[Effect of Flow Cytometric MRD Detection at Different Time Points during AML Chemotherapy on Prognosis].

Objective: To investigate the effect of flow cytometric minimal residual disease (MRD) detection at different time points during AML chemotherapy on prognosis.

Methods: 130 adult primary AML patients diagnosed and standardized with chemotherapy from March 2018 to March 2022 were retrospectively analyzed, MRD was detected by flow cytometry, Kaplan-Meier curves was used for survival analysis and log-rank test was used for variance analysis, and univariate and multifactor influencing patient survival with COX proportional risk regression model analysis. Cumulative incidence rate (CIR) analysis with competing risk model and variance analysis using Fine-Gray.

Results: There were 81 CR1, 26 CR2, 14 PR, and 9 NR patients in 130 patients. OS of the CR1 group was higher than that in the CR2, PR,and NR groups. OS of the CR2 group was higher than that in the PR group, but there was no statistically difference compared to the NR group. There was no statistically difference in OS between the PR and NR groups. 107 patients in CR1 and CR2 were grouped according to MRD detected by flow cytometry, and after the first induction chemotherapy, for patients in the MRD^- and MRD⁺ groups, the 4-year expected RFS rates were 65.3% and 27.9% respectively, the 4-year expected OS rates were 58.7% and 41.4% respectively, and the 4-year expected CIR were 34.7% and 69.7% respectively, with statistically significant differences between 2 groups (χ²=6.639, P =0.010; χ²=6.131, P =0.013 and χ²=6.637， P =0.010). After the second chemotherapy, for patients in the MRD^- and MRD⁺ groups, the 4-year expected RFS rates were 50.8% and 37.9% respectively, the 4-year expected OS rates were 49.2% and 44.5% respectively, and the 4-year expected CIR were 49.2% and 59.5% respectively, with no statistically significant differences between 2 groups (χ²=1.475, P =0.225; χ²=2.432, P =0.119 and χ²=1.416， P =0.234). During consolidation therapy, for patients in the MRD ^- and MRD⁺ groups, the 4-year expected RFS rates were 51.9% and 29.6% respectively, the 4-year expected OS rates were 67.5% and 24.6% respectively, and the 4-year expected CIR were 48.1% and 70.4% respectively, with statistically significant differences between 2 groups (χ²=20.982, P < 0.001; χ²=17.794, P < 0.001 and χ²=19.879， P < 0.001). For patients with MRD^- at all three time points and positive at either time point, the 4-year expected RFS rates were 69.9% and 33.3% respectively, the 4-year expected OS rates were 59.1% and 44.7% respectively, and the 4-year expected CIR were 30.1% and 65.1% respectively, with statistically significant differences between 2 groups (χ²=7.367, P =0.007; χ²=6.042, P =0.014 and χ²=7.662， P =0.006). Univariate analysis showed that karyotype at high risk of chromosome was an unfavorable factor affecting patients' RFS and OS, while 2 cycles of induction chemotherapy achieved CR, MRD^- after the first induction chemotherapy and MRD^- after the second induction chemotherapy was a protective factor affecting patients' RFS and OS. MRD^- during consolidation therapy and MRD^- at all three time points were all protective factors affecting patients' RFS, OS and CIR. Multivariate analysis showed that induction chemotherapy for 2 cycles achieved CR was a protective factor affecting patients' RFS and CIR, and MRD^- during consolidation therapy was a protective factor affecting patients' RFS, OS and CIR.

Conclusion: Early achievement of CR and MRD^- in adult AML patients, especially MRD^- during consolidation therapy, is a marker of good prognosis, and flow cytometry is the most commonly used method for MRD detection in AML patients.