Urinary calcium excretion in the monitoring of bone metastases from prostatic carcinoma

BACKGROUND. One of the greatest problems in treating advanced prostate carc inoma is monitoring the therapeutic response of bone metastases. As these m etastases are mainly osteosclerotic and lead to a markedly increased bone c alcium requirement that may give rise to an imbalance in calcium homeostasi s, the authors investigated whether changes in calcium balance may be usefu l for evaluating the response of bone metastases to treatment. METHODS. The study involved 268 prostate carcinoma patients: 142 in Stage A -C2 (International Union Against Cancer [UICC] staging system, 1998) and 12 6 with bone metastases who had failed to respond to hormone therapy and wer e receiving chemotherapy. Prostate-specific antigen (PSA), calcium and phos phate metabolism, and the main bone formation and resorption markers were a ll assayed before and after chemotherapy. RESULTS. Of the 126 patients on chemotherapy, 109 were evaluable for respon se: according to standard criteria, 25 (23%) had improved, 43 (39.5%) were unchanged, and 41 (37.5%) had worsened. All of the improved and 16 unchange d patients had decreased PSA and bone marker levels and an increased urinar y calcium/creatinine ratio (UCa/Cr); the worsened patients had increased PS A and bone marker levels, and their UCa/Cr decreased after only six treatme nt cycles. PSA and UCa/Cr were the biochemical markers whose changes showed the best agreement with treatment response. CONCLUSION, The UCa/Cr ratio was the most useful marker of clinical respons e, mainly because it allowed an early decision to continue or to stop chemo therapy. Furthermore, UCa/Cr and PSA together identified a percentage of pa tients classified as unchanged on the basis of standard criteria but whose condition had actually improved. (C) 2001 American Cancer Society.