Impact of Chronic Graft-Versus-Host Disease on Long-Term Outcomes of Reduced-Intensity Conditioning Allogeneic Hematopoietic Cell Transplantation for Adults with High-Risk Acute Lymphoblastic Leukemia in First Remission

Background : The role of reduced-intensity conditioning allogeneic hematopoietic cell transplantation (RIC-HCT) in adult acute lymphoblastic leukemia (ALL) remains unclear because the interpretation of transplantation outcome is mainly limited by the small sample size, short follow-up duration, various regimens for conditioning and graft-versus-host disease (GVHD) prophylaxis, and the heterogeneity of the criteria used to select patients for RIC-HCT. Previously, we conducted a phase 2 trial of RIC-HCT in adults with high-risk ALL who were ineligible for myeloablative conditioning and showed the potential role of this strategy, especially in patients in first complete remission (CR1). Here, we report the long-term outcomes of RIC-HCT by analyzing 122 consecutive adults with high-risk ALL in CR1, particularly focusing on the prognostic relevance of chronic GVHD.

Methods: During the period between 2000 and 2014, 122 patients in CR1 (median age, 52 years [range, 15-65 years]; 54 Ph-negative ALL and 68 Ph-positive ALL) were given an identical RIC regimen consisting of fludarabine (150 mg/m² in total) and melphalan (140 mg/m²in total). The indications for RIC-HCT were advanced age (≥50 years; n=79; 64.8%) and comorbid conditions (n=43; 35.2%). Graft sources were peripheral blood stem cells (n=118; 66 matched sibling donor, 23 matched unrelated donor, 29 mismatched unrelated donor) and bone marrow (n=4; 1 matched sibling donor, 1 matched unrelated donor, 2 mismatched unrelated donor). The median time to transplantation was 155.5 days (range, 103-291 days). GVHD prophylaxis was attempted by administering calcineurin inhibitors (cyclosporine for sibling donor transplants, tacrolimus for unrelated donor transplants) plus methotrexate. Antithymocyte globulin was administered to the patients who received mismatched unrelated donor grafts. If residual leukemia was detected in the absence of GVHD at 3 months after transplantation, calcineurin inhibitors were rapidly discontinued.

Results: The median time for neutrophil and platelet recovery was 12 days (range, 8-30 days) and 13 days (range, 5-60 days) after RIC-HCT. Sixty-two patients developed acute GVHD (53 grade II, 5 grade III, 4 grade IV). The cumulative incidence of acute GVHD at 1 year was 50.8% (42.6% for Ph-negative and 57.4% for Ph-positive, P=0.152). Except for 11 patients with early deaths within 100 days, 77 developed chronic GVHD (30 mild, 29 moderate, 18 severe), resulting in a 5-year cumulative incidence of 63.6% (69.1% for Ph-negative ALL and 58.8% for Ph-positive ALL, P=0.319). The median time to onset of chronic GVHD was 140 days (range, 37-843 days) after transplantation. Cytomegalovirus reactivation >10,000 copies/mL was observed in 40.2% (44.4% for Ph-negative ALL and 36.8% for Ph-positive ALL, P=0.447). After a median follow-up duration of 57.9 months (range, 17.7-206.8 months), the 5-year cumulative incidence of relapse (CIR) and non-relapse mortality (NRM) were 27.5% (23.9% for Ph-negative ALL and 30.2% for Ph-positive ALL) and 19.0% (17.4% for Ph-negative ALL and 20.3% for Ph-positive ALL), respectively, and the 5-year disease-free survival (DFS) and overall survival (OS) rates were 53.5% (58.4% for Ph-negative ALL and 49.7% for Ph-positive ALL) and 59.8% (60.2% for Ph-negative ALL and 59.3% for Ph-positive ALL). In multivariate analysis, the presence of chronic GVHD lowered CIR (HR, 0.23; 95% CI, 0.10-0.48; P<0.001), but severe chronic GVHD increased NRM (HR, 8.76; 95% CI, 3.39-22.6; P<0.001). Thus, the presence of mild to moderate chronic GVHD was closely related to better outcomes in terms of DFS (HR, 0.45; 95% CI, 0.32-0.64; P<0.001) and OS (HR, 0.44; 95% CI, 0.30-0.64; P<0.001) in all patients as well as in both subgroups of patients. In Ph-positive ALL subgroup of patients, patients without achievement of major molecular response until the time of transplantation had also significantly higher CIR (HR, 7.42; 95% CI, 3.04-18.10; P<0.001) and poorer DFS (HR, 3.47; 95% CI, 1.48-8.14; P=0.004) and OS (HR, 2.58; 95% CI, 1.03-6.47; P=0.043).

Conclusion: Our long-term follow-up data with a uniform treatment strategy suggest that RIC-HCT is a valid alternative choice for providing a long-term disease control for adult high-risk ALL patients in CR1. Minimal residual disease-based treatment strategies to reduce leukemia cell burden before HCT and to enhance the graft-versus-leukemia effect are needed in the future.