A study presented at ESMO World Congress on Gastrointestinal Cancer 2015 (1-4 July, Barcelona, Spain) evaluated the implementation of RAS-testing methods and variation in testing practice in Europe and estimated the RAS mutation prevalence in patients with metastatic colorectal cancer (mCRC). The study authors showed that implementation of full RAS-testing in Europe is 73%. Further observational studies will be able to clarify whether RAS-testing will be implemented to a higher level over the next few years.
The indication for anti-epithelial growth factor therapy in Europe is mCRC patients with wild-type RAS mutations. This requires prior testing for hot-spot mutations in KRAS exon 2 (codons 12 and 13) KRAS exon 3 and 4, and NRAS exon 2, 3 and 4. However, detection of RAS mutations may vary by testing method due to differences in sensitivity and specificity.
A total of 194 pathology laboratories in 26 European countries, which had previously participated in European Quality Assurance schemes, were invited to complete an online survey between October and December 2014. Survey results were collected in an anonymized and blinded fashion.
Each participating centre was asked to provide information on their RAS testing methods and aggregated RAS mutation data on approximately 20-30 of the most recent tested mCRC patients.
In total 96 pathology laboratories from 24 countries completed the survey; response rate was 49.5%. Most pathology laboratories (72%) test more than 80 mCRC patients per year for RAS mutation status. Routine testing of all mCRC patients for RAS mutations was only performed in 5% of laboratories. Most laboratories perform testing in their own institute (94%) on request by the treating oncologist (89%).
The turn-around time between the laboratory receiving the request and reporting the result back to the oncologist was 10 working days or less for most laboratories (89%). Only 9% of laboratories reported a turnaround time of more than 10 working days which was partly due to RAS-testing carried out external to the hospital. Turn-around time was unknown for the remaining 2% of laboratories.
The implementation of RAS testing for hot-spot mutations in KRAS exon 2 was 100% and 73% of laboratories test for all hot-spot RAS mutations.
Five DNA extraction methods were mainly used by the laboratories with the QIAamp DNA FFPE kit from Qiagen being the most common method (42%). Subsequent testing of the DNA was performed equally with commercially available kits and PCR+-sequencing methods. Dideoxy sequencing of the PCR-product was most frequently used (30%), followed by the commercially available Therascreen KRAS/NRAS pyro kit (15%). A next generation sequencing method was used by 10% of laboratories.
Aggregate data from 3,972 CRC patients were included in the survey results, the majority of which were mCRC. The overall RAS mutation prevalence was estimated as 46%. The crude prevalence estimates varied by country (p<0.001), DNA extraction method (p<0.001) and proportion of tumour cells tested below or above 10% (p<0.001). RAS-mutation prevalence was lower in laboratories that only tested for some of the RAS hot-spot mutations (40.3% vs. 48.5%).
This review of RAS-testing practices and variation in RAS-mutation prevalence in Europe showed that implementation of full RAS-testing in Europe is high.
Boleij A, Tembuyser L, Taylor A, et al. A survey on current RAS-mutation testing practices in Europe. Annals of Oncology 2015;26(4):Pp.iv105.