The prevalence of Lynch syndrome patients with high frequency microsatellite instability (MSI-H) or mismatch repair deficiency (MMR-D) tumors was higher than anticipated in a clinical study, suggesting changes in genetic testing criteria are warranted.1 The findings were published in the Journal of Clinical Oncology.

Between 2014 and 2017, researchers enrolled 15,045 patients with more than 50 cancer types on a clinical trial at Memorial Sloan Kettering Cancer Center (ClinicalTrial.gov Identfier: NCT01775072). Targeted next-generation sequencing was used to identify MSI status for each patient. Patients’ tumors were categorized as MSI-H, MSI-indeterminate, or microsatellite-stable. MMR-D was also assessed by immunohistochemical staining.

Lynch syndrome was found in 16.3% of patients with MSI-H, 1.9% of patients with MSI-indeterminate, and 0.3% of patients with microsatellite-stable tumors (P < .001).

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Half of Lynch syndrome patients with MSI-H or MSI-intermediate status tumors also had tumors that were not colorectal or endometrial; they included urothelial, prostate, pancreas, adrenocortical, small bowel, sarcoma, mesothelioma, melanoma, gastric, and germ cell tumors. Many of these patients (45%), however, did not meet the criteria that warrants genetic testing for Lynch syndrome. Nearly all patients (98.2%) with Lynch syndrome and MSI-H or MSI-intermediate tumors had mismatch repair deficiency (MMR-D).

“MSI-H/MMR-D is predictive of [Lynch syndrome] across a much broader tumor spectrum than currently appreciated,” the study authors concluded. “Given implications for cancer surveillance and prevention measures in affected families, these data support germline genetic assessment for LS for patients with an MSI-H/MMR-D tumor, regardless of cancer type or family cancer history.”

Reference

  1. Latham A, Srinivasan P, Kemel Y, et al. Microsatellite instability is associated with the presence of Lynch syndrome pan-cancer [published online October 30, 2018]. J Clin Oncol. doi: 10.1200/JCO.18.00283