Cleaning up large moderation queue

I’m overwhelmed by spam. After avoiding my blog for a month, I now have 4600 spam comments in the moderation queue. How do I get rid of these?

It’s so many messages that the moderation page times out before it can load. I can erase them using the comments management page, but the mass edit mode only allows me to moderate 20 comments at a time. That’s not a good solution.