Plasma osteopontin: associations with survival and metastasis to bone in men with hormone-refractory prostate carcinoma.

Background: Osteopontin (OPN) is a secreted glycoprotein that is detectable in human body fluids. Its increased expression has been found in many malignancies, and a stimulatory effect on human prostate carcinoma cells in vitro has been demonstrated. Plasma OPN levels have been associated with tumor burden and survival in patients with metastatic breast carcinoma. The authors explored these associations in men with hormone-refractory prostate carcinoma (HRPC).

Methods: Plasma samples from 100 men with HRPC were collected. OPN was measured using an antigen-capture enzyme-linked immunosorbent assay technique. Multivariable analyses were performed to identify predictors of OPN and survival.

Results: At the time of OPN sampling, the median patient age was 73 years (range, 50-86 years), and 92% of patients had metastases. The median plasma OPN level was 198.5 ng/mL (range, 15.0-2363.0 ng/mL), the median prostate specific antigen level was 67.8 microg/L (range, 0.1-7550.0 microg/L), and the median survival was 13.7 months. OPN plasma levels were higher in patients with versus patients without bone metastases (P = 0.024). Multivariable modeling demonstrated an independent association of the OPN level with alkaline phosphatase, hemoglobin, and creatinine levels. The log-transformed OPN level (hazard ratio [HR], 2.38; P < 0.0001), performance status (HR, 2.43; P = 0.007), and a history of prior radiotherapy for localized prostate carcinoma (HR, 0.48; P = 0.0229) were independent predictors of survival in a Cox multivariate model.

Conclusions: In this study, in men with established HRPC, the plasma OPN level was associated with the presence of metastases to bone and with other measures of tumor burden, and it was correlated independently and negatively with survival.