Abstract
P968
Introduction: The EMPIRE-2 trial () randomized men with detectable prostate-specific antigen (PSA) post prostatectomy to imaging with 68Ga-PSMA-11 PET/CT versus 18F-fluciclovine PET/CT. Here, we analyse the patients with tracer-avid bone lesions in the 68Ga-PSMA-11 arm of the trial.
Methods: Two experienced (> 20 years) nuclear medicine physicians performed a blinded review of the scans and rated all bone lesions on a 5-point Likert scale of I to V (I-definitively benign; II-probably benign; III-indeterminate; IV-probably malignant; V-definitively malignant). The location and SUVmax of the lesions were determined. For this analysis, a composite truth standard was used including, biopsy and/or MRI and/or follow-up post-treatment.
Results: Sixty-six patients completed a 68Ga-PSMA-11 PET/CT scan in the EMPIRE-2 trial, and 13 (19.70%) of them had 20 tracer-avid bone lesions. Four, seven, and nine lesions were respectively rated as I/II (negative), III (equivocal), and (malignant). The median (range) PSA of the patients rated I/II (n=2), III (n=6), and IV/V (n=5) were 0.55 (0.38 – 0.72) ng/mL, 0.51 (0.15 – 0.80) ng/mL, and 0.66 (0.27 – 75.90) ng/mL, respectively. The mean SUVmax of lesions rated I/II, III, and IV/V were 2.95 ± 1.87, 3.2 ± 1.72, and 9.88 ± 8.45, respectively. The bones involved were pelvis (8), ribs (n=6), spine (n=4), sternum (n=1), and clavicle (n=1). Of the four lesions with a score of I/II, two were confirmed benign by the absence of interval change on a CT scan obtained 12 months later, while the other two were not evaluated further. Of the seven lesions with a score of III, five were confirmed benign (MRI correlation, n=3; undetectable PSA after local radiotherapy to prostate bed only, n=1; and no interval change on follow-up Pylarify PET/CT two years later, n=1) while the other two have not been evaluated further. Of the nine lesions scored IV/V, seven were confirmed malignant (biopsy, n=5 and sclerosis on follow-up CT after systemic treatment, n=2), while the other two lesions have not been evaluated further.
Conclusions: Bone lesions are seen in 19.7% of post-prostatectomy patients evaluated with 68Ga-PSMA-11 PET/CT for disease recurrence. Bone lesions rated benign or indeterminate by expert readers are mostly confirmed benign when evaluated further. Benign and malignant lesions are seen in a wide array of bones in this series, but malignant lesions tend to have higher SUVmax and occur in patients with higher PSA levels.
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