Gynecologic Oncology Consult

Germline genetic testing: Why it matters and where we are failing


 

Historically, the role of genetic testing has been to identify familial cancer syndromes and initiate cascade testing. If a germline pathogenic variant is found in an individual, cascade testing involves genetic counseling and testing of blood relatives, starting with those closest in relation to the proband, to identify other family members at high hereditary cancer risk. Once testing identifies those family members at higher cancer risk, these individuals can be referred for risk-reducing procedures. They can undergo screening tests starting at an earlier age and/or increased frequency to help prevent invasive cancer or diagnose it at an earlier stage.

Genetic testing can also inform prognosis. While women with a BRCA1 or BRCA2 mutation are at higher risk of developing ovarian cancer compared with the baseline population, the presence of a germline BRCA mutation has been shown to confer improved survival compared with no BRCA mutation (BRCA wild type). However, more recent data have shown that when long-term survival was analyzed, the prognostic benefit seen in patients with a germline BRCA mutation was lost. The initial survival advantage seen in this population may be related to increased sensitivity to treatment. There appears to be improved response to platinum therapy, which is the standard of care for upfront treatment, in germline BRCA mutation carriers.

Dr. Katherine Tucker is assistant professor of gynecologic oncology at the University of North Carolina at Chapel Hill.

Dr. Katherine Tucker

Most recently, genetic testing has been used to guide treatment decisions in gynecologic cancers. In 2014, the first poly ADP-ribose polymerase (PARP) inhibitor, olaparib, received Food and Drug Administration approval for the treatment of recurrent ovarian cancer in the presence of a germline BRCA mutation. Now there are multiple PARP inhibitors that have FDA approval for ovarian cancer treatment, some as frontline treatment.

Previous data indicate that 13%-18% of women with ovarian cancer have a germline BRCA mutation that places them at increased risk of hereditary ovarian cancer.1 Current guidelines from the American Society of Clinical Oncology, the U.S. Preventive Services Task Force, the National Comprehensive Cancer Network, the Society of Gynecologic Oncology (SGO), and the American College of Obstetricians and Gynecologists recommend universal genetic counseling and testing for patients diagnosed with epithelial ovarian cancer. Despite these guidelines, rates of referral for genetic counseling and completion of genetic testing are low.

There has been improvement for both referrals and testing since the publication of the 2014 SGO clinical practice statement on genetic testing for ovarian cancer patients, which recommended that all women, even those without any significant family history, should receive genetic counseling and be offered genetic testing.2 When including only studies that collected data after the publication of the 2014 SGO clinical practice statement on genetic testing, a recent systematic review found that 64% of patients were referred for genetic counseling and 63% underwent testing.3

Clinical interventions to target genetic evaluation appear to improve uptake of both counseling and testing. These interventions include using telemedicine to deliver genetic counseling services, mainstreaming (counseling and testing are provided in an oncology clinic by nongenetics specialists), having a genetic counselor within the clinic, and performing reflex testing. With limited numbers of genetic counselors (and even further limited numbers of cancer-specific genetic counselors),4 referral for genetic counseling before testing is often challenging and may not be feasible. There is continued need for strategies to help overcome the barrier to accessing genetic counseling.

While the data are limited, there appear to be significant disparities in rates of genetic testing. Genetic counseling and testing were completed by White (43% and 40%) patients more frequently than by either Black (24% and 26%) or Asian (23% and 14%) patients.4 Uninsured patients were about half as likely (23% vs. 47%) to complete genetic testing as were those with private insurance.4

Genetic testing is an important tool to help identify individuals and families at risk of having hereditary cancer syndromes. This identification allows us to prevent many cancers and identify others while still early stage, significantly decreasing the health care and financial burden on our society and improving outcomes for patients. While we have seen improvement in rates of referral for genetic counseling and testing, we are still falling short. Given the shortage of genetic counselors, it is imperative that we find solutions to ensure continued and improved access to genetic testing for our patients.

Dr. Tucker is assistant professor of gynecologic oncology at the University of North Carolina at Chapel Hill.

References

1. Norquist BM et al. JAMA Oncol. 2016;2(4):482-90.

2. SGO Clinical Practice Statement. 2014 Oct 1.

3. Lin J et al. Gynecol Oncol. 2021;162(2):506-16.

4. American Society of Clinical Oncology. J Oncol Pract. 2016 Apr;12(4):339-83.

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