KRAS mutation testing of metastatic colorectal cancer in Australia: where are we at?

Aim: To carry out a nationwide study of KRAS testing in metastatic colorectal cancer as reported by nine major molecular pathology service providers in Australia, including mutation frequencies and turnaround times that might impact on patient care.

Methods: Participating laboratories contributed information on KRAS mutation frequencies, including the G13D mutation type, as well as turnaround times for tumor block retrieval and testing.

Results: The KRAS mutation frequency observed by nine different test sites for a total of 3688 metastatic colorectal cancers ranged from 34.4% to 40.7%, with an average across all sites of 38.8%. The average frequency of the G13D mutation type among all cases was 8.0%. The median turnaround time was 17 days (range 0-191), with 20% of cases requiring more than 4 weeks for a KRAS test result. The major contributor to long turnaround times was the time taken to retrieve archived blocks of primary tumor, particularly from sources external to the test site.

Conclusion: The frequency of KRAS mutations in metastatic colorectal cancer reported by the major Australian test sites is very similar to that reported by other large overseas studies. More widespread introduction of routine testing at the time of initial diagnosis should eliminate the long turnaround times currently being experienced in a significant proportion of cases. Future expansion of testing to include other KRAS and NRAS mutation hotspots may spur the introduction of next-generation sequencing platforms.