Sclerosis of lytic metastatic bone lesions during treatment with pamidronate in a patient with adenocarcinoma of unknown primary site.

Pamidronate disodium is a second-generation biphosphonate, a group of compounds that are being used increasingly to inhibit bone resorption in disorders that are characterized by excessive bone loss such, as hypercalcemia of malignancy, osteoporosis, and Paget's disease. The precise mechanisms whereby bisphosphonates inhibit bone resorption are still not completely understood. Pamidronate has previously been reported to induce sclerosis of lytic bone metastases in patients with breast cancer. We have had a similar experience in a patient with multiple bone metastases due to adenocarcinoma of unknown primary site who developed massive consolidation of lytic bone lesions after therapeutic infusions of pamidronate, leading to a satisfactory quality of life.