The course of the urinary DPD-crosslink secretion in metastatic breast cancer - A possibility for response assessment

Background: Urinary deoxypyridinoline (DPD)-crosslinks have been shown to b e a highly specific parameter for type I collagen metabolism. Materials and methods: In a prospective breast cancer study, urine samples were collecte d in after-care patients and in patients with bone metastases. DPD-crosslin ks were measured every three weeks using a fully automated chemiluminescenc e immunoassay. Bone metastases were confirmed by bone scan and/or x-ray, an d were followed-up over six months. To validate the test, a receiver operat ing characteristics (ROC)-curve was set up to find the DPD cut-off concentr ation which separates patients with no evidence of disease (NED) from patie nts with bone metastases. Results: 73 breast cancer patients (41 with NED, 32 with bone metastases) were included into the ROC analysis. At a DPD cut- off value of 8 nmol/mmol creatinine, we found the best sensitivity (84.4%) for the detection of bone metastases with a specificity of 70.7%. Patients with stable bone disease under intravenous pamidronate treatment (90 mg q3w ) and specific therapy had a significant (p = 0.007) fall of the DPD-crossl inks in comparison to the progressive subset with 72.7% falling below 8 nmo l/mmol. Conclusions: We conclude that the net bone turnover is not increase d at a DPD-crosslinks elimination < 8 nmol/mmol.