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Table 4 Advantages of germline versus somatic tumor testing of HRD genes

From: Homologous recombination deficiency (HRD) testing in ovarian cancer clinical practice: a review of the literature

Advantages of germline testing
 1. Germline testing is a more well established technique.
  DNA extraction is easier.
  The results are highly accurate and reproducible.
 2. Germline mutations have prognostic and predictive value.
  There is robust data supporting the prognostic and predictive value of germline BRCA1/2 mutations.
  Such data is limited for somatic mutations.
 3. Germline mutations can offer knowledge of risk for other associated cancers.
  As germline mutations often increase the risk for multiple cancers, awareness of germline mutations allows patients to pursue risk-reducing interventions for other cancers.
 4. Germline mutation identification is clinically relevant for family members and allows for cascade testing.
Advantages of somatic testing
 1. Somatic testing with NGS will identify a larger number of patients with HRD who can be therapeutically targeted.
  Including patients with somatic (and not germline) mutations who would be missed with germline testing alone.
 2. Somatic testing can help patients understand the magnitude of clinical benefit from targeted therapy in the context of risks and side effects of particular therapeutic agents.
 3. Somatic testing does not require genetic counseling which is often a limited resource.
 4. Somatic testing can serve as a triage for germline testing.
  Patients found to have a somatic mutation can then be referred to clinical genetics for germline testing, allowing for better utilization of genetic counselors and geneticists.