Diagnostic Accuracy of 68Ga-PSMA-11 PET/MRI Compared with Multiparametric MRI in the Detection of Prostate Cancer

Abstract

Purpose To compare the diagnostic accuracy of gallium 68 (68Ga)-labeled prostate-specific membrane antigen (PSMA)-11 PET/MRI with that of multiparametric MRI in the detection of prostate cancer. Materials and Methods The authors performed a retrospective study of men with biopsy-proven prostate cancer who underwent simultaneous 68Ga-PSMA-11 PET/MRI before radical prostatectomy between December 2015 and June 2017. The reference standard was whole-mount pathologic examination. Readers were blinded to radiologic and pathologic findings. Tumor localization was based on 30 anatomic regions. Region-specific sensitivity and specificity were calculated for PET/MRI and multiparametric MRI by using raw stringent and alternative neighboring approaches. Maximum standardized uptake value (SUVmax) in the tumor and Prostate Imaging Reporting and Data System (PI-RADS) version 2 grade were compared with tumor Gleason score. Generalized estimating equations were used to estimate population-averaged sensitivity and specificity and to determine the association between tumor characteristics and SUVmax or PI-RADS score. Results Thirty-two men (median age, 68 years; interquartile range: 62-71 years) were imaged. The region-specific sensitivities of PET/MRI and multiparametric MRI were 74% (95% confidence interval [CI]: 70%, 77%) and 50% (95% CI: 45%, 0.54%), respectively, with the alternative neighboring approach (P < .001 for both) and 73% (95% CI: 68%, 79%) and 69% (95% CI: 62%, 75%), respectively, with the population-averaged generalized estimating equation (P = .04). Region-specific specificity of PET/MRI was similar to that of multiparametric MRI with the alternative neighboring approach (88% [95% CI: 85%, 91%] vs 90% [95% CI: 87%, 92%], P = .99) and in population-averaged estimates (70% [95% CI: 64%, 76%] vs 70% [95% CI: 64%, 75%], P = .99). SUVmax was associated with a Gleason score of 7 and higher (odds ratio: 1.71 [95% CI: 1.27, 2.31], P < .001). Conclusion The sensitivity of gallium 68-labeled prostate-specific membrane antigen-11 PET/MRI in the detection of prostate cancer is better than that of multiparametric MRI. © RSNA, 2018 See also the editorial by Civelek in this issue.

Figures

Figure 1:

Patient flowchart. PET = gallium 68–labeled prostate-specific membrane antigen PET, mpMRI = multiparametric MRI.

Figure 2:

Images in 75-year-old man with prostate-specific antigen level of 25.6 ng/mL.A, Axial diffusion-weighted image (bvalue, 1350 sec/mm2) of midprostate and, D, corresponding apparent diffusion coefficient map demonstrate restricted diffusion in right posterior peripheral zone (arrow), with well-defined low signal intensity on, B, T2-weighted image.C, Corresponding PET scan demonstrates focal radiotracer uptake (arrow) with maximum standardized uptake value of 23.9.E, Enhancement curve with washout reconstructed from dynamic T1-weighted postcontrast images. F, Histopathologic slide of midprostate (hematoxylin-eosin stain; original magnification, ×1) confirms presence of tumor (Gleason score 4+5) with extraprostatic extension.

Figure 3:

Images in 72-year-old man with prostate-specific antigen level of 5.9 ng/mL.A, Axial diffusion-weighted image of midprostate (b value, 1350 sec/mm2) and,D, corresponding apparent diffusion coefficient map demonstrate single focus of restricted diffusion (arrow) in midline posterior peripheral zone. The focus (arrow) has ill-defined low signal intensity on, B, T2-weighted image and suspicious enhancement on, E, dynamic T1-weighted postcontrast image.C, Corresponding PET scan demonstrates two separate areas of focal radiotracer uptake, including one focus in midline posterior peripheral zone with maximum standardized uptake value (SUVmax) of 11.7 (arrow) and additional focus in central aspect of left anterior peripheral zone with SUVmax of 6.2 (arrowhead).F, Histopathologic slide of midprostate (hematoxylin-eosin stain; original magnification, ×1) confirms presence of two distinct tumors, one within midline posterior peripheral zone (Gleason score 4+5) with extraprostatic extension and one in central aspect of left anterior peripheral zone (Gleason score 4+3).

Figure 4:

Receiver operating characteristic curves generated with generalized linear models of maximum standardized uptake value for, A, gallium 68–labeled prostate-specific membrane antigen PET/MRI and,B, Prostate Imaging Reporting and Data System score with multiparametric MRI. With generalized linear model estimate, the area under the receiver operating characteristic curve for PET/MRI was higher than that for multiparametric MRI (P = .04).

Figure 5:

Box plot depicts maximum tumor standardized uptake value (SUVmax), on a logarithmic scale, across various tumor Gleason scores. Vertical borders of box represent 25th and 75th percentiles, and middle bar represents median. Error bars represent first and 99th percentiles, and circles represent outliers. Generalized linear model demonstrated an association between SUVmax and Gleason score of 7 or greater (odds ratio = 2.22 [95% confidence interval: 1.46, 3.35],P < .001).