Correlation Between Baseline Osteoprotegerin Serum Levels and Prognosis of Advanced-Stage Colorectal Cancer Patients

Abstract

Background/Aims: Osteoprotegerin (OPG) is a soluble receptor of the pro-apoptotic cytokine TRAIL which is thought to contribute to tumour development by inhibiting apoptosis or affecting other aspects of tumour biology, including cell proliferation and immune response. Although immunohistochemical studies suggest that OPG correlates with survival in metastatic colorectal cancer (mCRC), only scarce data are available on serum OPG in CRC patients. Methods: In this pilot study, we assessed the prognostic significance of serum OPG and CEA (Carcinoembryonic antigen) in 81 patients with UICC (Union for International Cancer Control) stage-IV mCRC. OPG was additionally assessed by immunohistochemistry in primary tissue samples from 33 patients of the same cohort. Results: Baseline serum OPG correlated with CEA (r=0.36, p=0.0011), but independently predicted survival of mCRC patients. Life expectancy was poorer in patients with OPG levels above the median concentration of 51ng/ml (median overall survival [95% confidence interval] 1.8 years [1.3-3.0] vs. 1.0 [0.7-1.2] p=0.013). Patients with high levels of both OPG and CEA had an even poorer life expectancy vs. low-OPG/low-CEA patients (0.9 years [0.6-1.5] vs. 3 years [1.2-4.4], p=0.015), indicating that CEA and OPG have additive prognostic significance. Immunohistochemical analysis of OPG failed to show a correlation between OPG staining and survival (p=0.055) or OPG concentration from matched serum samples. Conclusions: This pilot study provides evidence of independent prognostic significance of serum OPG in patients with advanced mCRC and warrants its further prospective validation.