Our study assessed microsatellite instability which is a genomic marker in tumours that is associated with a very large number of mutations due to a variance in the length of DNA fragments in the tumour and tumour versus normal tissue. Microsatellite instability is a marker of Lynch Syndrome and traditionally MSI has been assessed in endometrial and colorectal cancers but more recently MSI testing has been increasing due to MSI also being a biomarker for response to immunotherapy. So, in fact, because of the FDA approval of pembrolizumab many more advanced cancer patients are now getting MSI analysis on their tumour for a biomarker of immunotherapy. Our question was whether the prevalence of Lynch Syndrome was also increased across the board in MSI high patients.
And the answer?
And the answer is yes. We found that Lynch Syndrome was present actually in 16.3% of MSI high tumours and about 50% of those tumours were not the traditional colon and endometrial cancers associated with Lynch but rather other rare tumours or tumours that have not been implicated in Lynch beforehand. So our data suggests that any tumour that is being tested and if MSI high is found then those patients should really undergo genetic testing and genetic counselling to get tested for Lynch Syndrome.
And was the question raised as well of if that counselling and screening should be offered backwards to their family if there is that hereditary link?
Absolutely. Once Lynch Syndrome is identified it has implications for that patient in terms of what kind of cancer screening we would do or even risk reducing surgeries. Then down the line we would want to test those patients’ at risk relatives for the marker and many times we can identify Lynch Syndrome in that setting in unaffected individuals who would then really benefit from cancer prevention and cancer risk reduction measures.
A good quote here of ‘absolutely practice-changing,’ would you agree?
I would agree with that because now any time we see an MSI high tumour it should really prompt germline genetic testing for Lynch.