Optimising clinical care throughCDH1-specific germline variant curation: improvement of clinical assertions and updated curation guidelines

BackgroundGermline pathogenic variants inCDH1are associated with increased risk of diffuse gastric cancer and lobular breast cancer. Risk reduction strategies include consideration of prophylactic surgery, thereby making accurate interpretation of germlineCDH1variants critical for physicians deciding on these procedures. The Clinical Genome Resource (ClinGen)CDH1Variant Curation Expert Panel (VCEP) developed specifications forCDH1variant curation with a goal to resolve variants of uncertain significance (VUS) and with ClinVar conflicting interpretations and continues to update these specifications.MethodsCDH1variant classification specifications were modified based on updated genetic testing clinical criteria, new recommendations from ClinGen and expert knowledge from ongoingCDH1variant curations. TheCDH1VCEP reviewed 273 variants using updatedCDH1specifications and incorporated published and unpublished data provided by diagnostic laboratories.ResultsUpdatedCDH1-specific interpretation guidelines include 11 major modifications since the initial specifications from 2018. Using the refined guidelines, 97% (36 of 37) of variants with ClinVar conflicting interpretations were resolved to benign, likely benign, likely pathogenic or pathogenic, and 35% (15 of 43) of VUS were resolved to benign or likely benign. Overall, 88% (239 of 273) of curated variants had non-VUS classifications. To date, variants classified as pathogenic are either nonsense, frameshift, splicing, or affecting the translation initiation codon, and the only missense variants classified as pathogenic or likely pathogenic have been shown to affect splicing.ConclusionsThe development and evolution ofCDH1-specific criteria by the expert panel resulted in decreased uncertain and conflicting interpretations of variants in this clinically actionable gene, which can ultimately lead to more effective clinical management recommendations.