Genetic tests for hereditary cancer are designed to confirm or rule out if you have hereditary genetic mutations that are risk factors for a particular type of cancer. But what are the benefits of knowing if you have this predisposition? This article explains it all in detail!
If you have read our articles, “Hereditary cancer, can it be prevented?” and “Characteristics of cancer and genetic tests“, you will know that cancer is one of the biggest health concerns affecting society today, both in terms of the health impact on sufferers and the increase in diagnoses in recent years: it is estimated that 1 in 3 people will develop cancer in their lifetime.
What exactly is cancer? Firstly, there are more than 200 types of cancer, each with very different characteristics. So why do we use the umbrella term “cancer”? Because they all have a common denominator: how they originate.
All cancers occur when cells in a particular tissue begin to multiply uncontrollably. One of the main problems with cancer is that these cells can migrate from the initial tissue and spread to other parts of the body, where they continue to spread and potentially impair organ function, a process known as metastasis.
Cancer is a multifactorial disease, which means that it has both genetic and environmental risk factors.
The following section explains the influence of genetic factors.
In the article “Genes and chromosomes: how do they determine our life and our health?”, we liken DNA to a book that contains instructions for how our bodies function. Sometimes these instructions contain errors, also known as mutations. And these mutations, which are alterations in the DNA, can lead to various diseases, including cancer.
If one of the several genes that controls cell division mutates, it could potentially lead to uncontrollable cell division, resulting in a tumour.
Cancer is considered a genetic disease because it is normally caused by a mutation in the genes responsible for controlling cell division. An important point to note is that genetic does not mean hereditary. In fact, although all cancers are genetic, only 5-10% of cancers are hereditary. The remaining percentage of cancers develop sporadically as a result of environmental factors, such as unhealthy habits.
In the 5-10% of hereditary cancer cases, the genetic mutation occurs in the germline, i.e. in all the cells of the body, which have either been inherited from our parents or appeared de novo during embryogenesis. Note that these mutations can be passed on to offspring.
Cancerous mutations usually have an autosomal dominant inheritance pattern, i.e. only one copy of the gene needs to mutate to increase the risk of developing the disease. If you want to learn more about the transmission of hereditary genetic diseases, read our post, “Diseases and types of genetic inheritance”.
Here, we answer some of the most common questions that you may have about hereditary cancer.
No, but the risk of developing it is considerably higher than it would be for the average person.
For example, it is estimated that the average person has a 12% risk of developing breast cancer. However, for women with a particular BRCA1 gene mutation, the likelihood of being diagnosed with this type of cancer before the age of 80 increases to 72%, and to 69% in those who have certain BRCA2 gene mutations.
The fact that several members of one family have had cancer does not always mean that there is a hereditary component.
Most of the genetic mutations that give rise to cancer are a result of environmental factors. Remember that only 5-10% of cases are hereditary.
There may be a hereditary component in families with several cases of cancer or, alternatively, all family members might have been exposed to the same environmental risk factors, such as smoking, an unhealthy diet or sedentary lifestyles.
Some characteristics that might signal possible hereditary cancer are:
Thanks to modern scientific advances, if you think your family might be affected by hereditary cancer, there are a number of things you can do. A genetic test for cancer can confirm or rule out this suspicion, initiating a process (in the case of a confirmation) to try to prevent its onset or detect it early, thereby improving the prognosis.
It is very important to receive genetic counselling before taking one of these tests. The genetic counsellor will examine you and your family’s medical history in order recommend the most suitable genetic test for you. They will then interpret and explain the results, after which you can explore all your options moving forward.
Genetic testing for cancer is used to determine the risk of cancer. These have advanced significantly in recent years, using so-called multi-gene panels, whereas in the past, they only tested for a few select genes involved in the development of a particular type of cancer. These multi-gene panels facilitate the simultaneous examination of different genes responsible for several types of hereditary cancer.
For example, these panels detect approximately twice as many cases of suspected hereditary breast and ovarian cancer compared with the select analysis of just the BRCA1 and BRCA2 genes.
Negative: this means that no genetic variant linked to hereditary cancer has been detected in the analysed genes. We should stress that this result does not rule out the possibility that you might develop cancer, considering that most cases are sporadic anyway. There might also be other genes (both known and unknown) linked to hereditary cancer that are not covered by the genetic test. That is why it is important to minimise your risk of developing cancer by maintaining a healthy lifestyle.
Positive: this means that a genetic variant associated with hereditary cancer has been detected. Later on, we will look at what steps you need to take upon receiving a positive result.Inconclusive/ VUS: This result means that a Variant of Uncertain Significance (VUS) has been found in the DNA .This means that, it is currently unknown whether variant VUS is a risk factor for cancer due to limited or conflicting scientific knowledge, and the result is therefore inconclusive. These results should be monitored because it might become clear in the future whether or not the variant is involved in cancer development.
As we have seen, a positive result indicates that there is a genetic variant that is a risk factor for hereditary cancer. Alternatively, if the person already has the disease, this variant may explain why the tumour has developed, which is important when assessing treatment options.
The information provided by these tests is useful for both the person being screened, as well as their family members. If a family member tests positive, other family members can also be tested to establish whether they have the same variant.
As previously stated, a positive result does not necessarily imply that the disease will develop, but rather that there is a greater risk that the patient might suffer from it. Awareness is invaluable, since it allows you to take prompt action to prevent the onset of disease, e.g. leading a healthy lifestyle or quitting smoking, etc. Even more importantly, it ensures close monitoring of the patient, aimed at detecting the potential onset of cancer in its early stages, which significantly improves the effectiveness of the treatment.
Protocols vary depending on the type of cancer, but most measures should aim to prevent or detect cancer early or, to personalise medical treatment if it has already developed. Every step of the process should be monitored by a medical professional who can recommend the most appropriate options for each individual case.
For example, if the test detects a variant linked with breast and ovarian cancer, the doctor could make different recommendations depending on the type of variant. Options include screening for breast cancer with mammography (biannual or annual) starting from the age of 25, which is much younger than the recommended age for the general public (45-50 years, annual or biannual). In very specific cases, the doctor could recommend prophylactic surgery such as mastectomy or salpingo-oophorectomy, in an attempt to reduce the risk of developing this type of cancer.
In most cases, cancer cannot be avoided, but it can be prevented. Veritas’ myCancerRisk test examines 40 cancer-related genes to determine if you have a genetic variant linked to a hereditary cancer in your family, so that you can take preventive measures.
If you have no family history of the disease, but are concerned about your risk of cancer, other cardiovascular diseases, or you have an interest in multifactorial diseases, we also offer myGenome, which analyses 566 genes. Please be assured that at Veritas, you will always have a consultation with one of our genetic counsellors, who will explain the test, what you can expect from the results, and answer any additional questions you may have. Contact us for more information.
This article is based on the original written by Paula Penedo from the Scientific Department.
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