I had very bad case of IC soon after going through menopause (@ 20 yrs ago, (my theory not the Dr's, was that my bladder lining was thinning and the acid of the urine was irritating). I found an excellent urologist who understood IC and after many tests, some quite annoying, he prescribed Flomax (the prostate drug) and lo and behold I got better. I no longer have it and never have flare ups. I have been on the immunotherapy drug Jemperli for a year and a half for endometrial cancer; and all the radiation I had never caused a flare-up. This is my experience, and maybe something for you to consider with your doctors.