Gene Mutations and Inherited Cancer Risk

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If a certain type of cancer runs in your family, you may be a candidate for genetic testing. That's according to new recommendations by the U.S. Preventive Services Task Force (USPSTF).

About one in 400 people carry mutated BRCA1 or BRCA2 genes. A BRCA mutation occurs when the DNA that makes up the gene becomes damaged and may no longer effectively repair broken DNA.

If you inherited a mutated BRCA1 or BRCA2 gene, it can increase your risk of certain cancers.

Previously, the USPSTF has focused on women with a family history of breast, ovarian, fallopian tube, or peritoneal cancer. Now, women with a personal history of breast, ovarian, fallopian tube, or peritoneal cancer, and women with ancestry associated with breast cancer related to BRCA1/2 gene mutations (e.g., Ashkenazi Jews) are added to the list.

More women may benefit from gene testing for hereditary breast or ovarian cancer, especially if they've already survived these cancers.

Inherited risk is thought to account for five to 10% of common adult cancers, according to the USPSTF. If you have a mutation in either of the BRCA genes, you may have a high risk of breast cancer (60-80%). Mutations also raise ovarian cancer risk to 20-50% including fallopian tube and primary peritoneal cancer. Those two genes account for about 25% of hereditary breast cancers, but only three percent of all breast cancers.

Uncovering who is at more risk for cancer

Experts have known about genetic mutations in the BRCA1 and 2 genes for almost 25 years. Now, experts have identified other genes that contribute to the hereditary burden of breast cancer or other cancers. Thanks to new technology, providers can lower the costs of the testing and increase the ability to test more panels of genes.

“We don’t know the risk implications of some new genes yet, but mutations can be found in high risk or moderate risk genes. Management should, therefore, be individualized to the gene, personal and family history,” says Talia Donenberg, MS, a board-certified genetic counselor at Sylvester Comprehensive Cancer Center, who specializes in hereditary cancer syndromes. “Both the USPSTF and the National Comprehensive Cancer Network, while not sanctioning multigene panels for widespread use, state that they should be ordered by genetics professionals who can appropriately interpret them.”

Should you consider genetic testing?

Genetic counselors and doctors are trying to detect cancer at its earliest stage, or reduce the chances of developing cancer for people at high risk.

Options for prevention may include

  • tamoxifen therapy
  • birth control pills (to reduce ovarian cancer risk in 25-35 year-olds
  • surgical prevention

Genetic counselors will work with your primary care physician or oncology specialist to help you understand what this means so you can make the best decisions about your care.

If you had genetic testing in the past but are a long-term cancer survivor, Donenberg says it can be helpful to be retested.

Testing methods evolve, and the number of genes that may affect your future risk change over time.

“Genetic testing allows us to not only identify level and type of cancer risks but also the risk to your family members," Donenberg says. "Those who test positive for the gene mutation causing cancer in the family may benefit from early detection methods that begin as early as age 25 in some cases.”

People with more than a 20-25% lifetime breast cancer risk should think about getting a breast MRI starting at age 25, says Donenberg. “While there is no effective or reliable ovarian cancer screening test yet, if an identified gene has ovarian cancer risks, you may want to discuss the appropriate age for risk-reducing surgery”

Which cancers are inherited?

Hereditary cancer syndromes have been identified in some cases of breast, ovarian, colon, prostate, endometrial, pancreatic, and renal cancers, but the risk implications are unknown.

About eight percent of pediatric cancers have a hereditary component. There are even higher hereditary proportions of certain rare cancers, such as medullary thyroid, male breast cancer and neuroendocrine cancers.  Most cancer specialties see a small but significant percentage of hereditary cases.

There is not enough evidence to screen all women for these mutations. But women identified as being at increased risk would benefit. Talk to your primary care provider if you think you may be a candidate for evaluation.

 


Mary Jo Blackwood, RN, MPH, is a contributing writer for UMiami Health News.


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