hi Kerr Kerr,
it's tough feeling sick with something in the evening, especially as you probably want to get some rest before radiotherapy tomorrow.
If this hasn't been something like a muscular twinge that came and went and it's still hurting, no need to worry through the night...
maybe phone your treating hospital
although the radiotherapy people go home, there's always a nurse co-ordinator on for the whole overnight who's across things and can advise you while you're a patient.
As Lyn said in her comment, it's best to be wise about chest pain, though I don't know if the radio is a special cause for it.
The hospital switchboard (tell them your details and why you're calling) will connect you to the nurse co-ordinator.
Hoping all is well now and you're not reading this but sleeping, all ready for a fresh day getting through your second week. All the best, Jenny