The potential role of osteoporosis in unspecific [18F]PSMA-1007 bone uptake

Aim: Unspecific bone uptake is one of the main limitations of PET imaging with some PSMA-targeting radiopharmaceuticals, especially with [18F]PSMA-1007. We explored the potential association between osteoporosis and the occurrence of unspecific [18F]PSMA-1007 bone uptake investigating markers which might correlate with bone mineral density. Materials and methods: We retrospectively analyzed treatment-naïve patients with a confirmed diagnosis of prostate adenocarcinoma who underwent staging [18F]PSMA-1007 positron emission tomography (PET). Qualitative image analysis was performed independently by three experienced nuclear medicine physicians. Patients were divided in two groups according to the presence/absence of unspecific bone uptake. Clinical information, blood count parameters (assessed within 3 months to the PET scan), body mass index (BMI), and bone density as estimated by computed tomography were collected. The Kruskal-Wallis and t-test were used to compare parameters. Results: We analyzed 77 patients: 29 of them (38%) had unspecific bone uptake at [18F]PSMA-1007 PET, most commonly in the pelvic bones (69%) and ribs (62%). We did not find any significant difference in clinical parameters in the two groups. In patients with unspecific bone uptake, white blood cell, and neutrophil counts were significantly higher; in the same group, we observed lower values of BMI and bone density, although not statistically different. Conclusions: We observed unspecific bone uptake on [18F]PSMA-1007 PET in more than 1/3 of patients. In this exploratory analysis, we found a significant correlation between blood count parameters and unspecific [18F]PSMA-1007 bone uptake. We may speculate that [18F]PSMA-1007 unspecific bone uptake could be associated with osteoporosis. This hypothesis needs to be further investigated in larger populations and exploring more specific markers of osteoporosis.