The present invention discloses the use of PSP-94 for treating a patient suffering from hypercalcemia of malignancy. Prostate secretory protein of 94 amino acids (PSP-94) is known to serve as prognostic marker in hormone-dependent prostate. In the current study the effect of PSP-94 on prostate cancer growth, metastases to the skeleton and hypercalcemia of malignancy was examined. A marked dose-dependent decrease in primary tumor volume was seen in experimental animals receiving PSP-94. Furthermore, while control animals routinely developed hypercalcemia due to PTHrP production, treatment with PSP-94 led to a near normalization of plasma calcium and a marked reduction in PTHrP production as determined by radioimmunoassay and immunohistochemistry. Results obtained demonstrate the ability of PSP-94 to be an effective treatment modality for prostate cancer. Furthermore, decrease in plasma PTHrP and calcium levels can serve as useful biochemical markers for monitoring the efficacy of this novel anti-tumor agent.