Not to scare you or anything, but this sounds almost exactly like what happened to my grandfather. Had non hodgkin's lymphoma, had some chemo + surgury. Felt fine for about 1-2 weeks afterwords- then his back started killing him. Doctor's use a scale of 1-10 to judge pain- he was screaming "10 10 10 10!" to the nurse.
Anyway, the cancer took over soon after that. They didn't do radiation- it was too late. He ultimately died in hospice care from pneumonia while in a drugged up coma from all the pain killers.
I hope everything goes fine- I hope I didn't scare you, I just didn't "sugar coat it". Good luck with everything. You have my best wishes.