Myriad Genetics Blog Myriad Genetics Blog > More Than Just Risk: Genetic Testing Is Shaping Breast Cancer Treatment More Than Just Risk: Genetic Testing Is Shaping Breast Cancer Treatment November 13, 2025 Breast Cancer Oncology By Sucharu Chris Prakash, MD, Medical Director of Quality, Texas Oncology | Editor-in-Chief, Evidence-Based Oncology®/AJMC Genetic testing for breast cancer has entered a new era, transforming from a niche tool for assessing family risk into a mainstream component of patient care that can reveal potential intervention points. Recent guidelines now recommend offering germline BRCA1/2 testing to all breast cancer patients aged 65 or younger as well as most patients over 65 years old, which demonstrates a major expansion beyond the old practice of testing only those with obvious risk factors. This shift comes as evidence mounts that genetic results directly impact treatment decisions, not just prevention. By identifying inherited mutations early, oncologists can more confidently navigate targeted therapies like PARP inhibitors, tailor chemotherapy, plan surgeries, and manage long-term risks such as secondary cancers. In short, genetic testing is becoming standard-of-care, helping to close gaps that previously left many mutation carriers undetected. Prevalence and Key Germline Mutations in Breast Cancer Approximately 5–10% of patients with breast cancer carry a pathogenic germline mutation. The most familiar are BRCA1 and BRCA2, but several other genes are also clinically important. Genes like PALB2 and TP53 confer greatly elevated risks (often on par with BRCA), while moderate-risk genes such as CHEK2 and ATM are more common and still warrant attention. Using a multigene panel to test for all these mutations at once can reveal those that single-gene testing would miss. Identifying any one of these mutations can influence a patient’s care. For example, finding a BRCA1/2 or PALB2 mutation might prompt discussion of bilateral mastectomy to reduce future cancer risk.¹ Similarly, a CHEK2 or ATM mutation leads to intensified surveillance (e.g. adding annual breast MRI) and consideration of preventive measures.² How Germline Testing Guides Treatment Genetic test results now guide treatment and management decisions in breast cancer. For example, BRCA1/2 mutations open the door to PARP inhibitors. Similarly, in high-risk early breast cancer, adjuvant olaparib significantly improves outcomes for BRCA carriers.³ Thus, knowing a patient’s BRCA status can directly expand their therapy options. Germline testing can also influence chemotherapy selection. BRCA-associated tumors respond especially well to platinum drugs, so some oncologists include a platinum agent if a patient is BRCA–positive.¹ When it comes to surgical planning, high-risk mutations hold great relevance. A patient with a BRCA1 or BRCA2 mutation faces a significantly higher chance of a second breast cancer, so some choose bilateral mastectomy instead of lumpectomy.¹ In some cases, bilateral mastectomy may also be recommended for patients with other high-risk mutations beyond BRCA. Beyond targeted therapy and surgery decisions, germline results also inform survivorship planning and family counseling. A patient with an inherited mutation will need enhanced long-term surveillance for second cancers and may pursue preventive therapies or surgeries. Case Study: Genomic Test Changes a Treatment Plan In a de-identified case example, a woman with HR-positive, HER2-negative breast cancer underwent tumor genomic profiling with the Precise Tumor® Molecular Test. The analysis identified two pathogenic PIK3CA mutations (p.N345K and p.G1049R), both known to activate the PI3K pathway and drive tumor growth. Based on these results, her care team had clear, guideline-supported options for targeted therapy, including FDA-approved combinations such as alpelisib plus fulvestrant or capivasertib plus fulvestrant for PIK3CA-mutated breast cancer. Beyond supporting targeted treatment selection, the findings also raised the possibility of a hereditary component, prompting consideration of follow-up germline testing to clarify inherited risk and guide family counseling. Without this tumor profiling, opportunities for a more personalized therapy plan, and potentially for identifying inherited cancer risk, might have been missed. Gaps and Disparities in Genetic Testing Despite the clear benefits outlined above, many eligible patients are not getting genetic testing. Studies show that only about 1 in 4 women with breast cancer receive recommended germline testing, meaning most mutation carriers go undetected during treatment.⁴ Several factors contribute to this gap. Often the responsibility for ordering testing is unclear – surgeons, medical oncologists, and others may each assume someone else has done it.