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Implications of multiple germline variants identified by panel-based cancer genetic testing

Cancer Genetics and Therapeutics
  • Primary Categories:
    • Cancer
  • Secondary Categories:
    • Cancer
Introduction:
Increased uptake of multigene panels (MGPs) is increasing the number of patients identified with multiple pathogenic germline variants (PGV) in cancer predisposition genes. This study's purpose is to characterize the landscape of patients with multiple PGV and to identify clinical situations where multiple PGVs impact management.This is a single institution retrospective cohort analysis comprising patients seen in the Fox Chase Cancer Center Risk Assessment Program (FCCC RAP). The FCCC RAP Registry was queried for patients evaluated with MGP who have more than one PGV.

Methods:
This is a single institution retrospective cohort analysis comprising patients seen in the Fox Chase Cancer Center Risk Assessment Program (FCCC RAP). The FCCC RAP Registry was queried for patients evaluated with MGP who have more than one PGV.

Results:
64 patients (64/7961, 0.8%) from 58 families carried multiple PGVs. 22 patients (34%) carried at least two PGVs in high or moderate risk genes and 36 of these patients (56%) carry at least two PGVs that result in a change of management. 5% (30/557) of patients who underwent MGP testing and carry a BRCA1 or BRCA2 PGV also carry an additional PGV while 7% (19/284) of patients who underwent MGP testing and carry a PGV in an MMR gene also carry an additional PGV. The most common additional PGV in patients carrying a BRCA1/BRCA2 PGV is the low penetrance APC I1307K variant while the most common additional PGVs in patients with an MMR gene PGV are PGVs in BRCA2

Conclusion:
Though the overall percentage of patients with multiple PGVs is small, a significant percentage of these patients’ management was changed due to the identification of multiple PGVs; supporting the use of MGP testing as opposed to single site or familial variant testing.

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