Paired Tumor/Germline Testing for Lynch Syndrome

When I think back to the initial discussions about what is now TumorNext-Lynch, I remember a vision to offer a comprehensive and convenient test that would be able to confirm a diagnosis or indicate a significantly reduced likelihood of Lynch syndrome. It was clear that the best approach to achieve this was to develop a paired tumor/germline test, from which the germline results could confirm a diagnosis of Lynch syndrome and the tumor results could help provide another explanation for abnormal tumor screening results demonstrating mismatch repair deficiency.

In 2017, that vision came to life when Ambry launched TumorNext-Lynch. We recently published data in the Journal of Clinical Oncology from our first >700 cases.

Here are some key lessons learned:

  • TumorNext-Lynch provides answers for 76% of mismatch repair deficiency (MMRd) cases without prior germline testing and 61% of MMRd with prior germline testing.
  • For patients who have already undergone germline testing, TumorNext-Lynch can identify germline mutations that were previously missed.
  • Previous studies have shown that up to 59% of patients with tumors demonstrating mismatch repair deficiency remain unresolved due to the absence of a germline mutation or MLH1 promoter hypermethylation (Buchanan et al. Appl Clin Genet. 2014 Oct 6;7:183-93). Adding tumor sequencing and deletion/duplication analysis to germline testing helps resolve more cases. In fact, it provides an answer for about 50% of MMRd cases that traditionally would have remained unresolved.
  • Tumor screening results are not always consistent with the germline mutations identified. In our study, seven patients were identified to have a germline mutation in a gene that didn’t align with the reported pattern of protein loss on immunohistochemistry (IHC). Comprehensive germline testing of all Lynch syndrome genes increases your ability to detect a germline mutation and provide a clear diagnosis.

Read the full study here for more details, click here

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