The care team answer was interesting because radiation can cause an impact on blood counts. But maybe because your treatment was confined to a targeted area it limited exposure to surrounding tissue and didn’t impact the body. If that’s the case, that’s a plus. But it still doesn’t answer why you’re having the decline in white blood cells.

Were the RBC numbers good?
Did you have a CBC before starting your treatments?

Do you have any symptoms of an infection, any autoimmune diseases, viruses? Are you on any other medications besides the Elegard and Lupron, such as antibiotics?

In any case, this does warrant further investigation. Have you talked your PCP after receiving the results?