Long-term Bone Mineral Density Changes After Surgical Cure of Patients with Tumor-induced Osteomalacia

Introduction: No systematic data are available regarding long-term bone mineral density (BMD) changes after surgical cure of patients with tumor-induced osteomalacia.

Methods: From October 2001 through April 2018, we studied 10 consecutive patients (mean age ± SD, 45.5 ± 13.8 years; 5 males and 5 females) with tumor-induced osteomalacia. We evaluated BMD when initially presented at our Center and after surgical removal of the tumor.

Results: Basal BMD and corresponding Z-score values (mean values ± SD) measured by DXA were as follows: L-L = 0.692 ± 0.15 g/cm, Z-score = - 2.80 ± 1.60; femur neck 0.447 ± 0.10 g/cm, Z-score = - 2.66 ± 0.93; total femur = 0.450 ± 0.08 g/cm, Z-score = -3.04 ± 0.85). Furthermore, Trabecular Bone Score (TBS) was evaluated in three patients (basal values, 0.990 ± 0.32). Seven patients were intermittently followed after surgical excision of the tumor while supplemented with cholecalciferol and calcium salts; the remaining three were lost to follow-up. There was a striking increase of BMD values that peaked at 26.7 ± 6.50 months: L-L = 1.289 ± 0.247 g/cm, p < 0.001, Z-score + 1.75 ± 1.42; femur neck = 0.890 ± 0.235 g/cm, p = 0.028, Z-score = + 0.50 ± 1.40; total femur = 0.834 ± 0.150 g/cm, p = 0.005, Z-score = - 0.74 ± 1.14. In patients with the greatest bone involvement at lumbar site, there was a striking increase of an average 1.5% (p < 0.01) in respect to baseline Z-score value for each additional month of observation during the first 2-3 years post-surgery. An improvement of trabecular microarchitecture was also documented (TBS, 1.255 ± 0.16).

Conclusion: This is the first case series documenting an impressive increase of BMD at both lumbar and femoral sites, together with an improvement of trabecular microarchitecture as documented by TBS. This is the consequence of huge mineralization of the large amount of osteoid tissue after resolution of the disease.