Genetic Testing for Cancer in Turkey: An Overview

An Introduction to Genes and Cancer

Cancer is fundamentally a genetic disease, meaning it is caused by changes, or “mutations,” in the DNA of our cells that lead to uncontrolled growth. In the vast majority of cases, these mutations are “somatic,” meaning they are acquired randomly during a person’s lifetime and are only present in the tumor cells.

However, in a smaller but significant percentage of cases (about 5-10% of all cancers), a person can inherit a specific genetic mutation from a parent that puts them at a much higher risk of developing certain types of cancer. This is known as a hereditary cancer syndrome. Genetic testing is a powerful medical tool that can identify these inherited mutations, providing crucial information for cancer prevention, early detection, and treatment for both the patient and their family members. Advanced oncology centers in Turkey have integrated genetic counseling and testing into their comprehensive cancer care programs.

Understanding Hereditary Cancer Risk

Everyone inherits two copies of every gene, one from each parent. Most genes include instructions for making proteins that help control cell growth and repair DNA damage. A person with a hereditary cancer syndrome inherits one normal copy of such a gene and one mutated, non-working copy. While the normal copy is usually sufficient to do the job for a while, their cells are at a disadvantage. It only takes one acquired mutation in the remaining normal copy for the cell’s growth control to be lost, which can lead to cancer. This is why individuals with these inherited mutations have a much higher lifetime risk of developing cancer, often at a younger age than is typical.

The most well-known hereditary cancer syndromes are:

• Hereditary Breast and Ovarian Cancer (HBOC) Syndrome: Caused primarily by inherited mutations in the BRCA1 and BRCA2 genes. These mutations significantly increase the risk of breast, ovarian, prostate, and pancreatic cancers.
• Lynch Syndrome (Hereditary Non-Polyposis Colorectal Cancer): Caused by mutations in genes responsible for DNA mismatch repair. It dramatically increases the risk of colorectal, endometrial, ovarian, and stomach cancers, among others.

The Role of the Genetic Counselor

The process of genetic testing for hereditary cancer risk is more than just a blood test. It should always be managed through a process called genetic counseling. In Turkey, this service is provided by physicians or genetic specialists with specific training in medical genetics.

A genetic counselor plays several vital roles:

1. Risk Assessment: They begin by taking a detailed personal and family medical history, often looking back over three generations. They look for “red flags” that might suggest a hereditary cancer syndrome, such as cancer diagnosed at a young age, multiple family members with the same or related cancers, or an individual with multiple primary cancers.
2. Patient Education: The counselor provides detailed education about genetics, inheritance, and the specific syndromes for which testing is being considered. They explain the potential benefits, risks, and limitations of genetic testing.
3. Facilitating Informed Consent: They ensure that the patient understands what the test can and cannot tell them, and what the potential medical, emotional, and familial implications of a positive or negative result might be.
4. Interpreting and Disclosing Results: The counselor explains the test results in clear, understandable language and discusses what they mean for the patient’s future health management.
5. Providing Support and Guidance: They offer psychosocial support and help the patient communicate the results to at-risk family members.

The Genetic Testing Process

If, after counseling, a patient decides to proceed with testing, the process is usually straightforward.

• The Sample: Testing is typically done on a simple blood sample or, in some cases, a saliva sample.
• The Analysis: In the laboratory, DNA is extracted from the cells. Genetic specialists use advanced technology like Next-Generation Sequencing (NGS) to analyze a “panel” of genes known to be associated with hereditary cancer.
• The Results: The results can take several weeks to come back and will be disclosed to the patient by the genetic counselor or physician.

The results can fall into one of three categories:

• Positive: A pathogenic mutation known to increase cancer risk has been identified. This leads to a clear plan for increased screening and prevention.
• Negative: No known pathogenic mutation was found in the genes that were tested. This is reassuring but does not mean the person has zero risk of cancer; their risk is simply closer to that of the general population.
• Variant of Uncertain Significance (VUS): A genetic change was found, but it is not currently known whether that specific change increases cancer risk or is just a harmless variation. This can be a frustrating result, and management is based on personal and family history.

