Cancer in the family: when genes raise the risk

Inherited or not?

Almost every cancer arises from genetic changes, but the vast majority of these happen during a person's life, only in the tumor cells, and are not passed on to children. Only about 5% to 10% of cancers are hereditary: the person is born with a change in a protective gene, present in every cell of the body.

Anyone who carries one of these changes has a 50% chance of passing it on to each child. Having the change does not mean the person will get cancer; it means their risk is higher than that of the general population. That is why people who know can look after themselves earlier and better.

BRCA: the Angelina Jolie story

The BRCA1 and BRCA2 genes became known worldwide in 2013, when the actress Angelina Jolie revealed, in an article in The New York Times, that she carried a BRCA1 change. Her mother had died of cancer at 56. Her doctors estimated that Angelina had an 87% lifetime risk of breast cancer and a 50% risk of ovarian cancer.

She chose to have both breasts removed as a preventive measure, which lowered her breast cancer risk to less than 5%. Two years later, she also had her ovaries and fallopian tubes removed. Her decision led thousands of women to seek genetic testing, a phenomenon that became known as the "Angelina effect".

Besides breast and ovarian cancer, BRCA changes also increase the risk of prostate and pancreatic cancer. Preventive surgery is one option, but not the only one: there are also more frequent check-ups, such as breast MRI, and medicines. The choice is personal and should be made together with your care team.

Lynch syndrome: a focus on the bowel

Lynch syndrome is the most common hereditary cause of bowel cancer. It also increases the risk of cancer of the endometrium (lining of the womb), stomach, ovary, urinary tract and other sites. The good news is that prevention works: regular colonoscopies, usually every one or two years, make it possible to remove polyps before they turn into cancer. And tumors linked to Lynch syndrome usually respond very well to immunotherapy.

Li-Fraumeni, and why it matters so much in Brazil

The TP53 gene is known as the "guardian of the genome": it stops defective cells from multiplying. When someone is born with a change in this gene, they have Li-Fraumeni syndrome, with a high risk of several types of cancer from an early age, such as sarcomas, breast cancer in young women, brain tumors, leukemias and tumors of the adrenal gland.

Worldwide, the syndrome is rare. In Brazil, it has a particular history. In the South and Southeast of the country, a specific TP53 change called R337H is common. It came from a shared ancestor and was probably brought from the Iberian Peninsula centuries ago. In Paraná, a state in southern Brazil, about 1 in every 300 newborns carries this change. As a result, Paraná has one of the highest rates of childhood adrenal tumors in the world.

R337H is usually milder than the classic form of the syndrome: most carriers will never develop a tumor in childhood. Even so, knowing that the change is there makes a difference. In Paraná, a pioneering program tested newborns and followed the children who carried it, which made it possible to find tumors at a very early stage, when they are easier to cure. For adults with Li-Fraumeni, there are surveillance protocols that include whole-body MRI.

When to suspect it

• Several relatives on the same side of the family with cancer, especially of the same or related types.
• Cancer at a young age, before 50.
• The same person having more than one cancer.
• Less common cancers, such as breast cancer in a man, ovarian or pancreatic cancer, or an adrenal tumor in childhood.
• A genetic change already identified in a relative.

What to do

If you recognize yourself in this list, see an oncologist or a geneticist for a genetic counseling appointment. The doctor will review your family history, tell you whether testing makes sense and explain what the result means. The test is usually done on a blood or saliva sample. Health plans cover the test in situations defined by the ANS, Brazil's health-plan regulator.

Knowing is a way of protecting yourself. A positive result is not a sentence: it is a chance to take preventive steps, find cancer early and guide your whole family.

For information only. It does not replace an individual medical assessment or genetic counseling.