This phase II trial studies the use of 68Ga-PSMA-11 positron emission tomography (PET) in diagnosing patients with prostate cancer that continues to grow despite the surgical removal of the testes or medical intervention to block androgen production (castration resistant), and has spread to other places in the body (metastatic). 68Ga- PSMA-11 is a new imaging agent that may help get more detailed pictures of the tumor. This trial aims to see whether using 68Ga-PSMA-11 PET scans may help doctors learn more about where disease is located in the body.
PRIMARY OBJECTIVE: I. To determine whether the percent change from baseline to 16 weeks (+/- 8 weeks) in maximum standard uptake value (SUVmax) averaged across up to 16 lesions per patient (SUVmax-ave) is associated with \>= 50% decline from baseline in serum prostate specific antigen (PSA50) response. SECONDARY OBJECTIVES: I. To determine whether the percent change from baseline in SUVmax-ave on PSMA PET is associated with time-to-event endpoints including PSA progression-free survival and overall survival. II. To determine whether the percent change from baseline in SUVmax on PSMA PET is associated with objective response by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 on a per-lesion basis among measurable soft tissue lesions present at baseline. EXPLORATORY (CORRELATIVE) OBJECTIVES: I. To descriptively characterize the histologic, transcriptional, and genomic features of PSMA low/negative lesions among patients who undergo paired optional metastatic tumor biopsy. II. To descriptively characterize the relationship between SUVmax-ave on baseline Ga-PSMA PET with optional baseline fludeoxyglucose F-18 (FDG)-PET. III. To determine whether heterogeneity of PSMA expression on baseline Ga-PSMA PET is associated with overall survival. IV. To descriptively characterize the patterns of PSMA expression at the time of disease progression among patients who undergo optional PSMA PET. V. To determine whether the percent change from baseline in PSMA PET is associated with PSA50 response among subgroups of patients defined by treatment modality received, including androgen receptor (AR) targeting treatment, PSMA-targeting radioligand therapy, cytotoxic chemotherapy, and immunotherapy. OUTLINE: Patients receive gallium Ga 68-PSMA-11 intravenously (IV) and undergo PET at baseline, 16 weeks after initiating therapy, and at time of disease progression. After progression or study completion, patients are followed up every 3 months for up to 24 months
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
15
Given IV
Undergo PET
University of California San Francisco
San Francisco, California, United States
Mean Maximum Standard Uptake Value (SUVmax)
The mean SUVmax and standard deviation across the primary tumor and the 5 largest lesions in each of three metastatic sites (nodal, visceral and osseous; for a maximum of 16 lesions per patient) will be descriptively reported.
Time frame: Baseline, and up to 16 weeks after initiation of therapy
Median SUVmax
The median and range of SUVmax across the primary tumor and the 5 largest lesions in each of three metastatic sites (nodal, visceral and osseous; for a maximum of 16 lesions per patient) will be descriptively reported.
Time frame: Baseline, and up to 16 weeks after initiation of therapy
Percentage of Participants Who Progressed by Prostate-specific Antigen (PSA) Response Group
The percent of participants who fall into the PSA50 responders vs. non-responders based on PSMA treatment response criteria (PPP) for progression status will be reported. PPP uses 3 different criteria to determine response: 1) Appearance of 2 or more new PSMA positive distant lesions, 2) Appearance of 1 new PSMA positive lesion plus consistent clinical and/or laboratory data and recommended confirmation by biopsy or correlative imaging within 3 months of PSMA PET, and 3) Increase in size or PSMA uptake of 1 or more existing lesions by 30% plus consistent clinical and/or laboratory data and/or confirmation by biopsy or correlative imaging within 3 months of PSMA PET.
Time frame: Baseline, and up to 16 weeks after initiation of therapy
Comparison of Change in SUVmax-ave Group on Progression Free Survival (PFS)
The study cohort will be dichotomized by the median with respect to percent change from baseline in SUVmax-ave on PSMA PET. The time-to-event variables including PSA progression-free will be defined by Prostate Cancer Clinical Trials Working Group 3 (PCWG3).
Time frame: Up to 24 months
Comparison of Change in SUVmax-ave Group on Overall Survival (OS)
The study cohort will be dichotomized by the median with respect to percent change from baseline in SUVmax-ave on PSMA PET on overall survival defined as time from imaging until death or censored at study completion. OS will be compared between dichotomized subgroups using the log-rank test. Kaplan-Meier product limit method will be used to estimate median survival in each subgroup.
Time frame: Up to 24 months
Comparison Between Mean Percent Change in SUVmax With Objective Response Group
Amongst the subset of measurable soft tissue lesions by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria, on a per-lesion basis, the mean percent change from baseline in SUVmax on PSMA PET will be compared between responding lesions defined as a complete response or partial response by RECIST 1.1 criteria vs. those without response, using Mann-Whitney test.
Time frame: Baseline, and up to 16 weeks after initiation of therapy
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