That is very disappointing news and I, too, could be in that boat in the future.
Do you know if your husband’s pelvic lymph nodes were targeted during his IMRT?
Even though it has become standard protocol after the SPORTT trial many doctors still only target the prostate bed and not the pelvic lymph nodes; it has been estimated that 30% of all radiation failures come from this fact.
You can ask your current RO if radiation can be given to the pelvic nodes without causing any damage to areas already radiated.
Phil