I had fifteen treatment this last time, and 30 treatments in 2004. I had fewer treatments this time b/c they began with higher does than 2004 and I tolerated them well.

You go 5 days/week. Must be sure to be perfectly still on the table. Moving could change where the beam goes. The second time, it was on the left side so I had to hold my breath for the treatment b/c of my heart being on that side. You are tested before starting and must be able to hold your breath for at least 30 seconds for the left sided treatment b/c it moves the heart out of the way of the beam. Radiation to the heart can cause problems.
I really had no problems at all except some fatique toward the end of the treatments. tiredness was much worse the first time.
For me, radiation was the easiest part of my treatment for breast cancer, while five years of arimdex(first time) , and infusions of Faslidex(b/c I refused to take arimdex again), were a living hell.