Irradiation free conditioning regimen is associated with high relapse rate in Egyptian patients with acute lymphoblastic leukemia following allogeneic hematopoietic stem cell transplantation

Total body irradiation versus busulfan based intermediate intensity conditioning for stem cell transplantation in ALL patients >45 years-a registry-based study by the Acute Leukemia Working Party of the EBMT

Allogeneic hematopoietic cell transplantation is a potentially curative treatment in high-risk acute lymphoblastic leukemia (ALL). Conditioning regimens based on ≥12 Gray total body irradiation (TBI) represent the current standard in patients ≤45 years, whereas elderly patients frequently receive intermediate intensity conditioning (IIC) to reduce toxicity. To evaluate the role of TBI as a backbone of IIC in ALL, a retrospective, registry-based study included patients >45 years transplanted from matched donors in first complete remission, who had received either fludarabine/TBI 8 Gy (FluTBI8, n = 262), or the most popular, irradiation-free alternative fludarabine/busulfan, comprising busulfan 6.4 mg/kg (FluBu6.4, n = 188) or 9.6 mg/kg (FluBu9.6, n = 51). At two years, overall survival (OS) was 68.5%, 57%, and 62.2%, leukemia-free survival (LFS) was 58%, 42.7%, and 45%, relapse incidence (RI) was 27.2%, 40%, and 30.9%, and non-relapse-mortality (NRM) was 23.1%, 20.7%, and 26.8% for patients receiving FluTBI8Gy, FluBu6.4, and FluBu9.6, respectively. In multivariate analysis, the risk of NRM, acute and chronic graft-versus-host disease was not influenced by conditioning. However, RI was higher after FluBu6.4 (hazard ratio [HR] [95% CI]: 1.85 [1.16-2.95]), and LFS was lower after both FluBu6.4 (HR: 1.56 [1.09-2.23]) and FluBu9.6 (HR: 1.63 [1.02-2.58]) as compared to FluTBI8. Although only resulting in a non-significant advantage in OS, this observation indicates a stronger anti-leukemic efficacy of TBI-based intermediate intensity conditioning.

Total Body Irradiation-Based Conditioning Regimen Improved the Survival of Adult Patients With T-Cell Lymphoblastic Lymphoma After Allogeneic Peripheral Blood Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is one of the consolidation modalities for adult patients with T-cell lymphoblastic lymphoma (T-LBL). However, the optimal conditioning regimen needs to be explored. In the present study, 40 patients with T-LBL undergoing allo-HSCT were retrospectively analyzed, including 23/40 (57.5%) with total body irradiation (TBI)–based conditioning regimen and 17/40 (42.5%) with busulfan (BU)-based regimen. TBI–based regimen significantly increased the cumulative incidence (CI) of grade II to IV acute graft-versus-host disease (aGvHD) as compared with BU-based regimen (13.0% vs 0%, P = 0.000). The relapse risk was significantly lowered in TBI-based group with a 2-year CI of relapse (CIR) of 9.1% as compared with that of 49.6% in BU-based group (P = 0.008). The 1-year and 2-year non-relapse mortalities (NRMs) for all patients were 5.0% and 10.3%, respectively. The 1-year and 2-year NRMs were 8.9% and 16.0% in TBI-based group, and 0.00% and 0.00% in BU-based group (P = 0.140). The 2-year probabilities of overall survival (OS) and relapse-free survival (RFS) were 83.0% [95% confidence interval, 63.4%–100%] and 74.0% (95% confidence interval, 54.4%–93.6%) in TBI-based group, which were higher than that of 35.0% (95% confidence interval, 0.0%–72.2%) and 50.0% (95% confidence interval, 24.5%–75.4%) in BU-based group, respectively (P = 0.020 for OS and P = 0.081 for RFS). In multivariate analysis, TBI-based regimen significantly reduced the risk of relapse [subdistribution hazard ratio (SHR) = 0.030, 95% CI, 0.002–0.040, P = 0.000] and improved the OS [hazard ratio (HR) 0.121, 95% CI, 0.021–0.683, P = 0.017] as an independent prognostic factor. These results suggested that TBI-based regimen might be an optimal choice for adult patients with T-LBL undergoing allo-HSCT.

Busulfan-containing conditioning regimens in allogeneic hematopoietic stem cell transplantation for acute lymphoblastic leukemia: A Taiwan observational study

Background

Allogeneic stem cell transplantation (allo‐HSCT) is the ultimate cure for acute lymphoblastic leukemia (ALL).

Aim

This study was performed to compare the outcomes of ALL patients receiving busulfan (Bu) with cyclophosphamide (Cy)‐based or total body irradiation (TBI)‐based regimen in a Chinese population.

Methods

We enrolled 224 adult patients with ALL who received allo‐HSCT at National Taiwan University Hospital between 1997 and 2016.

Results

The median age at transplantation was 33 years. Before allo‐HSCT, 75.9% of patients attained first or late complete remission. A total of 141 patients (62.9%) received Bu/Cy‐based conditioning, either myeloablative (MA) or reduced‐intensity stem cell transplantation (RIST), and 83 patients received a TBI‐based regimen (MA‐TBI). Patients receiving the MA‐Bu regimen had longer relapse‐free survival (RFS) than those receiving the MA‐TBI regimen (median, 24.1 vs. 6.7 months, p = .044). There was no difference in overall survival (OS, MA‐Bu vs. MA‐TBI vs. RIST‐Bu: 39.4 vs. 28.2 vs. 13.1 months, p = .276), treatment‐related mortality (TRM), or incidences of grade 3–4 acute graft‐versus‐host disease (GvHD). Among patients receiving identical GvHD prophylactic regimens, there was no difference between MA‐Bu and MA‐TBI groups regarding the incidence of grade 3–4 acute GvHD, grade 2–4, and all‐grade chronic GvHD. In subgroup analysis, patients receiving oral busulfan had comparable RFS and OS to the intravenous busulfan group (p = .436 and p = .236, respectively), but a higher TRM (25% vs. 9.8%, p = .016). In the multivariable analysis, disease status before allo‐HSCT was the only risk factor impacting RFS and OS.

Conclusion

In summary, patients receiving Bu/Cy‐based or TBI‐based regimens as conditioning had similar results in terms of OS, TRM, and acute GvHD, whereas the use of myeloablative Bu/Cy resulted in a better RFS. A Bu‐based regimen could be an alternative conditioning choice for patients who are ineligible to receive TBI. Prospective and randomized controlled trials are warranted to validate the long‐term outcomes.