RT Journal Article
SR Electronic
T1 Matched-Pair Comparison of <sup>68</sup>Ga-PSMA-11 and <sup>18</sup>F-rhPSMA-7 PET/CT in Patients with Primary and Biochemical Recurrence of Prostate Cancer: Frequency of Non–Tumor-Related Uptake and Tumor Positivity
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1082
OP 1088
DO 10.2967/jnumed.120.251447
VO 62
IS 8
A1 Kroenke, Markus
A1 Mirzoyan, Lilit
A1 Horn, Thomas
A1 Peeken, Jan C.
A1 Wurzer, Alexander
A1 Wester, Hans-Jürgen
A1 Makowski, Marcus
A1 Weber, Wolfgang A.
A1 Eiber, Matthias
A1 Rauscher, Isabel
YR 2021
UL http://jnm.snmjournals.org/content/62/8/1082.abstract
AB Radiohybrid prostate-specific membrane antigen (rhPSMA) ligands are a new class of prostate cancer theranostic agents. 18F-rhPSMA-7 offers the advantages of 18F labeling and low urinary excretion compared with 68Ga-PSMA-11. Here, we compare the frequency of non–tumor-related uptake and tumor positivity with 68Ga-PSMA-11 and 18F-rhPSMA-7 in patients with primary or recurrent prostate cancer. Methods: This retrospective matched-pair comparison matched 160 18F-rhPSMA-7 with 160 68Ga-PSMA-11 PET/CT studies for primary staging (n = 33) and biochemical recurrence (n = 127) according to clinical characteristics. Two nuclear medicine physicians reviewed all scans, first identifying all PET-positive lesions and then differentiating lesions suggestive of prostate cancer from those that were benign, on the basis of known pitfalls and ancillary information from CT. For each region, the SUVmax of the lesion with the highest PSMA ligand uptake was noted. Tumor positivity rates were determined, and SUVmax was compared separately for each tracer. Results: 18F-rhPSMA-7 and 68Ga-PSMA-11 PET revealed 566 and 289 PSMA ligand–positive lesions, respectively. Of these, 379 and 100 lesions, equaling 67.0% and 34.6%, respectively, of all PSMA-positive lesions, were considered benign. The distribution of their etiology was similar (42%, 24%, and 25% with 18F-rhPSMA-7 vs. 32%, 24%, and 38% with 68Ga-PSMA-11 for ganglia, bone, and unspecific lymph nodes, respectively). All primary tumors were positive with both agents (n = 33 each), whereas slightly more metastatic lesions were observed with 68Ga-PSMA-11 in both disease stages (113 for 18F-rhPSMA-7 and 124 for 68Ga-PSMA-11). The SUVmax of 18F-rhPSMA-7 and 68Ga-PSMA-11 did not differ (P &gt; 0.05) in local recurrence or primary prostate cancer; however, the tumor-to-bladder ratio was significantly higher with 18F-rhPSMA-7 (4.9 ± 5.3 vs. 2.2 ± 3.7, P = 0.02, for local recurrence; 9.8 ± 9.7 vs. 2.3 ± 2.6, P &lt; 0.001, for primary prostate cancer). Conclusion: The tumor positivity rate was consistently high for 68Ga-PSMA-11 and 18F-rhPSMA-7. Both tracers revealed a considerable number of areas of uptake that were reliably identified as benign by trained physicians making use of corresponding morphologic imaging and known PSMA pitfalls. These were more frequent with 18F-rhPSMA-7. However, the matched-pair comparison could have introduced a source of bias. Adequate reader training can allow physicians to differentiate benign uptake from disease and be able to benefit from the logistical and clinical advantages of 18F-rhPSMA-7.