Characteristics of BRCAm breast cancer

Prevalence of BRCA mutations in breast cancer

What is known about BRCA mutated breast cancer?

BRCA-mutated breast cancer can be considered high risk due to its characteristics:

  • Pathogenic mutations in breast cancer (BRCA) genes are associated with increased risk of cancer.1-3 While lifetime risk for developing breast cancer in the general female population is 5%, mutations in BRCA1 and BRCA2 genes increase the risk to approximately 70% (72% for BRCA1 and 69% for BRCA2).1,2
  • Patients with BRCA-mutated (BRCAm) breast cancer also have distinct tumor characteristics compared with the sporadic population:4-8 BRCAm breast cancer is more aggressive, the patients are younger at the diagnosis (BRCAm, 40–45 years;9,10 non-BRCAm, 63 years11), tumor grade is higher with increased Ki67 proliferation marker expression, patients have more CNS metastases and more contralateral or ipsilateral disease compared with the sporadic breast cancer population.4-8
  • Patients with BRCA1/2 mutations also have higher rates of advanced disease, higher mitotic index than non-mutation carriers, and are most likely to have a high (BRCA1) or intermediate (BRCA2) risk of recurrence score.6,12

Prevalence of BRCA mutations in breast cancer

  • Germline BRCA mutation is present in about 5% of all breast cancers and the prevalence is higher in the individuals with family history or cancer diagnosed at a young age.5,13
  • Germline BRCA mutation also increases the risk of ovarian, pancreatic and prostate cancers.14
  • Hormone receptor positive (HR+) is the most common breast cancer subtype, accounting for over 70% of breast cancer cases.6,15 Of all HR+ cases, approximately 6% are also BRCA mutation carriers, predominantly BRCA2.6,15
    • In triple-negative breast cancer (TNBC) patients up to 16% carry BRCA mutations, predominantly a BRCA1 variant.16 However, due to the relative prevalence, the majority of BRCA mutation carriers are found in the HR+ patient population.
  • Additionally, in the HR low-positive (1–9% of cells expressing HRs), HER2-negative patient group the prevalence of BRCA mutations may be similar to that of the TNBC population.17

This highlights that both HR+ and TNBC patients have a risk of possessing BRCA mutations, and at diagnosis the patients should be submitted to BRCA testing early.

BRCA mutation status serves as predictive biomarker, in addition to indicating heredity

  • Previously, the purpose of BRCA testing was mainly to indicate heredity and prevent new cancers by testing family members of breast cancer patients. 3
  • Now the role of BRCA testing has changed: new therapeutics targeting BRCA-mutated, HER2-negative tumors are available (e.g., PARP inhibitors) and BRCA mutation status can also be used as a predictive biomarker to guide treatment selection.18,19
  • Therefore, different recently updated breast cancer treatment guidelines, e.g., NCCN and Swedish national guidelines, recommend BRCA testing for all patients who can benefit from PARP inhibitor treatment, i.e. patients with HER2-negative tumors.16,18,20
  • Since the results from BRCA testing also have therapeutic implications, the testing should therefore be discussed with the patient and carried out as early as possible.20,21

What is the role of BRCA in cancer development?

BRCA mutation is one of key drivers of cancer pathology and represent an opportunity for targeted therapy

Read more

Mechanism of action of PARPi and other treatments used in HER2-negative breast cancer

Targeted therapies for HER2-negative breast cancer - How do PARP, CDK4/6 and PD-L1 inhibitors work?

Read more

References

  1. Kuchenbaecker KB, et al. JAMA. 2017; 317:2402-2416.
  2. Sung H, et al. CA Cancer J Clin. 2021 May;71(3):209-249.
  3. Pujol P, et al. Eur J Cancer. 2021 Mar;146:30–47.
  4. Baretta Z, et al. Medicine. 2016;95:e4975
  5. Bu R, et al. Int J Cancer. 2016; 139:1091–1097
  6. Aleskandarany M, et al. Breast Cancer Res Treat. 2015;150:81–90
  7. Song Y, et al. Cancer. 2020;126(2):271–280.
  8. Valachis A, et al. Breast Cancer Res Treat. 2014;144:443–455
  9. Mavaddat N, et al. Cancer Epidemiol Biomarkers Prev. 2012;21:134–147
  10. Krammer J, et al. Breast Cancer Res Treat. 2017;163:565–571
  11. Winter C, et al. Ann Oncol. 2016; 27(8): 1532–1538.
  12. Lewin R, et al. Breast Cancer Res Treat. 2016;157:511–516
  13. De Talhouet S, et al. Sci Rep. 2020 Apr 27;10(1):7073.
  14. Balmaña J, et al. Ann Oncol. 2011;22(Suppl. 6):vi31–vi34
  15. Winter C, et al. Ann Oncol. 2016; 27(8): 1532–1538. Supplementary Table S4.
  16. NCCN Guidelines Genetic/Familial High-Risk Assessment: Breast, Ovarian and Pancreatic. V1.2023. https://www.nccn.org/guidelines/guidelines-detail?category=2&id=1503. Last accessed September, 2022.
  17. Sanford RA, et al. Cancer. 2015 Oct 1;121(19):3422–7.
  18. Lynparza SPC. https://www.ema.europa.eu/en/documents/product-information/lynparza-epar-product-information_en.pdf. Last accessed September, 2022.
  19. Talzenna SPC. https://www.ema.europa.eu/en/documents/product-information/talzenna-epar-product-information_en.pdf. Last accessed September, 2022.
  20. Nationellt vårdprogram bröstcancer. https://kunskapsbanken.cancercentrum.se/diagnoser/brostcancer/vardprogram/. Last accessed August 2022.
  21. Cardoso F, et al. Ann Oncol. 2020 Dec; 31(12):1623-1649.

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