The sample size calculation is carried out based on the statistical selection theory criterion as detailed in Simon et al (62) and Gibbons et al (63). Assuming a 90% probability of correctly selecting the best treatment, and anticipating a baseline response rate of 40%, then to detect a 15% superiority of the best treatment over the other, a trial size of 37 patients per treatment arm would be required. The total accrual target would thus be 74 patients.