Among patients with biochemically recurrent prostate cancer and negative/equivocal imaging at baseline, piflufolastat F 18 (18F-DCFPyL-PET/CT; Pylarify) effectively detected and pinpointed metastatic lesions with high positive predictive value (PPV), according to an update from the pivotal phase 3 CONDOR trial presented at the 2021 Society of Nuclear Medicine and Molecular Imaging (SNMMI) Annual Meeting.1,2
The researchers noted that PPVs with piflufolastat F 18 were higher in extra-pelvic lymph nodes and bone versus viscera/soft tissue regions. Findings from the CONDOR trial previously supported the FDA approval of the PSMA PET imaging agent piflufolastat F 18 for identifying suspected metastasis or recurrence of prostate cancer.
The multicenter phase 3 trial enrolled men with rising PSA after definitive therapy and negative or equivocal standard-of-care imaging. Patients were required to have a PSA level ≥0.2 if they had undergone radical prostatectomy (RP) or a PSA level ≥2.0 if they were treated with radiation therapy or cryotherapy.
The primary end point was correct localization rate (CLR), defined as percentage of patients with a 1:1 correspondence between at least 1 lesion identified by PyL–PET/CT and the composite standard of truth (pathology, correlative imaging, or PSA response). PyL scans were read by 3 blinded independent central readers.
Overall, there were 208 evaluable patients, about 85% of whom underwent RP, either alone or with radiation. Median PSA level of the cohort was 0.8 ng/mL, and 68.8% had a PSA level <2.0 ng/mL. Some 27.9% had received at least 1 prior systemic therapy.
Data presented at SNMMI showed that the median PPV (at least 1 confirmed lesion) by anatomic region per the 3 independent readers was 79.5% (n = 31/39) for prostate/prostate bed, 70.9% (n = 39 of 55) for pelvic lymph nodes, and 67.4% (n = 31/46) for extra-pelvic region. The median detection rates (N = 208) were 20.2%, 35.1%, and 26.4%, respectively.
The investigators also conducted extended analyses of the extra-pelvic region. The results of these examinations showed median PPVs of 61.5% (n = 16 of 26), 62.5% (n = 15 of 24), and 28.6% (n = 2 of 7) for lymph nodes, bone, and visceral/soft tissue respectively.
Findings reported prior to the SNMMI meeting showed that the detection of disease as manifested by a positive piflufolastat F 18 scan was 65.9%, 59.6%, and 59.1% by the 3 readers.
The prespecified criterion for CLR success was for the lower limit of the 95% CI to exceed 20% for at least 2 of the 3 readers. For every reader, the lower bound of the 95% CI for the CLR was well in excess of the 20% benchmark, meeting the primary end point of the study.
The CLRs were 85.6% (95% CI, 78.8%-92.3%), 87.0% (95% CI, 80.4%-93.6%), and 84.8% (95% CI, 77.8%-91.9%) by the 3 readers. Some 64% of the evaluable patients had a change in intended management due to the scan.
Overall, 63.9% of men in the CONDOR study with biochemically recurrent prostate cancer who had no evidence of disease on standard-of-care imaging had a change in intended management after their piflufolastat F 18 scan.
References
1. PSMA-Targeted Radiotracer Pinpoints Metastatic Prostate Cancer Across Anatomic Regions. Posted online June 16, 2021. Accessed June 16, 2021. https://bit.ly/3zBZqhO.
2. Rowe S, Gorin M, Saperstein L, et al. A Phase 3 study of 18F-DCFPyL-PET/CT in Patients with Biochemically Recurrent Prostate Cancer (CONDOR): An Analysis of Disease Detection Rate and Positive Predictive Value (PPV) by Anatomic Region. J Nucl Med.May 2021, 62 (supplement 1) 123.
Dr. Schuster highlights the FDA approval of imaging agent flotufolastat F 18 in prostate cancer
June 22nd 2023"We're excited that the FDA approval of this radiotracer gives us yet more tools at our disposal to diagnose prostate cancer in all its forms, from early to late in the disease process," says David M. Schuster, MD, FACR.