Purpose: 18F-Fluciclovine is indicated for evaluation of suspected prostate cancer (PCa) biochemical recurrence. There are few studies investigating fluciclovine with PET/MR and none evaluated osseous metastases. Our aim was to assess the performance of 18F-fluciclovine PET/MR (fluciclovine-PET/MR)...

Purpose: 18F-Fluciclovine is indicated for evaluation of suspected prostate cancer (PCa) biochemical recurrence. There are few studies investigating fluciclovine with PET/MR and none evaluated osseous metastases. Our aim was to assess the performance of 18F-fluciclovine PET/MR (fluciclovine-PET/MR) for detecting osseous metastases in patients with castration-resistant prostate cancer (CRPC). We also investigated possible correlations between SUVmax and ADCmean. Methods: We evaluated 8 patients with CRPC metastatic to bones, some before and some after radium therapy, who underwent 13 fluciclovine-PET/MR studies. We analyzed the performance of radionuclide bone scan (RBS), MR alone, fluciclovine-PET alone, and fluciclovine-PET/MR in detecting osseous metastases. Lesion size, characteristics (early sclerotic, late sclerotic, mixed, lytic), SUVmax, and ADCmean were assessed. The reference standard was a combination of clinical information and correlation with both prior and follow-up imaging. Results: Of 347 metastatic bony lesions in 13 studies, 238/347 (68%) were detected by fluciclovine-PET alone, 286/347 (82%) by RBS, 344/347 (99%) by MR alone, and 347/347 (100%) by fluciclovine-PET/MR. Fluciclovine-PET/MR and MR had the best performance (p < 0.001). There was no statistically significant difference between fluciclovine-PET/MR and MR alone (p = 0.25). Fluciclovine-PET had a lower detection rate especially with late sclerotic lesions (p < 0.001). There was a moderate inverse correlation between lesion SUVmax and ADCmean (r = − 0.49; p < 0.001). Conclusions: This study suggests that fluciclovine-PET/MR and MR have high sensitivity for detecting osseous metastases in CRPC. Fluciclovine-PET alone underperformed in detecting late sclerotic lesions. The inverse correlation between SUVmax and ADCmean suggests a possible relationship between tumor metabolism and cellularity.

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