Unless I'm wholly mistaken on terms, which I may be, prostitutes are a kind of sex worker rather than a replacement for the word sex worker.
What I'm trying to say is something like this:
Engineer = Sex worker
Chemical Engineer = Prostitute
Both operate in the same industry, yet the chemical engineer specializes within a certain part of the industry rather than the industry as a whole.
Edit: Yes, I'm saying you can use the word 'Prostitute'.