STATISTICAL CONSIDERATIONS To calculate the sample size the optimal two-stage design developed by Simon is used (Richard Simon, Controlled Clinical Trials 1989). Considering a 2 stage study, with a difference p1-p0=20% between a standard treatment (p0=40%) and the investigated treatment (p1=60%) and setting alfa error probability at 0.10 and beta error probability at 0.10, 28 patients will have to be treated in the 1st stage of the trial. If less or equal than 11 responses are observed among the 28 patients, then the study will be stopped. Otherwise the study will continue to a total of 41 patients will be treated in the second stage. If there are more than 20 responses in 41 patients in the second stage, this treatment could be considered active.