Adjunctive role of dual time point imaging in evaluating bone lesions with increased 18F-PSMA-1007 uptake

Background@#Non-specific focal uptake in the skeleton is a diagnostic pitfall on 18F-PSMA-1007 PET/CT, but adjunctive measures to aid interpretation of these lesions are currently lacking. We present two cases where dual time point imaging provided additional information. @*Case Presentation@#The first patient had a PI-RADS 3 lesion on MRI. No PSMA-avid abnormality was seen on PET, save for focal uptake in the right pubis with no anatomic correlate. Additional imaging showed a decrease in lesion SUV, and this was interpreted as benign. Another patient, diagnosed with prostate cancer, had multiple PSMA-avid pelvic foci. Two suspiciously malignant bone lesions had increasing SUV trend after dual time point imaging despite only faint sclerosis on CT. In contrast, one faint PSMA-avid lesion with no anatomic abnormality was read as benign after a decrease in SUV. A decrease in lesion SUV may point to a benign etiology, while an increase would heighten suspicion for malignancy. One possible molecular explanation is that a true PSMA-overexpressing lesion would bind to the tracer for a longer period than a false positive.@*Conclusion@#Dual time point imaging provides additional information that may be useful in the interpretation of non-specificskeletal lesions with increased 18F-PSMA-1007 uptake.

Role of early dynamic PET/CT scan imaging with 18F-PSMA-1007 in staging and restaging prostate cancer in a tertiary private hospital

Introduction@#18F-PSMA-1007 is a novel prostate-specific membrane antigen (PSMA)-based radiopharmaceutical for imaging prostate cancer. The recommended imaging time is 60 minutes post-injection of the radiotracer. However, during this time there is a physiologic accumulation of the radiotracer in the urinary bladder which sometimes may obscure lesions adjacent to it. @*Objective@#This study aims to determine if early dynamic imaging in addition to the recommended 60-minute postinjection static imaging can improve the detection of PSMA-avid lesions in the staging and restaging of prostate cancer. @*Methods@#This is a retrospective cross-sectional study of the detection rate of early dynamic and static imaging using 18F-PSMA-1007 PET/CT scan in patients with prostate cancer (PCa) who were referred for initial staging or restaging. The McNemar test was used to compare the detection rate between the two imaging. Spearman correlation was used to determine the correlation of Gleason score (GS), PSA, and SUVmax values.@*Results@#18F-PSMA-1007 PET/CT scans of 53 patients with prostate cancer, were referred for either staging (22/53) or restaging (31/53), all of whom had undergone both early dynamic and static imaging. Among the 53 patients, 5 had 2 lesions each, for a total of 58 lesions were included in the analysis. There were 48/58 lesions detected on both early dynamic and static imaging, 2/58 lesions were only detected in the early imaging, 1/58 lesions was only detected in the static imaging, and 7/58 were not detected on both imaging. McNemar the test was not statistically significant (p = 1.000) in the detection rate of the two methods. There is a positive correlation between serum PSA levels and SUVmax measurements for all the patients. Only the correlation between the GS and SUVmax in the static imaging of the staging group was statistically significant. @*Conclusion@#Early dynamic imaging may be an adjunctive procedure in detecting PSMA-avid lesions, particularly in the basal segment of the prostate gland near the urinary bladder. However, it is not recommended as a standard component of the comprehensive protocol for imaging using 18F-PSMA-1007 PET/CT in patients with PCa.