Abstract B18: Molecular cancer testing of KRAS and miR-21 from EUS-guided biopsies of pancreatic tissue: Utility of aspirates vs. cytology
Authors: Benesova Lucie , Halkova Tereza , Bunganic Bohus , Belsanova Barbora , Traboulsi Eva , Zavoral Miroslav , Minarik Marek 
Published: December 2016

Introduction: Currently, there is a lack of reliable markers useable in diagnosis and/or management of the pancreatic ductal adenocarcinoma (PDAC). Although detection of KRAS point mutations for the differential diagnosis and determination of miR-21 expression for diagnostic and prognostic purposes have been widely investigated with promising results, neither KRAS nor miR-21 testing have become routine in clinical practice so far. One of the reasons is that analysis of KRAS mutations and miRNA expression is mainly performed on resected pancreatic tissue the use of which is relevant only for a minority of PDAC patients undergoing of surgical treatment.

The present study describes development of a reliable methodology for analysis of KRAS mutations and miR-21 expression from samples acquired by endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB), applicable to all PDAC patients. Consequently, the success rates and clinical validity of KRAS mutation and miR-21 expression analysis in two common types of EUS-FNB samples, i.e. native aspirates and cytology specimens are compared.

Experimental: The study included 118 patients with a confirmed diagnosis of pancreatic ductal adenocarcinoma (PDAC). Each patient underwent EUS-FNB and the sample was divided into two parts, one part was stored in a stabilizing solution as native aspirate and the rest was processed into the cytology specimen. DNA/RNA was extracted and then analyzed for KRAS mutations and miR-21 expression. For both sample types, the yields of DNA/RNA and success rates for KRAS and miR-21 testing were compared along with evaluation of mutant cell fractions. Finally, confirmation of miR-21 prognostic role was tested by Kaplan-Meier analysis.

Data Summary: The overall amount of isolated DNA/RNA from native aspirates was significantly lower compared to the cytology specimens (147 ng vs. 642 ng for DNA, 10 ng vs 164 ng for RNA). The success rates for subsequent KRAS and miR-21 analysis was 100% for both sample types. The KRAS-mutant detection rates in native aspirates were 12% lower than in cytology specimens (78% vs. 90%). The average fraction of KRAS-mutant cells was lower in native aspirates (31%) compared to the cytology specimens (56%). The prognostic role of miR-21 in native aspirates did not reach statistical significance (p = 0.06), but was confirmed in cytology specimens (p = 0.02).

Conclusions: Although both types of EUS-FNB samples are suitable for DNA/RNA extraction and subsequent DNA mutation and miRNA expression analysis, reliable results with clinical validity were only obtained for cytological specimens. Native aspirates exhibit a low and undefined fraction of tumor cells leading to false interpretation of molecular testing results. EUS-FNB samples in the form of cytology specimens are a perspective source for the study of molecular markers in virtually all PDAC patients, including patients in inoperable stages.

Supported by Internal Grant Agency of the Czech Ministry of Health (IGA) grant No. NT 13638

Citation Format: Lucie Benesova, Tereza Halkova, Bohus Bunganic, Barbora Belsanova, Eva Traboulsi, Miroslav Zavoral, Marek Minarik.{Authors}. Molecular cancer testing of KRAS and miR-21 from EUS-guided biopsies of pancreatic tissue: Utility of aspirates vs. cytology. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B18.