Type I collagen degradation product (ICTP) gives information about the nature of bone metastases and has prognostic value in prostate cancer

Although osteosclerotic bone metastases are characteristic of prostate cancer, mixed metastases with a lytic component are not uncommon. Type I collagen is synthesised by osteoblasts and accounts for about 90% of the organic matrix of bone. We have used new specific immunoassays for PICP (carboxy-terminal propeptide of type I procollagen) and ICTP (cross-linked carboxy-terminal telopeptide of type I collagen) which allow simultaneous assessment of the synthesis and degradation of type I collagen respectively. Forty patients with bone metastases due to prostate cancer at the time of diagnosis were investigated with these methods. Twenty-three of them had sclerotic (S) and 17 had mixed metastases with sclerotic and lytic components (S + L) as assessed by radiographs. The concentrations of PICP and ICTP in serum as well as the activity of alkaline phosphatase (AP) were increased in all patients of the S + L group, who had more aggressive bone disease and a shorter survival than the S group (P < 0.017). The ICTP level was above the reference range in half of the patients in the S group, whereas the PICP and AP levels were elevated in 35%. Of the bone markers, only ICTP was of prognostic significance (P < .05). We conclude that ICTP and PICP give information about the type and activity of the skeletal metastases. In addition, ICTP predicts prognosis.