THE BRCA GENE
The brca1 gene lies on Chromosome 17.
BRCA INHERITANCE
The brca gene mutation is inherited in a dominant fashion, meaning that if either of your parents carry the mutation, you have a 50% chance of inheriting it. The number of carriers in men and women are the same.
CANCER RISK IN BRCA
Having a brca mutation increases your risk of certain kinds of breast and ovarian cancers. At the age of 60, the risk is approximately 60%, at the age of 80 about 80%. This is a very severe disease burden, and in the case of ovarian cancer, the survival rates are less than 1 in 3.
THE ROLE OF THE BRCA GENE
What does the brca gene do? The brca gene has a vital repair role in the cell cycle, when one cell divides to produce two daughter cells. Think of it like a pit stop in a Formula 1 race. An error in the placement of one wheel screw can cause the driver to lose control of the vehicle at high speed.
RISK OF PROSTATE CANCER
And this is not just a problem for women. Men have the brca gene mutation at the same rates as women, and it triples their risk of prostate cancer.
BRCA IN THE GENERAL POPULATION
In the general population, mutations in brca gene is quite rare: in a thousand people, there will only be about 2 individuals who carry the faulty gene. This goes some way to explain why BRCA gene testing is not offered as standard; it would simply be too costly.
BRCA IN THE JEWISH POPULATION
However, in some high-risk populations, like for example in the Jewish community, the rate of brca mutations is ten times higher than in the general population, affecting about one in 40.
That means that in a thousand individuals, there would be about 25 carriers, each with an 80% lifetime risk of cancer.
BRCA FOUNDER MUTATIONS
This is because there is naturally a great deal of genetic variability in the general population. By contrast, in the traditionally close-knit communities, any damaging founder mutation will have a higher chance of remaining within the gene pool.
THE FUTURE OF CARE
So what can we do about this? Well, at the moment there’s an intense research effort around the world to diagnose brca based on a blood test, to develop better risk prediction and treatment and even to develop a preventive strategy, like a brca vaccine.
HOW WE SPEAK ABOUT CANCER
Being diagnosed with a cancer-causing mutation is different than being diagnosed with a disease. We often speak about fighting cancer, beating it, but when we’re talking about a mutation that merely increases the risk of cancer, we need a new language. We need to think more in terms of what we can live with, what we can adapt, fix, optimise etc.
THE DIAMETER OF CANCER
Moreover, it’s important to remember that a genetic diagnosis will impact on a person’s life in profound ways. It can also be agonising for the immediate family, because if one person in a family tests positive, this actually dramatically changes the risk profile of all the other members of the family. And outside of that there is the community, which is affected by all the issues involved with genetic testing, including diagnosis, risk prediction, confidentiality and law. These issues are too big to be left to each individual person to decide; we need to deal with them as a community.
MISSED OPPORTUNITY
The problem is that at the moment, patients who are currently disease free but have received a genetic diagnosis, like brca carriers, fall between two stools. The medical community is set up to treat cancer, which they don’t have, and the charities are set up to support cancer victims. They often feel too guilty even to ask.
