Genetic testing helps guide cancer treatment and prevent new tumors

Genetic testing of cancer patients increases the chance of identifying a hereditary predisposition to the development of the disease and, with that, drawing up plans to improve the prognosis.

The opinion was shared by experts on the second day of debates at the 7th Seminar on Cancer, promoted by Sheet on Tuesday (16). The event, mediated by Vera Guimarães, former ombudsman of the newspaper, was sponsored by Bristol Myers Squibb, Hospital Sírio-Libanês and Pfizer.

“When we identify hereditary genetic alterations, we know the risk of developing new tumors and which organs should be closely monitored, which makes it possible to create a personalized prevention plan”, says Diogo Soares, physician in the department of oncogenetics at the ACCamargo Cancer Center.

A study with expanded genetic testing for 17,500 cancer patients at the Memorial Sloan Kettering Cancer Center, in the United States, indicated a genetic predisposition in 17% of the participants. The results were released on the 15th of this month.

This is a higher number than initially expected, between 5% and 10%, says Soares.

Today, the guidelines for conducting genomic studies are for patients who, in addition to family history, have had more than one type of tumor or have developed cancer in childhood or adolescence.

Tests that investigate the heritability of tumors are usually done on specific genes. In the expanded analysis, the doctor studies a broad panel with several genes.

It is necessary for only one individual to take the test to indicate the predisposition. If the analysis finds any hereditary syndrome, it is possible to examine other family members, look for asymptomatic people and draw up screening plans for rapid diagnosis.

The doctor says that there is still no evidence to support the indication of this type of test for the healthy population. But those who seek medical advice, due to cases of cancer in the family, will be referred for genetic counseling.

The pre-test stage seeks to understand the type of disease and whether the spread between relatives indicates hereditary predisposition.

The test needs doctors with experience to assess the characteristics of the genetic code and which mutations are really dangerous, says Maria Isabel Achatz, an oncogeneticist at Hospital Sírio-Libanês.

“Each person has a huge number of mutations in cells. We have to interpret what each one represents. A wrong analysis can generate unnecessary stress on the patient or disregard a risk.”

She emphasizes the importance of the counseling phase, in which the patient is guided about the results and what measures can be taken.

Among the possibilities are frequent tests to monitor organs such as the pancreas and ovary, in which tumors are difficult to track, identification of family members without symptoms and reproductive genetic counseling, to prevent transmission of the condition to children.

In addition to genes, environmental and behavioral factors are considered when designing preventive actions.

“Depending on the person’s lifestyle and predisposition, mutations can interfere with genes that regulate cell growth, which is one of the causes of the appearance of tumors”, says Mariano Zalis, director of research and development at OC Precision, laboratory of precision of the Oncoclínicas Group.

Poor diet, smoking, alcohol consumption and physical inactivity interfere with the patient’s health and interact with inherited predispositions.

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The doctor draws attention to the difficulty of accessing exams. This is because Brazil still has few doctors and laboratories able to carry out genome mapping.

According to the Brazilian Society of Medical Genetics and Genomics, the country had 332 geneticists in 2020, the equivalent of 1 doctor per 1.25 million Brazilians. The WHO recommendation is one geneticist for every 100,000 inhabitants.

Today, the analysis is paid for by health plans in some cases, as in the identification of heredity of breast and ovarian cancer. Since 2020, a bill that provides for the mandatory of these exams in SUS is being processed.

For the three guests, it is important to assess the cost-effectiveness of the analyses, a calculation to demonstrate how much an intervention costs the patient compared to the value of treating late-stage disease. “Prevention tests cost less than treating metastatic cancer,” says Soares.