King Charles hospitalized briefly as ongoing cancer treatment caused “temporary side effects,” palace says

London — Britain’s King Charles had a setback in his cancer treatment on Thursday and he was taken to a hospital in London for observation. Coming more than a year after Charles revealed that he had been diagnosed with an unspecified form of cancer and begun treatment, the incident renewed concern about the 76-year-old monarch’s health.

Buckingham Palace said that after a scheduled cancer treatment on Thursday morning, “the king experienced temporary side effects that required a short period of observation in hospital.” 

The palace has never said what type of cancer the king has, nor what type of treatment he is receiving.

The king was seen in public in London just a day before his visit on Thursday to a private clinic in central London, seemingly healthy and smiling at a farm exhibition. He reappeared Friday morning, leaving his London residence Clarence House and waving to well-wishers from inside a black Audi.

Tourist Julian Mati told The Associated Press he was relieved to see Charles looking well as he left Clarence House. 

“We were horrified when we heard the news yesterday,” Mati told the AP. “We had come down to the palace today to take pictures but we never imagined we would see the king. To see him smiling and waving, it’s such a relief.”

Charles returned to Clarence House on Thursday night, but his events for Friday, which included a trip to Birmingham, about two hours north of London, were all canceled.

The king has maintained a busy schedule of official events in recent weeks, having steadily ramped up his work after returning to public duties in April last year, just several months after beginning his treatment. He made his first foreign trip during the treatment in July 2024, to Australia.

Last week, Charles was in Northern Ireland with Queen Camilla, and he met with Ukraine’s President Volodymyr Zelenskyy earlier this month.

His next scheduled overseas trip, to Italy with the queen next week, was still planned as of Friday.

Cancer has hit several members of the royal family in recent years, with the king’s daughter-in-law Catherine, the Princess of Wales, announcing only two months ago that she was in remission after about 10 months of treatment. The princess had announced last March that cancer was discovered following an abdominal surgery and she was undergoing preventative chemotherapy.

While the palace has never provided details of her diagnosis, former British Prime Minister Boris Johnson claimed in his memoir that Queen Elizabeth II, King Charles’ mother, was diagnosed with bone cancer before her death in September 2022 at the age of 96.