Myeloablative radioimmunotherapy with re-188-labeled anti-cd66a,b,c,e-antibody for conditioning of high-risk all and cml patients prior to stem cell transplantation

Purpose. Determination of biodistribution, radiation absorbed organ doses, toxicities and outcome of myeloablative radioimmmunotherapy (RIT) with Re-188 labelled anti-CD66 monoclonal antibody (mAb) in 20 high-risk ALL (n=l 1) and CML (n=9) patients prior to stem cell transplantation (SCT). High-risk was defined as Philadelphia + or >lst CR (ALL) or accelerated / > 1st chronical phase (CML). Materials and methods. Dosimetric measurements were performed 1.5, 3, 20, 26, and 44 h p.i., followed by RIT with 10.8 plusminus 2.4 GBq Re-188 14 days prior to SCT. Standard conditioning consisted of highdose chemotherapy and 12 Gy total body irradiation (TBI). Ten patients received unrelated and 10 patients related allogeneic stem cell grafts. Results. The radiation absorbed doses (Gy) were 14.3 plusminus 4.6 bone marrow (BM), 5.2 plusminus 2.5 liver, 27.5 plusminus 21.5 spleen, 5.7 plusminus 2.6 kidneys, 0.7 plusminus 0.7 lungs, 1.8 plusminus 0.3 total body. Specific BM doses did correlate neither with state of disease prior to SCT nor type of leukemia. BM doses of patients relapsing after SCT were not significantly lower than specific BM doses from patients in ongoing CR. Immediate side effects were mild. All patients showed primary engraftment. After a median follow-up of 8.6 plusminus 5.9 months 10/20 patients (50%) are still in ongoing complete remission. Ten patients died: Eight treatmentrelated, 2 of leukemic relapse. Conclusion. Myeloablative RIT is a promising approach for the improvement of conventional conditioning of high-risk leukemia patients prior to SCT.