Resistance to drugs is a huge issue. There is a whole journal devoted to drug resistance -

http://www.drupjournal.com/home

It includes recent work on EFGR targeted resistance in HNSCC - I can only get at the abstracts on my login. I stumbled on the journal trying to find references to recent work by Posner and Bonner. Will try to post the best links for these this weekend.

CG to husband - SCC Tonsil T1N2M0 HPV+ Never Smoker
First symptoms 7/2010, DX 12/2010
TX 40 IRMT (1.8 gy) + 10 Cetuximab
PET Scans 6/2011 + 3/2012 clear, 5 year physical exam clear; chest CT's clear of cancer. On thyroid pills. Life is good.