Chemotherapy is being used to treat the Princess of Wales after her cancer diagnosis earlier this year.

In a statement on Friday, she said she was “making good progress” and that her treatment would continue “for a few more months”.

She said: “I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days. On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well.

“My treatment is ongoing and will be for a few more months. On the days I feel well enough, it is a joy to engage with school life, spend personal time on the things that give me energy and positivity, as well as starting to do a little work from home.”

Kate has been receiving regular doses of drugs, which kill existing cancer cells and can help prevent the disease returning, with the treatment believed to have begun in late February.

The princess was diagnosed after a major abdominal operation in January, and it was initially thought she did not have the disease, but tests after surgery found cancer had been present.

Chemotherapy can be used even when surgeons believe they have removed all the cancer, because of the risk the disease might come back, and it can reduce the chances of a new cancer.

Professor Bob Phillips, professor of paediatric oncology at the University of York, said: “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.”

Prof Andrew Beggs, consultant colorectal surgeon at the Queen Elizabeth Hospital Birmingham, echoed Prof Phillips’ comments, saying preventive chemotherapy was “a bit like mopping a floor with bleach when you’ve spilt something on it, chemotherapy kills any spilt cells”.

There are many different types of chemotherapy drugs and patients can take the treatment via tablets at home, with regular check-ups from medical staff, or intravenously, with the liquid drug fed into the body through a vein during an outpatient hospital appointment.

Chemotherapy can also be combined with other treatments like radiotherapy to make them more effective, and the length of treatment depends on the stage and type of cancer.

Prof Phillips said the timeframe for chemotherapy treatment was “hugely variable”, adding that it was “traditionally between four and six ‘cycles’ (blocks) of chemo, each cycle lasting 21 days and consisting of a day or few days of chemo”.

He added there would then be “time for the body to recover from it, while the chemo keeps damaging the cancer cell.

“There are also some which are daily, some which are four-weekly and some which are two-weekly”.

The treatment has side effects, as healthy cells are damaged alongside cancer cells, and patients can experience tiredness, vomiting, hair loss and have an increased risk of getting infections, dry, sore or itchy skin and bowel issues.

More than 375,000 people are diagnosed with cancer each year in the UK, and there are more than 167,000 deaths from the disease.

Half of people with cancer survive for a decade or longer after diagnosis.

Cancer survival depends on the cancer type and whether the disease is caught early.

Breast cancer is the most common cancer in the UK, followed by prostate cancer, lung cancer and bowel cancer.

Asked whether age was a factor in survival rates and the success of chemotherapy treatment, Prof Phillips said: “Sort of, but not in a simple way.

“Generally speaking, the healthier someone is before cancer treatment, the closer to optimal the amount of chemo and the gaps between chemo can be.

“Generally, the younger someone is, the healthier they will be.”

Prof Beggs said: “Young onset cancer is by no means rare. I run a clinic for early-onset cancer in adults and we are seeing more and more people in their 40s with cancer.”

He went on: “Age has no effect on the success rate of chemotherapy except when the cancers are ‘immune hot’, which are commoner in young people, in this case a type of chemotherapy called immunotherapy could be given.

“Young people also better tolerate higher doses of chemotherapy and so can be given stronger regimens that are more likely to kill any leftover cells.”