To add, complicate matters further, chemo is sometimes used as "adjunct treatment", after radiation, Chemoradiation. How long, I'm not sure, maybe piggybacking on making radiation work better, as mop up for any microscopic cancer, which can't been seen by the eye, testing, only in pathology under the microscope. 1cm is small, but not microscopic, and to my understanding, radiation keeps working just as long as treatment lasted, like 6 weeks. One risk with adjunct chemo is "radiation recall." Some I know of are on Erbitux or Tarceva as maintenance chemo, mostly with distant mets, unresectsble tumors, but one of my oncologists was looking into it or me for "chemoprevention."

I had 35 IMRT, 70Gy, bilaterally, alone in 2011. My oncologist said my body would not be able to handle chemo then, a year after disastrous induction chemo. Radiation alone is being looked into, especially with HPV related HNC, which is different biology than tobacco/carcegenic related caused, but not all HPV related HNC are as favorable, a small group reacts like tobacco/carcegenic caused.