Discussion 
Acute lymphoblastic leukemia is the most common type of cancer in children and unfortunately, about 15% of children with high-risk B-ALL relapse after chemotherapy treatment, so there is a need for new treatment options for these patients.18 Blinatumomab is an adequate bridge therapy to consolidate with transplantation in these patients, since it has been shown to be more effective and is associated with a lower number of toxicities and less severe complications, compared to intensive chemotherapy, allowing to obtain favorable hematological conditions for the performance of a transplant in terms of complete remission and residual disease, with satisfactory clinical tolerance, however, it is a treatment of high cost and difficult access for developing countries, such as Mexico. This series of patient cases represents a clear example of this situation. HITO is the unique specialized pediatric cancer hospital in Mexico. It was inaugurated in 2013 and began offering the HSCT service in 2014. At the beginning the number of HSCT procedures were approximately 4 to 5 per year. Through the years, this has been changing for the better, growing and improving the quality of care, allowing us to offer HSCT services to more patients. In 2019, the opportunity arises to introduce blinatumomab as a treatment in our institution. Nine patients were included in the present study. Comparing our results with other series is difficult; mainly because of the number of patients and because we do not randomize them. However, comparing the overall survival of these patients with those who do not have access to blinatumomab, as is the case with most of the patients in developing countries, the use of blinatumomab gives us a better prognosis and clearly a statistically better incentive for our country and institution. Probably all patients with positive MRD would have died. The international literature describes an overall survival of 2 years with blinatumomab use of 71. 3% versus 58.4% without the use of it.19