Cryotherapy may not SEEM to be as effective as it might be because of the way different clinicians apply it.  A liquid nitrogen cold-burn which goes sufficiently deep enough to kill all the infected cells is very painful, akin to a cigarette burn.  When a doctor applied this technique to a wart on my hand, the surface layers of the wart did die off and flake away after a few days, but the wart recurred in a couple of months. I found by treating myself that a very painful burn with repeat applications of liquid nitrogen on one occassion seemed to get rid of the wart permanently. It could be that doctors are being too gentle.