Can radiotherapy cause asthma?

I am 4.5 years out from radiotherapy and over the last year have had a few breathing problems, culminating in a serious illness (started by a virus and definitely not a recurrence) and I have now been diagnosed with asthma ........even the Doctor could hear there is more noise on my radiated side. 

There is no family history of asthma or breathing related allergies..........

I googled but could not find anything specific so wondered if others have had this, or if it may actually be unconnected (although my gut tells me it is radiation induced)