ATP assay-guided chemosensitivity testing for gemcitabine with biopsy specimens obtained from unresectable pancreatic cancer using endoscopic ultrasonography-guided fine-needle aspiration

Objectives This study evaluates the feasibility of chemosensitivity testing by use of endoscopic ultrasonography-guided fine-needle aspiration (EUS-FNA) samples and determines the optimum cut-off value for gemcitabine. Methods Thirty-four consecutive patients with unresectable pancreatic cancer were enrolled. Chemosensitivity (treated/control ratio: T/C ratio) was calculated as the quantity of adenosine triphosphate for a tumor treated with gemcitabine as a percentage of that for the control. To identify the cut-off value sufficient to predict 180 days of progression-free survival (PFS), the receiver operating characteristic curve and the corresponding area under the curve (AUC) were calculated. Results The success of this assay was 88.2% (30/34); therefore, 30 patients were assessable and included in the population of analyzable patients.. The response was 6.7%. Median PFS was 96 days and median overall survival was 241 days, respectively. The cut-off value was determined as 74% (AUC, 0.745; p = 0.053; 95% CI 0.485–1.005). According to this cut-off value, we predicted 180 days PFS with a sensitivity and specificity of 71.4 and 91.3%, respectively. When patients were divided into two groups at T/C ratio 74%, a significant difference was found in PFS (median 77 vs. 205 days, p = 0.0036). Moreover, T/C ratio