Controlling The Quality Of Ras Mutation Testing By A Dichotomous Approach: Ring Trials And Benchmarking Mutation Frequencies By A Ras Monitor

536 Background: The PRIME study (Douillard et al. New Engl. J. Med. 2014) demonstrated that testing all coding exons of both KRAS and NRAS proto-oncogenes (all-RAS) predicted response for anti-EGFR targeting antibody panitumumab better than testing only KRAS exon 2 (PFS: 8.9 vs 9.6 mo, OS: 20.2 vs. 26 mo). Thus, the EMA changed the label of this drug for Europe. Now all RAS testing has to be done on a high quality level. Therefore, an improved quality assurance (QA) system was developed. Methods: The German RAS Advisory Board as part of QuIP (Quality initiative Pathology) launched ring-trials to assure quality of RAS mutation detection. 12 test cases of metastatic colorectal cancers (mCRC) containing WT or mutated sequences in one of the three coding exons 2 – 4 of either the KRAS or the NRAS oncogenes. Additionally many QA passed participants supplied the results of all-RAS testing of mCRC for one year resulting in a RAS monitor. Results: In less than half a year an area-wide coverage of quality certified all-RAS testing laboratories was reached. In three ring-trials 89 of 93 (96%) institutions for pathology passed the QA using Sanger-Sequencing (60%), pyrosequencing (25%) or the COBAS system (15%). None of the methods was superior to another as comparable amounts of methods passed or failed the ring trials. As only 12 cases were tested the result is reliable with a lower limit of confidence of only 0.7. Thus, a RAS monitor was introduced as an additional instrument of QA. Here, the results of almost 4000 cases of mCRC tested for all-RAS were collected indicating RAS mutations in 45.7% of investigated cases (KRAS: 41.5%, NRAS: 4.2%). Conclusions: Ring-trials are a versatile tool to establish a network of quality tested diagnostic laboratories in a short time. In parallel data sets for benchmarking the frequencies of RAS mutations were generated region specifically. Thereby quality was brought to a higher level than without the RAS monitor.