P569: allogeneic hematopoietic stem cell transplantation improves overall and relapse-free survival in pregnant women with acute myeloid leukemia

Background: Acute myeloid leukemia (AML) is the most common type of acute leukemia in adult pts, including pregnant. AML accounts for two-thirds of all cases of acute leukemia diagnosed during pregnancy. Formulated more than 25 years ago, the postulate about the neсessity for “saving two lives” formed the basis of a systematic approach to the treatment of acute leukemia in pregnant pts with AML, and allowed to develop appropriate clinical protocols. Aims: To assess prognostic impact of allo-HSCT conducted in CR1 in pregnant pts with AML. Methods: In total 45 pregnant pts with AML were included in the multicenter research. All pts were divided into two groups: the 1st group included 20 pts (a set of pts from 1997 to 2014), who were scheduled to undergo allo-HSCT in the first complete remission (CR1) only in the presence of an unfavorable karyotype, the 2nd group - 25 pts (a set of pts from 2015 to 2021), who were scheduled to undergo allo-HSCT in CR1, regardless of the karyotype. The control group consisted of non-pregnant fertile women who received treatment at the National Medical Research Center for Hematology from 2015 to 2021 (n=55). Landmark analysis was performed in group of pregnant pts with CR1 of AML (n = 35) and in the control group (n = 49). The landmark point for pts who underwent allo-HSCT was the date of allo-HSCT, and for the rest – the date of CR plus the median time to allo-HSCT, which in pregnant pts was 190 days (6.3 months) (17-270 days). Results: CR was achieved in 78% of pregnant pts in total (n=35): in 75% of pts from 1st group (n=15) and in 80% of pts from 2nd group (n=20). In the control group the frequency of CR was 89% (n=49). The percent of pts who underwent allo-HSCT was 2.5 times greater in group 2 than in group 1: 68% and 30%, respectively (p = 0.029). In the control group, this indicator was 60%. It was found that performing allo-HSCT in CR1 significantly improved RFS in pregnant women with AML compared to those who did not underwent allo-HSCT (Fig. 1A). In order to assess the combined prognostic impact of various factors on RFS for groups of pts treated under a single program (group 2 and comparison group), a multifactorial analysis of RFS with step-by-step selection of factors was carried out. The following factors were included in the model as candidates: pregnancy, ELN risk group, time when CR was achieved (after the 1st course of induction, or after the 2nd course of induction) and the performance of allo-HSCT in CR1 as a time-dependent factor (the factor does not act until the time of transplantation). The only factor selected for the final model was the performance of allo–HSCT (p = 0.0108). Thus, this factor neutralized impact of other factors, including pregnancy. Figure 1B shows the OS estimated for three subgroups of pts: pregnant women with AML who were treated before 2015 (1st group), pregnant women with AML who were treated after 2015 (2nd Group), and non-pregnant fertile women with AML (control group). The median follow-up time was 17.5 months. Although there were no statistically significant differences between the subgroups, the OS in 2nd group was higher than in 1st group. This difference is observed due to the performance of allo-HSCT in CR1. Summary/Conclusion: It was found that pregnancy is an unfavorable prognostic factor in pts with AML. However, the implementation of allo-HSCT in CR1 allows to neutralize the negative influence of this factor. Thus, women who are diagnosed with AML during pregnancy are candidates for performing allo-HSCT in CR1.Keywords: Chemotherapy, Pregnancy, Acute myeloid leukemia