Is cancer inherited?

What type of cancer is hereditary? What are the probabilities of getting cancer? From Quirónsalud Torrevieja they clear up our doubts about cancer.

Cancers are predominantly genetic diseases, mostly due to the accumulation of mutations, which are also influenced by environmental and other factors, which in some cases may be the triggers.

A small proportion of these tumours are hereditary. “Hereditary cancers are the consequence of germline mutations in specific genes that increase susceptibility to cancer,” explains Dr. Ramón González Manzano, oncologist at the Quirónsalud Torrevieja Platform.

“This susceptibility is transmitted between family members according to different inheritance patterns. Susceptibility to cancer is inherited, which does not imply the certainty of developing it in all cases,” explains Dr. González.

Hereditary cancer

The predisposition to inherit cancer is due to the presence of mutations or other genetic alterations that alter the function of a gene that is critical for the regulation of biological processes related to the onset, development or progression of some types of cancer.

“The mutation can be inherited from parents or new-onset in a subject. Cancers of hereditary origin account for around 5% of all cancers that are diagnosed,” says Dr González.

What type of cancer is hereditary?

More than 160 genes related to hereditary predisposition to cancer are known.

When a genetic defect (i.e. pathological mutation) of one of these genes is inherited, the carrier of the altered gene has an increased risk of developing cancer, which is higher or lower depending on the gene in question.

Each of these genes related to hereditary predisposition to cancer can lead to one or more specific types of cancer in the carrier. For example, women with a mutation in the BRCA1 or BRCA2 gene may develop breast cancer at a younger age (usually before the age of 50) than breast cancers occurring in the general population. But other patients may develop ovarian cancer instead of breast cancer, or even both types of tumour in the same patient.

Chances of getting cancer

According to Dr González, this is one of the questions frequently asked by patients diagnosed with any type of tumour: Will my relative have the same type of cancer as me? The answer is that “it depends on the inheritance pattern of the hereditary predisposition gene under consideration”.

The most common inheritance patterns are as follows. The most common is autosomal dominant. In the case of autosomal dominant inheritance (as is the case with BRCA1 or BRCA2), there is a 50% chance that a parent carrying a pathological mutation in one of these genes will pass it on to their offspring.

Other genes, such as those causing the rare disease “xeroderma pigmentosum”, which is characterised by an extreme sensitivity to ultraviolet radiation from sunlight that is associated with the development of skin cancers, follow an autosomal recessive inheritance, and in this case the probability is 25%, generally requiring both parents to be carriers. Furthermore, in these cases, half of the offspring are likely to be carriers of the genetic alteration even if they do not suffer from the disease.

It should be borne in mind that not all patients with a pathological mutation in genes with a hereditary predisposition to cancer develop it.

When should a hereditary cancer syndrome be suspected?

According to the expert, there are some warning signs that should alert us to the possible presence of a genetic alteration in genes with a hereditary predisposition to cancer:

– The appearance of tumours at a very early age.
– Presence of bilateral tumours in the case of double organs (e.g. breasts, kidneys, etc.) or several synchronous tumours.
– Presence of multiple cases of cancer in a family.

In these eventualities, a specialist in cancer genetics should be consulted, who will indicate the relevant genetic tests to detect the genetic alterations that cause a hereditary predisposition to cancer.

How do you know if you have a mutation in any of the hereditary cancer predisposition genes?

The diagnosis is mostly indicated in the person affected by cancer by means of a genetic test.

How is a genetic test carried out?

This type of study simply requires a blood or buccal mucosa sample.

From these samples, DNA is extracted for sequencing. The most common technique currently used for genetic studies of DNA sequence is next-generation sequencing using ultra-sequencing, a technique that allows simultaneous sequencing of multiple genes.

The current trend is to use multi-gene panels, confirming the presence of any positive findings with conventional DNA sequencing.