Hypercalcemia in children with rhabdomyosarcoma

Purpose: Hypercalcemia complicating malignancy is a serious and frequent occurrence in adults but rare in children. The aim of this study was to determine the incidence, symptoms, outcome, and cause of hypercalcemia in children with rhabdomyosarcoma. Patients and Methods: Among 93 children with rhabdomyosarcoma, six with hypercalcemia were identified and their clinical course, pathologic findings, treatment, and outcome were evaluated. In addition, serum and intratumor parathyroid hormone-related protein (PTHrP) concentrations were measured to ascertain the potential of hypercalcemia. Results: All six patients with hypercalcemia had bone metastasis, and four with severe hypercalcemia had multiple bone metastases. Serum PTHrP levels were moderately elevated. There were no significant trends detected based on age, gender, primary site, and pathologic type. All patients achieved transient resolution of hypercalcemia after treatment. However, none survived for a long period of time because their original tumor eventually recurred. Conclusions: Hypercalcemia is not an uncommon complication in patients with rhabdomyosarcoma. Bone absorption seems to be the predominant factor that induces the hypercalcemia in in rhabdomyosarcoma. However, PTHrP may be a powerful stimulator of bone absorption, which contributes to the growth of bone metastasis.