How genetic tests work for the predisposition of gynecological cancer

Breast cancer is the cancer with the highest incidence in women worldwide, with approximately 2.3 million new cases estimated in 2020, according to the World Health Organization (WHO).  

In addition to breast cancer, gynecological cancer has great relevance among the cancers that most affect women, being the second most common type, and includes cancer of the cervix, ovary, endometrium, vulva and vagina.  

Genetic predisposition is considered an important epidemiological factor, since 5 to 10% of all cases are related to the inheritance of genetic variants. The family history of breast cancer is a risk factor for the disease, in which variants in genes, such as those of the BRCA family, increase the risk of the onset of the disease. 

What are genetic tests? 

Genetic tests are those that look for changes in DNA, changes that are called mutations or variants, useful in many areas of medicine, and that can change the clinical conduct for patients and their families. 

These tests were performed on, at the most, one or a few genes. However, in recent years, genetic testing has been carried out on several genes at the same time, referred to as genetic panel or panel test, and this has led to a significant boost in the identification of actionable genetic variants. Genetic panel tests are generally grouped into categories based on different types of clinical manifestations. 

Genetic Predisposition Syndrome 

In cancer, hereditary predisposition syndrome is characterized by genetic alterations (variants), in which certain neoplasms become more prevalent in individuals of the same family, that is, the presence of gene variants can increase a person’s risk of developing cancer. 

The ability to distinguish a proportion of all cancers that develop in individuals who have inherited a genetic variant and that confers greater susceptibility to specific cancers, allows targeted efforts in cancer surveillance and prevention. 

The hereditary risk of variants in the BRCA1 and BRCA2 genes  

The process of neoplastic formation begins when variants alter the function of genes that directly or indirectly regulate cell proliferation and differentiation, or even the survival of cells; very important and strictly controlled processes in our organism. 

The most well-known genes associated with the hereditary breast and ovarian cancer syndrome are the BRCA1 and BRCA2 genes. About 30% of patients with hereditary breast and ovarian cancer present point mutations in the germ line, or structural genomic rearrangements that result in variations in the number of copies (CNVs) in the BRCA1 and BRCA2 genes.  

The other cases are generally due to acombination of the effects produced by variants in known genes of high penetrance, such as for example in the P53, PTEN and ATM genes (about 1%), or by variants in other genes not yet described. 

When considering pathogenic variants of the germline and its association with cancer, the genes are grouped by their penetrance, that is, by the risk throughout life for the development of the disease. The terms high, moderate and low penetrance provide an assessment of the associated cancer risks.  

The origin of this genetic susceptibility often consists of variants in the BRCA1 and BRCA2 genes. Approximately 10% of breast cancer cases that occur each year are associated with a hereditary predisposition and with strongly penetrating variants in these genes. However, there are other genes related to breast, ovarian and endometrial cancer that must be studied to provide more complete information for a more comprehensive medical analysis.  

Thus, the screening test for variants in the tumor suppressor genes BRCA1 and BRCA2, and in associated genes, is of great importance for the prevention and early detection of gynecological cancer. When a variant is identified, the risk of developing cancer can be reduced by prophylactic strategies. In addition, if a mutation is detected, the genetic test can be extended to relatives who can enter specific screening programs for carriers or follow the strategy for the general population (non-carriers).  

Which panel does SYNLAB offer and which genes are analyzed? 

Synlab offers the genetic panel, BRCA Plus  which aims to detect point variants and small insertions and deletions in 18 genes related to hereditary gynecological cancer. 

The included genes are related to cell cycle control and DNA repair during cell division. Variants in these genes presuppose a loss of cell control and the ability to repair DNA, which may imply a greater risk of developing cancer than in the general population. 

The genes analyzed in BRCA Plus (ATM, BRCA 1, BRCA 2, BRIP 1, CDH1, CHEK2, EPCAM, MLH1, MSH2, MSH6, NBN, PALB2, PMS2, PTEN, RAD51C, RAD51D, STK11, TP53) were correlated with breast, ovarian (including somatic), endometrial, cervical, uterine tubes and hereditary breast and ovarian cancer. 

SYNLAB’s BRCA Plus Test 

BRCA Plus is a non-invasive test by blood collection, which consists of analyzing the patient’s DNA by mass sequencing NGS (Next Generation Sequencing) to detect point variants and small insertions / deletions (indels) in 18 genes related to gynecological cancer hereditary.  

