SERUM CONCENTRATIONS OF TYPE-I COLLAGEN CARBOXYTERMINAL TELOPEPTIDE (ICTP) AND TYPE-I PROCOLLAGEN CARBOXYTERMINAL AND AMINOTERMINAL PROPEPTIDES (PICP, PINP) AS MARKERS OF METASTATIC BONE-DISEASE IN BREAST-CANCER

The most abundant protein in bone is type I collagen. During type I co llagen formation two extension peptides from both ends of the procolla gen molecule, carboxy- and aminoterminal propeptides (PICP and PINP), are liberated in equimolar concentrations into the circulation. Type I collagen carboxyterminal telopeptide (ICTP) is formed during bone col lagen breakdown and is liberated into the circulation. Serum concentra tions of the propeptides reflect bone formation, and the concentration of the telopeptide, bone resorption. We evaluated the usefulness of t hese bone remodelling markers in diagnosing and monitoring metastatic bone disease in breast cancer patients. Serum concentrations of ICTP, PICP and PINP were measured and the PICP/PINP-ratio calculated in 25 p atients with bone metastases, 12 patients without metastases and their age matched healthy controls. S-ICTP and S-PINP were significantly hi gher in metastatic patients (p=0.0061 and 0.02 respectively), and the S-PICP/PINP-ratio lower (p=0.002) than in controls. S-PICP in metastat ic patients did not differ significantly from that of controls. ICTP v alues in patients without metastases also differed from those of contr ols (p=0.01). The clinical sensitivity for diagnosing metastatic bone disease was 56 % for the ICTP, 24 % for PICP, 30 % for PINP and 52 % f or PICP/PINP ratio. The clinical specifities were 93 %, 100 %, 98 % an d 91 % respectively. During follow-up the changes in the marker values were parallel to the behaviour of the disease. We conclude that these markers alone are not sensitive enough for diagnosis, but they seem t o be of use in detecting bone metastases and monitoring the activity o f bone disease.