Surgical Treatments of Tumor-Induced Osteomalacia Lesions in Long Bones: Seventeen Cases with More Than One Year of Follow-up.

BACKGROUND

Tumor-induced osteomalacia is a rare and fascinating paraneoplastic syndrome usually caused by a small, benign phosphaturic mesenchymal tumor. Most tumors are treated surgically, but we are unaware of any reports that compare the results of curettage and segmental resection for lesions in long bones.

METHODS

Seventeen patients (ten male and seven female) with tumor-induced osteomalacia lesions in long bones, who underwent surgical treatment from December 2004 to August 2013 in our hospital, were included in this retrospective study. The mean follow-up (and standard deviation) was 35 ± 27 months (range, twelve to 116 months). The characteristics of the tumor and the effects of different surgical treatments (curettage compared with segmental resection) were evaluated.

RESULTS

All patients showed typical clinical characteristics of tumor-induced osteomalacia, including elevated serum fibroblast growth factor-23 (FGF-23); 82% of tumors were in the epiphysis, and 82% grew eccentrically. The mean maximum diameter of the tumors was 2.4 ± 2.0 cm. The complete resection rates were similar for curettage (67%) and segmental resection (80%). However, the recurrence rate after curettage (50%) was higher than that after segmental resection (0%). The complete resection rate for secondary segmental resection (75%) was not different from that for primary segmental resection (83%). All of our cases of tumor-induced osteomalacia were caused by phosphaturic mesenchymal tumors. After successful removal of tumors, serum FGF-23 returned to normal within twenty-four hours and serum phosphorus levels returned to normal at a mean of 6.5 ± 3.5 days.

CONCLUSIONS

Most lesions in long bones are located in the epiphysis, so curettage is first suggested to maintain joint function. If curettage is incomplete or there is a recurrence, secondary segmental resection should be considered curative. Changes of serum FGF-23 and phosphorus levels before and after the operation may be of prognostic help.