Factors Predicting Metastatic Disease in ⁶⁸Ga-PSMA-11 PET–Positive Osseous Lesions in Prostate Cancer

Abstract

Bone is the most common site of distant metastatic spread in prostate adenocarcinoma. Prostatespecific membrane antigen uptake has been described in both benign and malignant bone lesions, which can lead to false-positive findings on 68 Ga-prostate-specific membrane antigen-11 positron emission tomography (68 Ga-PSMA-11 PET). The purpose of this study was to evaluate the diagnostic accuracy of 68 Ga-PSMA-11 PET for osseous prostate cancer metastases and improve bone uptake interpretation using semi-quantitative metrics. METHODS. 56 prostate cancer patients (18 pre-prostatectomy, 38 biochemical recurrence) who underwent 68 Ga-PSMA-11 PET/MRI or PET/CT examinations with osseous PSMA-ligand uptake were included in the study. Medical records were reviewed retrospectively by boardcertified nuclear radiologists to determine true or false positivity based on a composite endpoint. For each avid osseous lesion, biological volume, size, PSMA-RADS rating, maximum standardized uptake value (SUVmax), and ratio of lesion SUVmax to liver, blood pool, and background bone SUVmax were measured. Differences between benign and malignant lesions were evaluated for statistical significance, and cutoff values for these parameters were determined to maximize diagnostic accuracy. RESULTS. Among 56 participants, 13 patients (22.8%) had false-positive osseous 68 Ga-PSMA-11 findings and 43 patients (76.8%) had true-positive osseous 68 Ga-PSMA-11 findings. Twentytwo patients (39%) had 1 osseous lesion, 18 (32%) had 2-4 lesions, and 16 (29%) had 5 or more lesions. Cutoff values resulting in statistically significant (p<0.005) differences between benign and malignant lesions were: PSMA-RADS ≥4, SUVmax ≥4.1, SUVmax ratio of lesion to blood by on November 1, 2020. For personal use only. jnm.snmjournals.org Downloaded from pool ≥2.11, to liver ≥0.55, and to bone ≥4.4. These measurements corresponded to lesion-based 68 Ga-PSMA-11 PET lesion detection rate for malignancy of 80%, 93%, 89%, 21%, 89%, and a specificity of 73%, 73%, 73%, 93%, 60%, respectively. CONCLUSION. PSMA-RADS rating, SUVmax, and SUVmax ratio of lesion to blood pool can help differentiate benign from malignant lesions on 68 Ga-PSMA-11 PET. SUVmax ratio to blood pool above 2.2 is a reasonable parameter to support image interpretation and presented superior lesion detection rate and specificity when compared to visual interpretation by PSMA RADS. These parameters hold clinical value by improving diagnostic accuracy for metastatic prostate cancer on 68 Ga-PSMA-11 PET/MRI and PET/CT.

The significance of equivocal bone findings in staging PSMA imaging in the preoperative setting: validation of the PSMA-RADS version 1.0

“…Data on the significance of these indeterminate lesions on staging PSMA-targeted imaging are lacking. Several systems have been proposed to facilitate the interpretation of PSMA-targeted PET scans [30][31][32][33]. These systems allow for better communication between nuclear physicians and referring clinicians and offer a standardized classification scheme of equivocal findings to guide further management.…”

Single-Photon Emission Computed Tomography/Computed Tomography Image-Based Radiomics for Discriminating Vertebral Bone Metastases From Benign Bone Lesions in Patients With Tumors

“…In addition, their study also showed that SUVmax was related to bone disease progression. Le et al ( 27 ) showed that the differential of malignant bone metastases also achieved satisfactory diagnostic performance based on the factor of PSMA-RADS rating, SUVmax, and SUVmax ratio of the lesion to blood pool by 68Ga-PSMA-11 PET/CT image. In fact, SUVmax only reflects the metabolic information of the tumor within a single pixel in the image and cannot quantify the spatial heterogeneity of the overall metabolic distribution.…”

PET-CT in Clinical Adult Oncology—IV. Gynecologic and Genitourinary Malignancies

“…Two interpretative schemes that serve as models for structured reports have been proposed for diagnostic PSMA PET-CT, including a system proposed by a single institution (Johns Hopkins University) ( Table 7 ) [ 89 ] and a system used in the PROMISE trial ( Table 8 ) [ 90 ]. For [ 68 Ga]-PSMA identification of bone metastases, it has been additionally proposed that positive lesions be defined as having a lesion:normal tissue SUVmax ratio of 2.2 for blood pool and 4.1 for normal bone [ 91 ]. However, neither these indices nor the structured reporting classifications have been prospectively and independently validated in large series and, at this point, are best regarded as consensus recommendations.…”