Unmanipulated Haploidentical Bone Marrow Transplantation and Post-Transplant Cyclophosphamide for Hematologic Malignanices Following A Myeloablative Conditioning.

Abstract 3034

Despite a large number of unrelated donors (UD), not more than 30% of patients who have activated a donor search, undergo an allogeneic UD stem cell transplant. HLA haploidentical family members are being increasingly considered as an alternative donors, both using T cell depleted or T cell replete grafts. Post-transplant high dose cyclophosphamide (PT-CY), introduced by the Baltimore group, has shown very promising results following non myeloablative conditioning regimens. We are now reporting 50 patients with high risk hematologic malignancies, who received a myeloablative regimen, followed by unmanipulated haploidentical bone marrow transplant (hBMT) and PT-CY. The myeloablative conditioning consisted of thiotepa (10 mg/kg), busulfan (9,6 mg/m2̂), fludarabine (150 mg/m2̂)(n=35), or total body irradiation (9,9–12 Gy), fludarabine (120 mg/m2̂) (n=15). The median age was 42 years (18–66); 23 patients were in remission and 27 had active disease; 10 patients were receiving a second allograft. Graft versus host disease (GvHD) prophylaxis consisted in PT-CY on day+3 and +5, cyclosporine (from day 0), and mycophenolate (from day +1).

The median nucleated cell dose was 3.6 ×108̂/kg (range: 1,4 – 7,7). The median time to neutrophil counts of >0.5×10⁹/L was 18 days (range, 13–30 days) and to platelet counts of >20×10⁹/L 23 days (range, 14 – 58 days), respectively. There was no correlation between infused number of nucleated cells and days of neutrophil engraftment. The cumulative incidence of engraftment was 90%for neutrophils and 86% for platelets. Three patients died before engraftment, and 2 patients had autologous recovery: 45 patients (90%) had full donor chimerism on day +30. The cumulative incidence of grade II-III acute GvHD was 12%, and of moderate chronic GvHD 10%. With a median follow up for surviving patients of 333 days (149–623), the cumulative incidence of transplant related mortality is 18%, and the rate of relapse 26%. The actuarial 22 months disease free survival is 68% for patients in remission and 37% for patients with active disease (p<0.001). Causes of death were pneumonia (n=3), haemorrhage (n=3), sepsis (n=3) and relapse (n=7).

In conclusion, a myeloablative conditioning regimen followed by h-BMT with PT-CY, results in a low risk of acute and chronic GvHD and encouraging rates of transplant related mortality and disease free survival.