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Oncogenetic test: what is it, who needs it and how does it help?
An oncogenetic test is a genetic test that looks for inherited changes in genes that can increase the risk of developing certain types of cancer. The most important thing to understand right away is that this test is not a «cancer test.» It does not diagnose cancer in itself, but rather shows whether a person has hereditary predisposition to certain cancers. According to the US National Cancer Institute, approximately 5–101% of all cancers are linked to inherited harmful genetic changes.
That is why oncogenetic testing is most often of interest to people whose family has had cancer repeatedly, at a young age or in several generations. In such situations, testing can help to understand whether the cases in the family are associated with an inherited syndrome, and whether the person needs more frequent examinations, a different screening schedule, or consultation with a specialist. Genetic testing for hereditary cancer risk is also different from genetic testing of the tumor itself: analysis of the tumor looks for changes that have appeared during life, while oncogenetic testing looks for changes inherited from the parents.
What does the oncogenetic test show?
In practice, an oncogenetic test looks for mutations or pathogenic variants in genes associated with hereditary cancer syndromes. The most famous examples are BRCA1 and BRCA2, which are associated with hereditary breast and ovarian cancer, and Lynch syndrome, which is associated with an increased risk of colorectal, endometrial, and certain other cancers. Inherited changes may also be associated with other syndromes, such as TP53 in Li–Fraumeni syndrome, but these are rarer situations.
The result of an oncogenetic test does not mean that cancer already exists or will definitely appear. It means that the risk may be higher than average. For the patient, this is a very important difference. A positive result is not a sentence, but a basis for more careful monitoring and personalized prevention. A negative result also does not mean zero risk: a person still has the general population risk, and sometimes there may be a hereditary factor in the family that modern panels do not yet detect or that has not been included in a specific test.
Who is usually recommended for oncogenetic testing?
Not everyone needs an oncogenetic test. It is most often recommended when a personal or family history of cancer suggests a hereditary syndrome. This may include multiple cases of the same type of cancer in a family, cancer at a young age, a combination of certain types of cancer in the same patient or close relatives, or situations where a specific mutation is already known in the family. Separately, clinical guidelines advise considering testing for people with certain diagnoses, including ovarian cancer, triple-negative breast cancer, pancreatic cancer, metastatic prostate cancer, male breast cancer, and colorectal cancer at a young age.
For hereditary Lynch syndrome, the reference point may be colorectal cancer, endometrial cancer at a relatively young age, several related cancers in the family, or already known Lynch syndrome in one of the relatives. For BRCA testing, the suspicion is increased by the combination of breast, ovarian, pancreatic, or prostate cancer in the family. In such situations, the key is not one fact, but the whole family picture.
Table: When is it really worth discussing an oncogenetic test with a doctor?
| Situation | Why is this important? | What to do next |
|---|---|---|
| There have been several cases of the same type of cancer in the family | This may indicate a hereditary syndrome. | Collect a family history and seek genetic counseling |
| A close relative developed cancer at a young age | Early onset is more likely to raise concerns about hereditary risk | Discuss the feasibility of an oncogenetic test |
| Have a family history of breast, ovarian, pancreatic, or prostate cancer | This may be related to BRCA-associated syndromes | Consider a medical genetics consultation |
| A family history of colorectal cancer or endometrial cancer, especially at a young age | This may be consistent with Lynch syndrome. | Discuss screening and genetic testing |
| A specific mutation is already known in the family | The risk to blood relatives can be significant | Testing often begins with a targeted search for a known change. |
This tactic is supported by the NCI, CDC, and NHS: first they assess personal and family history, and only then decide which test is needed and whether it is needed at all.
How is the oncogenetic test performed?
In most cases, a blood or saliva sample is used for an oncogenetic test. The process of taking the material itself is simple, but the real value of the test is not in the collection itself, but in the correct selection of the gene panel and the correct interpretation of the results. That is why international recommendations emphasize the role of genetic counseling before and after testing. A person must understand what exactly is being tested, what are the possible results, how they may affect further examinations, treatment and even family members.
There is another practical detail: if there is a family history of cancer, when possible, it is more informative to test the relative who has had the cancer first. For BRCA-associated syndromes, the CDC explicitly states that it is preferable to test the first person in the family who has already had a BRCA-associated cancer. This increases the chance of finding a truly significant change and then correctly testing other blood relatives.
How is the oncogenetic test useful in practice?
The biggest benefit of oncogenetic testing is that it allows you to move from general advice to personalized tactics. If a person is found to have an inherited mutation, a doctor may recommend a different age for starting screening, more frequent screening, specific prevention strategies, or, if cancer has already been diagnosed, sometimes even consider the test result when choosing treatment. In addition, the results can be important for blood relatives, who will be able to more accurately assess their own risk.
But there are limits. The oncogenetic test does not replace mammography, colonoscopy, ultrasound, MRI or other standard examinations. It also does not cancel the consultation of the doctor if there are already symptoms. It is a tool for assessing hereditary risk, not a universal replacement for all oncodiagnostics.
Can I do such a test myself?
Direct-to-consumer genetic tests exist, but caution is needed. The NCI and CDC caution that at-home or direct-to-consumer tests do not always provide a complete picture of hereditary cancer risk. They may test for only a subset of variants, may not cover all clinically significant mutations, or may provide a false sense of security if a negative result is obtained. Therefore, this approach should not replace comprehensive medical genetic counseling.
When someone searches for «cancer genetic testing,» they are most likely looking for answers to two questions: whether they need it and what difference the results will make. The best answer is that testing can be very helpful, but only when it is prescribed for the right reasons, interpreted correctly, and used for a specific plan of action. That’s why the first step should not be to randomly choose a test, but to evaluate your personal and family cancer history with your doctor or medical geneticist.
