Osteopontin is a useful predictor of bone metastasis and survival in patients with locally advanced nasopharyngeal carcinoma

Bone is the most common metastatic site in nasopharyngeal carcinoma (NPC). Osteopontin (OPN) and bone sialoprotein (BSP) are demonstrated to be involved in multiple steps of distant metastasis and correlate with bone metastasis (BM) in cancers. We aim to explore the impacts of OPN and BSP on the prognosis of the patients with locally advanced NPC. A tissue microarray including 162 locally advanced NPC specimens was generated for immunohistochemical evaluation. All of the patients received curative treatment. Twenty-two patients developed BM during follow-up. The OPN expression level was higher in patients with BM than in those without BM (p = 0.005), whereas no significant difference of the BSP expression level was noted (p = 0.634). Univariate analysis demonstrated that a higher level of OPN expression associated with a poorer 8-year metastasis-free survival (MFS) rate (p < 0.001), 8-year bone metastasis-free survival (BMFS) rate (93.6 vs. 87.5 vs. 64.5% for immunoreactivity score 1, 2 and 3, respectively; p = 0.001) and median overall survival (OS) time (p < 0.001). Multivariate Cox analysis confirmed that high level of OPN expression was independent factor associated with decreased BMFS (p = 0.02), MFS (p < 0.001) and OS (p < 0.001). Our findings indicate that OPN is a prognostic biomarker for BM and survival in patients with locally advanced NPC, and therefore it is useful in identifying the patients with an increased risk of cancer progression and BM to guide tailored therapy.