With appropriate induction therapy, adults with acute lymphoblastic leukemia (ALL) can achieve a complete remission (CR) rate of 70%-90%, but the relapse rate (RR) is high and the long-term survival rate is only 30%-40%, which is much lower than the efficacy of childhood ALL. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has become one of the most effective treatments for adult ALL, and has made great progress in both basic research and clinical applications in recent years. Ren Hanyun, Department of Hematology, Peking University First Hospital, Beijing, China 1. Adult ALL prognostic factors Adult ALL is a group of highly heterogeneous diseases, and individualized treatment is often chosen according to the different prognosis of ALL, which is very important to improve the efficacy. The more recognized prognostic factors associated with adult ALL include: age >35 years at diagnosis; leukemia count >30×109/L (B-ALL) or >100×109/L (T-ALL); immunophenotyping as pro-B or early-T ALL; cytogenetic abnormalities such as t(9;22)/BCR/ABL (+), t(4;11)/ Patients with more than one adverse factor were considered to be in the high-risk group and vice versa in the standard-risk group. Among them, cytogenetic and molecular genetic abnormalities and MRD monitoring were the most meaningful prognostic factors. 2. allo-HSCT for adult ALL The specific timing and indications for allo-HSCT for adult ALL are not fully established. For patients with high risk of relapse, it is mostly believed that allo-HSCT should be performed at CR1; whether HSCT should be performed at CR1 in low-risk or standard-risk patients varies. Cornelissen JJ et al. (Blood 2009;113:1375) similarly demonstrated that allo-HSCT in CR1 stage has the greatest potential for GVL effects, but in older, high-risk patients, transplant-related mortality may offset the reduced risk of recurrence and affect overall survival. The 5-year EFS of patients undergoing allo-HSCT in CR1 was significantly higher than that of patients undergoing chemotherapy/autograft (60% vs. 42%). Risk factor analysis revealed that the benefit of allo-HSCT was more pronounced in standard-risk patients, with a 5-year survival rate of up to 69%. Similar results have been obtained in several large prospective trials, with a higher recurrence rate in sibling donor allo-HSCT and a higher TRM in unrelated donor allo-HSCT, with no significant difference in OS. pre-HSCT treatment intensity, pretreatment regimens, post-HSCT immunosuppressive use, and the conditions and experience of each HSCT center may affect transplantation prognosis. Larger multicenter collaborations are needed to evaluate the efficacy of allo-HSCT as first-line therapy, primarily to balance the efficacy of allo-HSCT with pre-transplant chemotherapy and pretreatment toxicity to reduce transplant-related mortality (TRM) and to determine the optimal timing of allo-HSCT. Our results showed that allo-HSCT in ALL patients in sustained remission for approximately 6 months significantly improved long-term survival and that prolonged chemotherapy resulted in a significant increase in transplant-related mortality (TRM) (Chinese Journal of Hematology 2004;25:87). Some studies have reported that patients with suitable donors should start allo-HSCT as soon as they reach CR1, and that multiple cycles of chemotherapy do not reduce the post-transplant relapse rate, but rather increase TRM. our findings are similar to foreign results. Most current studies endorse the selection of allo-HSCT indications based on risk factors. 2007 Annual Meeting of American Hematology gave recommendations for allo-HSCT according to risk stratification in adults under 55 years of age with ALL: 10-3), ≥ CR2, or primary refractory ALL patients, allo-HSCT is recommended as long as HLA compatible donors are available. in some study centers In some study centers, allo-HSCT was performed in all patients at CR1 to improve treatment outcome. Recent health economic analyses have demonstrated that allo-HSCT at CR1 has a better efficacy ratio. 3. Factors influencing transplantation efficacy 3.1 Pretreatment regimen For all patients, the 5-year DFS rate was significantly better in those with a TBI-containing pretreatment regimen than in those with a marilyn-containing pretreatment regimen, but the optimal TBI dose remains unclear. Our findings support this conclusion (Chinese Journal of Hematology 2004;25:87).The pretreatment regimen of VP16 combined with TBI has a good anti-lymphocytic leukemia effect, with a 3-year DFS rate of 64% and a relapse rate of only 12% after allo-HSCT in adult ALL CR1 patients treated with this pretreatment regimen [9].Marks et al [10] compared the prognostic impact of different TBI doses in Cy-TBI and VP16-TBI pretreatment regimens and found that the dose of TBI in the pretreatment regimen (13GY) did not significantly differ in TRM, DFS, OS, and RR for ALL patients transplanted in CR1 stage. However, for patients with CR2 stage, the regimen with VP16-TBI or CY-TBI (>13 Gy) was more efficacious than CY-TBI (