Diagnostic value of bone-turnover metabolites in the diagnosis of bone metastases in patients with lung carcinoma

BACKGROUND. Several biochemical markers of bone formation and bone resorption have been developed recently. The authors evaluated the usefulness of new biomarkers, such as urinary deoxypyridinoline (D-PYD), serum pyridinoline cross-linked C-telopeptides of Type I collagen (1CTP), and urinary pyridinoline cross-linked N-telopeptides of Type I collagen (NTx), in the assessment of bone metastases in patients with lung carcinoma. METHODS. The serum concentrations of 1CTP and the urinary concentrations of D-PYD and NTx were measured in 100 lung carcinoma patients, of whom 20 patients had bone metastases and 80 patients did not. Receiver operating characteristic (ROC) curves were drawn for these markers to compare their usefulness in detecting bone metastases originating in lung carcinoma. RESULTS. Urinary concentrations of NTx in patients with bone metastases were significantly greater than in patients without bone metastases (147.1 ± 129.3 pmol bone collagen equivalents [BCE]/μmol Cr vs. 47.2 ± 29.9 pmol BCE/μmol Cr; P < 0.0001). Urinary concentrations of D-PYD in patients with bone metastases also were significantly greater than in patients without bone metastases (10.O ± 3.6 BCE/μmol Cr vs. 6.6 ± 2.2 pmol BCE/μmol Cr; P = 0.0001). No significant difference was observed in serum concentrations of 1CTP between patients with and without bone metastases. A moderate but significant correlation was seen between NTx and D-PYD (correlation coefficient [R] = 0.435; P < 0.0001) and between D-PYD and 1CTP (R = 0.525; P < 0.0001). NTx had a better ROC curve than D-PYD and 1CTP (the areas under the ROC curve were 0.84, 0.79, and 0.62, respectively). Using the threshold of 62.5 pmol BCE/μmol Cr for NTx, sensitivity, specificity, and accuracy were 0.800, 0.737, and 0.750, respectively. CONCLUSIONS. In the current study, the measurement of NTx appeared to be most useful as a marker of bone metastases in patients with lung carcinoma.