Markers of type I collagen degradation and synthesis in the monitoring of treatment response in bone metastases from breast carcinoma

Thirty-six patients with bone metastases included in a trial of supportive calcitonin on the treatment response to systemic therapy were monitored by conventional radiography, conventional indicators of bone metabolism [alkaline phosphatase (AP), osteocalcin (gla), urinary hydroxyproline excretion (OHP), urinary calcium (uCa), serum calcium (sCa)] and collagen metabolites (ICTP, the pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen; PICP, the carboxy-terminal propeptide of type I procollagen; and PIIINP the amino-terminal propeptide of type III procollagen). All patients had been on the same systemic treatment for at least 3 months at the start of the trial. There was a positive correlation between the concentrations of ICTP and PICP at baseline (Spearman's rank-order correlation coefficient r(s)=0.62). Both ICTP and PICP showed statistically significant correlations to the other markers of bone metabolism (except sCa and uCa) as well as to the number of bone metastases on bone scans. Reduction in ICTP correlated significantly with the treatment response at three months (r(s)=-0.57) while PICP showed a borderline negative correlation to therapy response (r(s)=-0.37). Of all the biochemical parameters studied the changes in ICTP showed the best correlation with the treatment response. PICP and ICTP changes in patients with progressive disease differed significantly from those in patients with responding and stable metastases, whereas no difference was found between responders and stable patients.