Steroids Versus ECP and Steroids as First-line Treatment of Grade II Acute GVHD

The goal of this clinical trial is to compare as a first line of grade II skin acute GVHD sconventional treatment with steroids alone to a combination of steroids and extracoporeal photopheresis (ECP) The primary end point will compare Freedom from treatment failure at 6 months from randomization as defined by meeting all the following 4 conditions: * to be alive * without relapse of the hematological disease * without having required a new line of treatment for acute GVHD * without initiating a systemic treatment for chronic GVHD.