| Summary: | <p>Abstract</p> <p>Background</p> <p>MicroRNA-126 is the only microRNA (miRNA) known to be endothelial cell-specific influencing angiogenesis in several ways. The aim of the present study was to analyse the possible predictive value of miRNA-126 in relation to first line capecitabine and oxaliplatin (XELOX) in patients with metastatic colorectal cancer (mCRC).</p> <p>Methods</p> <p>The study included 89 patients with mCRC. <it>In situ </it>hybridization (ISH) was performed to detect miRNA-126 in formalin-fixed paraffin embedded tissue from primary tumours. The expression of miRNA-126, area per image (μm<sup>2</sup>), was measured using image analysis. Clinical response was evaluated according to RECIST. Progression free survival (PFS) was compared using the Kaplan-Meier method and the log rank test. Tumours were classified as low or high miRNA-126 expressing tumours using the median value from the patients with response as cut-off.</p> <p>Results</p> <p>The median miRNA-126 expression level was significantly higher in patients responding to XELOX, 3629 μm<sup>2 </sup>(95% CI, 2566-4846), compared to the patients not responding, 1670 μm<sup>2 </sup>(95% CI, 1436-2041), <it>p </it>< 0.0001. The positive predictive value was 90%, and the negative predictive value was 71%. The median PFS of patients with high expressing tumours was 11.5 months (95% CI, 9.0-12.7 months) compared to 6.0 months (95% CI, 4.8-6.9 months) for patients with low expressing tumours, <it>p </it>< 0.0001.</p> <p>Conclusions</p> <p>Angiogenesis quantified by ISH of miRNA-126 was related to response to first line XELOX in patients with mCRC, translating to a significant difference in PFS. The predictive value of miRNA-126 remains to be further elucidated in prospective studies.</p>
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