Kate Middleton said she's having preventative chemotherapy — here's what that could mean

• Kate Middleton was diagnosed with cancer and is undergoing preventative chemotherapy.
• That could mean a few different things, according to oncologists.

Kate Middleton, the Princess of Wales, said she was diagnosed with cancer and is undergoing "preventative chemotherapy," which could refer to a treatment to prevent cancer from re-occurring after surgery.

The 42-year-old announced the diagnosis Friday in a short message, following weeks of public speculation about her whereabouts and well-being. Kensington Palace had previously said that she had undergone a planned abdominal surgery for a condition believed to be "noncancerous." Subsequent testing found cancerous cells were present, Kate said in her announcement.

Kate said in her recent statement that she is now in the early stages of a course of preventative chemotherapy at the recommendation of her medical team. Her specific type of cancer has not been disclosed.

It's not clear what the statement means by "preventative chemotherapy," according to doctors specializing in cancer treatment.

It could mean that Kate is ongoing a treatment commonly known as adjuvant chemotherapy to get rid of any remaining cancer cells after an operation.

"For some types of cancers, chemotherapy can be given after to act to 'mop up' if there are any cancer cells left. The value of this varies between cancer types, and even the size and place of the same cancer type," Bob Phillips, professor of pediatric oncology at the University of York, said in a press release.

It could also refer to chemoprevention, a range of medications and supplements that work to stop cancerous cells from developing, according to the cancer education site OncoLink. The specific substances used in the treatment depend on the type of cancer and the patient.

Cancer occurs when cells begin to grow uncontrollably, forming a mass called a tumor. Chemoprevention may be used for people with a high risk of cancer or who have had cancer previously to interrupt this process.

Chemoprevention is different from chemotherapy, which is used to destroy cancer cells that have already developed, according to the National Institute of Health.

The typical length of time for treatment can vary widely depending on the type of cancer, according to Phillips.

Side effects and recovery times also vary depending on the type of drugs used, although it can take months before a person is back to full strength, he said.

"'Chemo' is a word used to describe a huge variety of medicines used to treat cancer. There are a number of families of chemo and chemo-like drugs which all have their own varied schedules and side effects," Phillips said in the press release.