Of all women diagnosed with breast cancer, only about 5–10% carry one of the known inherited genetic mutations linked to the disease. The odds seem relatively low. But behind those percentages are real people and real stories. And that’s not a small thing.

Cancer came as a huge shock to me.

For years, I trained for hours every day. I had no major health issues. After giving birth, I cut back significantly because life became more complicated, but over the last year I had started finding my way back. As recently as September, I was sparring with men on the mats and had no trouble getting through intense hour-long training sessions.

Then October arrived.

My abdomen started swelling. I felt tired. Sometimes I had a fever. There was discharge. Some days were good, others weren’t. In November, I was told I had Stage III or Stage IV ovarian cancer. Later, I learned that my type of cancer may have started developing somewhere in my body five to fifteen years ago, only becoming more aggressive and widespread during the last one to three years.

Before pregnancy, I attended my gynecological checkups every year. Nothing was ever found. After my premature delivery, I spent plenty of time seeing doctors because of various complications, but again, nobody found anything alarming. Eventually, I stopped going. I worked on strengthening my pelvic floor and simply waited for things to improve. Gradually, many things did improve. The issues that remained became my new normal. Ovarian cancer is often called the silent killer because it is usually discovered only after it has already reached an advanced stage.

Just like mine.

When I started reading about the BRCA1 mutation that was eventually confirmed in my case, I kept seeing the same sentence over and over:

“It’s not your fault.”

The mutation has been there since birth. It’s a bit like buying a brand-new car that leaves the factory with one faulty brake. But even that alone is usually not enough to cause cancer. For cancer to actually develop, researchers believe a second event must occur inside a cell—a so-called “second hit.” This can happen through normal aging, a combination of additional genetic changes, or simply a random mistake during cell division. Considering that our cells divide billions of times throughout our lives, the chances of that second hit eventually happening are surprisingly high.

So how common are these mutations?

According to estimates from GHC Genetics, around 0.51% of people of European ancestry carry a BRCA1 or BRCA2 mutation. That’s roughly one person in every 195. Based on those estimates, it is thought that approximately 22,500 people in the Czech Republic may carry a BRCA1 mutation (about 0.21% of the population), while around 33,200 may carry BRCA2 (about 0.31%). These are still only estimates, because healthy people are not routinely tested.

According to the Czech National Breast Cancer Screening Programme and the National Cancer Registry, approximately 7,650–7,918 new breast cancer cases are diagnosed in Czech women every year. In 2022, there were 7,918 newly diagnosed cases. Not all patients undergo genetic testing, but the official estimate remains that about 5–10% of breast cancer cases are linked to inherited mutations such as BRCA1 and BRCA2. That means somewhere between roughly 400 and 800 breast cancer cases each year in the Czech Republic may be hereditary.

Ovarian cancer tells a different story.

Each year, approximately 980–1,000 Czech women are diagnosed with ovarian cancer. In 2022, there were 988 new cases. Genetic studies suggest that inherited mutations play a much larger role in ovarian cancer than they do in breast cancer. Around 25% of ovarian cancer cases are linked to hereditary mutations, most commonly BRCA1 and BRCA2. In other words, about one in every four ovarian cancer diagnoses may have a genetic cause rather than being purely random. That translates to roughly 200–250 women every year.

The reason I’m writing about this today is because those numbers don’t sound particularly dramatic at first glance.

“Only 5–10%.”

“Only a few hundred cases.”

But numbers have a way of hiding people.

Behind every statistic is somebody’s daughter, somebody’s sister, somebody’s uncle, somebody’s friend. That’s why I would encourage anyone with a family history of cancer to pay attention and ask questions. Talk to your doctors. Be proactive. It’s better to be a little annoying than to overlook something important. And that applies even if the cancers in your family are different from one another. My BRCA1 mutation is most strongly associated with an increased risk of breast and ovarian cancer. We’re still waiting for my parents’ genetic test results to find out which side of the family it came from, but we already know that neither side has a history of those two specific cancers.On my father’s side, there have been cases of colon cancer, thyroid cancer, and kidney cancer. On my mother’s side, there have been cancers of the uterus, lungs, and possibly the cervix. As for my grandparents, we simply don’t know. Whatever stories their DNA carried, those details disappeared with them.

Now we’re trying to piece the puzzle back together.