The study is powered to evaluate equivalence between the two strategies under the assumption that, in the control arm, the primary end-point would be observed in a proportion of subjects < 7% and that the same proportion in the STI arm would not exceed 10% with a maximum allowed 95%CI of 12%. 320 patients will be needed for alfa = 5% and 1-beta = 80%. The primary analysis will be made according to the intention-to-treat approach and therefore no correction for eventual drop outs is needed. In addition, a secondary per-protocol analysis will be performed.