Metastatic Colorectal Cancer
One of the major advances in the treatment of CRC has been the development of targeted therapies including monoclonal antibodies in metastatic CRC which target the EGFR protein.
Data derived from multiple phase III trials have indicated that KRAS mutations can be considered a highly specific negative biomarker of benefit to anti-EGFR monoclonal antibodies.
Marc Ladanyi, MD
We can offer targeted testing of KRAS, NRAS and BRAF by Next Generation Sequencing which screens for specific reported mutations within codons 12, 13, 59, 61, 117 and 146 of the KRAS gene, codons 12, 13, 59 and 61 of the NRAS gene and codon 600 of the BRAF gene. Together these account for >95% of all KRAS, NRAS and BRAF mutations in colorectal cancer (Catalogue of Somatic Mutations In Cancer).
Recent evidence has suggested that testing one tissue block from colorectal cancers may miss a significant number of RAS and BRAF mutations due to intratumoural heterogeneity (Anal Cell Pathol (Amst) 2011; 34: 61-6). Although the optimum number of tumour blocks to test is not clear, we recommend testing a minimum of two blocks and up to a maximum of five blocks where they are available. RAS and BRAF mutations are believed to be early events and there is no good evidence that testing the diagnostic biopsy, surgical resection or metastatic disease will give differential results. For this reason, we recommend testing multiple blocks from the primary resected tumour to ensure that the tumour is sufficiently sampled, although testing the biopsy and metastatic disease is acceptable if this is the only tumour available.
For the laboratory address and contact details, see the laboratory contacts page.
The standard turnaround time (TAT) from receipt into the genetics lab is generally 7 to10 days.
Lynch Syndrome Screening
Cascade testing for Lynch Syndrome: Analysis of MLH1 promoter hypermethylation by pyrosequencing
Lynch syndrome (LS) is an inherited disorder involving germ-line mutation of DNA mismatch repair genes. The mismatch repair system involves a series of proteins including MSH2, MLH1, PMS2 and MSH6, which maintain DNA integrity. A germ-line mutation in any of these genes therefore increases the risk of a number of cancers, primarily colorectal cancers (50 to 70% lifetime risk), and endometrial cancers (40 to 60% lifetime risk) (Sehgal et al, 2014). As the age of cancer onset is younger than expected for sporadic cancers, diagnosis of LS families has relied on age and family history in the past. However, lack of reliability using this approach has led to an improvement in NICE guide-lines to detect LS families, and the current diagnostic strategy in Leeds.
MLH1 loss (visualised by immunohistochemistry performed in Histopathology), is observed in mismatch repair deficient colorectal tumours from LS patients. However, it is also observed in a significant minority of sporadic colorectal tumours resulting from somatic hypermethylation of the MLH1 promoter. Given that MLH1 promoter hypermethylation is rarely seen in LS cases harbouring MLH1 deficient tumours, this test can be used to discriminate these two possibilities. In cases where MLH1 loss is likely to have arisen from a germ-line mutation, (i.e. MLH1 protein loss shown not to result from MLH1 promoter hypermethylation), families can then undergo further constitutional genetic screening of mismatch repair genes.
Our laboratory now offer MLH1 promoter hypermethylation testing by pyrosequencing to MLH1 deficient, BRAF wild-type, colorectal cancer referrals as requested.
Please note, this is a routine test, currently not accredited by UKAS, with variable turn-around times as samples are batched, typically taking between 2 to 4 weeks.Previous