FISH test

I have had three FISH (Florescence in situ hybridization) tests in the last year and a half -- all of them, positive. Cystoscopies and CT scans reveal no cancer. In 2002, I had radiation therapy for microscopic prostate cancer. Since then, psa tests have been 0.7 or less and prostate exams have been normal. However side effects of the radiation have included radiation proctitis and radiation cystitis. Could the radiation be causing the positive results in the fish test?