RT Journal Article SR Electronic T1 Unspecific 18F-PSMA-1007 Bone Uptake Evaluated Through PSMA-11 PET, Bone Scanning, and MRI Triple Validation in Patients with Biochemical Recurrence of Prostate Cancer JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 738 OP 743 DO 10.2967/jnumed.118.215434 VO 64 IS 5 A1 Seifert, Robert A1 Telli, Tugce A1 Opitz, Marcel A1 Barbato, Francesco A1 Berliner, Christoph A1 Nader, Michael A1 Umutlu, Lale A1 Stuschke, Martin A1 Hadaschik, Boris A1 Herrmann, Ken A1 Fendler, Wolfgang P. YR 2023 UL http://jnm.snmjournals.org/content/64/5/738.abstract AB 18F-PSMA-1007 PET is used in the management of patients with prostate cancer. However, recent reports indicate a high rate of unspecific bone uptake (UBU) with 18F-PSMA-1007, which may lead to a false-positive diagnosis. UBU has not been evaluated thoroughly. Here, we evaluate the frequency of UBU and bone metastases separately for 18F-PSMA-1007 and 68Ga-PSMA-11 in biochemical recurrence (interindividual comparison). Additionally, we investigate UBU seen in 18F-PSMA-1007 through follow-up examinations (intraindividual comparison) using 68Ga-PSMA-11 PET, bone scintigraphy, and MRI. Methods: First, all patients (n = 383) who underwent 68Ga-PSMA-11 PET between January 2020 and December 2020 and all patients (n = 409) who underwent 18F-PSMA-1007 PET between January 2020 and November 2021 due to biochemical recurrence were included for an interindividual comparison of bone metastases and UBU rate. In a second approach, we regarded all patients with UBU in 18F-PSMA-1007, characterized by focal bone uptake with an SUVmax > 4 and prostate-specific antigen (PSA) ≤ 5 ng/mL, who underwent additional 68Ga-PSMA-11 PET (n = 17) (interindividual comparison). Of these, 12 patients also had bone scintigraphy and whole-body MRI within a 1- to 5-wk interval. Bone uptake seen on 18F-PSMA-1007 but not on any of the other 4 modalities (CT, MRI [n = 1], bone scanning, and 68Ga-PSMA-11 PET) was recorded as false-positive. Results: Patients scanned with 18F-PSMA-1007 PET had a significantly higher rate of UBU than those scanned with 68Ga-PSMA-11 (140 vs. 64; P < 0.001); however, the rate of bone metastases was not significantly different (72 vs. 64; P = 0.7). In the intraindividual comparison group, workup by CT, MRI, bone scanning, and 68Ga-PSMA-11 PET resulted in a positive predictive value for 18F-PSMA-1007 focal bone uptake (mean SUVmax, 6.1 ± 2.9) per patient and per lesion of 8.3% and 3.6%, respectively. Conclusion: In patients with PSA ≤ 5 ng/mL and SUV > 4 at biochemical recurrence, most 18F-PSMA-1007 focal bone uptake is likely to be false-positive and therefore due to UBU. In the case of low clinical likelihood of metastatic disease, 18F-PSMA-1007 bone uptake without morphologic surrogate should be assessed carefully with regard to localization and clinical context. However, the rate of bone metastases was not higher with 18F-PSMA-1007 in the clinical routine, indicating that experienced reporting physicians adjust for UBU findings.