The article by Gucalp and colleagues,1 comparing rapid and slow intravenous infusion regimens of pamidronate in the treatment of malignancy-associated hypercalcemia, was interesting and informative. In this context, I would like to draw the authors' attention to some further data concerning this subject.
The authors took into account several laboratory parameters in the randomized groups of patients receiving either a 4- or 24-hour infusion of 60 mg of pamidronate. Two other parameters have, however, also been shown to affect the response of tumor-induced hypercalcemia to pamidronate. Gurney and associates2 showed that the concentration of parathyroid hormone-related protein is an important predictor of this response. An undetectable level of parathyroid hormone-related protein (<2 pmol/L) was associated with normalization of the serum calcium concentration in seven of seven patients, and the levels of 2 to 12 pmol/L were associated with a similar response in 10 of 14 patients, while the