When I made my decision to have the five day treatment versus a longer course, it was based on a discussion with my oncologist. She said that recent new parameters had come down, that she checked and my margins were clean and wide enough that my case qualified for the shorter course. She explained that in her opinion, the only potential downside was the fact that it could cause a little more impact to the appearance of the breast in the form of thickening the scar is how she described it. Hope this helps. I am 10 months out, doing great and have very little disfiguration. Basically just a small dent in the lumpectomy area. I'm extremely pleased I went that route. While I did experience minor fatigue for two to three weeks, that's about it. I did use Mepitel film so did not have a skin reaction. Good luck to you and I'm sure either decision will render a positive result for you.