Genetic Testing for Hereditary Breast Cancer: How It Works and Who Should Get Tested

Breast cancer is the most common cancer in women worldwide, with approximately 2.3 million new cases estimated in 2020, according to the World Health Organization (WHO). Therefore, genetic testing for breast cancer is essential for assessing risks and supporting diagnosis.

In addition to breast cancer, gynecological cancers are highly significant among the most common cancers affecting women. These include cervical, ovarian, endometrial, vulvar, and vaginal cancers.

Genetic predisposition is considered an important epidemiological factor, as 5 to 10% of all cases are related to the inheritance of genetic variants (1). A family history of breast cancer is a risk factor for the disease, with variants in genes, such as those in the BRCA family, increasing the risk of developing the disease.

This article aims to explain how genetic testing for breast cancer and other hereditary gynecological cancers works, as well as to clarify details about genetic predisposition.

What are genetic tests?

Genetic tests search for changes in DNA, known as variants, that are useful in many areas of medicine and can influence clinical management for patients and their families (2).

These tests used to be performed on just one or a few genes. However, in recent years, genetic tests have expanded to analyze groups of genes simultaneously, known as genetic panels or panel tests. This has significantly advanced the identification of actionable genetic variants (3).

Genetic panel tests are generally categorized based on different clinical manifestations.

How are genetic alterations related to breast cancer?

Breast cancer can arise from genetic variants that alter the behavior of breast cells, leading to uncontrolled growth. Changes in the BRCA1 and BRCA2 genes, which are responsible for DNA repair, are the most well-known examples. When these changes occur, cells lose their ability to repair DNA damage, increasing the risk of breast cancer development (4).

Studies indicate that inherited variants in these genes may increase breast cancer risk compared to the general population (4). In addition to BRCA1 and BRCA2, other gene alterations, such as in TP53, PALB2 and ATM, have also been associated with an increased risk of breast and other gynecological cancers.

Can breast cancer be hereditary?

Yes, breast cancer can be hereditary. About 5 to 10% of all breast cancer cases are related to inherited genetic alterations. A family history of breast cancer, especially in first-degree relatives like a mother or sister, significantly increases the risk.

These signs indicate the need to consider genetic testing to evaluate hereditary predisposition:

• Diagnosis of breast cancer at an early age (before 50 years old);
• Family history of breast, ovarian, or other cancers related to BRCA1 and BRCA2 gene variants;
• Occurrence of bilateral breast cancer (in both breasts);
• Family history of breast cancer;
• Diagnosis of triple-negative breast cancer, often associated with BRCA1 alterations.

Genetic Predisposition Syndrome

In cancer, hereditary predisposition syndrome is characterized by genetic alterations (variants) that make certain cancers more prevalent within families. In other words, the presence of genetic variants can increase an individual’s risk of developing cancer (5).

The ability to identify a proportion of all cancers that develop in individuals who have inherited a genetic variant that increases susceptibility to specific cancers allows for targeted efforts in cancer surveillance and prevention (5).

The hereditary risk of variants in BRCA1 and BRCA2 genes

The neoplastic formation process begins when variants alter the function of genes that directly or indirectly regulate cell proliferation, differentiation, or survival—processes that are critical and tightly controlled in our bodies (6).

The most well-known genes associated with hereditary breast and ovarian cancer syndrome are BRCA1 and BRCA2. Approximately 30% of patients with hereditary breast and ovarian cancer carry germline point mutations or genomic structural rearrangements that result in copy number variations (CNVs) in BRCA1 and BRCA2 genes (7).

Other cases are generally due to a combination of effects produced by variants in highly penetrant genes, such as P53, PTEN and ATM (about 1%), or by variants in other genes not yet described (8).

When considering pathogenic germline variants and their association with cancer, genes are grouped by their penetrance, that is, the lifetime risk of developing the disease (9). The terms high, moderate, and low penetrance provide an assessment of cancer risks associated with these genes.

The origin of this genetic susceptibility often lies in variants in BRCA1 and BRCA2 genes. Approximately 10% of breast cancer cases each year are associated with hereditary predisposition and strongly penetrant variants in these genes (10).

However, there are other genes related to breast, ovarian, and endometrial cancer that should be studied to provide more comprehensive information for a thorough medical analysis.

