When we say “genetic test”, we are not talking about a single analysis. In oncology, a genetic test sometimes comes into consideration to evaluate a person’s hereditary risk, and sometimes to understand the genetic characteristics of the tumour and help plan the treatment options. As the personalised approach has been talked about more in recent years, the visibility of these tests has increased. Still, it cannot be said that the same test is necessary in every patient. The test strategy is planned by physician teams in line with the type and stage of the cancer, the pathology findings and the clinical goals.
This content is for general information purposes and does not replace a medical assessment. The test decision and the interpretation of the results should be made by health professionals, taking the person-specific conditions into account.
What Is a Genetic Test, What Does It Aim For in Oncology?
A genetic test is the general name for the laboratory methods that examine some changes on the DNA. In oncology, these tests seek answers to two main questions.
The first is to evaluate the presence of hereditary changes that a person may carry from birth and that can be associated with some cancers. This approach can come into consideration in situations where the family history is prominent or where some clinical clues are present.
The second is to examine the tumour-specific changes that develop over time within the tumour tissue. This information can, in some situations, make it easier to evaluate the treatment options and can provide an answer to the question “which biological mechanisms are more dominant”.
This distinction is important. The test meant by two people who say “I had a genetic test” may not be the same. One may be describing the hereditary assessment carried out from a blood or saliva sample, while the other may be describing the molecular profiling carried out from the tumour tissue.
What Is the Difference Between a Hereditary Test and a Tumour Test?
Hereditary genetic tests are generally carried out from a blood or saliva sample and evaluate some variants in the person’s congenital genetic structure. Situations such as a history of cancer at an early age in the family, a clustering of similar cancers in the same family or a history of more than one primary cancer in the same person can cause these tests to come into consideration. The aim here is most often not “to make a diagnosis on its own”, but to make the risk discussion more systematic and to help plan the monitoring approaches deemed suitable.
Tumour genetic tests, on the other hand, examine the changes present in the cancer tissue itself. This information can be supporting in evaluating the suitability of some drug classes or in discussing the treatment plan in a more targeted way. Tumour tests are most often carried out on surgery or biopsy material. In some situations, methods that examine the tumour DNA circulating in the blood can also be talked about, but how much information which method will provide varies according to the clinical question and the available sample.
What Kind of Questions Does a Genetic Test Seek Answers to in the Treatment Plan?
The value of a genetic test in the clinic generally takes concrete form in the following questions.
Are there certain biomarkers in this tumour, and do these findings help in the evaluation of some treatment options? Besides the standard approaches, are there options that can be discussed in a person-specific way? In some situations, can a door be opened in terms of suitability for clinical research?
There is a critical boundary here. A genetic test result does not always mean “a single correct treatment”. The same change can have a different clinical meaning in different cancer types. In addition, tumour heterogeneity, that is, the tumour being able to carry different characteristics in different regions, can make interpretation difficult. For this reason, the results are generally addressed together with pathology, imaging, staging and the general clinical picture.
In Which Situations Can a Genetic Test Come Into Consideration?
A genetic test decision is most often shaped by certain clinical clues. For example, in some advanced-stage situations, tumour profiling can be talked about more frequently to map the treatment options better. Situations such as a prominent clustering in the family history, a diagnosis at a young age, some rarely seen tumour types or a history of more than one primary cancer in the same person can bring the hereditary assessment into consideration.
Still, a single-sentence rule such as “in this situation it is definitely carried out” is generally not correct. Which test will be necessary, which panel will be chosen and what the test is expected to answer become clear through a physician’s assessment.
How Does the Test Process Work, Sample Types and Reporting
In tumour tests, the sample is most often pathology material. The pathology team evaluates the suitability of the tissue for the test with technical criteria such as the tumour cell ratio. In hereditary tests, a blood or saliva sample is generally used. In some situations, the physician may discuss, in addition to the tissue sample or if the tissue is not suitable, different methods.
The reports generally include headings such as the changes detected, their possible clinical meaning and the evidence level. The most important point is not to “read” the report, but to interpret the report within the clinical context. The same finding can mean something different at different stages or in different cancer types.
Which Limitations Should Be Known When Interpreting the Results?
Genetic tests are powerful tools, but they are not flawless. Some results can be reported as a “variant of uncertain significance”. This can mean that the clinical importance of the detected change is not clear for the moment. In addition, the scope of the tests can be limited. Not every change may be caught in every panel. The sample quality, the sample amount and the methods used can affect the result.
For this reason, genetic test results are most often seen not as data that makes a decision on its own, but as data that supports the decision process. In some centres, the results can be addressed in meetings where the relevant disciplines evaluate them together. This approach helps the findings to be framed more accurately.
Frequently Asked Questions
Does having a genetic test definitely change the treatment?
In some situations it can help to evaluate the treatment options. However, it cannot be said that the results will definitely change the treatment plan in every patient. The clinical picture and the guideline recommendations are determining.
Are a hereditary genetic test and a tumour genetic test the same thing?
No. A hereditary test evaluates the congenital genetic structure. A tumour test examines the changes that the cancer tissue acquires over time. The aim and interpretation are different.
Does a liquid biopsy always replace a tissue biopsy?
Not always. In some situations it can be a complementary option. Which method is suitable in which situation is determined according to the clinical question.
If the genetic test result is negative, was nothing found?
A negative result can mean that no clinically meaningful finding was detected within the scope of the test. However, this may not mean that all possibilities are completely ruled out. The result is interpreted together with the clinical context.
Does a genetic test also concern family members?
In hereditary tests, some findings may also require assessment in terms of family members. This process is generally planned, when deemed suitable, accompanied by counselling.
What should one be prepared for before a genetic test?
Getting information from the physician team about the aim of the test, the possible types of result and the limitations of the test is useful. In this way, when the report arrives, what may mean what is framed more clearly.
This content is for general information purposes and does not replace a medical assessment. Whether genetic tests are necessary in your situation and which test will be meaningful are clarified through clinical assessment.
