Use of long-term intravenous phosphate infusion in the palliative treatment of tumor-induced osteomalacia

Tumor-induced osteomalacia is characterized by paraneoplastic defects in vi tamin D metabolism, proximal renal tubular functions, and phosphate transpo rt. The resulting hypophosphatemia can cause generalized pain and muscle we akness, which significantly affect the quality of Life of the patients. Pal liative treatment with calcium, vitamin D, and phosphate replacement is ind icated for patients in whom the causative tumor cannot be completely resect ed. In this report we describe a case of tumor-induced osteomalacia in whom adequate oral doses of phosphate could not be used because of gastrointest inal side-effects. Long term (3-6 months) iv phosphate infusion delivered b y ambulatory infusion pumps in combination with oral calcium and vitamin D was used successfully to decrease pain and increase muscle strength. Carefu l monitoring of serum calcium, phosphate, and creatinine levels and reliabl e microinfusion technology have allowed the long term use of iv phosphate i nfusion without serious morbidity. This patient received repeated (three ti mes) phosphate infusions over 8 yr, resulting in laboratory and symptomatic improvement after each course. However, this patient did suffer two episod es of central Venous catheter-related infection. Because of potentially ser ious complications, such as severe hypocalcemia, calcified right Ventricula r thrombi, and nephrocalcinosis, long term iv phosphate infusion should be reserved for patients who cannot tolerate adequate doses of oral phosphate and for whom the benefits outweigh the risks.