Should I kick him out?

I made the mistake of letting my ex-husband move back in with me a few years ago. I have 2 teenagers at home (these are his kids). He lives downstairs but my problem is he's a heavy drinker. I was going to ask him to move out this year but then we just learned that his melanoma cancer came back. He is currently doing the clinical trial. But I'm worried that my kids are around this drinking and what effect this is having on them. I don't want to support his alcohol use and be an enabler. I am torn what to do. Should I have him move out or let him stay? Please help.