Pathogenic mutations in high- and moderate-risk breast cancer genes were detected in 23% of young women with an additional 3% having pathogenic mutations in colon cancer predisposition genes. VUS were observed in 14% of women in genes such as ATM, BRCA2, CDH1, CHEK2, and PALB2. Identification of those non-genetic factors is critical to reduce the burden of breast cancer in this population.

Currently, genetic testing is offered only to women diagnosed with breast cancer who meet a defined set of criteria and is not included as standard-of-care treatment at the time of diagnosis. Thus, a significant number of women diagnosed with breast cancer may miss the opportunity for precision medical treatment and risk management. The effects of eligibility, timing, and uptake of genetic testing were evaluated in a cohort of women with invasive breast cancer diagnosed between 2001–2018. Risk status was estimated using NCCN BRCA1/2 testing criteria and panel testing was performed for all women who had genomic DNA available. Of the 1231 women, 57.8% were eligible for genetic testing. Uptake of testing within high-risk women was 42.7% of which 6.6% pursued clinical testing only after a second tumor event. Mutation frequencies were 15.8%, 5.5%, and 4.0% in high-risk women with clinical testing, high-risk women without clinical testing, and low-risk women, respectively. More than 4% of all patients harbored pathogenic or likely pathogenic mutations detected only in the research setting. Inclusion of panel testing at the time of diagnosis would allow for appropriate surveillance and treatment strategies to be employed to reduce the risk of secondary tumors and improve patient outcome.

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In 2010, the genetic testing criteria was changed to allow women diagnosed ≤ 60 years old with triple negative breast cancer (TNBC) to undergo germline testing. In the same year, estrogen receptor (ER) positivity was defined as having ≥1% ER staining cells. While tumors with 1–10% ER staining cells and HER2 negative (HER2-) status share characteristics with TNBC, the utility of germline testing in women with ER low positive/HER2- (ERLP/HER2-) tumors is not well-understood. To this end, all patients with hormone receptor positive staining cells ≤ 10% and negative HER2 status were identified. Clinical genetic test results were extracted for patients who underwent testing. Panel testing was performed for those women who had genomic DNA available for research purposes. ERLP/HER2-tumors constituted 2.7% of all tumors in the database. Patients did not differ significantly from those with TNBC by age at diagnosis, ethnicity, family history or tumor size, stage or grade (p > 0.05). Mutation frequency did not differ significantly (p = 0.757) between groups (ERLP/HER2- 16.1%; TNBC 16.7%). Hereditary forms of breast cancer were similar in both ERLP/HER2- and TNBC, thus current guidelines may result in the under testing of women with low ER tumors, resulting in missed opportunities to improve patient management.

Black women in the US have significantly higher breast cancer mortality than White women. Within biomarker-defined tumor subtypes, disparate outcomes seem to be limited to women with hormone receptor positive and HER2 negative (HR+/HER2−) breast cancer, a subtype usually associated with favorable prognosis. In this review, we present data from an array of studies that demonstrate significantly higher mortality in Black compared to White women with HR+/HER2-breast cancer and contrast these data to studies from integrated healthcare systems that failed to find survival differences. Then, we describe factors, both biological and non-biological, that may contribute to disparate survival in Black women.