Sorry to hear that you have to take a 2nd treatment of Efudex. I am already dreading if that could possibly happen to me again someday. I just bought my 3rd tube of SPF 70 sunscreen. I have been putting it on every day since my treatment ended. I got a spray bottle this time.
I'm not sure about the sunscreen during treatment, I was only told to wear sunscreen after my treatment was finished.
As far as medical advances, this thread was very interesting and explained the difference between Efudex and Carac. It seems that the advances are what you mix with the Fluorouracil.
http://www.cancercompass.com/message-board/message/all,21073