Differential Association between Blood Glucose Levels and Nonrelapse Mortality after Allogeneic Hematopoietic Cell Transplantation Based on Presence or Absence of Preexisting Diabetes.

Malglycemia, defined as hyperglycemia, hypoglycemia, or increased glycemic variability, has been associated with increased mortality after allogeneic hematopoietic cell transplantation (HCT). Among critically ill non-HCT recipients with diabetes and poor glycemic control, compared to those without diabetes, stringent blood glucose control has been associated with increased mortality. This study investigated whether a pre-HCT diagnosis of diabetes and the type of pre-HCT diabetes treatment modulate the previously reported negative impact of malglycemia on post-HCT nonrelapse mortality (NRM). We performed a single-institution retrospective analysis of mortality outcomes after allogeneic HCT as a function of post-HCT blood glucose levels, pre-HCT diagnosis of diabetes, and type of pre-HCT diabetes treatment (insulin, no insulin). A total of 1062 patients who underwent allogeneic HCT between 2015 and 2020 were included in this study. Among these patients, 84 (8%) had a pre-HCT diagnosis of diabetes, of whom 38 (4%) used insulin and 46 (4%) used a noninsulin antiglycemic agent. Post-HCT blood glucose values measured within 100 days from HCT, modeled as a continuous nonlinear time-varying covariate, were associated with day-200 NRM, with both lower and higher glycemic values associated with higher NRM compared to normoglycemic values (adjusted P < .0001). The association between post-HCT blood glucose and NRM varied, however, depending on the presence or absence of a pre-HCT diagnosis of diabetes; that is, there was evidence of a statistical interaction between blood glucose levels and diabetes (adjusted P = .008). In particular, the detrimental impact of hyperglycemic values was more pronounced in patients without a pre-HCT diagnosis of diabetes compared to those with a pre-HCT diagnosis of diabetes. As reported previously, higher and lower blood glucose levels measured within 100 days after allogeneic HCT were associated with an increased risk of NRM; however, this association was more pronounced among patients without a pre-HCT diagnosis of diabetes compared to those with a pre-HCT diagnosis of diabetes, suggesting that patients with diabetes are relatively protected from the downstream effects of hyperglycemia. These data support the notion that patients with pre-HCT diabetes may need a different approach to blood glucose management after transplantation compared to those without diabetes. © 2024 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.