- Microsatellite instability (MSI) screening should be done for all tumors. Many are MSI High (different outcomes and treatment response).
Why it matters
Genetic risk assessment is useful for:
- Pre-surgical decision making.
- Predictive and prognostic treatment implications.
- Cancer prevention and surveillance for survivors and their families.
- Hereditary susceptibility to colorectal cancer (CRC): 65 – 85% sporadic, 15 – 25% are familial, 3% are Lynch Syndrome (LS).
- An assessment of 15,000 tumor samples showed MSI High is relatively frequent in CRC (14%) and gastric (6%).
- MSI High is predictive of LS (45% of LS are MSI High).
- No improvement with 5 Fluorouracil (NCCN guidelines).
- All MSI-H cancer should be tested for Lynch Syndrome.
Multi gene panel testing is available and appropriate in some patients:
- Simultaneous analysis of a set of genes.
- Testing can be difficult, using these panels helps.
- May or may not be associated with a specific cancer phenotype.
- Variants and incidental findings are a real limitation! The risks of using this panels are incidental findings and questions about preventive resections (hysterectomy, colon).
- Inclusion of genes with limited clinical validity and clinical utility.