To investigate the efficacy of three-dimensional intensity modulated radiation therapy (IMRT) on extramedullary relapse after allogeneic haematopoietic stem cell transplantation (allo-HSCT) for acute myeloid leukaemia (AML).

The clinical data of 77 AML patients treated with allo-HSCT in the First People′s Hospital of Guiyang from November 2018 to August 2022 were retrospectively analysed and divided into the chemotherapy group (41 cases) and the IMRT group (36 cases) according to the treatment modality. The general data, recent efficacy, biomarkers and prognosis of patients between the two groups were compared. Survival analysis was performed using the Kaplan-Meier method, and log-rank test was used for comparison. Measurement data between the groups were compared using the paired t-test or the repeated measures analysis of variance for comparison of data, and count data were compared between the groups using the χ² test or Fisher′s exact probability method. P<0.05 was considered statistically significant.

The incidence of complications in the IMRT group was 5.56% (2/36), while in the chemotherapy group it was 24.39% (10/41), with a statistically significant difference (χ²=5.169, P<0.05). The proportion of complete and partial remission in the IMRT group was 91.67% (33/36), which was higher than that in the chemotherapy group [70.73% (29/41)], with a statistically significant difference (χ²=5.356, P<0.05). Before and after 1, 3, and 5 months of treatment, the serum VEGF levels in the IMRT group were (754.14±66.27), (586.03±50.24), (364.08±48.62) and (253.26±45.20) pg/mL, respectively; the proportion of CD56⁺ NK cells was (6.14±1.27)%, (10.03±1.65)%, (11.62±1.34)% and (11.36±1.63)%, respectively. The VEGF levels in the chemotherapy group were (748.26±64.25), (526.15±50.76), (407.43±47.32) and (303.85±45.86), respectively. The proportion of CD56⁺ NK cells was (6.32±1.30), (10.53±1.47), (11.86±1.66) and (11.09±1.78). The difference of serum VEGF levels between the two groups were statistically significant (F_time-group=19.661, P<0.05). No significant difference of the ratio of CD56⁺ NK cells was seen between the two groups (F_time-group=0.084, P>0.05), but significant difference of the ratio of CD56⁺ NK cells in different time points was seen within each group (F_time=203.602, P<0.05). The patients were followed up until December 2023, the ratio of progression-free survival of the chemotherapy group and the IMRT group were 63.41% and 91.67%, respectively, there was significant difference (χ²=8.542, P<0.05).

IMRT has a certain therapeutic effect in the treatment of extramedullary recurrence in AML patients after allo-HSCT, which can improve clinical efficacy, alleviate local symptoms, and is related to the mechanism of tumor angiogenesis inhibition.