The King will continue his cancer treatment into the new year, according to reports.
Buckingham Palace sources told Sky News that "his treatment has been moving in a positive direction and as a managed condition the treatment cycle will continue into next year".
However, despite being diagnosed last February, the palace has still not disclosed the type of cancer Charles, 76, has.
A palace source has revealed to The Times the poignant reason why the monarch has kept details of his diagnosis and treatment private.
They said it was a conscious choice in order for the King to reach out to the widest number of people who are experiencing the disease, rather than narrow the focus onto a particular form of cancer.
The news of the monarch's diagnosis was announced on 5 February, with Charles having undergone treatment for an enlarged prostate just weeks before.
The King temporarily stepped from public duties to begin his medical care, but continued to go through paperwork in his daily red boxes and hold private meetings.
In that time, Charles also made an appearance while attending church on Easter Sunday in Windsor with the royals.
On 28 April, the palace confirmed he would resume some of his public duties and just days later, he and the Queen visited the Macmillan Cancer Centre at University College London Hospital, as he was announced as Cancer Research UK's new patron.
The King has regularly been in London throughout the year for his private appointments, but he has carried out some major public engagements while undergoing treatment.
In June, Charles celebrated his official birthday at Trooping the Colour, which also marked the Princess of Wales's first public appearance since her cancer diagnosis was disclosed.
Kate, 42, completed her course of chemotherapy in September and is making a gradual return to her royal duties.
The King and Queen underwent a tour of Australia and Samoa in October and hosted the Emir of Qatar for a state visit in December.
Charles appointed the third prime minister of his reign in July – Labour leader Sir Keir Starmer – and presided over the State Opening of Parliament just weeks later. He also travelled to France for D-Day commemorations in June.
As the Prince of Wales, Charles was the nation's longest-serving heir to the throne, and he became King on 8 September 2022 on the death of his mother, the late Queen.
Later on Friday, the King and Queen will attend a reception at Waltham Forest Town Hall to celebrate community cohesion in the London borough.
They will meet local community volunteers, young people, emergency services, and faith representatives operating in Waltham Forest.