Her update came as she attended the official launch of Maggie’s cancer support centre at London’s Royal Free Hospital.
The King was discharged on Monday, having spent three nights in the London Clinic private hospital.
Earlier, the Princess of Wales left the same hospital, almost two weeks after undergoing “abdominal surgery”.
As the Queen toured the new £6m centre, hospital donor Sir Gerald Ronson asked after the King’s health.
“He’s getting on, doing his best,” the Queen replied.
Later, Sir Michael Pakenham, a supporter of Maggie’s, told her: “All best wishes to His Majesty for the very best recovery.”
The Queen replied: “Thank you very much, that’s very kind, I’ll pass it on.”
Camilla has been president of Maggie’s since 2008. The charity supports cancer patients and their families, with its 24 centres all based in hospital grounds.
Charles walked out of the London Clinic private hospital on Monday, and smiled and waved to cameras, with Camilla, before getting into his car.
At the time, Buckingham Palace said he would have to postpone his public engagements “to allow for a period of private recuperation”.
The King, 75, had been treated for a non-cancerous, benign prostate problem – a common condition in older men, according to the NHS.
About one in three men over the age of 50 will have some symptoms of an enlarged prostate, which is a gland that sits just below the bladder. https://brewokkiri.com/
Charles’ “corrective procedure” for his prostate was made public as a way of encouraging other men to get prostate checks.
Earlier on Monday, the Princess of Wales, left the London Clinic, having spent 13 nights there since her operation. The exact nature of her surgery is unknown.