You need to be careful and not compare apple with oranges.
Not all IMRT radiation schedules are equal. In some cases one or both partoid glads are spared. If you talk the RO you should find out exactly how much of the maximum dose the gland(s) are getting (this and many other things should be charted in the IMRT plan anyway). If they are getting a low enough dose one or the other will survive/recover. This may be one reason, why some of the RO dismiss amifostine, the other may be side effects.

Talk to the RO!
a) are the glands likely to be non functional due to the radiation dose?
b) with the radiation dose they are getting could amifostine be beneficial.
c) if they are getting the full radiation dose IS amifostine still expected to be beneficial

Markus