Factors influencing haematological recovery after allogeneic haemopoietic stem cell transplants: graft-versus-host disease, donor type, cytomegalovirus infections and cell dose

Platelet recovery after allogeneic haemopoietic stem cell transplant (HSCT) and predictive factors were analysed in 342 patients with haematological m alignancies. All patients were prepared with cyclophosphamide plus total bo dy irradiation, and received an unmanipulated HSCT from an HLA-identical si bling (n = 270), a matched unrelated donor (n = 67) or an identical twin (n = 5). The source of stem cells was peripheral blood (n = 15) or bone marro w (n = 327). Graft-vs.-host disease (GvHD) prophylaxis consisted of cyclosp orin A with or without methotrexate. The proportion of patients with < 50 x 10(9)/l platelets on d +50, d +100, d +200 and d +365 after HSCT was 26%, 27%, 14% and 11% respectively. Thrombocytopenia was independent of the degr ee of complete donor chimaerism. Four variables were predictive of platelet recovery: donor type, acute GvHD, cytomegalovirus (CMV) infection and numb er of cells infused at transplant. Recipients of an unrelated graft had low er platelet counts (49 x 10(9)/l) on d +50 than identical sibling grafts (1 08 x 10(9)/l) (P < 0.001) and twin grafts (149 x 10(9)/l) (P < 0.001). Pati ents with GvHD grades 0, I, II, III and IV had significantly different plat elet counts on d +50 (153 x 10(9)/l, 102 x 10(9)/l, 85 x 10(9)/l, 32 x 10(9 )/l and 22 x 10(9)/l; P < 0.001) and thereafter. Thrombocytopenia was more frequent in patients with high-level CMV antigenaemia (> four positive cell s/2 x 10(5)) (P < 0.0001) and in patients who received a low cell dose at t ransplant (less than or equal to 4.1 x 10(8)/kg) (P = 0.009). Platelet coun ts predicted transplant-related mortality (TRM) and were higher at all time intervals in patients surviving the transplant. Patients with grade II GvH D and > 50 x 10(9)/l platelets had a lower TRM than patients with grade II GvHD and less than or equal to 50 x 10(9)/l platelets (14% vs. 40%, P < 0.0 001). In conclusion, (i) a significant proportion of allogeneic HSCT recipients a re thrombocytopenic long-term, irrespective of complete donor chimaerism, ( ii) thrombocytopenia identifies patients at greater risk of lethal complica tions, and (iii) platelet recovery is influenced by GvHD, donor type, CMV i nfections and cell dose, not by stem cell source or other patient-disease-r elated variables.