This study will be monitored by an independent data and safety monitoring board (DSMB) of the Medical University of Vienna (MUW). Interim analyses will be performed by the DSMB after completion of 10 and 20 cases in the treatment group. The Lan & DeMets extension of the O'Brian-Fleming stopping rules will be applied (DeMets, LD et al. 1994). The trial will be stopped if the observed p-value is <0.00001 (first interim analysis after 10 patients) or <0.00305 (second interim analysis after 20 patients).