Yauch was diagnosed with the disease in July 2009. He was later reported to be cancer-free, but later clarified that this was not the case.
Talking about Yauch's health, Horovitz told The Guardian: "He's doin' okay. He's still in treatment, so it's not 100%. But things are lookin' good.
"We're not touring, we're just getting the record out - and we're not making any plans until he is better. Which is definitely gonna happen."
Beastie Boys released their eighth studio album Hot Sauce Committee Part Two earlier this week.
Mike 'D' Diamond added of Yauch's condition: "It's a very strange thing. Unfortunately, we've had a high attrition rate of friends growing up in New York, but more from drug overdoses and crazy s**t like that.
"This is, actually, the first time that a friend who is a contemporary - basically one of my best friends for life - called me up to say, 'Hey, I've got some really bad news', and having a really serious illness.
"And when you're friends for a long time, and one of that group of friends gets a very serious, potentially terminal illness, it's just kind of like... It's a game-changer, if you will."
> Beastie Boys stream explicit new album online
Watch the full-length Beastie Boys 'Fight For Your Right Revisited' video below: