Elevated serum M-CSF level predicts reduced survival in metastatic breast cancer patients

Abstract

10591 Background: Macrophage colony stimulating factor (M-CSF) and its receptor (CSF-1R, the c-fms oncogene protein product) have been reported to be expressed in a variety of cancers, including breast cancer. The M-CSF produced by breast cancer cells and surrounding stromal cells increases osteoclast formation and maturation and enhances the expression of stromal RANK ligand, both of which increase osteolytic bone degradation. In this study we evaluated the predictive and prognostic potential of circulating M-CSF in metastatic breast cancer patients treated with hormone therapy. Methods: Using an M-CSF ELISA (R&D Systems, Minneapolis, MN), M-CSF concentration was determined in pretreatment sera from 204 metastatic breast cancer patients enrolled in a phase III 2nd-line hormone therapy trial of fadrozole vs. megace, and also in sera from 25 post-menopausal control female subjects. Results: The serum M-CSF level from the 25 healthy post-menopausal female control subjects had a mean ± SD of 835.6 ± 276.1 pg/ml (range 319.0 - 1,465.8 pg/ml). The upper limit of normal was defined as the 95th percentile of the serum M-CSF level from the female control group (1277 pg/ml). Pretreatment serum M-CSF levels from the metastatic breast cancer patients ranged from 82.2 - 3,019.8 pg/ml, and were found elevated above the upper limit of normal in 15 of 204 patients (7.35 %). Patients with elevated pretreatment serum M- CSF did not have a significantly different objective response rate, clinical benefit rate, or time to progression to hormone therapy; but these patients did have significantly reduced overall survival (median survival 10.0 months) compared to patients with normal serum M-CSF levels (median survival 24.3 months)(p = 0.007). In multivariate analysis with serum HER-2/neu included as a covariate, elevated serum M-CSF level remained a significant independent variable for reduced survival (p= 0.032). Conclusions: Pretreatment serum M-CSF levels were elevated in 7 % of metastatic breast cancer patients compared to healthy female control subjects, and these patients had significantly reduced overall survival. Serum M-CSF deserves further study to determine its predictive and prognostic biomarker potential in breast cancer patients. No significant financial relationships to disclose.