The royal mother of three took to social media to share the news, letting it be known she had already begun preventive chemotherapy. But what exactly does that mean?

Fans had begun to worry about the princess’ health due to her extended absence. Their fears were warranted, as the future queen shared a video on March 22 to announce she had been diagnosed with cancer. 

While doctors first suggested the princess’ condition was noncancerous, tests after the surgery “found cancer had been present,” said Catherine, per CNN. 

“My medical team, therefore, advised that I should undergo a course of preventive chemotherapy, and I’m now in the early stages of that treatment,” she said, per NBC News.

A spokesperson from Kensington Palace later revealed Catherine began her treatment in late February.

According to Dr. Andrea Cercek, a gastrointestinal oncologist at Memorial Sloan Kettering Cancer Center in New York City, “It’s almost like an insurance policy” (via NBC News).

“The person has had surgery to remove all the cancer that is visible, and then we give chemotherapy to try to eliminate or get rid of any remaining cells that might be in the body but are too small to be seen,” he said. 

The head of breast and gynecologic medical oncology at Valley Health System in New Jersey went on to explain preventive chemotherapy helps “reduce the chance for the cancer to come back in the future.”

“You get one shot on goal when you have cancer that’s been surgically removed,” he said.

“Hey, should we be as aggressive as possible to make sure that this cancer will never come back?” Park said. 

“Depending on which drug she’s getting, there may be more individual side effects that we assess for and monitor,” Teplinsky said.

Catherine’s diagnosis may help influence other young people to get tested and catch the disease early enough to treat it.