Study: Genetic testing among people with cancer can find mutations that may affect treatment and prevention

Relevance: High

Strength of Science: High

Research Timeline: Post Approval

Relevance Rating Details

What is this study about?

This study looked at whether people diagnosed with cancer who meet the guidelines for genetic testing are actually tested.

Why is this study important?

Genetic testing can help people and their doctors decide the best course of cancer treatment. When a person has an inherited mutation in a gene that increases their risk of cancer, they are said to have hereditary cancer. Targeted treatments such as PARP inhibitors and immunotherapy drugs may work particularly well for treating some hereditary cancers. Genetic testing can also help people learn their risk for a new cancer diagnosis. Knowing one’s genetic status may be useful for family members, including siblings, children or parents who may also be at risk.

Study findings

This study looked at information from the Surveillance, Epidemiology and End Results (SEER) national registry that tracks cancer cases. The researchers reviewed the data of more than 1.3 million cancer patients who were diagnosed in California and Georgia between 2013 and 2019 and met national guidelines for genetic testing. The patients included people diagnosed with breast, colorectal, endometrial, ovarian (including fallopian and peritoneal), pancreatic, prostate or lung cancer. People with more than one type of cancer were grouped separately.

Researchers asked whether cancer patients who were eligible for genetic testing according to national guidelines were tested within two years after their diagnosis. Of the more than 1.3 million patients represented in this study, only 6.8 percent of eligible cancer patients had genetic testing.

• Rates of testing were different by age:
  • 18% among people age 40
  • 2% among people age 80

Non-Hispanic white patients had higher rates of testing compared to all other racial groups:

• 6% Asian patients
• 6% Black patients
• 6% Hispanic patients
• 8% non-Hispanic white patients

This testing gap did not improve during this study (2013 to 2019). In the later years of this study, genetic testing rates remained the same among Asian and Black patients but declined among Hispanic patients.

• The largest differences in genetic testing rates among racial and ethnic groups were among people with breast cancer (men or women) or ovarian cancer.

Results of genetic testing among patients diagnosed with cancer

Among patients who completed genetic testing, 11-36 percent tested positive for a mutation associated with an increased risk of cancer, also known as a pathogenic variant. (The data below reflects 2019 data):

• female breast: 11%
• male breast: 36%
• colorectal: 17%
• endometrial: 12%
• ovarian: 15%
• pancreatic: 14%
• prostate: 11%
• lung: 13%
• multiple primary tumor types: 17%

Treatment or prevention options based on national guidelines were available for most harmful mutations (pathogenic variants)—68-95% depending on the type of cancer.

In addition to harmful mutations, genetic testing also finds Variants of Uncertain Significance or VUS. VUS are uncertain results, meaning that it is unclear whether or not the mutation increases a person’s cancer risk. Some VUS are eventually reclassified as harmful mutations when more data is collected, but many turn out to be harmless or remain as VUS because they are rare.

The chance of having a genetic test that found a VUS was higher among non-white racial groups and has increased with time. Data from 2019 shows that:

• Among white patients, VUS were found nearly twice as often (25%) as harmful mutations linked to cancer (14%).
• Among Hispanic patients, VUS were found just over twice as often (29%) as harmful mutations (13%).
• Among Asian and Black patients, VUS were found about four times (39-40%) as often as harmful mutations (10-11%).

Because VUS are inconclusive results, they cannot be used to guide treatment. These racial disparities in VUS results mean that more people of color receive inconclusive test results. This suggests that more research including people from diverse racial and ethnic groups is needed to close this testing gap and improve these disparities.

What does this mean for me?

National guidelines recommend who should receive genetic testing. These recommendations vary by cancer type and other factors (linked here). In some cases, a single diagnosis of cancer at any age may be enough to recommend genetic testing (for example, male breast cancer, pancreatic or ovarian cancer). For breast cancer, colorectal cancer or certain other cancers, genetic testing may be recommended if you have a family history of cancer, cancer before age 50 or other factors suggesting hereditary cancer based on tumor testing (for example, triple-negative breast cancer or MSI-High colorectal or endometrial cancer).

If you have been diagnosed with cancer, talk to a genetics expert about whether you should consider genetic testing. Genetic testing may clarify whether you have a mutation that increases your cancer risk or a variant with uncertain impact. Genetic testing can also provide information that helps other family members understand whether they may have an increased risk of cancer.

If you have an inherited mutation, this knowledge may alter available treatment options. Some medications or treatments are only indicated for people with particular inherited mutations. Having an inherited mutation may increase your risk of other cancers. Consider discussing with your doctor whether increased surveillance or risk-reducing approaches are available. For more information on genetic testing guidelines, visit the FORCE website.

Reference

Kurian AW, Abrahamse P, Furgal A, et al. Germline genetic testing after cancer diagnosis. JAMA; 2023; 330:43-51. Published online June 5, 2023.

Disclosure: FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.

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posted 3/15/24