Nagar, Himanshu

Treatment of participants with intermediate-risk prostate cancer with focal irreversible electroporation and radiation therapy was technically feasible and showed acceptable patient-reported outcomes and no severe adverse events over 1 year.

387 Background: Level 1 evidence supports treatment of high-risk and node positive PCa using 4-9 weeks of radiotherapy (RT) combined with 18-36 months of androgen deprivation therapy (ADT) with or without abiraterone acetate plus prednisone (AAP). While effective, some cancers recur, and this prolonged treatment is associated with inconvenience and variable morbidity. We aimed to determine whether the biological synergy of stereotactic body radiotherapy (SBRT) with a 6-month combination of ADT, AAP, and the PARP inhibitor niraparib, could enable a shorter intensified, yet safe and effective, therapeutic alternative. Methods: ASCLEPIuS (NCT04194554) is a multicenter investigator-initiated phase I/II trial in high-risk or node positive, homologous recombination unselected, PCa. Patients received 6 months of ADT, AAP, niraparib and SBRT to the prostate (37.5-40 Gy) +/- pelvic lymph nodes (25 Gy). Focal prostate/nodal boosting was permitted. The phase I primary endpoint was the maximum tolerated dose (MTD) of niraparib using the time-to-event continuous reassessment method (3 dose levels: 100 mg and 200 mg held during SBRT, or 200 mg concurrent with SBRT). Dose limiting toxicities (DLT) were any persistent grade 4+ hematologic toxicity or any grade 3+ rectal/urinary toxicity at least possibly related to treatment as assessed by CTCAE v5.0. Patient reported quality of life (QOL) was assessed with the EPIC-26 short form. Linear mixed models were used to compare scores over time. Results: Accrual began in Nov. 2020 with a transition from phase I to phase II in May 2023 after enrolling 54 men. Median follow-up of the phase I cohort is 12.1 months (IQR 9.4-18.9), 80% (n=43) had Grade Group 4-5, median PSA was 17 ng/mL (range, 1-73), 15% (n=8) had cN+ disease, and 76% (n=41) received nodal RT. There were 0 DLTs to date, no grade 3+ rectal or urinary toxicities, and 5 serious adverse events at least possibly attributable to study treatment (anemia, non-rectal gastrointestinal, syncope, infection, musculoskeletal). The most common grade 3 toxicities were hypertension (n = 11, 21%) and leukopenia (n=6, 11%). Transient dose reductions or holds of AAP or niraparib occurred in 10 and 11 patients, respectively. There were no statistically significant declines in patient reported urinary QOL at 6- or 12-months post-treatment compared to baseline (all p >0.15). A transient decline in bowel QOL at 6-months occurred (p<0.01), which improved by 12-months (p=0.16). Conclusions: Our phase I findings support the short-term safety and tolerability of the combination of SBRT to the prostate and nodes, ADT, AAP, and niraparib at an MTD of 200 mg in men with high-risk or node positive PCa. Our trial completed phase II enrollment in May 2024, and longer-term safety, efficacy, and genomic correlations will be presented in the future. Clinical trial information: NCT04194554 .

TPS589 Background: In patients (pts) with metastatic unresectable urothelial cancer, platinum-based chemotherapy remains the standard of care for first-line treatment followed by switch maintenance avelumab if disease control is achieved with chemotherapy. Outside of this setting, single agent immunotherapy is often used in pts that have recurrence after platinum-based chemotherapy or are platinum ineligible. Atezolizumab is a PD-L1 inhibitor currently approved for pts that have urothelial cancers expressing positive PD-L1 or pts ineligible for receiving platinum-based chemotherapy. Tumor-targeted radiotherapy can generate immune-stimulating effects without immune suppression as was previously thought. Moreover, it has become clear that radiotherapy can induce profound effects on tumor cells and the tumor microenvironment that can enhance or trigger an anticancer immune response. While numerous trials have investigated the abscopal effect, this trial will have specific parameters regarding drug type, radiation dose and administration. Methods: A032002 is a phase 2 trial addressing pts that are platinum ineligible or refractory to platinum-based chemotherapy. 144 pts will be randomized to receive either atezolizumab or atezolizumab and single site radiation therapy. The atezolizumab regimen is 1200 mg every 3 weeks. Administration of radiotherapy will occur to one non-target site (8 Gy x 3) for pts randomized to the atezolizumab + radiotherapy arm. All pts will undergo centralized PD-L1 testing (SP142 monoclonal primary antibody), which can be performed on archival tissue; a new biopsy is only required if no archival tissue is available. Key eligibility criteria include age ≥ 18 years, ECOG performance status 0-2, histologically confirmed metastatic urothelial cancer, having at least one measurable site per RECIST 1.1 to monitor for abscopal response, one site targetable for radiation, and tissue available for PD-L1 testing. The primary endpoint is tumor response within 6 months of randomization. Tumor response is defined as a complete response (CR) or partial response (PR) as assessed by the treating physician using RECIST 1.1 criteria. For a one-sided log rank test with a type 1 error rateof 0.10, the study has 90% power to detect a 20% increase in response rate. Key secondary endpoints include tumor response using iRECIST, progression-free survival and overall survival. Quality of life assessments include EORTC QLQ-C30, QLQ-BLM30 and PROMIS-Fatigue. Tissue, urine and blood samples will be collected and biobanked for future correlative science. Enrollment to ART began in December 2021. The study is available for participation at all US NCTN sites with a projected enrollment of 3 years. Support: U10CA180821, U10CA180882. Clinical trial information: NCT04936230 .