P-0198 - KRAS mutations in colorectal cancer patients in Serbia: 5 years experience of central testing

Date 28 June 2014
Event World GI 2014
Session Poster Session
Topics Biomarkers
Colon Cancer
Rectal Cancer
Presenter Radmila Jankovic
Citation Annals of Oncology (2014) 25 (suppl_2): ii14-ii104. 10.1093/annonc/mdu165
Authors R. Jankovic, K. Brotto, E. Malisic, A. Krivokuca, M. Cavic, K. Jovanovic, I. Boljevic, M. Tanic, S. Radulovic
  • Institute for Oncology and Radiology of Serbia, Belgrade/RS

Abstract

Introduction

The number of newly diagnosed patients with colorectal cancer (CRC) in Serbia is increasing: from year 1999 when 2893 new CRC cases were diagnosed up to 4180 in 2010. With the appearance of two anti epidermal growth factor receptor (EGFR) targeted antibodies, cetuximab and panitumumab, the era of personalized treatment of metastatic CRC has begun. Mutations of the KRAS gene occur in approximately 35%-45% of colorectal cancers, and about 90% of these mutations are located in codons 12 and 13. Clinical trials have shown that only CRC with wild type (wt) KRAS gene will respond to anti EGFR treatment, whereas no response is observed in CRC with KRAS mutation. Following the approval of cetuximab for wt KRAS CRC patients in 2007, KRAS mutation testing became a part of routine clinical practice in Serbia since 2008. In 2010, Laboratory passed external quality assessment, conducted by QuIP (Quality Initiative in Pathology).

Methods

From April 2008 to December 2013, 1292 patients with CRC were tested for presence of KRAS mutations. Formalin-fixed and paraffin-embedded (FFPE) tumor samples from various centers were referred to Laboratory for molecular genetics as central one in Serbia. In 1198 tumor samples, DNA extraction was done by QIAamp®DNA FFPE Tissue kit, whereas in 94 samples DNA was isolated by cobas DNA Isolation kit. The presence of KRAS mutations was analyzed with TheraScreen° KRAS Mutation kit in 901 samples, KRAS StripAssayTM in 194 samples, Therascreen® KRAS RGQ PCR Kit in 103 samples and cobas® KRAS Mutation Test in 94 samples.

Results

Of all samples investigated, 543 (42.0%) had KRAS mutations and 749 (58.0%) showed wt KRAS status. The group comprised of 841 (65.1%) men and 451 (34.9%) women. The overall mutation frequency was 42.7% in men and 41.3% in women. The seven most frequent mutations in 1198 patients tested for the presence of mutations in codons 12 and 13, were G12D (41.5%), G12V (20.0%), G12A (8.0%), G12C (7,9%), G12S (4.7%), G12R (2.4%) and G13D (15.5%). In the group of 94 patients, analyzed with cobas® KRAS Mutation Test, it was possible to distinguish only mutations in codons 12/13 from mutations in codon 61. 93.6% of patients had mutations in codons 12/13 and 6.4% showed mutations in codon 61. KRAS testing turnover time was approximately 7 days.

Conclusion

KRAS mutation testing was successfully implemented in routine management of patients with colon cancer. Having one central laboratory was proven to be a good choice for a small country as Serbia. Our experience on large group of patients showed that use of commercial Real-Time based diagnostic kits has significantly improved reliability and sensitivity of analysis, and in the same time has shortened testing turnover time. It should be mandatory to include analysis of mutations in codons 61 and 146 in order to select the group of patients that would benefit most from specific treatment. External quality assessment for KRAS testing is needed.