PSMA11 PET/CT and/or 177Lu-PSMA-617 SPECT done. Primary efficacy by PSA changes with 2ndary outcomes with CT/bone scans, PSMA PET, circulating tumor cell (CTC; CellSearch) counts, plasma DNA (PCF_SELECT), and survival. Results: Between 1/2017 – 2/2021, 50 pts treated with median PSA 164.3, 35 (70%) CALGB (Halabi) poor risk. 47 (94%) bone, 38 (76%) nodal, 12 (24%) lung, 5 (10%) liver mets (4 additional pts with PSMA PET+ liver mets not apparent on CT). 29 (58%) with prior >2 ARPI, 29 (58%) with >1 chemo, 14 (28%) with Ra-223, 2 (4%) with 177Lu-J591. 27 (54%) treated at 22 GBq. No dose-limiting toxicity during Ph I. 38 (76%) with any PSA decline, 27 (54%) with >50% PSA. Median rPFS 8.3 mo [5.6-16.7], and OS 15.7 mo [10.9-20.6]. Of 17 RECIST measurable, 6 (35.3%) responded, 7 (41.2%) stable, 4 (23.5%) progressed. Of 31 with paired CTC counts, 16 (52%) decreased, 5 (16%) were stable; 10 (32.3%) converted to favorable/undetectable. Plasma DNA with high allele-specific ploidy and ARcopy number gain associated with OS (univariate). Treatment emergent adverse events (TEAE): 32 (64%) dry mouth, 22 (44%) pain flare, 22 (44%) fatigue, 19 (38%) nausea, 15 (30%) anemia, 15 (28%) thrombocytopenia (plts), 9 (18%) neutropenia (ANC). All TEAEs restricted to grade (Gr) 1-2 except 6 (12%) with Gr 3 anemia, 2 (4%) Gr 3/4 plts, 1 (2%) Gr 3 ANC. TEAE incidence and Gr were not related to dose. On multivariable analysis, 177Lu dose administered (p=0.09), CALGB risk (p=0.04), prior chemo (p=0.009), associated with OS; dose (p=0.1), CALGB risk (p=0.2), and AR copy number (p=0.2) associated with PSA50 decline. Baseline PSMA imaging (by imaging score or SUVmax) was not associated with OS or response. Conclusions: A single-cycle of fractionated-dose 177Lu-PSMA-617 is safe. Despite no pre-selection for PSMA expression, most had PSA decline with favorable PFS and OS compared to historical controls and similar to PSMA-selected targeted radionuclide studies administering multiple cycles in a less dose-intense approach. Clinical trial information: NCT03042468 .

Background: Management strategies for metastatic castration-resistant prostate cancer (mCRPC) have rapidly shifted in recent years. As novel imaging and therapeutic approaches have made their way to the clinic, providers are encountering increasingly challenging clinical scenarios, with limited guidance from the current literature. Materials and Methods: The US Prostate Cancer Conference (USPCC) is a multidisciplinary meeting of prostate cancer experts intended to address the many challenges of prostate cancer management. At the first annual USPCC meeting, areas of controversy and consensus were identified during a 2-day meeting that included expert presentations, full-panel discussions, and postdiscussion responses to questions developed by the USPCC cochairs and session moderators. Results: This narrative review covers the USPCC expert discussion and perspectives relevant to mCRPC, including neuroendocrine/aggressive-variant prostate cancer (NEPC/AVPC). Areas of broad agreement identified among USPCC experts include the benefits of poly (ADP-ribose) polymerase (PARP) inhibitors for patients with BRCA1/2 mutations, the use of radioligand therapy in patients with prostate-specific membrane antigen (PSMA)–positive mCRPC, and the need for clinical trials that address real-world clinical questions, including the performance of novel therapies when compared with modern standard-of-care treatment. Ongoing areas of controversy and uncertainty included the appropriateness of PARP inhibitors in patients with non-BRCA1/2 mutations, the optimal definition of PSMA positivity, and systemic therapies for patients with NEPC/AVPC after progression on platinum-based therapies. Conclusions: The first annual USPCC meeting identified several areas of controversy in the management of mCRPC, highlighting the urgent need for clinical trials designed to facilitate treatment selection and sequencing in this heterogeneous disease state.