Efficacy of Low-Dose Olanzapine for the Prevention of Conditioning Therapy-Induced Nausea and Vomiting in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for hematological malignancies. Conditioning therapy often causes severe chemotherapy-induced nausea and vomiting (CINV). To prevent CINV, olanzapine (OLZ) is recommended as part of a four-drug antiemetic regimen for highly emetogenic chemotherapy; however, evidence in the allo-HSCT setting remains limited. This study aimed to evaluate the effectiveness and safety of low-dose OLZ in preventing CINV in patients undergoing allo-HSCT. We conducted a retrospective single-center cohort study of adult patients with hematological malignancies who underwent their first allo-HSCT between January 2019 and August 2023. Patients were divided into the non-OLZ group (n = 75) and the OLZ group (n = 48). OLZ was administered at 5 mg/d once daily from the start of conditioning therapy for five consecutive days in the OLZ group. The OLZ dose was recommended to be reduced to 2.5 mg/d in cases of intolerance due to adverse effects. All outcomes were assessed over three periods: the acute phase (the period from the first dose of conditioning therapy to 24 hours after the last dose), the delayed phase (the subsequent 96-hour period), and the overall period (the acute and delayed phases combined). The vomiting rate was defined as the percentage of patients who vomited at least once during each period (acute phase, delayed phase, overall period). The primary endpoint was the vomiting rate during the overall period. Statistical analyses were performed using the chi-square test for categorical variables and the Mann-Whitney U test for continuous variables. The threshold for statistical significance was set at P < .05. The median age of the two groups was 55 years in the non-OLZ group and 46.5 years in the OLZ group, and the proportion of female patients was 41.3% and 43.8%, respectively. The vomiting rate during the overall period was significantly lower in the OLZ group (46.7% versus 22.9%; P = .014). The acute-phase vomiting rate was also lower in the OLZ group (41.3% versus 20.8%; P = .031), whereas the delayed-phase difference was not statistically significant (25.3% versus 14.6%; P = .231). The most common adverse event associated with OLZ was somnolence (54.2%). No signal of serious safety concerns attributable to OLZ was observed in this study. In our study, OLZ was associated with improved control of conditioning therapy- induced nausea and vomiting in patients undergoing allo-HSCT. No grade 2 or higher adverse events associated with OLZ were observed in this study. Overall, OLZ may be a potential option for the prevention of conditioning therapy induced nausea and vomiting in allo-HSCT.