Current Breast Cancer Genetic Testing Guidelines Leave Out Many People With Harmful Mutations

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Current National Comprehensive Cancer Network (NCCN) guidelines on who should have genetic testing after a breast cancer diagnosis miss about half of people with a genetic mutation linked to the disease, according to a study.

The research was published online on Dec. 7, 2018, by the Journal of Clinical Oncology. Read the abstract of “Underdiagnosis of Hereditary Breast Cancer: Are Genetic Testing Guidelines a Tool or an Obstacle?”

The NCCN is a nonprofit group of cancer centers dedicated to improving care for people with cancer.

What is hereditary breast cancer?

About 5% to 10% of breast cancers are thought to be hereditary, caused by genetic mutations passed from parent to child. Three of the most well-known genes that can mutate and raise the risk of breast and/or ovarian cancer are BRCA1, BRCA2, and PALB2. Women who inherit a mutation, or abnormal change, in any of these genes — from their mothers or their fathers — have a much higher-than-average risk of developing breast cancer and/or ovarian cancer. Men with these mutations have an increased risk of breast cancer, especially if the BRCA2 gene is affected, and possibly of prostate cancer. Many inherited cases of breast cancer have been associated with mutations in these three genes.

You are substantially more likely to have a genetic mutation linked to breast cancer if:

  • you have blood relatives (grandmothers, mother, sisters, aunts) on either your mother's or father's side of the family who had breast cancer diagnosed before age 50
  • there is both breast and ovarian cancer on the same side of the family or in a single individual
  • you have a relative(s) with triple-negative breast cancer
  • there are other cancers in your family in addition to breast, such as prostate, melanoma, pancreatic, stomach, uterine, thyroid, colon, and/or sarcoma
  • women in your family have had cancer in both breasts
  • you are of Ashkenazi Jewish (Eastern European) heritage
  • you are African American and have been diagnosed with breast cancer at age 35 or younger
  • a man in your family has had breast cancer
  • there is a known genetic mutation linked to breast cancer in your family

Among other criteria, current guidelines recommend genetic testing for someone diagnosed with breast cancer if:

  • there is a known mutation in the family
  • the person was diagnosed at age 50 or younger
  • the person has been diagnosed with two primary breast cancers
  • a first-degree female relative (mother, sister) was diagnosed with breast cancer at age 50 or younger or was diagnosed with ovarian cancer
  • two or more first-degree relatives were diagnosed with breast, prostate, and/or pancreatic cancer
  • a man in your family has been diagnosed with breast cancer

Comparing people who do and don’t meet genetic testing guidelines

This study included 959 people ages 18 to 90 years old who had been diagnosed with breast cancer and had not had genetic testing:

  • 959 were women, 3 were men.
  • 477 women and 2 men met current genetic testing guidelines.
  • 479 women and 1 man did not meet current genetic testing guidelines.

Other characteristics of the people in the study:

  • About 80% were white.
  • About 6% were black.
  • About 7% were Asian.
  • About 11% had a history of other cancers.
  • About 65% had a family history of breast cancer.

As part of the study, all the participants had genetic testing with an 80-gene panel test. This means that the test looked for mutations in 80 genes.

Overall, 83 of the 959 people in the study had a mutation that was linked to breast cancer. Of these 83 people:

  • 45 met current genetic testing guidelines.
  • 38 did not meet current genetic testing guidelines.

The difference in the number of people who tested positive for a genetic mutation between the two groups was not statistically significant. This means that it was likely not because one group met genetic testing guidelines and the other did not.

“The rate of [harmful] variants in a large 80-gene panel was similar among patients with breast cancer who did and did not meet 2017 NCCN guidelines for genetic testing; the difference was not statistically significant,” the researchers wrote. “In fact, the results of our study suggest that a strategy that simply tests all patients with a personal history of breast cancer would almost double the number of patients identified as having a clinically actionable genetic test result.”

What does this mean for you?

The results of this study echo other research suggesting that many people with mutations linked to breast cancer are not having genetic testing because they don’t meet testing guidelines. This means that people who don’t know they have a genetic mutation may not be told about all their options for reducing their risk of recurrence (the cancer coming back) or a new cancer.

NCCN genetic testing guidelines for people diagnosed with breast cancer were developed about 20 years ago when testing was limited to two genes: BRCA1 and BRCA2. Genetic testing at that time also was very expensive, approximately $5,000 per test.

Since that time, genetic testing technology advanced rapidly, allowing multiple genes to be tested at the same time. The cost of genetic testing also dropped dramatically; today, some genetic testing can be done for as little as $250.

"Economically based guidelines for genetic testing of breast cancer patients are anachronistic, miss a significant number of pathogenic variants, and we believe they should be abolished immediately," said Peter Beitsch, M.D., of TME Breast Care Network in Dallas, the lead author of the study.

If you’ve been diagnosed with breast cancer, you may want to talk to your doctor or a licensed certified genetic counselor about your diagnosis and your family history and ask if having a multigene panel test makes sense for you. A licensed certified genetic counselor or your doctor can help you understand the test and accurately interpret the results.

For more information on genetic testing, including types of genetic tests and how results are reported, visit the Breastcancer.org Genetic Testing pages.

For more information on genes and genetic mutations linked to breast cancer, as well as all the risk-lowering steps you can take if you have a genetic mutation, visit the Breast Cancer Risk Factors: Genetics page in the Breastcancer.org Lower Your Risk section.

To discuss high breast cancer risk with others, join the Breastcancer.org Discussion Board forum High Risk of Breast Cancer. If you've tested positive for a breast cancer mutation and would like to talk about this with others, join the forum Positive Genetic Test Results.

Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser


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