Breast cancer: risk factors
What determines the probability of breast cancer
Kirill Stasevich, "Science and Life", based on the materials of the University of Cambridge: Family history and location of genetic fault affect risk for carriers of key breast and ovarian cancer genes
One of the most well–known genes in oncology are the BRCA1 and BRCA2 genes. They encode proteins that repair DNA, and if mutations appear in the BRCA genes themselves, then their proteins begin to work poorly, DNA is damaged more and more, and, in the end, everything ends with the degeneration of the cell into a malignant one.
Usually mutant BRCA causes breast tumors (the abbreviation BRCA itself stands for BReast CAncer, i.e. breast cancer) and ovarian tumors, which are often closely related to each other.
The link between BRCA and oncological diseases turned out to be so unambiguous that now, if genetic analysis reveals a mutant BRCA gene in the genome, doctors advise a woman to remove her mammary glands in advance, even if she does not have any signs of a tumor yet - because the probability that a tumor will appear sooner or later is very, very high. However, this probability still turns out to be different, for someone it is higher, for someone it is lower, and, obviously, there are many factors on which the manifestation of a malignant mutation depends. For example, it was previously shown that mutations in the BRCA1 gene increase the likelihood of breast cancer by 40-87%, and in the BRCA2 gene – by 20-84%
In an article in JAMA (Kuchenbaecker et al., Risks of Breast, Ovarian, and Contralateral Breast Cancer for BRCA1 and BRCA2 Mutation Carriers), researchers from Cambridge, together with colleagues from Australia, France, the USA and the Netherlands, describe such factors that make the probability spread so significant. In general, as Antonis C. Antoniou and his colleagues write, you need to be very attentive to several things: age, family history and the location of mutations in genes. The authors analyzed the genes of almost 10,000 women of all ages; about half of them had already been treated for cancer at one time, but no one had done preventive removal of the ovaries or breast. After five years of observations , the following figures were obtained:
1) those who did not have cancer before, but who had mutations in the BRCA1 gene, by the age of eighty had a 72 percent chance of getting a breast tumor, and with a 44 percent chance of an ovarian tumor. For the BRCA2 gene, the same figures were lower – 69% and 17% for each cancer, respectively.
2) in those who already had a tumor in one breast, and everything ended with a successful operation followed by successful treatment, a second tumor arose within the next twenty years with a probability of 40% – if the mutation was in the BRCA1 gene, and with a probability of 26% – if the mutation was in the BRCA2 gene.
3) new breast cancer often occurred in young women (who had mutations in BRCA genes), but then the probability of it decreased - by the age of 30-40 in those who had mutations in BRCA1, and by the age of 40-50 in those who had mutations in BRCA2. But with an ovarian tumor, everything turned out to be the opposite: in young people, a new tumor after the old one appeared relatively infrequently, but its probability increased markedly by the age of 40-50.
4) if a woman had two close relatives (for example, a sister, mother or aunt) with breast cancer, then the probability of a tumor herself doubled (although such a high probability occurred by the age of 70).
5) finally, depending on where exactly the mutation got into the BRCA genes, the probability of a breast tumor could grow by 1.5–2 times.
These figures look boring from the outside, but it is thanks to such studies that doctors manage to understand what awaits the patient in the future, whether it is worth waiting for a relapse, how often preventive examinations should be undertaken, etc. – and it would not be an exaggeration to say that such figures can literally save a life.
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22.06.2017