The BRCA Plus test also allows the detection of variations in the number of copies (CNVs), and large deletions and duplications, of the BRCA1, BRCA2 and EPCAM genes, in addition to confirmatory for all pathogenic or probably pathogenic variants detected. Thus, the BRCA Plus Test is the only genetic panel for the study of gynecological cancer that integrates the three molecular techniques, NGS + MLPA and bidirectional Sanger sequencing, in a single analysis.  

This unique integration of methodology guarantees greater coverage and depth of sequencing to the test and a high level of excellence in diagnosis. 

The report includes changes such as:  

• Pathogenic variants: variants related to pathology.  
• Probably pathogenic variants: variants probably related to the pathology.  
• Variants of uncertain significance (VOUS): suspicious variants, but without determinant evidence of pathogenicity. 

For whom is the BRCA Plus test indicated? 

• Women over 30 without a history, as a preventive measure against breast and / or ovarian cancer.  
• Women with a family history of breast cancer (male or female) and/or ovarian cancer.  
• Family member with variant in BRCA1 or BRCA2 genes.  
• Patients suffering from this type of tumor, in order to determine their possible hereditary profile.

   

What are the methodologies used in the test? 

• Next generation sequencing (NGS) 

With the rapid progress that has been made in, next-generation sequencing technology, or NGS, simultaneous sequencing of multiple genes has become available through cheaper and faster multi-gene panel testing than testing a single gene. In addition, the use of these panels increased the rate of detection of variants compared to conventional gene-by-gene testing. Therefore, the NGS can be considered as an automated, parallel and high-throughput sequencing, that is, a method of automatic sequencing of millions of DNA sequences simultaneously. 

Since the NGS allows to sequence the entire genome (or specific areas of the genome, as in the exome) or a small number of genes, it is possible to detect point variants, such as substitutions, or small insertions and deletions of nitrogenous bases in the sequence of DNA.  

However, due to a technique limitation, sequencing does not allow the detection of large deletions and insertions.  

• Multiplex Ligation-dependent Probe Amplification (MLPA):  

The Multiplex Ligation-dependent Probe Amplification technique,better known as MLPA, is the most reliable and economical method that allows variations in the number of copies (CNVs), deletions and duplications to be detected in specific and previously known regions of the genome, by performing PCR (polymerase chain reaction) multiplex, which aims to amplify several different DNA sequences simultaneously. 

Since the presence of structural genomic rearrangements resulting in CNVs in genes that predispose breast cancer together with specific point variants in the BRCAs genes have been associated with gynecological cancer, the analysis of these genes by MLPA is necessary and complements the analysis of NGS in the detection of pathogenic variants. 

• Sanger Sequencing 

Sequencing consists of determining the exact sequence in which the nucleotides are found in a gene. Sanger sequencing is considered to be first generation, and allows the sequencing of stretches of DNA with about 500 to 900 base pairs only.  

They are indicated for sequencing small regions of DNA, fragments obtained by PCR, or for confirming pathogenic variants, probably pathogenic or of uncertain significance detected in NGS sequencing.  

Other important information about the test  

The presence of pathogenic changes in the genes included in the BRCA Plus test implies an increased risk of developing hereditary gynecological cancer (mainly breast, ovarian and endometrial cancer), when compared to the general population. The test in asymptomatic women allows to implement measures to prevent the development of these types of cancers (in those patients with a higher risk).  

The detection of a pathogenic variant in patients diagnosed with gynecological cancer justifies the analysis also in their family members to determine whether they are carriers of the same variant. 

Since cancer is a multifactorial disease, the risks for the development of gynecological cancer involve several factors such as: hereditary predisposition, being over 40 years old, not having children or having been a mother after 40 years of age, continuous use of contraceptives and hormone replacement. In addition to other factors related to lifestyle, such as alcohol consumption, overweight, physical inactivity and exposure to ionizing radiation, that can cause damage to the genome. 

In recent years, several new genes of high and moderate penetrance have been introduced in the study of women with increased risk of gynecological malignancy. The knowledge of these new genes and the availability of new panel tests of several genes is essential for professionals working on the frontline of women’s health. 

Genetic tests for hereditary cancer syndromes can identify individuals and families at increased risk of developing cancer, and with that they can be referred for risk assessment and personalized management that can include intensive cancer surveillance, risk reduction surgery and genetic counseling. 

About the SYNLAB Group 

The SYNLAB Group is a leader in providing medical diagnostic services in Europe, providing a full range of clinical laboratory analysis services to patients, healthcare professionals, clinics and the pharmaceutical industry. Resulting from the Labco and SYNLAB merger, the new SYNLAB Group is the undisputed European leader in medical laboratory services.