- Written by Aoife Walsh and Sean Seddon
- BBC News
Rishi Sunak told the BBC that King Charles III's cancer was “detected early” and that normal communications between the monarch and Number 10 were continuing.
The Prime Minister said he was “shocked and saddened” by the news but was “in regular contact” with the monarch.
The king, 75, postponed all his public duties and began “regular treatment” for his condition on Monday.
The palace said he did not have prostate cancer, but few additional details were revealed.
“He will be in our thoughts and prayers – many families across the country listening to this will be affected by the same thing and they know what it means to everyone,” Sunak told BBC Radio 5 Live.
It is understood that the King's weekly meetings with Mr Sunak will continue in person, unless doctors advise limiting such contact.
The palace confirmed that the king will continue his constitutional role as head of state, including completing paperwork and holding private meetings.
The palace said on Monday that the king “remains completely positive” about his treatment and “looks forward” to returning to his normal schedule.
The King returned to London to receive outpatient cancer care from his home in Sandringham, where he was seen waving to crowds during a 10-minute walk to church the day before.
Diagnosis of King Charles Cancer
The King personally informed his two sons of his diagnosis, and Prince William is said to be in regular contact with his father.
The Duke of Sussex, who lives in the United States, spoke to his father and is traveling to the United Kingdom to see him. According to reports, it could arrive as early as Tuesday afternoon.
The palace did not clarify when the king would return to his public duties.
It is unclear whether official visits to Canada, Australia, New Zealand and Samoa scheduled for later this year will continue.
The king's cancer diagnosis comes following a procedure performed in a private hospital in London more than a week ago to treat a “benign” prostate condition.
“A separate matter of concern was noted and later diagnosed as a form of cancer” during this treatment, the palace said on Monday.
The palace said that the king chose to announce his cancer treatment because he was a patron of a number of cancer-related charities when he was Prince of Wales.
The Royal Society of Medicine thanked the King for highlighting “how random cancer is” and urged members of the public eligible for cancer screenings to make an appointment.
Simon Lewis, who was Queen Elizabeth II's press secretary between 1997 and 1999, praised the monarch for his openness, adding: “Twenty years ago there would have been a very short, abrupt statement, and that would have been the case.”
He told Radio 4's Today program that being diagnosed with cancer would be “a very difficult thing” but said “I know from people around him that he would be very keen to carry on” with his official constitutional duties behind the scenes.
One in two people in the UK will develop some form of cancer during their lifetime.
There are more than 200 types of cancer, the most common in the UK being breast, lung, prostate and bowel, according to the NHS website.
For many types of cancer, the chance of developing it increases with age. UK figures show that, on average, each year, more than a third (36%) of new cancer cases were in people aged 75 or over.
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Additional reporting by Sean Coughlan, royal correspondent
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