Do you recommend treating pre-chemo volumes to full prescription dose for locally advanced nasopharyngeal cancer following induction chemotherapy?

A modified pre-chemo volume, because for example we are not going to treat air.

I think it is reasonable if the purpose of the chemo was to shrink the primary away from OARs like the optic chiasm. Obviously, as @Dr. First Last says, if the tumor was exophytic, you don't need to treat the air. However, I would still include in my high dose CTV the pre-chemo routes of spread, e.g...

It is still investigational but there are some small series on reducing the dose to the prechemotherapy volume in WHO types II and III disease. This study used 60 Gy to the prechemotherapy disease. I would not extrapolate this to WHO type I.

Wang L et al., Cancer Res Treat. 2019 April. Reduction of T...

I know the 2018 international consensus guidelines say yes; but for what it's worth, there is a phase III randomized trial to support adjustment based on post-IC volumes.

Updated answer - June 30, 2023

The phase III randomized trial for treating pre- vs post-IC volumes cited above recently published l...

In adult patients, no, we do not decrease the dose after IC. I would not feel comfortable offering that to any NPX patient even based on the small series posted above. Areas that previously had gross disease still get 70 Gy. Risk stratification for microscopic dose levels is still done based on init...