How do I conduct BRCA testing?

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How do I conduct BRCA testing?

Testing for germline BRCA1/2 mutations has been available since the 1990s and is currently used to assess cancer risk and inform treatment decisions. More recently tumour testing for BRCA mutations has also become available.1,2

A BRCA mutation can be either germline or somatic.3,4

  • A germline mutation occurs in a sperm cell or an egg cell and is passed directly from the parent, hence this type of mutation can be inherited, and therefore, can inform familial risk. These mutations become incorporated into the DNA of every cell in the body of the offspring.5 Although not everyone with a gBRCAm will have a family history of ovarian cancer there is the risk that it can be passed onto a carrier’s offspring6
  • A somatic mutation is a spontaneous genetic alteration that a cell acquires after conception. This type of mutation can develop in any cell in the body except the germ cells. This is a non-inheritable mutation7

A tumour BRCA test analyses DNA taken from a tumour biopsy and identifies both germline and somatic BRCA1/2 mutations but is unable to distinguish the origin. If a mutation is detected, a subsequent blood test is carried out to determine if the mutation is of germline origin.2,8 Germline mutations in BRCA1/2 are found in ~14% and of patients with high grade serous epithelial ovarian cancer, and somatic mutations in ~6%.9

Whilst blood tests can detect mutations of germline origin, the ~6% of patients with acquired somatic BRCA1/2 mutations will not be identified.8,9

Prevalence of BRCA1/2 mutations in ovarian cancer1,12

Prevalence-of-BRCA1-2-mutations-in-ovarian-cancer
Prevalence-of-BRCA1-2-mutations-in-ovarian-cancer

A BRCA mutation can be either germline or somatic3,4

Evolution in Genetic Testing for Breast Cancer
Evolution in Genetic Testing for Breast Cancer

Tumour Testing

Molecular testing of tumour samples can be utilised to identify genetic changes in cancer cells that may be driving the growth of an individual’s cancer.10 Previous challenges associated with tumour testing, such as difficulty in conducting accurate gene sequencing from formalin fixed paraffin embedded (FFPE) tissue samples, have since been overcome and many advances have been made.13 FFPE blocks are now routinely prepared in the pathology departments of most hospitals and are commonly used for a wide variety of tests.8,10 With the advances in next-generation sequencing (NGS), FFPE tissue can now also be reliably used for molecular testing.14

Tumour testing detects both somatic and germline mutations, and a follow-up germline test can confirm whether any mutations identified are inherited.2,11

The utility of tumour testing is growing as more targeted therapies are developed. Genomic instability tests also use DNA isolated from FFPE tumour tissue to assess genomic aberrations that are characteristic of homologous recombination deficiency.15-17

Tumour testing is required to detect somatic BRCA1/2 mutations18,19

Compared with a blood test alone, use of a tumour test can increase the proportion of women with ovarian cancer who can be identified as harbouring BRCA1/2 mutations18

Tumour testing is required to detect somatic BRCA1/2 mutations
Tumour testing is required to detect somatic BRCA1/2 mutations

Blood germline testing

A blood sample is taken from the patient and sent to an internal or external lab for DNA extraction. The DNA is processed and tested to determine the presence of germline BRCA mutation(s).8

*Tumour testing – A BRCA test can assess DNA directly from tumour cells, taken from a biopsy, to determine the presence of a mutation. This test can identify mutations of both somatic and germline origin, though is typically unable to distinguish the origin. If a mutation is found, a subsequent blood test is typically employed to determine if the mutation is in the germline.2,8

Evolution in Genetic Testing for Breast Cancer
Evolution in Genetic Testing for Breast Cancer

Learn more about limited-gene and multi-gene panels

In addition to BRCA testing with limited- or multi-gene panels, another method of genetic testing for ovarian cancer has been developed called a genomic instability test. This uses single nucleotide polymorphisms (SNPs) to identify genomic aberrations throughout the genome which are associated with homologous recombination deficiency.22

BRCA, breast cancer gene; gBRCAm, germline BRCA mutation; DNA, deoxyribonucleic acid; CDH1, cadherin 1; CHEK2, checkpoint kinase 2; ESMO, European Society for Medical Oncology; FFPE, formalin fixed paraffin embedded; FIGO, Federation of Gynecology and Obstetrics; NCCN, National Comprehensive Cancer Network® (NCCN®); NGS, next generation sequencing; PALB2, partner and localiser of BRCA2; PSR, platinum-sensitive relapsed; PSR, platinum-sensitive relapsed; PTEN, phosphatase and tensin homolog; RNA, ribonucleic acid; SNP, single nucleotide polymorphism; TP53, tumour protein p53.

