"She's so sweet, so beautiful, so kind, so supportive to all of us," Karina gushes.
"And she's so fit," Apolo adds. "Like you never expect — you know, I mean, cancer affects everybody. It's got no — it doesn't matter. But it's sad."
They went on to say Brooke has been looking great on set. "She looks amazing, her energy's amazing," Apolo explains.
They both note that there's not much they can do, they want to be there for Brooke in whatever way they can. "More than anything we want to be the smile for her, the laughter," Karina says. "Be that support system for Brooke."
Check out the full interview below.
Catch a new episode of Dancing With the Stars Season 15: All-Stars on Monday, November 12 at 8 p.m. ET/PT onABC.