I am 4b as well. I had essentially the same therapy as you (Johns Hopkins calls it Total Eradication Therapy-TET). My PSA is currently undetectable one and a half years after treatment and I am off all meds. My MO at Hopkins is heavily involved in research and I have read some of his articles. When cancer cells are stressed (chemo, radiation etc) some of them go into a hibernation state with double DNA; the cells look different under the microscope than the other cancer cells. After a time (don't know how long) when the stress is no longer present they begin dividing again. That is why some MO believe it is futile to have excessive chemo treatments which can have significant side effects. No matter how many you get you won't kill them all. The first 4 or so treatments kills 99% of what the chemo will do.

Good luck to you.