Osteoprotegerin and osteopontin serum values in postmenopausal advanced breast cancer patients treated with anastrozole

Abstract

Osteoprotegerin (OPG) is a potent antiresorptive molecule that binds NF-kappaB ligand, the final effector for osteoclastogenesis. OPG production is regulated by a number of cytokines and hormones. Osteopontin (OPN) is a secreted adhesive glycoprotein involved in tumour angiogenesis, and also a non-collagenous protein involved in bone turnover. OPN serum value is associated with tumour burden and survival in advanced breast cancer patients. The short-term effects of anastrozole on OPG and OPN serum values, and the usefulness of these analytes during follow-up were studied in 34 consecutive advanced breast cancer patients receiving anastrozole 1 mg/day. Blood samples were taken before treatment and at 2, 4, 8 and 12 weeks. OPG and OPN values were measured by ELISA. The results were analysed for all patients, and also separately for patients with (group A, 22 patients) and without (group B, 12 patients) bone metastasis. Whether the survival of all patients was related to their OPN serum values was also tested by placing patients into three groups (terciles) according to their baseline OPN values. No significant changes in OPG and OPN values were observed in the complete patient group. There was no difference in baseline OPG and OPN serum values between patients in groups A and B. In group A, a significant percentage increase in both OPG and OPN values from baseline was detected during treatment. No significant changes were reported for group B patients. Furthermore, in group A, a significant increase in both analytes was evident only for patients with progressive disease (PD). The Kaplan–Meier adjusted survival estimates for patients grouped according to tercile OPN values differed significantly (P = 0.001, log rank test). In conclusion, in the short term, anastrozole does not seem to affect OPG and OPN serum values in patients without bone disease. OPG and OPN appear to be useful predictors of the outcome of skeletal disease and elevated OPN values may be associated with short survival in advanced breast cancer patients.