What criteria do you use for replanning with a new CT simulation for patients being treated definitively for head and neck cancer?

Whenever nodal shrinkage or weight loss reduces the fit of the mask we make a new mask in same position and re-calculate doses using existing IMRT beam and dose fluences. Tumor dose never reduces based on our experience, and the main issue are doses to organs. Skin dose may increase and it may be worth re-planning if the increase is substantial. Parotid and submandibular mean doses may also increase, however the increase is usually in the range of 1-2 Gy. If it is higher, take into account data from studies of saliva output vs. planned and actually delivered doses, demonstrating that the SD of saliva vs. actual dose or planned dose is about 3.8 Gy, meaning that a rise of less than about 4 Gy in parotid mean dose will not be measurable as re...