Royal doctors gave Charles, 75, permission to briefly halt the weekly cycle in order to fly around the world for his key next visit, followed by a state visit to Samoa in the South Pacific.

The monarch, who was diagnosed with an undisclosed form of the disease in February, will receive treatment up until his departure, and resume the outpatient appointments when he returns to the UK, the Daily Mail reported on Monday.

He will be away for 11 days, with the tour covering nine days with two days of travel either side, and his entourage will include, as is usual for Charles's official overseas visits, his doctor.

The long-haul trip with the Queen is a major milestone for the King.

It will be his most significant overseas tour since his cancer diagnosis and his first to Australia as the nation's head of state, looking set to prompt debate about the future of the monarchy in the country and whether it should become a republic.

With AAP.