Reclassification of clinical exome data leads to significant clinical assessment changes in almost half of the patients

Purpose: With the global accumulation of genetic/clinical data, we are understanding the clinical significance of the reclassification of pathogenicity for gene variants. We hypothesized that this evolution in classification(s) may cause clinically-relevant discrepancies in the genetic risk assessment of subjects. In this study, we sought to reclassify the clinical exome sequence (CES) data of our patients to assess whether these changes would have clinical significance. Materials and Methods: The study included CES data of 23 cases diagnosed with cancer or familial cancer predisposition. The variants were first classified in 2020 and then reclassified a year after based on the ACMG database. Chart reviews were performed to record clinical history and interventions. Results: In the first classification of CES data, a total of 80 variants were identified as being not benign (26 likely pathogenic/pathogenic and 54 variants of undetermined significance (VUS)). The clinical significance of fifteen variants (19%) changed after reclassification in 10 patients (43%). The only upgraded variant was the c.9097 dup in exon 23 of BRCA2 gene (likely pathogenic to pathogenic). Fourteen variants were downgraded at reanalysis in 9 patients: from pathogenic to likely pathogenic (2 variants), pathogenic to VUS (2), likely pathogenic to VUS (4), and VUS to benign (6). Conclusion: Considering that the clinical significance of CES data changed due to reclassification in almost half of the studied patients, we believe genetic variant-related data should be assessed at regular intervals, regardless of follow-up status in the clinic.