[Clinical usefulness of cross-linked N-telopeptide of type I collagen (NTx) as a bone metastatic marker in patients with prostate cancer--comparison with serum PICP, PINP and ICTP].

Type I collagen cross-linked N-telopeptide (NTx) in urine, the degraded form of type I collagen cross-linked in bone, has been evaluated as a marker of bone resorption. In this study, the clinical usefulness of NTx as a marker of bone metastasis of prostate cancer was compared with that the carboxyterminal propeptide of type I procollagen (PICP), the aminoterminal propeptide of type I procollagen (PINP), and the pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) in serum. We assessed 37 cases of prostatic cancer in which the diagnosis had been confirmed pathologically. The patients were 15 patients with prostatic cancer with bone metastasis (before treatment or during a relapse) (Group 1); 11 patients, with bone metastasis, but for whom treatment was effective and condition had stabilized (Group 2); and 11 patients, with localized prostatic cancer and no evidence of bone metastasis (Group 3). The serum PICP, PINP, and ICTP levels and concentration of NTx in urine were compared among the three groups with the Mann-Whitney U test, with p values less than 0.05 considered significant. Urine NTx concentrations in Groups 1, 2 and 3 were 539.3 +/- 202.9, 160.6 +/- 97.6 and 48.6 +/- 7.6 nMBCE/mMCr, respectively. The differences between the Group 1 and Group 2 and between Group 1 and Group 3 were significant (p < 0.01 and p < 0.001). The differences between Group 1 and Group 3 and between Group 2 and Group 3 were significant for serum PICP, PINP and ICTP concentrations (p < 0.05). The correlation coefficient between urine NTx and each serum bone metabolic marker was 0.8 for PICP, 0.4 for PINP and 0.5 for ICTP. These bone metabolic markers are promising clinical markers of bone metastatic and may be useful for prediction of therapeutic efficacy and recurrence in bone and quantification of the extent of bone metastates.