Correspondence To

the editor: Transplantation-related toxicity and acute intestinal graft-versus-host disease after conditioning regimens intensified with Rhenium 188–labeled anti-CD66 monoclonal antibodies Bunjes et al recently reported encouraging results of a phase 1 to 2 study on the ability of Rhenium 188 (188Re)–labeled anti-CD66 (a, b, c, e) monoclonal antibodies (mAbs) to intensify the conditioning regimen prior to stem cell transplantation for patients with high-risk acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS).1 Bunjes et al gave 32 patients allografts after a conditioning with the radiolabeled mAb in combination with total body irradiation (TBI) or busulfan-based conditioning regimens.1 Thirty patients received T-cell–depleted periph-eral blood stem cells or bone marrow. The authors observed a transplantation-related mortality (TRM) of 24%. Only 3 patients devel-oped a clinically relevant acute graft-versus-host disease (GvHD) grade II; no patient developed a severe GvHD. Here we report our results on 19 patients receiving allografts after conditioning regimens intensified by 188Re-labeled anti-CD66 (a, b, c, e) mAbs as listed in Table 1. In contrast to Bunjes and colleagues we experienced a very high rate of severe acute GvHD and TRM. All patients suffered from advanced or high-risk leukemia (10 patients