KRAS mutation testing in colorectal cancer as an example of the pathologist’s role in personalized targeted therapy: a practical approach

Abstract

Identifying targets for personalized targeted therapy is the pathologist's domain and a treasure. For decades, pathologists have had to learn, understand, adopt and implement many new laboratory techniques as they arrived on the scene. Pathologists successfully integrate the results of those tests into final pathology reports that were, and still are, the basis of clinical therapeutic decisions. The molecular methods are different but no more difficult to comprehend in the era of "kit procedures". In recent years, the development of targeted therapies has influenced routine practices in pathology laboratories because the use of molecular techniques is required to include clinically useful predictive information in the pathology report. Pathologists have the knowledge and expertise to identify particular gene mutations using the appropriate molecular tests currently available. This review focuses on the most important recent developments in KRAS mutation testing in metastatic colorectal cancer (CRC), and shows that a pathologist is involved in 10 stages of this procedure. Recent studies have shown that highly sensitive, simple, reliable and rapid assays may significantly improve the identification of CRC patients resistant to anti-EGFR therapy. Thus, direct sequencing does not seem to be an optimal procedure of KRAS testing for clinical purposes. Twelve currently available high-sensitivity diagnostic assays (with the CE-IVD mark) for KRAS mutation testing are briefly described and compared. The suggested pathology report content for somatic mutation tests is described. In conclusion, evidence is presented that sending away paraffin blocks with tumor tissue for KRAS mutation testing may not be in the best interest of patients. Instead, an evidence-based approach indicates that KRAS mutation testing should be performed in pathology departments, only with the use of CE-IVD/FDA-approved KRAS tests, and with the obligatory, periodic participation in the KRAS EQA scheme organized by the European Society of Pathology as an independent international body.

Mutation of the PIK3CA gene as a prognostic factor in patients with colorectal cancer

“…It has been established that KRAS mutation is a marker of resistance to anti-EGFR therapy in patients with CRC (4,(18)(19)(20)(21). Despite the exclusion of patients with KRAS-mutant tumours, anti-EGFR treatment fails in numerous patients with CRC.…”

Blood circulating tumor DNA for non‐invasive genotyping of colon cancer patients

“…The assessment of the KRAS / NRAS mutational status of CRC is now commonly ascertained using formalin‐fixed paraffin embedded (FFPE) tissue (Domagała et al., 2012; Ma et al., 2009). Difficulties in accessing samples from resistant tumors are among the reasons that have so far impaired research on this topic.…”

Key differences between 13 KRAS mutation detection technologies and their relevance for clinical practice

“…11 Sanger capillary sequencing has long been the gold standard for DNA sequence analysis; however, it does not offer the high sensitivity required to detect somatic mutations at allelic frequencies less than ~20%. 12 Numerous comparisons of technology platforms for EGFR 13 14 and KRAS (mainly in CRC [15][16][17][18][19][20][21][22][23] ) mutation testing conclude that quantitative PCR (qPCR)-based methods offer the sensitivity, tissue economy and turnaround time required by physicians to guide treatment decisions. The advent of next-generation sequencing (NGS) platforms offers pathology laboratories an unparalleled insight into the cancer genome including de novo detection of variants as well as known actionable targets.…”