Two (or more) LRU caches for a Node.js app
As mentioned in the comments, remove the functions. Don't even go into OOP. As to why, they're simply unnecessary wrappers to your cache objects which you can just access directly. detailThreadCache.set is just as verbose as detailThreadSetCache.

Improving code doesn't necessarily mean reuse or encapsulation or a paradigm shift. Often times, the best code... is the one that's never written.