Safety and efficacy of bisphosphonates beyond 24 months in cancer patients

Purpose: Bisphosphonate therapy has decreased the risk of skeletal complica tions associated with osteolytic bone lesions in patients with breast cance r and multiple myeloma. The large prospective studies have used 21 to 24 mo nths of treatment. We studied the safety and efficacy of bisphosphonates in a subset of patients who received therapy for more than 24 months. patients and Methods: Patients who received bisphosphonates (pamidronate or zoledronic acid) were identified. Data on skeletal events and laboratory p arameters were gathered by chart review. Results: We studied 22 patients who received intravenous pamidronate or zol edronic acid for a duration of 3.6 years (range, 2.2 to 6.0 years), Prolong ed therapy wets well tolerated. No significant calcium, phosphorus, electro lyte, or WBC count abnormalities were encountered. There was ct clinically insignificant decrease in hemoglobin and platelet count and an increase in creatinine in these patients, The fracture rate beyond 2 years was no great er than during the first 2 years of: treatment. There were no stress fractu res of long bones with prolonged therapy. Conclusion: prolonged treatment with the potent bisphosphonates pamidronate and zoledronic acid seems to be well tolerated and should be studied in pr ospective, randomized studies to document prolonged skeletal efficacy. (C) 2001 by American Society of Clinical Oncology.