Bone Impairment in a Large Cohort of Chinese Patients with Tumor-induced Osteomalacia Assessed by HR-pQCT and TBS.

Tumor-induced osteomalacia TIO is a rare paraneoplastic syndrome caused by excessive production of fibroblast growth factor 23 FGF23 by a tumor. Previous studies have revealed generalized mineralization defects and low areal bone mineral density aBMD in TIO. However, data on the bone microarchitecture in TIO are limited. In this study, we evaluated the microarchitecture in the peripheral distal radius and tibia and axial lumbar spine skeleton using high-resolution peripheral quantitative computed tomography HR-pQCT and trabecular bone score TBS and investigated related factors in a large cohort of Chinese patients with TIO. A total of 186 patients with TIO who had undergone dual-energy X-ray absorptiometry DXA or HR-pQCT scans were enrolled. Compared with age-, sex- and BMI-matched healthy controls, TIO patients n=113 had lower vBMD, damaged microstructure and reduced bone strength in the peripheral skeleton, especially at the tibia. The average TBS obtained from 173 patients was 1.15 ± 0.16. The proportion of patients with abnormal TBS <1.35 was higher than that with low L1-4 aBMD Z-score Z≤-2 43.9% vs. 89.6%, p < 0.001. Higher intact fibroblast growth factor 23 iFGF23, intact parathyroid hormone iPTH, alkaline phosphatase and β-isomerized C-terminal telopeptide of type I collagen β-CTx levels, more severe mobility impairment and a history of fracture were associated with poorer HR-pQCT parameters but not with lower TBS. However, greater height loss and longer disease duration were correlated with worse HR-pQCT parameters and TBS. Moreover, TBS was correlated with both trabecular and cortical HR-pQCT parameters in TIO. In conclusion, we revealed impaired bone microarchitecture in the axial and peripheral skeleton in a large cohort of Chinese TIO patients. HR-pQCT parameters and TBS showed promising advantages over aBMD for assessing bone impairment in patients with TIO. A longer follow-up period is needed to observe changes in bone microarchitecture after tumor resection.