Focal Unspecific Bone Uptake on [18F]-psma-1007 Pet: A Multicenter Retrospective Evaluation of the Distribution, Frequency, and Quantitative Parameters of a Potential Pitfall in Prostate Cancer Imaging

Abstract

PurposeImproved logistics and availability led to a rapid increase in the use of [18F]-PSMA-1007 for prostate cancer PET imaging. Initial data suggests increased uptake in benign lesions compared to [68Ga]-PSMA-11, and clinical observations found increased unspecific bone uptake (UBU). We therefore investigate the frequency and characteristics of UBU in [18F]-PSMA-1007 PET.MethodsWe retrospectively analyzed [18F]-PSMA-1007 PET scans from four centers for the presence of UBU, defined as a focal mild-to-moderate uptake (SUVmax < 10.0) not obviously related to a benign or malignant cause. If present, up to three leading UBUs were quantified (SUVmax), localized, and correlated to clinical parameters, such as age, PSA, injected dose, Gleason-score, tumor size (T1–T4), and type of PET scanner (analog vs. digital). Additionally, clinical and imaging follow-up results and therapeutic impact were evaluated.ResultsUBUs were identified in 179 out of 348 patients (65.2%). The most frequent localizations were ribs (57.5%) and pelvis (24.8%). The frequency of UBUs was not associated with PSA, Gleason-score, tumor size, age, or the injected [18F]-PSMA-1007 dose. UBUs were significantly more frequent in images obtained with digital scanners (70.1%) than analog scanners (p=.0001). In 80 out of 179 patients (44.7%), the interpretation of UBUs was critical for therapeutic management and therefore considered clinically relevant. For 65 UBUs, follow-ups were available: three biopsies, three radiotherapies with PSA follow-up, and 59 cases with imaging. After follow-up UBUs were still considered unclear in 28 of 65 patients (43.1%), benign in 28 (43.1%), and malignant in nine (13.8%) patients.ConclusionUBUs occur in two-thirds of patients imaged with [18F]-PSMA-1007 PET/CT and are significantly more frequent on digital PET scanners than analog scanners. UBUs should be interpreted carefully to avoid over-staging.

Comparison of 18F-PSMA-1007 PET/CT With 68Ga-PSMA-11 PET/CT for Initial Staging in Intermediate- and High-Risk Prostate Cancer

“…These additional lesions potentially upstaged the M stage categorization in 2 patients and did not impact the overall M stage categorization in rest 3 patients. Different studies 28,30–32 have reported equivocal radiotracer uptake with PSMA PET tracers at marrow and skeletal sites with a higher frequency on 18 F-PSMA-1007 than 68 Ga-PSMA-11 PET. These findings suggest that interpretation of 18 F-PSMA PET-positive skeletal lesions requires reader familiarity with known pitfalls and reporting based on the overall clinical context.…”

Phase III Study of18F-PSMA-1007 Versus18F-Fluorocholine PET/CT for Localization of Prostate Cancer Biochemical Recurrence: A Prospective, Randomized, Crossover Multicenter Study

“…The compound showed a high detection rate at low PSA values and high sensitivity and specificity in both biochemical recurrence and primary staging (8,9). In some patients, nonspecific bone uptake may be a confounding factor (10).…”

Hot needles can confirm accurate lesion sampling intraoperatively using [18F]PSMA-1007 PET/CT-guided biopsy in patients with suspected prostate cancer

“…The first tracer with broad application was [ 68 Ga]PSMA-11; with a high urinary excretion, this tracer sometimes limited the detection of local recurrence. The now also available tracer [ 18 F]PSMA-1007 is excreted more over the hepatobiliary path and reduces spill over in the pelvis; on the other hand, a higher number of unclear bone uptake are still considered limiting the specificity for bone lesions [12]. For the detection of primary tumors, however, there are no published reports about differences between both tracers.…”