Thus, screening for variants in the BRCA1 and BRCA2 tumor suppressor genes, along with associated genes, is of great importance for the prevention and early detection of gynecological cancer (11).

When a variant is identified, the risk of cancer development can be reduced through prophylactic strategies. Furthermore, if a variant is detected, genetic testing can be extended to relatives who may join specific screening programs for carriers or follow the general population strategy for non-carriers.

How can genetic testing help detect breast cancer?

Genetic testing plays a crucial role in detecting and preventing breast cancer and other hereditary gynecological cancers. By identifying variants in the BRCA1, BRCA2 genes and other cancer-associated genes, genetic testing allows for early risk assessment, enabling the implementation of preventive measures such as intensive surveillance, prophylactic surgeries, or targeted treatments.

Additionally, genetic testing can provide guidance for the patient’s family members. If a pathogenic variant is identified, relatives can be tested to assess their risk and adopt specific preventive strategies suited to their situation.

What panel does SYNLAB offer and which genes are analyzed?

SYNLAB offers the BRCA+16 genetic panel, designed to detect point mutations and small insertions and deletions in 18 genes related to hereditary gynecological cancer.

These genes are involved in cell cycle control and DNA repair during cell divisions. Variants in these genes may lead to a loss of cellular control and DNA repair capabilities, which can result in a higher cancer risk compared to the general population.

The genes analyzed in the BRCA+16 panel (ATM, BRCA1, BRCA2, BRIP1, CDH1, CHEK2, EPCAM, MLH1, MSH2, MSH6, NBN, PALB2, PMS2, PTEN, RAD51C, RAD51D, STK11, TP53) are linked to breast cancer, ovarian cancer (including somatic types), endometrial cancer, cervical cancer, and hereditary breast and ovarian cancer.

SYNLAB’s BRCA+16 Test

The BRCA+16 test is a non-invasive blood test that analyzes the patient’s DNA through Next Generation Sequencing (NGS) to detect point mutations and small insertions/deletions (indels) in 18 genes related to hereditary gynecological cancer.

Additionally, the BRCA+16 test can detect copy number variations (CNVs), large deletions, and duplications in the BRCA1, BRCA2 and EPCAM genes, as well as confirm all pathogenic or likely pathogenic variants detected. This makes the BRCA+16 test the only genetic panel for the study of gynecological cancer that integrates three molecular techniques: NGS, MLPA, and bidirectional Sanger sequencing, in a single analysis.

This unique integration of methodologies ensures greater sequencing coverage and depth, providing a high level of diagnostic excellence.

The report includes the following types of alterations:

• Pathogenic variants: variants linked to pathology;
• Likely pathogenic variants: variants likely related to pathology;
• Variants of uncertain significance (VOUS): suspicious variants, but without decisive evidence of pathogenicity.

Who should take the BRCA+16 Test?

• Women over 30 years old with no history of cancer, as a preventive measure for breast and/or ovarian cancer.
• Women with a family history of breast (male or female) and/or ovarian cancer.
• Relatives of individuals carrying variants in the BRCA1 or BRCA2 genes.
• Patients diagnosed with these types of tumors, to determine their potential hereditary profile.

What methodologies are used in the Test?

The main methodologies used in SYNLAB’s BRCA+16 test are:

• Next-Generation Sequencing (NGS)

With rapid advancements in Next-Generation Sequencing (NGS) technology, simultaneous sequencing of multiple genes is now available through multi-gene panel tests, which is cheaper and faster than single-gene testing (12).

Furthermore, these panels have increased the detection rate of variants compared to traditional single-gene testing. NGS is an automated, parallel, high-throughput sequencing method, allowing millions of DNA sequences to be analyzed simultaneously.

NGS enables the sequencing of the entire genome (or specific areas like the exome) or a small number of genes, detecting point mutations, substitutions, and small insertions/deletions in DNA sequences.

However, due to a technical limitation, NGS cannot detect large deletions and insertions.

• Multiplex Ligation-dependent Probe Amplification (MLPA)

MLPA, or Multiplex Ligation-dependent Probe Amplification, is a reliable and sensitive method used to detect copy number variations (CNVs), deletions, and duplications in specific, known regions of the genome. This technique uses multiplex PCR (Polymerase Chain Reaction) to amplify multiple different DNA sequences simultaneously, making the process more efficient.

