Radiation Treatment

I have stage 3 tumor extending into bladder.  I have received 11 of 28 treatments and just this past weekend had to go to ER for catheterization due to blockage, urine was deep purple before block.  Doctor said tumor breaking up and causing block.  Has anyone experienced this side effect?  Did it happen more than once? 

What is likelihood of happening again if I continue treatments?

Good luck, John. No experience here. Whatever the Dr say, make sure you understand what they are recommending. Ask questions. If possible get 2nd opinions