Objective: This study sought to investigate the characteristics of bone metastasis (BM) and the association of BM with clinicopathological factors in prostate cancer (PCa) patients presenting with BM on the initial staging gallium-68-prostate-specific membrane antigen (68Ga-PSMA) positron emission tomography/computed tomography (PET/CT).
Materials and methods: Patients with at least one BM in the initial staging 68Ga-PSMA PET/CT between January 2018 and December 2021 were reviewed retrospectively. Types of BM were classified according to 68Ga-PSMA PET/CT findings as osteoblastic (OB), osteolytic (OL), intramedullary (IM) and coexistence of these types. Patients were divided into two groups according to the number of BM: Oligo-BM for those with five or fewer BMs and poly-BM for those with more than five BM. Receiver-operating characteristic (ROC) curves were generated for serum bone-specific alkaline phosphatase (ALP) and prostate-specific antigen (PSA) levels to discriminate between oligo-BM and poly-BM groups. Univariate and multivariate logistic regression tests were performed to find independent predictors of poly-BM.
Results: A total of 53 patients with a median age of 70 (range: 49-88) were included in the study. The median Gleason score of the patients was 8 (range: 6-10). Among the patients, 23 had solely OB-type; 10 had solely IM type; 12 had OB and IM type; four had IM and OL type, two had OB and OL type; one had solely OL type, and one had IM and OB and OL type BM. Oligo-BM was detected in 25 patients (47.2%) and poly-BM was detected in 28 patients (52.8%). In multivariate analyses, serum ALP levels ≥122U/L and PSA levels ≥85.4ng/mL were found to be independent predictors of poly-BM.
Conclusion: In characterizing BM of PCa, we found that OB-type metastases were the most common type, followed by IM-type and OL-type metastases, respectively. High ALP and PSA levels were found to be independent predictors of poly-BM.