What is the recommended approach for genetic risk evaluation and germline and somatic biomarker testing in ovarian cancer?

Genetic Risk Evaluation and Biomarker Testing in Ovarian Cancer

All women diagnosed with epithelial ovarian cancer should undergo germline genetic testing for BRCA1/2 and other ovarian cancer susceptibility genes at the time of diagnosis, regardless of family history or clinical features, followed by somatic tumor testing for BRCA1/2 if germline testing is negative. 1

Who Should Be Tested

Universal Germline Testing

• Every woman with epithelial ovarian cancer requires germline testing for BRCA1/2 and other ovarian cancer susceptibility genes
• Testing should occur at diagnosis, not delayed until treatment planning 1
• Family history is not required to justify testing—approximately 25% of ovarian cancers have hereditary components, but family history-based referral misses many carriers 1, 2
• Testing should include genes beyond BRCA1/2: Lynch syndrome genes (MLH1, MSH2, MSH6), BRIP1, RAD51C, RAD51D, PALB2, and other Fanconi anemia pathway genes 1, 3

Somatic Tumor Testing Strategy

Sequential approach:

1. If germline testing shows no pathogenic BRCA1/2 variant, proceed with somatic tumor testing for BRCA1/2 1
2. For clear cell, endometrioid, or mucinous histologies: somatic testing for mismatch repair deficiency (dMMR) is required 1
3. For other epithelial histologies: dMMR testing may be offered 1

The ASCO guideline explicitly recommends this sequential germline-first approach, though recent cost-effectiveness data suggests tumor-first strategies may be equally effective at lower cost 4. However, the guideline-recommended approach remains germline testing first 1.

Clinical Utility of Identified Variants

BRCA1/2 Pathogenic Variants (Germline or Somatic)

• Qualify for FDA-approved PARP inhibitor therapy in both upfront maintenance and recurrent settings 1
• These variants predict higher response rates to platinum-based chemotherapy and PARP inhibitors 1
• Treatment decisions should be based on either germline OR somatic BRCA pathogenic variants—both have therapeutic implications

Mismatch Repair Deficiency (dMMR)

• Qualifies for FDA-approved immunotherapy in the recurrent setting 1
• Particularly important in clear cell, endometrioid, and mucinous histologies where prevalence is higher 1

Homologous Recombination Deficiency (HRD)

• Testing for HRD is recommended in advanced high-grade cancers 3
• Predicts magnitude of benefit from PARP inhibitor therapy 3

Critical Implementation Details

Genetic Counseling Requirements

• Testing must be conducted in conjunction with genetic counselors or providers familiar with hereditary cancer management 1
• Counseling should address implications for the patient AND first- or second-degree relatives 1
• Mainstream testing models (oncologist-initiated) with genetic counselor support are acceptable and improve uptake 5, 6

Cascade Testing for Relatives

First- or second-degree blood relatives of patients with identified germline pathogenic variants should be offered:

• Individualized genetic risk evaluation
• Genetic counseling
• Targeted genetic testing for the familial variant 1

This is not optional—cascade testing should be measured and resourced as part of ovarian cancer care, not treated as passive family responsibility 2.

Common Pitfalls to Avoid

Variants of Uncertain Significance (VUS)

Clinical decisions should NOT be made based on VUS 1. These variants lack sufficient evidence to guide treatment or risk management.

Tumor-Only Testing Limitations

• Tumor testing alone cannot replace germline testing when hereditary evaluation is indicated 2
• Tumor testing identifies somatic variants for treatment selection but misses germline variants critical for family risk assessment
• Some centers use tumor testing as triage (VAF ≥40% triggers germline referral), but this is not the guideline-recommended primary approach 7

Timing Errors

• Do not delay primary treatment for genetic counseling referral 1
• Testing should occur at diagnosis, with results ideally available within 3 months 6
• Early referral allows integration of results into upfront treatment planning, particularly for PARP inhibitor maintenance eligibility

Access Barriers

Despite guidelines recommending universal testing, only approximately 30% of eligible patients complete genetic testing 1. Barriers include:

• Lack of oncologist knowledge about testing processes
• Patient feeling overwhelmed at diagnosis
• Financial and privacy concerns
• Language barriers requiring multilingual consent options 6

Solutions: Implement mainstream testing protocols, use digital consent platforms, provide navigation support, and offer testing at multiple care points rather than only at initial diagnosis 6.

Testing Sequence and Logistics

Optimal workflow:

1. At diagnosis: Initiate germline testing for BRCA1/2 and ovarian cancer gene panel
2. Simultaneously: Obtain tumor tissue for somatic testing (can be done via comprehensive tumor sequencing panels like MSK-IMPACT or targeted panels) 6
3. If germline negative: Complete somatic BRCA1/2 testing
4. For appropriate histologies: Add dMMR/MSI testing
5. For high-grade cancers: Consider HRD testing to inform PARP inhibitor benefit 3

Testing should be performed in CLIA-approved facilities with validated molecular testing methods 1.