For patients with acute myeloid leukemia (AML) in need of allogeneic hematopoietic cell transplantation (alloHCT), reduced-intensity/nonmyeloablative conditioning (RIC/NMA) offers a lower risk of infection than myeloablative conditioning (MAC), based on a retrospective study involving more than 1,700 patients.

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Within 100 days of treatment, patients who underwent MAC were significantly more likely to develop a bacterial infection, and develop it at an earlier date, than patients who had undergone RIC/NMA, reported lead author Celalettin Ustun, MD, of Rush University in Chicago, and colleagues.

“The incidence of infections, a common and often severe complication of alloHCT, is expected to be lower after RIC/NMA compared with MAC and thus contribute to the decreased [nonrelapse mortality],” the investigators wrote in Blood Advances, noting that this hypothesis has previously lacked supporting data, prompting the present study.

The retrospective analysis involved 1,755 patients with AML who were in first complete remission. Data were drawn from the Center for International Blood and Marrow Transplant Research (CIBMTR). The primary end point was incidence of infection within 100 days after T-cell replete alloHCT in patients receiving MAC (n = 978) versus those who underwent RIC/NMA (n = 777). Secondary end points included comparisons of infection types and infection density.

Patients who received RIC/NMA were generally older and more likely to have myelodysplastic syndrome than patients in the MAC group; the groups were otherwise similar, based on comorbidities, cytogenetic risks, and Karnofsky performance scores.

The proportion of patients who developed at least one infection was comparable between groups: 61% of MAC patients versus 58% of RIC/NMA patients (P = .21), but further analysis showed that MAC was in fact associated with some relatively increased risks. For instance, patients in the MAC group tended to develop infections sooner than patients treated with RIC/NMA (21 vs. 15 days), and more patients treated with MAC had at least one bacterial infection by day 100 (46% vs. 37%).

Although the proportion of patients developing at least one viral infection was slightly lower in the MAC group than the RIC/NMA group (34% vs. 39%), overall infection density was higher, which takes into account multiple infections.

The increased bacterial infections after MAC were caused by gram-positive bacteria, while the increased viral infections with RIC/NMA were caused by cytomegalovirus, the investigators reported.

“RIC/NMA alloHCT is associated with a decreased risk of any infection and particularly early bacterial infections,” the investigators wrote. “The risk of viral and fungal infections per days at risk is similar.”

The Center for International Blood and Marrow Transplant Research is supported by grants from the U.S. government and several pharmaceutical companies. The investigators reported having no conflicts of interest.

SOURCE: Ustun C et al. Blood Adv. 2019 Sep 10;3(17):2525-36.