M. H. Gerber1, D. Delitto1, B. DiVita1, S. Han1, R. M. Thomas1, J. Trevino1, S. J. Hughes1 1University Of Florida,Department Of Surgery,Gainesville, FL, USA
Introduction: Cytological analysis of fine needle aspiration (FNA) of pancreatic lesions fails to confirm pancreatic ductal adenocarcinoma (PDAC) in up to one third of patients. We discovered that a 4-analyte protein signature from tumor lysates distinguishes PDAC from other lesions including chronic pancreatitis, thus raising the notion protein signatures could prove superior to FNA cytological analysis in the diagnosis of PDAC. Here, we aim to translate this observation to the FNA biopsy platform.
Methods: At time of operation, a “virtual” FNA biopsy of various pancreatic pathologies was obtained using a 19-gauge needle with six passes through the intestinal wall into the region of interest. Biopsy samples were placed in various quantities of lysis buffer and protein concentrations of each sample determined. IL-6 concentrations (one of the informative analytes in the diagnostic protein signature) were determined for each FNA biopsy sample, with and without spiking of “contaminant” plasma.
Results: Samples were collected from 27 consecutive patients undergoing pancreatectomy (PDAC n = 18; normal n = 3; pancreatitis n = 6). Protein concentrations from FNA biopsy samples diluted in 150 ul of lysis buffer ranged from 1.8 – 260.8 mg/ml with a median of 17.1 mg/ml (Interquartile range (IQR): 11.5 – 32.6 mg/ml). IL-6 levels in the FNA samples ranged from 185 – 2941 pg/ml with a median of 486 pg/ml (IQR: 247 – 740 pg/ml). Plasma concentrations of IL-6 from the same patients ranged from 59 – 312 pg/ml with a median of 111 pg/ml (IQR: 65 – 203 pg/ml). When patient FNA samples were compared to plasma samples, FNA samples had IL-6 concentrations 3.1 to 14.9 times higher than the matched patient plasma concentration.
Conclusion: Pancreatic FNA biopsy produces adequate quantities of protein for multiple replications on a variety of protein assay platforms. Normalization of cytokine concentrations to total protein may be subject to blood/plasma contamination inherent to the FNA procedure; thus alternative normalization to a resident, soluble protein may be necessary. Soluble protein analysis of pancreatic FNA biopsy samples remains a realistic supplement to cytology in the diagnosis of PDAC.