Diagnostic Value of Circulating Free DNA Integrity and Global Methylation Status in Gall Bladder Carcinoma

The current study investigates the role of circulating free DNA (cfDNA) as a liquid biopsy in diagnosis gall bladder carcinoma (GBC) utilizing levels of long DNA fragments (ALU247) derived from tumor necrosis, short apoptotic fragments (ALU115) denoting total cfDNA and cfDNA integrity denoting ratio of ALU247 and ALU115. The global methylation status of cfDNA was also estimated with the hypothesis that these parameters provide a diagnostic distinction between cancer and non-cancer subjects, with higher or altered values favoring presence of malignancy. Study group included 60 cases of GBC and 36 controls including diseased controls (cholecystitis) and healthy subjects. Median levels of ALU115, ALU247 and cfDNA integrity were significantly different in GBC at 1790.88, 673.75, 0.4718 vs. controls at 840.73, 165.03, 0.1989 ng/ml respectively. Global DNA methylation was not significantly different between GBC at 0.679% and controls at 0.695%. The sensitivity and specificity of ALU 247 in discriminating GBC from controls was highest with a sensitivity, specificity and diagnostic accuracy of 80.0%, 86.1% and 82.2% respectively. Global DNA methylation showed lowest sensitivity of 55.0% and specificity of 50.0%. Clinico-pathological parameters showing significant association with cfDNA integrity, on ROC curve analysis, showed significant diagnostic discrimination of the tumor stage, lymphovascular invasion, disease stage and grade histology. This is a first time analysis of ALU115, ALU247 and cfDNA integrity in the diagnosis of GBC and confirms that the combination of ALU247 and cfDNA integrity provides good sensitivity, specificity and diagnostic accuracy in discriminating GBC from controls as well correlates with aggressive disease parameters.