Can dysphagia be avoided with radiation???

[gail p-m]

My elderly father may be restaged from a 4 to 3. If he is, the oncologist talked about radiation to the lung instead of continuing chemotherapy. (They don't want to do both together because it would be too hard on my father due to his age). My father has had dysphagia for the past 4 months; it came on shortly after his cancer operation though no one has found a cause. However, I've read many postings on this board which talk about dysphagia brought about by radiation. Can anyone enlighten me about why this happens? Is it because radiation hits the esophagus or what??? The dysphagia has been very hard on him and has very slowly improved minimally with swallowing therapy. He doesn't want to do anyghing which might worsen it.

Any advice would be appreciated.