Follow-up of Lesions with Equivocal Radiotracer Uptake on PSMA-Targeted PET in Patients with Prostate Cancer: Predictive Values of the PSMA-RADS-3A and PSMA-RADS-3B Categories

Abstract

Prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) imaging has become commonly utilized in patients with prostate cancer (PCa). The PSMA reporting and data system version 1.0 (PSMA-RADS version 1.0) categorizes lesions on the basis of the likelihood of PCa involvement, with PSMA-RADS-3A (soft tissue) and PSMA-RADS-3B (bone) lesions being indeterminate for the presence of disease. We retrospectively reviewed the imaging follow-up of such lesions to determine the rate at which they underwent changes suggestive of underlying PCa. PET/CT imaging withF-DCFPyL was carried out in 110 patients with PCa and lesions were categorized according to PSMA-RADS Version 1.0. 56/110 (50.9%) patients were determined to have indeterminate PSMA-RADS-3A or PSMA-RADS-3B lesions and 22/56 (39.3%) patients had adequate follow-up to be included in the analysis. The maximum standardized uptake values (SUV) of the lesions were obtained and the ratios of SUV of the lesions to SUVmean of blood pool (SUV-lesion/SUVmean-bloodpool) were calculated. Pre-determined criteria were used to evaluate the PSMA-RADS-3A and PSMA-RADS-3B lesions on follow-up imaging to determine if they demonstrated evidence of underlying malignancy. A total of 46 lesions in 22 patients were considered indeterminate for PCa (i.e. PSMA-RADS-3A (32 lesions) or PSMA-RADS-3B (14 lesions)) and were evaluable on follow-up imaging. 27/46 (58.7%) lesions demonstrated changes on follow-up imaging consistent with the presence of underlying PCa at baseline. These lesions included 24/32 (75.0%) PSMA-RADS-3A lesions and 3/14 (21.4%) lesions categorized as PSMA-RADS-3B. The ranges of SUV and SUV-lesion/SUVmean-bloodpool overlapped between those lesions demonstrating changes consistent with malignancy on follow-up imaging and those lesions that remained unchanged on follow-up. PSMA-RADS-3A and PSMA-RADS-3B lesions are truly indeterminate in that proportions of findings in both categories demonstrate evidence of malignancy on follow-up imaging. Overall, PSMA-RADS-3A lesions are more likely than PSMA-RADS-3B lesions to represent sites of PCa and this information should be taken into account when guiding patient therapy.

Prospective Comparison of PET Imaging with PSMA-Targeted 18F-DCFPyL Versus Na18F for Bone Lesion Detection in Patients with Metastatic Prostate Cancer

“…Soft-tissue lesions were also noted on both scans, with SUV max and SUL max recorded for those lesions appreciated on 18 F-DCFPyL PET. All detected lesions were also assigned a PSMA reporting and data system (PSMA-RADS) score (17)(18)(19)(20).…”

Interobserver agreement of [68Ga]Ga-PSMA-11 PET/CT images interpretation in men with newly diagnosed prostate cancer

“…Prior prospective evaluation and validation of these approaches is needed before being able to implement them in clinical trials and routine clinical practice. Authors who proposed PSMA-RADS classification showed an excellent interobserver agreement for an overall scan when applying this classification to imaging interpretation of [ 18 F]DCFPyL PET/CT in a population of patients with PC, the majority of whom had already received prior therapy [8,9]. The inter-reader agreement of the PC molecular imaging standardized evaluation (PROMISE) proposed by Eiber et al was substantial for interpretation of [ 68 Ga]Ga-PSMA-11 PET/CT in a population of patients with biochemically recurrent PC [7,10], though authors recently showed that PROMISE criteria agreement was significantly lower for [ 18 F]fluciclovine than for [ 68 Ga]Ga-PSMA-11 [11].…”

The Future of Nuclear Medicine as an Independent Specialty

“…Important imaging probes that will become available include various 68 Ga-and 18 F-labeled PSMA ligands (51)(52)(53)(54)(55). Additional imaging probes that should become available-although phase 3 clinical imaging trials without commercial sponsors will be difficult to complete-include L-amino-acid transporter-1 (LAT-1) substrates, such as 11 C-methionine (56), 18 F-tyrosine (57), and 18 F-FDOPA (58,59), for use in brain tumors, movement disorders, and NETs.…”