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Abstract

We thank Melzer et al for their constructive comments regarding our article “Clinical impact of K-ras mutation analysis in EUS-guided FNA specimens from pancreatic masses”1Ogura T. Yamao K. Sawaki A. et al.Clinical impact of K-ras mutation analysis in EUS-guided FNA specimens from pancreatic masses.Gastrointest Endosc. 2012; 75: 769-774Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar and welcome the opportunity to respond. We agree that K-ras mutation analysis in serum samples has some utility in the differential diagnosis of pancreatic ductal adenocarcinoma (PDAC), as they have reported. However, the incidence of mutant K-ras in PDAC in their study was 70%, which is not particularly high, and the subject population was limited to 20 patients, which is insufficient to determine the utility of the test.2Theodor L. Melzer E. Sologov M. et al.Detection of pancreatic carcinoma: diagnostic value of K-ras mutation in circulating DNA from serum.Dig Dis Sci. 1999; 44: 2014-2019Crossref PubMed Scopus (36) Google Scholar A similar study reported an absence of mutations in only 6.9% of cases3Zambon C. Navaglia F. Basso D. et al.ME-PCR for the identification of mutated K-ras in serum and bile of pancreatic cancer patients: an unsatisfactory technique for clinical applications.Clin Chim Acta. 2000; 302: 35-48Crossref PubMed Scopus (13) Google Scholar; thus, sensitivity is an issue in K-ras mutation analysis in serum samples. Conversely, K-ras mutation analysis using EUS-FNA specimens is possible with only a small sample volume, eliminating the need for additional punctures for the purpose of this analysis alone. Additional use of cycleave polymerase chain reaction method during analysis leads to an excellent sensitivity of 89%, procedural errors are unlikely, and reliable results can be achieved. Furthermore, our analysis method is similar to analysis of serum samples with regard to procedural ease and time. The utility of K-ras mutation analysis in serum samples is also reported for other carcinomas, such as colorectal4Salbe C. Trevisiol C. Ferruzzi E. et al.Molecular detection of codon 12 K-RAS mutations in circulating DNA from serum of colorectal cancer patients.Int J Biol Markers. 2000; 15: 300-307PubMed Google Scholar and lung cancers.5Kovalchuk O. Naumnik W. Serwicka A. et al.K-ras codon 12 mutations may be detected in serum of patients suffering from adeno- and large cell lung carcinoma: a preliminary report.Folia Histochem Cytobiol. 2001; 39: 70-72PubMed Google Scholar Therefore, detection of K-ras mutations in serum samples from patients with some extrapancreatic carcinomas may lead to a false-positive diagnosis of concomitant PDAC. Therefore, we believe that because of higher sensitivity and the absence of false-positive results, K-ras mutation analyses conducted on EUS-FNA specimens obtained directly from the tumor are superior for the diagnosis of PDAC. Clinical impact of K-ras mutation analysis in EUS-guided FNA specimens from pancreatic massesGastrointestinal EndoscopyVol. 76Issue 3PreviewIn their article “Clinical impact of K-ras mutation analysis in EUS-guided FNA specimens from pancreatic masses,” Ogura et al1 report the findings of their investigation of the clinical impact of K-ras mutation analysis in EUS-FNA specimens from pancreatic masses. Full-Text PDF