A Stem Cell Donor for Every Adult Requiring an Allograft for Acute Lymphoblastic Leukemia?

Younger Matched Unrelated Donors Confer Decreased Relapse Risk Compared to Older Sibling Donors in Older Patients with B Cell Acute Lymphoblastic Leukemia Undergoing Allogeneic Hematopoietic Cell Transplantation

Although allogeneic hematopoietic cell transplantation (alloHCT) offers cure for older patients with acute lymphoblastic leukemia (ALL), disease relapse remains a major issue. Whether matched sibling donors (MSDs) are still the preferred donor choice compared to younger matched unrelated donors (MUDs) in the contemporary era of improved transplantation practices remains unknown. This retrospective cohort registry study queried the Center for International Blood and Marrow Transplant Research (CIBMTR) database in patients with B cell ALL (B-ALL) age ≥ 50 years undergoing alloHCT from older MSDs (age ≥ 50 years) or younger MUDs (age ≤ 35 years) between 2011 and 2018. The study included common allograft types, conditioning regimens, and graft-versus-host disease (GVHD) prophylaxis strategies. The primary outcome was relapse risk, and secondary outcomes included nonrelapse mortality (NRM), GVHD, leukemia-free survival (LFS), and overall survival (OS). Among 925 eligible patients in the study cohort, 386 underwent alloHCT with an older MSD (median donor age, 58 years) and 539 underwent alloHCT from a younger MUD (median donor age, 25 year). In multivariable analysis, younger MUDs conferred a significantly decreased risk of relapse (hazard ratio [HR], .68; P = .002) compared with older MSDs. The adjusted cumulative incidence of relapse at 5 years was significantly lower with younger MUDs than with older MSDs (26% versus 37%; P = .001). Younger MUDs were associated with a greater risk of chronic GVHD compared to older MSDs (HR, 1.33; 95% confidence interval [CI], 1.10 to 1.61; P = .003). Compared to older MSDs, younger MUDs conferred an increased NRM (HR, 1.38; P = .02) and higher adjusted cumulative incidence of NRM at 5 years (31% versus 22%; P = .006). There were no differences in post-alloHCT OS or LFS rates between younger MUDs and older MSDs (OS: HR, 1.09; [P = .37]; LFS: HR, .95 [P = .57]). The use of younger MUDs could be considered as a possible way to prevent relapse after alloHCT in older adults with ALL. Combining the use of younger MUDs with improved strategies to reduce GVHD merits further exploration to improve outcomes.

Impact of Donor Age on Allogeneic Hematopoietic Cell Transplantation Outcomes in Older Adults with Acute Myeloid Leukemia

Allogeneic hematopoietic cell transplantation (alloHCT) provides cure for older patients with acute myeloid leukemia (AML); however, disease relapse remains a major concern. Based on recent data suggesting that younger donor age confers the greatest benefit for alloHCT with matched unrelated donors (MUDs), we attempted to answer a practical question: which donor type provides the best outcomes when an older patient with AML has a matched sibling donor (MSD, also older) versus the best MUD? This retrospective cohort registry study accessed data from the Center for International Blood and Marrow Transplant Research (CIBMTR) in patients with AML age ≥ 50 years undergoing alloHCT from older MSDs (age ≥ 50 years) or younger MUDs (age ≤ 35 years) between 2011 and 2018. The study included common allograft types, conditioning regimens, and graft-versus-host disease (GVHD) prophylaxis. The primary outcome was relapse risk. Secondary outcomes included nonrelapse mortality (NRM), GVHD, disease-free survival (DFS), and overall survival. Among 4684 eligible patients, 1736 underwent alloHCT with an older MSD (median donor age, 60 years), and 2948 underwent alloHCT from a younger MUD (median donor age, 25 years). In multivariable analysis, compared to older MSDs, the use of younger MUDs conferred a decreased relapse risk (hazard ratio [HR], .86; P = .005) and a significantly lower adjusted 5-year cumulative incidence of relapse (35% versus 41%; P = .003), but was associated with an increased risk for chronic GVHD (HR, 1.18; 95% confidence interval [CI], 1.08 to 1.29; P = .0002) and greater NRM only in the earlier period of 2011 to 2015 (HR, 1.24; P = .016). The corresponding NRM rates were significantly lower in the more recent period of 2016 to 2018 (HR, .78; P = .017). The adjusted 5-year DFS probability was 44% (95% CI, 42% to 46%) with an alloHCT from younger MUDs compared to 41% (95% CI, 38% to 43%) with older MSDs (P = .04). In summary, for older patients with AML undergoing alloHCT, the use of younger MUDs is associated with decreased relapse risk and improved DFS compared with the use of older MSDs.

Severity of Cytokine Release Syndrome and Its Association with Infections after T Cell-Replete Haploidentical Related Donor Transplantation

An increased risk of infections has been described after T cell-replete haploidentical cell transplantation (haploHCT). Cytokine release syndrome (CRS) after haploHCT is a known phenomenon, but the impact of CRS severity on the risk of infections remains unexplored. We retrospectively evaluated 78 consecutive adult haploHCT recipients from 2012 to 2018 for the development of CRS (graded based on the criteria of Lee et al) and examined the incidence and mortality due to infections in correlation with CRS severity. In our study cohort, which was stratified into 3 groups by severity of CRS, 80% of the patients developed infections within 180 days of HCT. Significantly higher proportions of patients with CRS grade 2 (89%) and grade ≥3 (90%) than patients with CRS grade 0-1 (68%) had at least 1 infection in the first 100 days (P = .04). Bloodstream infections (BSIs) were seen more frequently in patients with CRS grade 2 and grade ≥3 in the first 6 months. Multivariable analysis for time to infection showed that CRS grade ≥3 was independently associated with an elevated risk of any infection compared with CRS grade 0-1 (hazard ratio [HR], 3.05; P = .007). CRS grade ≥3 was also associated with a higher hazard of viral (HR, 3.42; P = .04) and bacterial infections (HR, 2.83; P = .03) compared with CRS grade 0-1. After adjusting for time to neutrophil engraftment as a time-dependent covariate, CRS grade ≥3 still had a significant effect on viral infections (HR, 2.49; P = .03), but not on bacterial infections (HR, 1.32; P = .57). CRS grade was also a significant predictor for infection density (overall, bacterial, and viral). The incidence of infection-related mortality by day +100 was higher in patients with severe CRS. Severe CRS developing after post-transplantation cyclophosphamide-based haploHCT is independently associated with viral infections and an increased risk of bacterial infections, likely through delayed neutrophil engraftment.