Feasible, maybe. But has it ever been done before? Are you aware of any papers where lidocaine is used as a treatment for solid tumors, and not simply as an analgesic during or following surgery? Studies in humans would be most relevant, but I'd even be interested in rodent studies if lidocaine is used systemically. (i.e. given orally or injected IP/SC/IV. Having researchers inject lidocaine directly into mouse tumors is not terribly relevant to what you were recommending.)