CHIMERISM ANALYSIS IN LONG-TERM SURVIVOR PATIENTS AFTER BONE-MARROW TRANSPLANTATION FOR SEVERE APLASTIC-ANEMIA

Background and Objective. Allogeneic bone marrow transplantation (BMT) is the most common treatment for young patients with severe aplastic anemia (SAA). Late graft failure represents one of the possible unfavo rable outcomes in this setting. Mixed chimerism might represent a risk factor for late graft failure. We examined this relationship by study ing chimerism in long-term survivor SAA patients after allogeneic BMT. Methods. We analyzed long-term hematopoietic chimerism in 15 patients who received BMTs for SAA: 9 with an irradiation-based conditioning r egimen and 6 with ATG. We used a PCR method targeting VNTR loci. Sensi tivity of the technique ranged between 0.5 and 1.5%. Results. All pati ents conditioned with radiation-based schemes showed complete donor ch imerism. Conversely, out of six patients who received cyclo-phosphamid e and ATG as a conditioning regimen, only one of them had late graft f ailure (day +168). In this patient, durable mixed chimera status was f irst detected two months after BMT. Interpretation and Conclusions. Ou r results suggest that in long-term survivors of SAA after BMT there i s almost always complete donor chimerism in both irradiated and ATG-co nditioned recipients. Mixed chimerism might predict graft failure in t hese patients. (C) 1997, Ferrata Storti Foundation.