Given that genomic structural rearrangements leading to CNVs in cancer-predisposing genes, alongside point mutations in the BRCA genes, are associated with gynecological cancers (13), analyzing these genes with MLPA is essential and complements NGS in detecting pathogenic variants.

• Sanger Sequencing

Sanger sequencing determines the exact order of nucleotides in a gene, typically sequencing small regions of DNA, around 500 to 900 base pairs.

It is recommended for sequencing small DNA regions, PCR fragments, or confirming pathogenic, likely pathogenic, or uncertain variants detected in NGS sequencing.

Additional Important Information About the Test

The presence of pathogenic variants in the genes included in the BRCA+16 test implies an increased risk of developing hereditary gynecological cancers (mainly breast, ovarian, and endometrial cancer) compared to the general population. Testing asymptomatic women allows for the implementation of measures to prevent the development of these cancers in those at higher risk.

Detection of a pathogenic variant in patients diagnosed with gynecological cancer justifies testing their relatives to determine whether they carry the same variant.

Because cancer is a multifactorial disease, the risks of developing gynecological cancer involve various factors, such as hereditary predisposition, age over 40, childlessness or having children after age 40, continuous contraceptive use, and hormone replacement therapy. Other lifestyle-related factors, such as alcohol consumption, excess weight, lack of exercise, and exposure to ionizing radiation, which can cause DNA damage, also play a role.

In recent years, several new high- and moderate-penetrance genes have been introduced into the study of women with an increased risk of gynecological malignancies. Knowledge of these new genes and the availability of multi-gene panel testing are essential for healthcare professionals on the frontlines of women’s health.

Genetic testing for hereditary cancer syndromes can identify individuals and families at an increased risk of developing cancer, allowing them to be referred for risk assessment and personalized management. This may include intensive cancer surveillance, risk-reducing surgery, and genetic counseling (14).

Learn more about SYNLAB, a leading provider of medical diagnostic services!

Accurate and up-to-date testing is essential for making more precise diagnoses and guiding treatments effectively. SYNLAB is here to help.

We offer diagnostic solutions with strict quality control to the companies, patients, and physicians we serve. We’ve been operating in Brazil for over 10 years, across 36 countries and three continents, and we are a leader in service provision in Europe.

Contact the SYNLAB team to learn more about available tests.

References

1. INCA – disponível em: livro-abc-3-edicao.pdf (inca.gov.br)
2. CDC Disponível em: Genetic Testing | Genomics and Your Health | CDC
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4. Garber J, Offit K. Hereditary cancer predisposition syndromes. J Clin Oncol. 2005 Jan 10;23(2):276-92. doi: 10.1200/JCO.2005.10.042.
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7. Ponder BA. Cancer genetics. Nature. 2001 May 17;411(6835):336-41. doi: 10.1038/35077207.
8. Domchek SM, Robson ME. Update on Genetic Testing in Gynecologic Cancer. J. Clin. Oncology. DOI https://doi.org/10. 1200/JCO.19.00363.
9. Antoniou A, et al. Average risks of breast and ovarian cancer associated with BRCA1 or BRCA2 mutations detected in case Series unselected for family history: a combined analysis of 22 studies. Am J Hum Genet. 2003 May;72(5):1117-30. doi: 10.1086/375033.
10. Plevritis SK, Kurian AW, Sigal BM, Daniel BL, Ikeda DM, Stockdale FE, Garber AM. Cost-effectiveness of screening BRCA1/2 mutation carriers with breast magnetic resonance imaging. JAMA. 2006 May 24;295(20):2374-84. doi: 10.1001/jama.295.20.2374.
11. Disponível em The Cost of Sequencing a Human Genome
12. Silva FC, Lisboa BCG, Figueiredo M, et al. Hereditary breast and ovarian cancer: assessment of point mutations and copy number variations in Brazilian patients. BMC Med Genet. 2014 May 15:15:55. doi: 10.1186/1471-2350-15-55.
13. Shin HC, Lee HB, Yoo TK, et al. Detection of Germline Mutations in Breast Cancer Patients with Clinical Features of Hereditary Cancer Syndrome Using a Multi-Gene Panel Test. Cancer Res Treat. 2020 Jul;52(3):697-713. doi: 10.4143/crt.2019.559. Epub 2020 Feb 4.