Serum levels of procollagen type I carboxyterminal extension peptide in cancer patients with bone metastases.

Serum levels of procollagen type I carboxy-terminal extension peptide (PICP) reflect the synthesis of type I collagen. As PICP is produced by osteoblasts and is not incorporated into bone matrix, serum PICP levels have been suggested as a marker of bone formation. In 37 cancer patients (21 men and 16 women; age: 72.4 +/- 8.6 (mean +/- SD) years) with bone metastases and 23 women (age: 77.3 +/- 6.64 years) as controls, the following biochemical variables were measured: serum PICP, calcium (Ca), phosphorus, alkaline phosphatase (AP) and tartrate-resistant acid phosphatase (TRAP), and urinary hydroxyproline and calcium corrected for creatinine excretion. Higher serum levels of PICP were observed in cancer patients than in control (245 +/- 177 micrograms/l vs 121.7 +/- 36 micrograms/l, p < 0.01). Cancer patients also had higher AP levels than controls (704 +/- 755 U/l vs 216.5 +/- 56 U/l, p < 0.01). Abnormal PICP and AP serum concentrations (above the mean + 2SD of controls) were found in 46% and 51% of patients, respectively. Moreover, patients showed significantly lower serum calcium concentrations (p < 0.001), and higher TRAP and hydroxyproline levels although statistical significance was not reached. In the patients, PICP was correlated directly with AP (r = 0.50, p < 0.01) and TRAP (r = 0.34, p < 0.05). In conclusion, patients with bone metastases have increased bone turnover as shown by serum markers. Serum PICP may be used as an adjunctive, non-invasive index to assess bone metabolism. However, the clinical usefulness of PICP in cancer patients needs further evaluations.