The King was diagnosed with an undisclosed form of cancer in February 2024 and continues to receive regular treatment, which is said to be successful and that he is getting better.
There was a brief hospital stay for the King in March after he suffered side effects, but he was well enough in April for a state visit to Italy with a busy schedule and is said to have plans for further overseas trips.
There has been an attempt to be more open about his health problems - and this latest message reflects his sense of a shared experience with the many other families affected by cancer.
The King's statement continued: "But as one among those statistics myself, I can vouch for the fact that it can also be an experience that brings into sharp focus the very best of humanity."
He praised the "community of care" of those who helped cancer patients, for their humanity as well as their expertise.
The King highlighted "the profound impact of human connection - whether in the careful explanation from a specialist nurse, the hand held by a hospice volunteer, or the shared experience in a support group".
"While every patient's journey may be different, together you are ensuring that a cancer diagnosis need never mean facing the future without hope and support," said the King.
He quoted Dame Deborah James, who died of bowel cancer in 2022, who said: "Have no regrets; and always, always have rebellious hope."
Her parents, Alistair and Heather James, were guests at the reception, and said they had only been told "minutes before" that the King was going to quote some of their daughter's last words.
