Editing Colon cancer (section)

=== '''Molecular markers for treatment planning''' ===

*** KRAS
**** Independently associated with a worse prognosis
**** May provide a target for immunotherapy targeting EGFR - tumours that harbour activating mutations for KRAS or NRAS are resistant to EGFR inhibitors, whereas those that are wild-type can have them
*** BRAF
**** If a BRAF mutation is present, probably not HNPCC, despite MSI-H
**** BRAF mutations induce resistance to EGFR inhibitors
*** MSI
**** MSI-H: two or more of a set of five nucleotide repeats are affected by instability
**** MSI-L: one or none are affected by instability
**** MS-S (stable): no instability
*** MMR
**** Cells deficient in MMR will likely have high MSI - MMR is a surrogate marker for MSI
**** If MMR-deficient, immunotherapy will be given for advanced stage disease (see below)
**** MMR deficient makes HNPCC more likely
*** HER2
**** Allows use of immunotherapy for stage IV disease