Trial design is much more straightforward if you are looking at one factor at a time - the addition (or not) of a single chemo agent, or the radiotherapy fractionation protocol. If you design a trial that has multiple factors, it's harder to tell definatively which tweek gave better results, or if it was the combination that did it. Science Daily had another article that explains a combination. It is way pre-clinical (unless you are a fruit fly) but very interesting and less depressing that the cancer and the Darwinian cancer evolution one:

http://www.sciencedaily.com/releases/2012/06/120615141716.htm

Maria