From the way the treatment plan is specified; i.e. 2yg by 35 fractions = 70gy, then that aligns with constant dosing throughout. As to altering the map over time, that seems less likely. Just from what I saw of the process of identifying the areas to be radiated and the contouring and creation of the actual plan that is fed to the accelerator, it seems like more work for the dosimetrist and the risk outweigh the benefits.
Of course, my guessing is about as good as counting grains of sand on the beach. :-)