LONDON (AP) — King Charles III has been diagnosed with a form of cancer and has begun treatment, Buckingham Palace said Monday. Less than 18 months into his reign he will suspend public duties but will continue with state business, and won’t be handing over his constitutional roles as head of state.

The palace said the cancer is not related to the king’s recent treatment for a benign prostate condition. It did not say what form of cancer the 75-year-old monarch has.

The palace said “a separate issue of concern was noted” during Charles’ treatment for an enlarged prostate last month, when he spent three nights in a London hospital.

“Diagnostic tests have identified a form of cancer,” it said in a statement.

“His Majesty has today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties,” the palace said. “Throughout this period, His Majesty will continue to undertake State business and official paperwork as usual.”

It said Charles “remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible.”

The palace added that the king “has chosen to share his diagnosis to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer.”

Charles became king in September 2022 when his mother Queen Elizabeth II died at the age of 96.

News of the king’s diagnosis comes as his daughter-in-law Kate, Princess of Wales, recovers from abdominal surgery that saw her hospitalized for about two weeks.

U.K. political leaders sent messages of support. Prime Minister Rishi Sunak tweeted: “Wishing His Majesty a full and speedy recovery. I have no doubt he’ll be back to full strength in no time and I know the whole country will be wishing him well.”

Charles departed from royal tradition with his openness about his prostate condition. For centuries Britain’s royal family remained tight-lipped about health matters.