@fig1971 It depends on what damage has been done - just a little or a lot.

There are many adverse side-effects that radiation can cause if advance precautions aren’t taken and/or if the radiation is administered badly. (I’ve attached a chart showing many possible side-effects.) My RO and I spent months discussing ways to minimize/avoid them.

Remedies - some simple, others more involved - may be needed to get resolved. It depends on the diagnosis.