⁵ For medical oncologists, a lack of formal genetics training and uncertainty around how to interpret or act on test results can lead to hesitation. Limited access to genetic counselors and concerns about financial toxicity for patients can also be barriers. This communication breakdown leads to missed opportunities. There are also disparities in access: patients from some racial/ethnic minority groups and rural areas are tested at lower rates.⁶ Additionally, some clinicians mistakenly think genetic testing is only about hereditary risk, not realizing its immediate impact on therapy. While growing awareness helps bridge some of this gap, quality measures are also beginning to incentivize genetic testing as part of standard care. Medicare’s MIPS program, which nonexempt providers are required to participate in,7 now tracks whether patients received germline testing, reflecting how genetics is becoming a care-quality metric.⁸ Overcoming the testing gap requires education, lab support services, streamlined workflows, and a mission to ensure every appropriate patient is offered testing. Putting Genetic Testing into Practice To fully realize the benefits of genetic testing, oncology teams can integrate testing into routine care using a few key strategies. The first step is testing early and automatically, making germline testing a standard step at diagnosis for new breast cancer cases. Testing early ensures results are available to guide surgery and adjuvant therapy decisions, which helps prevent oversight. The next step is using a focused multigene panel that includes high-penetrance genes such as BRCA1, BRCA2, PALB2, TP53, CHEK2, ATM, and other clinically relevant genes. Multigene panel testing maximizes the chance of finding any actionable mutation in one swoop. This approach aligns with current guideline recommendations. An important, often overlooked part of this approach is ensuring patients have access to genetic counseling to help them understand the process and results. Pre-test counseling sets expectations, while post-test counseling explains the findings and next steps. While medical oncologists are increasingly involved in ordering the initial germline testing themselves, many reserve genetic counselor involvement for difficult or positive cases, and although not ideal, this may be a reasonable compromise when resources are limited. For practices managing high volumes or limited internal resources, support from outside genetic counselors such as Myriad Oncology’s certified team of genetic counselors, who provide guidance and coordination support rather than full patient counseling, can help extend care while maintaining consistency and access. By making genetic testing a routine part of oncology care, we all play a role in improving patient outcomes and family health. This is no longer just about estimating future risk, it is a tool for tailoring today’s treatment and tomorrow’s surveillance. As Breast Cancer Awareness Month emphasizes proactive, personalized care, the message to us clinicians is clear: embrace genetic testing early and integrate it into your practice. References Tung NM,et al.. Management of Hereditary Breast Cancer: American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology Guideline. J Clin Oncol. 2020 Jun 20;38(18):2080-2106. doi:10.1200/JCO.20.00299. Epub 2020 Apr 3. PMID: 32243226. Facing Our Risk of Cancer Empowered (FORCE). Should all breast cancer patients receive genetic testing? Published October 27, 2020. Updated December 13, 2023. Accessed July 28, 2025. https://www.facingourrisk.org/XRAY/genetic-testing-all-breast-cancer-patients?campaign=698450 Toner C. OlympiA Trial: Adjuvant Olaparib Extends Disease-Free Survival in BRCA-Mutated Early Breast Cancer. The ASCO Post. October 10, 2021. Accessed July 28, 2025. https://ascopost.com/issues/october-10-2021-supplement-breast-cancer-almanac/olympia-trial-adjuvant-olaparib-extends-disease-free-survival-in-brca-mutated-early-breast-cancer National Cancer Institute. (2023, September 5). Germline Testing for Cancer Is Underused, Study Confirms. Cancer Currents Blog. https://www.cancer.gov/news-events/cancer-currents-blog/2023/germline-testing-for-cancer-underused Iowa Oncology Society. (2022). A Multidisciplinary Consortium to Advance Genetic Counseling in Oncology. Retrieved from https://www.accc-cancer.org/docs/ossn-network/ia/lunch-and-learn/a-multidisciplinary-consortium-to-advance-genetic-counseling-in-oncology.pdf National Cancer Institute. (2023). Germline Testing for Inherited Cancer Risk Is Underused, Study Finds. Retrieved from https://www.cancer.gov/news-events/cancer-currents-blog/2023/germline-testing-for-cancer-underused Retrieved from https://mdinteractive.com/MIPS-Participation Centers for Medicare & Medicaid Services. Quality Measure 507: Appropriate Germline Testing for Ovarian Cancer Patients. 2025 Measure Specifications. Accessed July 24, 2025.