My WBC went so low that my GP was starting to plan special treatment by the time it finally started rising off near-zero about
18 months after RT. Now, two years after RT, it only hovers around the minimum. I still have specific instructions about
being out in groups, public places, and running in the other direction if anyone sneezes.
The timing was clear, as I had been doing 6 month blood work for a few years, and the WBC count fell from dead-center in the normal range to almost undetectable during RT. The Rad Oncologist swore that it had nothing to do with RT, but both my uro/surgeon and GP are convinced it was caused by RT's impact.
Just my experience.