Distinguishing Hereditary Testing from Tumor Testing

It is crucial to understand the difference between two types of genetic testing in oncology.

• Germline Testing (Hereditary Testing): This is the type of testing described above. It looks for inherited mutations that are present in every cell in a person’s body (the “germline”). The purpose is to assess hereditary risk for the patient and their family.
• Somatic Testing (Tumor Testing or Molecular Profiling): This type of testing analyzes the DNA from the cancer cells only. Its purpose is to find mutations that were acquired by the tumor and are driving its growth. The goal is to identify targets for personalized treatments like targeted therapy or immunotherapy. This is not for assessing hereditary risk; it is for guiding treatment.

In some cases, the two are linked. For example, if an ovarian cancer patient’s tumor (somatic) test shows a BRCA mutation, they will be referred for germline testing to see if they inherited it.

Medical Management After a Positive Result

A positive result from a germline genetic test does not mean a person has cancer or will definitely get cancer. It means they have a significantly increased risk. This knowledge is powerful because it allows for a proactive medical management plan to be put in place.

This plan, developed by the medical team, may include:

• Increased Surveillance: Starting cancer screenings (like mammograms or colonoscopies) at a much younger age and having them more frequently.
• Risk-Reducing Medications: Taking certain medications that have been shown to lower the risk of developing specific cancers.
• Risk-Reducing Surgery: For individuals with very high risks, such as BRCA mutation carriers, a preventative (prophylactic) surgery to remove the organs at highest risk (e.g., ovaries and fallopian tubes) may be recommended.

This personalized screening and prevention plan is designed to either prevent cancer from developing in the first place or to detect it at its earliest, most treatable stage.

Frequently Asked Questions

1. What is the difference between an inherited (germline) mutation and an acquired (somatic) mutation?
An inherited, or germline, mutation is a genetic change that you are born with. It was passed down from a parent and is present in every cell of your body. An acquired, or somatic, mutation is one that occurs randomly in a single cell during your lifetime and is only present in the cancer cells that grow from it. Germline testing looks for inherited risk, while somatic testing looks for targets for treatment.

2. Who should consider genetic counseling and testing for hereditary cancer?
You might be a candidate if you have a strong family history of cancer. This includes having multiple relatives on the same side of the family with cancer, cancer being diagnosed at unusually young ages (e.g., breast or colon cancer before age 50), or having a personal or family history of a known hereditary cancer syndrome (like breast and ovarian cancer, or colon and uterine cancer) appearing together.

3. Does a positive genetic test result mean I will definitely get cancer?
No. A positive result means that you have a significantly higher lifetime risk of developing certain cancers compared to the general population. It does not guarantee that you will get cancer. The knowledge allows you and your doctors to create a personalized plan of increased screening and prevention strategies to manage that risk.

4. What is a “Variant of Uncertain Significance” (VUS)?
A VUS is a result where the genetic test finds a change in a gene, but medical science does not yet have enough evidence to know if that specific change is harmful (pathogenic) or harmless (benign). A VUS result does not change a patient’s medical management; recommendations will continue to be based on their personal and family history until more is known about that variant.

5. If I have a BRCA mutation, should my family members be tested?
If you are found to have a hereditary cancer mutation like BRCA1 or BRCA2, it means your first-degree relatives (parents, siblings, and children) each have a 50% chance of carrying the same mutation. It is strongly recommended that they undergo genetic counseling to discuss their own risk and to consider having a “single-site” test to see if they inherited the specific mutation found in your family.

6. What is genetic counseling and why is it important?
Genetic counseling is a process where a trained professional helps you understand complex genetic information. It is important because the decision to have a genetic test has significant medical and emotional implications for both you and your family. A counselor ensures you are fully informed about the test’s potential benefits and limitations before you make a decision, and they help you understand and cope with the results afterward.

7. Where is genetic counseling and testing offered in Turkey?
This specialized service is typically offered within the medical genetics departments of major university hospitals and comprehensive cancer centers. A referral for genetic counseling is usually made by a patient’s oncologist or surgeon based on their personal or family medical history.