Clinical usefulness of serum pyridinoline cross‐linked carboxyterminal telopeptide of type I collagen for diagnosis of bone metastases in patients with primary lung cancer

OBJECTIVE: Recently, various blood and urine markers of bone metabolism have been developed and applied to the diagnosis of bone metastases. However, the cut-off values for each parameter have not yet been completely defined. In this study, the usefulness of serum pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (I CTP) was assessed for detecting bone metastases from primary lung cancer and the most efficient cut-off value for I CTP based on the receiver operating characteristic curve was calculated. METHODOLOGY: Over a 1-year period, serum I CTP and serum alkaline phosphatase (ALP) were assayed for 87 primary lung cancer patients, including 21 bone metastases-positive cases at Nagoya Ekisaikai Hospital, Nagoya, Japan. RESULTS: I CTP was significantly higher in patients with bone metastases than in the group without bone metastases. In contrast, there was no significant difference in serum ALP between the two groups. The most efficient cut-off value for I CTP computed in this study was 6.4 ng/mL. This was higher than the recommended value (4.5 ng/mL) based on the data from the summated values obtained for lung cancer, breast cancer and prostate cancer, as well as the maximum value for healthy controls (4.9 ng/mL). CONCLUSION: These results suggest that measurement of serum I CTP is a useful test for diagnosing bone metastases from lung cancer. Each type of cancer has a different pattern of bone turnover at the site of bone metastases. Considering that lung cancer mainly metastasizes to bone in an osteolytic pattern, it is proposed to set a higher cut-off value for lung cancer patients than the currently recommended value.