Lynch Syndrome Patients with Limited Family History Identified in a Laboratory Setting: A Descriptive Study

Objective: Patients diagnosed with colorectal cancer before the age of 50 years are recommended for Lynch syndrome (LS) testing according to current clinical guidelines. However, many patients are not identified because of the stringent guidelines on existing diagnostic criteria. The aim of this analysis was to evaluate the ability of existing criteria to adequately ascertain patients appropriate for LS genetic testing.

Method: To determine whether existing clinical diagnostic criteria underascertain individuals who would be appropriate candidates for hereditary cancer risk assessment, we stratified the detection rate of deleterious mismatch repair (MMR) mutations in 9,109 patients with a personal history of colorectal cancer who were diagnosed between the ages of 30 and 74 years with little or no family history suggestive of LS by 5-year age-at-detection intervals.

Results: There was little difference in the aggregate positive mutation rate in individuals diagnosed between the ages of 50 and 59 years compared to the positive mutation rate in patients diagnosed before the age of 50 years.

Conclusion: These results suggest that cancer diagnosis under the age of 50 years is an insufficiently sensitive predictor of hereditary cancer susceptibility.