C-11 Choline PET/CT in Paget’s Disease: Qualitative and Quantitative Appearance with Scintigraphic, Conventional Imaging, and Laboratory Correlation

1758 Objectives To investigate the qualitative and semi-quantitative appearance of Paget’s disease on C-11 choline PET/CT and to correlate these findings with serum alkaline phosphatase level and uptake on bone scan. Methods With IRB approval, our institutional C-11 choline PET/CT database between 9/2005 and 6/2015 was cross-referenced to the electronic medical record for patients with Paget’s disease. The diagnosis of Paget’s disease was established by characteristic CT features and/or stability over time. Site of osseous involvement, appearance on non-contrast, low-dose CT attenuation images, and semi-quantitative measures such as lesion SUVmax, liver SUVmax and SUVmean, and blood pool (BP) SUVmax and SUVmean were noted. C-11 choline PET/CT findings were correlated with serum alkaline phosphatase level and degree of uptake on bone scan (mild, moderate, marked). Results Our search identified 10 patients [all male, mean age 79.6-years +/- 7.8 years (SD)]. Four patients had polyostotic disease; including one patient with six sites of involvement, one with four sites, and two patients with two sites. There were a total of 20 bones involved by Paget’s disease including the innominate bone, sacrum, humerus, femur, scapula, and T1, T6, T12, L2, L3, and L5 vertebral bodies. Seven patients had more than one C-11 choline PET/CT. In total, 58 affected bones were evaluated on 25 C-11 choline PET/CT examinations. Bone scan and serum alkaline phosphatase levels were each available in 9 out of 10 patients. In total, 29 affected/involved bones evaluated by C-11 choline PET/CT had an alkaline phosphatase within 3 months of the exam. The mean lesion SUVmax was 2.6 +/- 0.89 (range 1.0 - 4.4), SUVmax/Liver SUVmean was 0.33 +/- 0.13 (range 0.12 - 0.61), SUVmax/Liver SUVmax was 0.29 +/- 0.11 (range 0.10 - 0.52), SUVmax/BP SUVmean was 2.47 +/- 0.86 (range 0.91 - 4.22), and SUVmax/BP SUVmax was 1.92 +/- 0.71 (range 0.68 - 3.45). There was no significant correlation between serum alkaline phosphatase and lesion SUVmax (r = 0.09), SUVmax/Liver SUVmean (r = -0.10), SUVmax/Liver SUVmax (r = -0.05), SUVmax/BP SUVmean (r = 0.07), and SUVmax/BP SUVmax (r = 0.14). All affected bones had typical appearance on CT attenuation-correction images characterized by cortical thickening, trabecular coarsening, fat attenuation of internal bone marrow, and whole bone involvement. Bone scan uptake was marked in 41 affected bones, moderate in nine bones, and mild in six. There was no significant correlation between lesion SUVmax and degree of uptake on bone scan (p = 0.26). Conclusions Paget’s disease on C-11 choline PET/CT demonstrates mild to moderate choline activity, which does not correlate to the degree of bone scan uptake or serum alkaline phosphatase levels. Given the known variable choline activity of osseous prostate cancer metastases, especially in the context of systemic chemohormonal therapy and/or radiation therapy, it is important to be aware of Paget’s disease as a potential pitfall. However, the characteristic appearance of Paget’s disease on low-dose CT attenuation correction images should allow confident differentiation from prostate cancer osseous metastases.