Usefulness of serum carboxy-terminal telopeptide of type I collagen (ICTP) as a marker of bone metastasis from lung cancer

Background: Serum pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen (ICTP) is a metabolite of type I collagen comprising 90% or more of organic substances in bone. Its usefulness as a marker of bone metastasis from malignant tumors is expected. Method: We measured ICTP to evaluate its clinical usefulness for diagnosis of bone metastasis in 140 patients with lung cancer. For comparison, serum carcinoembryonic antigen (CEA), cytokeratin 19 fragment (CYFRA 21-1), gastrin-releasing peptide precursor (ProGRP), alkaline phosphatase and calcium were simultaneously measured. ICTP was measured by double-antibody radioimmunoassay. Results: ICTP was significantly higher in patients with bone metastasis from lung cancer than in the group without bone metastasis, patients with other pulmonary diseases or healthy control subjects and showed excellent sensitivity and specificity, indicating that this marker is highly useful for complementary diagnosis of bone metastasis from lung cancer. Moreover, the survival duration was significantly shorter in the ICTP-positive group than in the ICTP-negative group, suggesting that ICTP can be a prognostic factor in lung cancer. Conclusion: it is suggested that measurement of ICTP is worthwhile as a serological diagnostic method of bone metastasis from lung cancer. Moreover, since repeated measurements are possible, this measure was considered very helpful in complementary diagnosis of bone metastasis and also as a standard to determine the timing of examinations such as bone scintigraphy.