Treatment of osteolytic myelomatosis with mithramycin.

The treatment of rapidly progressive skeletal demineralisation in myelomatosis has been studied with the help of metabolic calcium balance in two patients; In one, osteoporosis accelerated during treatment with melphalan and prednisolone, although he remained normocalcaemic throughout, suggesting that osteoporosis was aggravated by corticosteroid therapy. In the other patient, who was initially hypercalcaemic, conventional treatment produced clinical remission before eventual relapse with more hypercalcaemia and skeletal dissolution. Both patients were then treated with mithramycin alone, and, although neither obtained haematological remission, bone pain was relieved, hypercalciuria and hypercalcaemia were abolished, and calcium balances proved that mithramycin was effective in restoring calcium equilibrium. The results indicate that mithramycin may abolish excessive bone resorption in myelomatosis and that severe bone dissolution may occur in the absence of hypercalcaemia. Regular determination of 24-hour urinary calcium excretion as well as of plasma-calcium is important in monitoring process. Mithramycin should be considered in the early treatment not only of hypercalcaemia but also of severe hypercalciuria, if these complications do not rapidly remit during the first course of conventional myeloma therapy, with or without steroids. Finally, these results add to evidence that a humoral factor may be responsible for osteoclast stimulation in myelomatosis.