High incidence of hypocalcemia and serum creatinine increase in patients with bone metastases treated with zoledronic acid

Background. Zoledronic acid belongs to the new generationof bisphosphonates with demonstrated clinicalbenefit for the treatment of bone metastases from differentkinds of neoplasms. Hypocalcemia and serumcreatinine elevation are expected adverse events duringthis therapy. The monitoring of serum calcium and creatinine is therefore recommended. The primary aim of this study was to establish the actual incidence of hypocalcemia and serum creatinine elevation during treatment with zoledronic acid. Skeletal-related eventsand side effects were also assessed.Methods. Serum creatinine and calcium levels were evaluated in 240 consecutive patients (83 males, 157 females; mean age, 62 years) with metastatic bone lesionsfrom different solid tumors treated with zoledronicacid.Results. Overall, 93 of 240 patients (38.8%) developedhypocalcemia, which was grade (G)1 in 45 patients (48.4%), G2 in 37 patients (39.8%), G3 in 10 patients(10.8%), and G4 in one patient (1.1%). The median time to occurrence of hypocalcemia (any grade) was 2.3months after the beginning of the treatment (range,0–34.9 months).Increased serum creatinine was observed in 33 of 240patients (13.7%), of whom 19 had G1 (57.6%), 11 hadG2 (33.3%), and three had G3 (9.1%). The median timeto serum creatinine increase (for any grade) was 4.7months (range, 0–29.2 months).Conclusions. Our analysis shows a high incidence ofhypocalcemia and increased serum creatinine level duringtreatment with zoledronic acid. These resultsstrongly support the need for accurate monitoring ofplasma calcium and creatinine levels.