E3357. The Role of PSMA PET/CT in Distinguishing Malignant from Benign Solitary Bone Lesions in Patients With Prostate Cancer
Authors
Nadia Shah;
Massachusetts General Hospital, Harvard Medical School
Ashkan Eighaei Sedeh;
Massachusetts General Hospital, Harvard Medical School
Caitlin Deffler;
Massachusetts General Hospital, Harvard Medical School
Umar Mahmood;
Massachusetts General Hospital, Harvard Medical School
Pedram Heidari;
Massachusetts General Hospital, Harvard Medical School
Shadi Esfahani;
Massachusetts General Hospital, Harvard Medical School
Objective:
A solitary bone lesion (SBL) is very commonly detected in patients with prostate cancer (Pca). Both benign and malignant SBLs have been reported to demonstrate uptake on PSMA PET/CT scans. Depending on their nature, SBLs can serve as a challenge to physicians and may impact clinical management decisions. The aim of this study is to evaluate the diagnostic ability of PSMA PET/CT in detecting and differentiating between benign and malignant SBLs in correlation with other standard imaging and clinical features.
Materials and Methods:
The reports of <sup>18</sup>F-DCFPyL and <sup>68</sup>Ga-PSMA-11 PSMA PET/CT scans of 1480 Pca patients with Pca between September 2021 and February 2023 were retrospectively reviewed for the presence of SBLs. SBLs were then classified as either benign, malignant, or indeterminate based on imaging report interpretation at the time of the PSMA PET/CT scan. Data on patient demographics and characteristics of the SBL such as location, standardized uptake value (SUVmax), and presence of other sites of metastasis were reported. Patients with SBLs that were classified as indeterminate at the time of the scan were followed up by reviewing medical records and reclassified as benign or malignant using concurrent or follow-up imaging findings within 6 months of the initial PSMA PET/CT scan, biopsy, treatment, and/or trend of PSA. The SBLs that had insufficient follow-up information remained indeterminate.
Results:
From preliminary data analysis, a total of 208 out of 1480 PSMA PET/CT scan reports (14.26%) indicated an SBL. Based on imaging report interpretation, 106/208 (50.96%) SBLs were classified as malignant, 56/208 (26.92%) SBLs were classified as benign, and 46/208 (22.12%) SBLs were classified as indeterminate. Upon follow-up of the indeterminate SBLs, 4/46 (8.7%) were classified as malignant, 20/46 (43.48%) were classified as benign, and 22/46 (47.83%) remained indeterminate. Although the majority of malignant SBLs were located in the pelvis, (37/106, 34.91%), most of the benign SBLs were in the rib (31/56, 55.36%), revealing a statistically significant difference between the location of SBLs (P < 0.001). Moreover, the SUVmax of malignant SBLs was significantly higher than those of benign SBLs (mean SUVmax: 8.82 ± 9.2, vs. mean SUVmax: 2.54 ± 1.54, P < 0.001). 60/106 (56.6%) of the malignant SBLs had other sites of metastasis present at the time of the PSMA PET/CT scan, while 28/56 (50%) of the benign SBLs had other sites of metastasis present. Of the indeterminate SBLs, the most common location was the rib (19/46, 41.30%), the mean SUVmax was 2.72 ± 2.2, and 20/46 (43.48%) had other metastases present.
Conclusion:
The distribution of SBL locations, as well as differences in SUVmax on PSMA PET/CT and the presence of other sites of metastasis, are the most important factors to consider in distinguishing malignant from benign SBLs. Given the significant impact on the clinical care of patients with Pca, SBLs should be evaluated with caution and in correlation with other factors.
