The singer — who shared in 2020 that he had been diagnosed with an inoperable brain tumour — has been having treatment in Spain and won't make it back in time for the start of the tour, which is due to kick off today. 3 March.
He said on Instagram that he was "gutted" not to be there.
"So, as most of you know, I’ve been out in Spain on a treatment programme for the past couple of weeks," Parker wrote.
"It was only meant to last 20 days but due to a couple of logistical changes with tests and results it won’t be complete until the end of the week now which has delayed our journey home.
"I’m obviously gutted that I’ll be missing the first few shows but as I’m sure you will understand, I have to complete my treatment cycle."
He went on: "I’ve been zooming into rehearsals all week and I know that the show will be incredible and that my boys will hold the fort until I’m back.
"Can’t wait to see you all very soon, hope you all enjoy the show.
"Much love, Tom x."
Parker was diagnosed with “inoperable” stage-four glioblastoma in 2020, while his wife Kelsey was pregnant with their second child.
In October last year he told The Sun he was determined to defy the odds.
“They give you 12 to 18 months of survival,” he said. “But that’s the general statistics. Everyone we’ve spoken to has been way, way beyond that.
“Now, we’re aiming to be cancer free by March. That’s the aim. This disease is always there. You might have residual cells but just not active.”
Watch: Tom Parker announces brain tumour is 'under control'