Date Degree Awarded

Spring 5-16-2020

Degree Type

Open Access Master's Thesis

Degree Name

Master of Science in Human Genetics and Genetic Counseling

First Thesis/Dissertation Advisor

John Lee

Second Thesis/Dissertation Advisor

Danielle Dondanville

Third Thesis/Dissertation Advisor

Heather McArthur

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Women who harbor mutations in breast cancer susceptibility genes are at an increased lifetime risk of developing breast cancer and are faced with decisions about managing their risks, including the decision of whether to undergo a risk reducing mastectomy (RRM). While decision making for risk management has been studied extensively for BRCA1 and BRCA2 carriers, there is much less information surrounding risk management for women with mutations in moderate penetrance genes. This is a retrospective study of 280 women undergoing genetic counseling at a Los Angeles-based academic hospital between 2009 and 2019. The study used medical records to examine rates of RRMs in both affected and unaffected women with 1) no known mutation (N=92), 2) a mutation in a moderate penetrance gene CHEK2, ATM, NBN, or PALB2 (N=90), or 3) a BRCA mutation (N=98). Participants had a mean age of 45.7 years and were 78% Caucasian, 34% affected with breast cancer, and 31% never married. Results showed that mutation status was associated with RRM decision (p<.001), with 8.6% (8/92) of women with no known risk mutations, 30% (27/90) of moderate penetrance gene carriers, and 39.8% (39/98) of BRCA mutation carriers undergoing RRM. Women were more likely to undergo RRM if they were affected with breast cancer (p<.001), had a younger age at diagnosis (p<.001), were presented with a higher lifetime risk (p=.006), and were married or partnered (p=0.02). Participants with a moderate risk mutation without breast cancer were more likely to have RRM if they had a first degree relative with breast cancer (p=.03). The NCCN Guidelines® does not typically recommend consideration of RRM for moderate penetrance carriers, but their rates of RRM approach those of BRCA carriers. Genetics providers must better equip surgeons and patients with knowledge of risks associated with moderate penetrance mutations, and healthcare providers must strive to understand why surgical decisions are made.

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