Vaccine That Kills Cancer With 2 Shots?!?

Color me confused, but doesn't a vaccine *prevent* something before it happens?  In this case, researchers used this "vaccine" on patients that already had multiple myeloma and it's supposed to "train" the body to seek out and destroy cancer cells - so wouldn't this be a treatment (after the fact that one already has cancer) rather than a vaccine (to prevent cancer)? 

It certainly sounds interesting; at least they admit they haven't tested it nearly enough to be presented in a peer-reviewed or scientific journal.  Wouldn't it be wonderful if it turned out to work?