References:

  1. Frey MK et al. Gynecol Oncol Res Pract. 2017; 4:4.
  2. Robson ME et al. J Clin Oncol. 2010; 28: 893-901.
  3. Griffiths AJF et al. An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000. Somatic versus germinal mutation. Available from: https://www.ncbi.nlm.nih.gov/books/NBK21894/. [Accessed March 2021].
  4. Neff RT, Senter L and Salani R. Ther Adv Med Oncol. 2017; 9: 519-531.
  5. National Cancer Institute. NCI Dictionary of Terms – germline mutation. Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/germline-mutation [Accessed March 2021].
  6. Neff T et al. Ther Adv Med Oncol. 2017; 8(9): 519-531.
  7. National Cancer Institute. NCI Dictionary of Terms – somatic mutation. Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/somatic-mutation [Accessed March 2021].
  8. Capoloungo E et al. Sem in Oncol. 2017; 44(3): 187-197.
  9. Konstantinopoulos PA et al. Cancer Discov. 2015; 5(11): 1137–1154.
  10. Normanno N et al. J Cell Biochem. 2013; 114: 514–524.
  11. Robson, ME et al. J Clin Oncol. 2015; 33: 3660-3667.
  12. George A et al. Sci Rep. 2016: 6; 29506.
  13. Kato M et al. Genome Med. 2018; 44(10): 1-11.
  14. McDonough SJ et al. PLoS One. 2019; 14(4): e0211400.
  15. D’Argenio V et al. Clinica Chimica Acta. 2015; 446: 221-225.
  16. Watkins JA et al. Breast Cancer Res. 2014; 16(3): 211.
  17. Timms KM et al. Breast Cancer Res. 2014; 16(6): 475.
  18. Pennington KP et al. Clin Cancer Res. 2014; 20: 764–75 [Supplementary Table 1].
  19. Kamps R et al. Int J Mol Sci. 2017; 18: 308.
  20. Lynce F and Isaacs C. Am Soc Clin Oncol Educ Book. 2016; 35: e72-e78.
  21. Tavtigian SV. Homologous Recombination Repair Genetics (HRR genes). Available at: https://uofuhealth.utah.edu/utah-genome-project/projects-list/breast-ovarian-pancreatic-cancers.php [Accessed March 2021].
  22. Mei R et al. Genome Res. 2000; 10: 1126–1137.
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INTERPRETING RESULTS

How do I interpret the results of a BRCA test and what does it mean for patients?

New improvements to the BRCA testing process can help provide results much faster, and using fewer resources

Learn more about what the results might mean for your patients

Germline and Somatic Mutation
Germline and Somatic Mutation

The field of genetic testing for ovarian cancer has evolved over the years. Originally single genes were sequenced, which was labour intensive and expensive.19 With advances in NGS, multigene panels have been introduced, allowing for wider genetic assessment, a faster testing process, with higher throughput, without being cost prohibitive.20

Clinically relevant target gene sequences have been incorporated into NGS gene panels, providing effective diagnostic tools to potentially personalise cancer therapies. These gene panels can assess multiple genes at once for specific cancer-related mutations.21

There are several approaches to testing for ovarian cancer mutations:4

  • Limited-gene panel: BRCA1 and BRCA2 – a sequence analysis of BRCA1 and BRCA2 that is performed concurrently with deletion/duplication analysis.20
  • Multi-gene panel:* Multiple mutations – tests the mutation status of many genes with just one sample and includes BRCA1 and BRCA2, alongside other cancer-associated genes of interest10,20

*Multi-gene panel testing has not been proven to support decision making in the newly diagnosed ovarian cancer setting.

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