March 10, 2020
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Genetic testing may benefit some postmenopausal women with breast cancer

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Allison W. Kurian, MD, MSc
Allison W. Kurian

Postmenopausal women with breast cancer had a threefold higher prevalence of pathogenic variants in breast cancer-associated genes than their cancer-free counterparts, according to results of a case-control study published in JAMA.

The results suggest genetic testing may be warranted even for postmenopausal women with newly diagnosed breast cancer who have no known hereditary risk factors for the disease.

“[Although] genetic testing is increasingly relevant for the care of patients with cancer, little was known about the prevalence of inherited mutations in cancer susceptibility genes among the most common group of women with breast cancer — those diagnosed after menopause and without a strong family history of cancer,” Allison W. Kurian, MD, MSc, associate professor of medicine and health research and policy at Stanford University School of Medicine, told Healio.

Kurian and colleagues analyzed data of women with banked DNA samples who participated in the Women’s Health Initiative, which enrolled more than 160,000 postmenopausal women aged 50 to 79 years between 1993 and 1998.

Postmenopausal women with breast cancer had a threefold higher prevalence of pathogenic variants in breast cancer-associated genes than their cancer-free counterparts

Researchers compared the prevalence of breast cancer-associated mutations in 10 genes — BRCA1, BRCA2, ATM, BARD1, CDH1, CHEK2, NBN, PALB2, STK11 and TP53 — among 2,195 women diagnosed with breast cancer (median age at diagnosis, 73 years; 66.3% white) vs. 2,322 women without breast cancer (median age at last follow-up, 81 years; 84.9% white).

Pathogenic variants were detected among 6.74% (95% CI, 5.73-7.87) of women with breast cancer compared with 4.01% (95% CI, 3.24-4.88) of women without breast cancer.

Results showed pathogenic variants in one of the 10 breast cancer-associated genes among 3.55% (95% CI, 2.82-4.42) of women with breast cancer compared with 1.29% (95% CI, 0.87-1.84) of cancer-free women.

Moreover, 2.21% (95% CI, 0.82-4.76) of women diagnosed at younger than age 65 years carried BRCA1 or BRCA2 mutations compared with 1.09% (95% CI, 0.67-1.68) of women diagnosed at age 65 years or older.

Only 30.8% of women with breast cancer and 20% of women without breast cancer who carried BRCA1 or BRCA2 mutations appeared likely to have met current National Comprehensive Cancer Network guidelines for genetic testing.

“Data on the prevalence of pathogenic variants in breast cancer susceptibility genes among postmenopausal women should now inform testing guidelines,” the researchers wrote.

Limitations of the study included the fact that women chose to participate in the Women’s Health Initiative; thus, the study population may not represent all U.S. women and potentially represents a small number of pathogenic variants.

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“We found that approximately 3.6% of women who developed breast cancer after menopause carry inherited mutations in breast cancer susceptibility genes, and approximately 2.2% of women diagnosed younger than age 65 years carry mutations in BRCA1 or BRCA2. These numbers are high enough that it is reasonable to consider genetic testing for these patients,” Kurian told Healio. “Future research should evaluate the magnitude of cancer risks, the response to specific cancer treatments and the long-term outcomes associated with inherited mutations in breast cancer risk genes among postmenopausal women. We and others are engaged in this work.” – by Jennifer Southall

For more information:

Allison W. Kurian, MD, MSc, can be reached at Stanford University School of Medicine, 150 Governor’s Lane, HRP Redwood Building, Room T254A, Stanford, CA 94305; email: akurian@stanford.edu.

Disclosures: The study was supported by the BRCA Foundation, the Jan Weimer Faculty Chair in Breast Oncology, Myriad Genetics and the Suzanne Pride Bryan Fund for Breast Cancer Research. Kurian reports research funding to her institution from Myriad Genetics. Please see the research letter for all other authors’ relevant financial disclosures.

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