Multicentric phase II trial to evaluate efficacy and safety of ibrutinib in combination with rituximab, gemcitabine, oxaliplatin and dexamethasone followed by Ibrutinib maitenance in patients with refractory/relapsed non-GCB DLBCL non candidates to autologous stem-cell transplantation (ASCT) An extensive biological study will be conducted in order to further characterize this population of DLBCL patients and correlate the response obtained with the biological profile of the tumor.