Welcome in H.C.M.
I have gone through your query regarding feeling of lump in throat, though you have already been exposed to radiation
and your narrow oesophagus had been dilated.
I would like to say that after radiation there appears oedema in pharynx and oesophagus followed by fibrosis
which some times results in stenosis. This is most of the time gives rise to feeling of obstruction in degulitition to patient. Second important fact is in such situations reflex oesophagitis is also comes in viscinity and again gives feeling of lump.
After dilatation recurrence of stricture is very common so please remain in touch with your gastroenterologist.
Probably above answers your query.