Kate Middleton is in remission from cancer. This does not always mean that the disease is cured.

Princess Catherine, wife of Prince William, announced Tuesday that her cancer is in remission. But what does it mean to be in remission from cancer?

Doctors discovered her cancer unexpectedly last March when she had abdominal surgery. She did not disclose what type of cancer she had, or how advanced it was when it was discovered.

But she said she had chemotherapy, which she said ended in September. She told British news agency PA Media that she has a port, a small device that is implanted under the skin and attached to a catheter that goes into a large vein. It allows drugs such as chemotherapy drugs to be delivered directly into veins in the chest, avoiding needle sticks.

Catherine told PA Media that the chemotherapy was “really hard”.

“It’s a relief to be in remission now and I’m staying focused on my recovery,” she wrote on Instagram.

Her announcement is “certainly good news and reassuring,” said dr. Kimmie Ng, associate chief of gastrointestinal oncology at the Dana-Farber Cancer Institute in Boston.

But cancer experts like Dr. Nga say that the meaning of remission in patients can vary.

Generally, when doctors and patients talk about remission, they mean that there is no evidence of cancer on blood tests or scans.

The problem is that complete remission does not mean that the cancer is gone. Even when cancer is “cured”—defined as being free of cancer for five years—it may not be defeated.

This makes life emotionally difficult for patients, who must visit the oncologist frequently for physical exams, blood tests, and imaging.

“It’s really scary,” said Dr. Ng. “The amount of uncertainty is very, very difficult,” she added.

But that constant monitoring is necessary, despite the toll it takes on patients.

“Different forms of cancer have different propensities to return or not return,” said Dr. Elena Ratner, a gynecologic oncologist at Yale Cancer Center.

As many as 75 to 80 percent of ovarian cancers, she noted, can return an average of 14 to 16 months after remission, depending on the stage the cancer reached when it was found and the biology of the cancer.

“When the cancer comes back, it becomes a chronic disease,” said Dr. Ratner. He tells his patients: “You will live with this cancer. You will be on and off chemotherapy for the rest of your life.”

Patients with gynecological cancer dr. The Ratners must come in every three months for CT scans to monitor for evidence that the cancer has returned.

“Women live CT scan to CT scan,” she said. “They say they had a wonderful life for two and a half months, but then, in time for the next CT scan, the fear comes back.”

“It costs them — it costs them a lot,” she said.

“It’s horrible, but I’m amazed every day by their strength,” she said of her patients.