[ 18 F]Flotufolastat PET/MRI in Patients with Suspected Prostate Cancer: Correlation with Histopathologic Biopsy Results

This retrospective analysis investigated the detection accuracy of [¹⁸F]flotufolastat ([¹⁸F]rhPSMA-7.3) PET/MRI in patients with suspected prostate cancer (PCa), read using the PRIMARY score. Performance was compared with that of multiparametric MRI (mpMRI) assessed per Prostate Imaging Reporting and Data System (PI-RADS) criteria. Methods: [¹⁸F]flotufolastat PET and mpMRI scans of the prostate were read independently using PRIMARY and PI-RADS scores, respectively. Imaging data were analyzed per patient and by prostate gland sextant, and scores were compared with transrectal histopathologic biopsy results (clinically significant PCa: International Society of Urological Pathology grade ≥ 2). Diagnostic performance parameters (sensitivity, specificity, and positive and negative predictive values) were calculated; receiver-operating characteristic analyses with 95% CI were performed per patient and by sextant to compare the detection accuracy of [¹⁸F]flotufolastat PET, mpMRI, and combined PET/MRI. Results: Data from 72 patients (median prescan prostate-specific antigen level, 10.1 ng/mL) were reviewed. Twenty patients had histopathologically confirmed, clinically significant PCa, versus 27 by PRIMARY criteria (score, 3-5) and 43 by PI-RADS criteria (score, 3-5). Patient-level sensitivity, specificity, and positive and negative predictive values were, respectively, 85%, 81%, 63%, and 93% for [¹⁸F]flotufolastat PET versus 85%, 50%, 40%, and 90% for mpMRI and 95%, 42%, 39%, and 96% for PET/MRI combined. Sextant-level sensitivity, specificity, and positive and negative predictive values were, respectively, 63%, 93%, 53%, and 95% for [¹⁸F]flotufolastat PET versus 45%, 88%, 33%, and 92% for mpMRI and 69%, 83%, 35%, and 95% for PET/MRI combined. For both patient- and sextant-level receiver-operating characteristic analysis, comparisons of area under the curve for [¹⁸F]flotufolastat/PRIMARY score (0.88 [95% CI, 0.79-0.97]) versus mpMRI/PI-RADS score (0.75 [95% CI, 0.62-0.87) and combined PET/MRI (0.82 [95% CI, 0.72-0.92]) did not reach statistical significance (all P > 0.05). Conclusion: The PRIMARY score was easily adopted for [¹⁸F]flotufolastat PET, which outperformed mpMRI (read using PI-RADS) for the detection of histopathologically confirmed PCa. Although combined PET/MRI showed the highest sensitivity, specificity was lower than for PET or MRI alone.