Comparison of the novel quantitative ARMS assay and an enriched PCR–ASO assay for K-rasmutations with conventional cytology on endobiliary brush cytology from 312 consecutive extrahepatic biliary stenoses

Abstract

Background: Extrahepatic biliary stenosis (EBS) has malignant and benign causes. Patients with EBS are at risk of having or developing malignancy. Accurate diagnostic tests for early detection and surveillance are needed. The sensitivity of biliary cytology for malignancy is low. K-ras mutation analysis on brush cytology is a valuable adjunct, but specificity is low. A quantitative test for K-ras mutations has been developed: the amplification refractory mutation system (ARMS). Aim: To assess the test characteristics and additional value of ARMS in diagnosing the cause of EBS. Methods: Brush samples from endoscopic retrograde cholangiopancreatography were collected from 312 patients with EBS. K-ras mutation analysis was performed using ARMS-allele specific amplification was coupled with real time fluorescent detection of PCR products. Results were compared with conventional cytology and K-ras mutation analysis using allele specific oligonucleotide (ASO) hybridisation, and evaluated in view of the final diagnosis. Results: The test characteristics of ARMS and ASO largely agreed. Sensitivity for detecting malignancy was 49% and 42%, specificity 93% and 88%, and positive predictive value (PPV) 96% and 91%, respectively. The sensitivity of ARMS and cytology combined was 71%, and PPV was 93%. The specificity of ARMS could be increased to 100% by setting limits for the false positives, but reduced sensitivity from 49% to 43%. Conclusions: ARMS can be considered supplementary to conventional cytology, and comparable to ASO in diagnosing malignant EBS. A specificity of 100% can be achieved with ARMS, which should be considered in the surveillance of patients at risk for pancreatic cancer.

Comparison of KRAS Mutation Analysis and FISH for Detecting Pancreatobiliary Tract Cancer in Cytology Specimens Collected During Endoscopic Retrograde Cholangiopancreatography

“…Previous reports suggest that KRAS mutation analysis can be used to detect cancer in pancreatobiliary tract brushings, 10,22 bile fluids, 9,23 and fine needle aspirates from pancreatic masses. 8,24 Comparisons of KRAS mutation analysis to conventional cytology have generally shown that KRAS mutation analysis increases sensitivity, but often at the expense of test specificity.…”

Molecular biomarkers: their increasing role in the diagnosis, characterization, and therapy guidance in pancreatic cancer

“…However, a sensitive assay has been developed that can quantify not just the presence but also the levels of mutant KRAS in blood and pancreatic juice, and it remains possible that this quantification of mutant KRAS levels could improve the diagnostic utility of KRAS as an end point in pancreatic cancer (13). In addition, the addition of KRAS mutation detection may improve the diagnostic accuracy of brush cytology done in extrahepatic biliary obstruction (14).…”

Review: Beyond KRAS: perspectives on new potential markers of intrinsic and acquired resistance to epidermal growth factor receptor inhibitors in metastatic colorectal cancer

“…Lièvre and colleagues [Lievre et al 2006] reported for the first time that KRAS codon 12 and 13 mutations predict resistance to cetuximab in a series of 30 mCRC patients. Last year, the same authors [Lievre et al 2008] [Simi et al 2008]; amplification refractory mutation system (ARMS) [Van Heek et al 2005], and new technologies such as pyrosequencing are under development [Ogino et al 2005].…”