World GI 2017: Tips for Practice: MSI Testing in GI Cancers

Speaker: Fatima Carneiro

Fatima Carneiro explains that tumours with microsatellite instabilty (MSI) can also express PD-L1 which is a target for immune checkpoint inhibitors that can bring a better outcome for these patients.

MSI is a molecular phenotype and she explains how, in some regions of the genoma with repetitive sequences, the repetition make them prone to errors during replication and it can lead to MSI.

There are several reasons to look for these phenotypes, first because they have a positive prognostic factor, second because they can guide the treatment regimen, and third because some patients with MSI have the over-expression of PD-L1 and may benefit from immuno therapies.

As a pathologist, she explains how the presence of proteins that control the mismatch phenomenon allows to detect MSI.The testing for MSI testing is becoming more important, and the interaction clinician / pathologist is key for better patient's management.

For the future next-generation sequencing could be used for a better characterisation of MSI to refine applicability of immunotherapy. 

Discussion Points

  • A role of MSI in GI cancers
  • When to test - Tips for practice
  • The pathologist point of view and collaboration with clinicians

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