Impact of postgrafting immunosuppressive regimens on nonrelapse mortality and survival after nonmyeloablative allogeneic hematopoietic stem cell transplant using the fludarabine and low-dose total-body irradiation 200-cGy

A Tender Reduced-Intensity Conditioning for the Unfit: A Novel 4 Gy Total Body Irradiation-Based Conditioning Followed by Two-Step Haploidentical Stem Cell Transplant, Results of a Prospective Trial

Allogeneic hematopoietic stem cell transplant (HSCT) remains the only potentially curative treatment for many hematologic malignancies (HM). We previously developed a two-step approach that separates the lymphoid and myeloid portions of the graft, allowing a consistent T cell dosing and sparing the stem cells from the effect of post-transplant cyclophosphamide (CY). The two-step approach demonstrated safety and efficacy in patients treated with myeloablative and reduced-intensity conditioning. Here, we extended our two-step platform to older and less fit patients and explored the effects of using a high dose of T cells on disease relapse and transplant outcomes. Thirty-four patients with HM were treated. Median age was 68 years old and included a minority population constituting 32%. Eighty-two percent had a hematopoietic cell transplantation comorbidity index score ≥3. Ninety-one percent were haploidentical, and the rest were matched-related donor HSCT. Following administration of fludarabine and 2 Gy total body irradiation (TBI) (13 patients) or 4 Gy TBI (21 patients) conditioning regimen, a fixed dose of 2 × 108/kg CD3+ T cells was given, followed 2 days later by CY, then infusion of CD34-selected stem cells. Overall survival (OS) was 70% at 1 year and 48% at 3 years. The cumulative incidence (CI) of non-relapse mortality (NRM) and relapse were 22% and 33% at 3 years. However, the CI of relapse was much lower for patients treated with 4 Gy TBI versus those treated with 2 Gy TBI (11% versus 54%, P = .045), while NRM was similar (23% versus 15%, P = .399). This contributed to a high OS of 64% in patients who received 4 Gy TBI-based conditioning at 3 years, with median OS not reached, although this was not statistically significant (P = .68). The median time to neutrophil and platelet recovery was 12 and 17 days, respectively. The CI of grade II acute graft-versus-host-disease (aGVHD) was 22% and 26% at 100 days and 6 months, respectively. The CI of chronic GVHD (cGVHD) was 7.5% at 3 years. There was no grade III or IV aGVHD, no severe cGVHD, and no deaths attributable to GVHD. In conclusion, the two-step approach HSCT demonstrated a low disease relapse rate and high survival in patients treated with 4 Gy TBI-based conditioning, despite a generally older and more medically compromised patient population.

Low incidence of acute graft-versus-host disease with short-term tacrolimus in haploidentical hematopoietic stem cell transplantation

Although tacrolimus (Tac) has immunosuppressive properties and exhibits promising efficacy against graft-versus-host disease (GVHD), little is known about Tac in the prophylaxis of GVHD after HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT). In a multicenter randomized controlled trial, 174 patients received haplo-HSCT with GVHD prophylaxis involving short-term Tac (from -8days to +30days) or cyclosporine (CsA). The 100day cumulative incidences of acute GVHD (aGVHD) and grade III-IV aGVHD with the short-term Tac regimen and CsA regimen were 29.1 (19.5-38.7)% vs. 50.0(39.6-60.4)% (p=0.005) and 3.6(0.0-7.5)% vs. 13.5(6.1-20.9)% (p=0.027), respectively. There were no significant differences in the incidences of chronic GVHD (cGVHD), relapse and cytomegalovirus infection. Lymphocyte subset analysis showed that T cells decreased to lower levels on the short-term Tac regimen within 3 months of transplantation. The disease-free survival and overall survival on the short-term Tac and CsA regimens were 59.3 (48.9-69.7)% vs. 55.7 (45.3-66.1)% (p=0.696) and 65.1 (55.1-75.1)% vs. 61.4 (51.2-71.6)% (p=0.075), respectively. Our findings indicate that the short-term Tac regimen for GVHD prophylaxis in patients undergoing haplo-HSCT is associated with a low incidence and slight severity of aGVHD and did not increase the incidence of relapse and cytomegalovirus infection.

Favorable impact of pre-transplant ATG on outcomes of reduced-intensity hematopoietic cell transplants from partially mismatched unrelated donors

Reduced-intensity conditioning (RIC) permits allogeneic hematopoietic progenitor cell transplantation in patients who would not be considered candidates for transplantation using a myeloablative preparative regimen because of age, comorbidities or prior therapy. In the setting of myeloablative transplantation, use of antithymocyte globulin (ATG) can reduce the risk of GVHD without negatively affecting transplant outcomes; however, limited data exist on the impact of ATG in the setting of RIC, particularly when there is HLA-mismatch. We performed a retrospective analysis of 85 patients who received unrelated donor transplants at our institution for hematologic malignancies following conditioning with fludarabine and melphalan (FluMel), with or without rabbit ATG (6 mg/kg). ATG was targeted to patients receiving HLA-mismatched grafts. With a median follow-up of 36 months, those receiving ATG and a mismatched graft had similar rates of acute and chronic GVHD, relapse, and similar OS compared with those receiving HLA-matched grafts without ATG. In a multivariate analysis, HLA-mismatched donor was not associated with a decrement in OS. We conclude that this intermediate dose of ATG is effective in preventing severe GVHD in the setting of HLA-mismatch, without undue compromise of the graft versus tumor effects on which RIC transplants depend.

Potential for a pluripotent adult stem cell treatment for acute radiation sickness

Accidental radiation exposure and the threat of deliberate radiation exposure have been in the news and are a public health concern. Experience with acute radiation sickness has been gathered from atomic blast survivors of Hiroshima and Nagasaki and from civilian nuclear accidents as well as experience gained during the development of radiation therapy for cancer. This paper reviews the medical treatment reports relevant to acute radiation sickness among the survivors of atomic weapons at Hiroshima and Nagasaki, among the victims of Chernobyl, and the two cases described so far from the Fukushima Dai-Ichi disaster. The data supporting the use of hematopoietic stem cell transplantation and the new efforts to expand stem cell populations ex vivo for infusion to treat bone marrow failure are reviewed. Hematopoietic stem cells derived from bone marrow or blood have a broad ability to repair and replace radiation induced damaged blood and immune cell production and may promote blood vessel formation and tissue repair. Additionally, a constituent of bone marrow-derived, adult pluripotent stem cells, very small embryonic like stem cells, are highly resistant to ionizing radiation and appear capable of regenerating radiation damaged tissue including skin, gut and lung.