Will.i.am said it was a “beautiful moment” to see his bandmate Taboo back on form five years after his cancer went into remission.
The Black Eyed Peas star, 43, was diagnosed with stage two testicular cancer after he rushed himself to A&E in 2014, thinking he had flu.
On Thursday the American rapper appeared alongside his bandmates, Will.i.am and apl.de.ap, at House Festival in Hampstead, London.
Will.i.am said seeing Taboo held aloft by the crowd brought back memories of him in hospital, weak from chemotherapy treatment.
But the rapper, real name William Adams, said it was a “beautiful moment” to see how far he had come.
Speaking at the O2 Silver Clef Awards in London, he said: “Yesterday we played the House festival and Taboo was crowd surfing.
“And I just remembered Taboo sitting in the hospital with IVs in him, bags under his eyes from going through chemo and him saying: ‘I just want to go back on stage, man’.
“To see him being tossed around crowd surfing was just a magical moment. We did it bro. We did it! That was a beautiful moment.”
He recalled the trauma of his diagnosis but said music had been his therapy.
He said: “I’m celebrating my five years of being cancer-free. Actually June 24 was my five-year. I’ve been in remission for five years so I’ve had music as my therapy.
“First time I was doing chemo I would watch a lot of music videos and listen to a lot of different styles of music, just to keep my mind off the trauma I was experiencing.
“I know firsthand what it is like to have music as a healing power and therapy. It was an honour when they asked us to be part of this amazing event.”
The Black Eyed Peas picked up the gong for best international group at the event, which helps to raise vital funds ensuring that music therapy charity Nordoff Robbins is able to continue to support vulnerable people across the UK.