Acute Promyelocytic Leukemia Can be Fully Treated on an Outpatient Basis: A Single Institution's 30-Year Experience
Authors: Ruiz-Argüelles Guillermo José , García-Vélez Danae , Gallardo-Pérez Moisés Manuel , Cruz-Pérez Gloria Erendy , Melgar-de-la-Paz Miranda , Hamilton-Áviles Luis Enrique , Negrete-Rodríguez Paola , Olivares-Gazca Juan Carlos , Garcés-Eisele Solón Javier , Ruiz-Delgado Guillermo José 
Published: December 2024

Background
Acute promyelocytic leukemia (APL) is the most frequent variant of acute myelogenous leukemia (AML) in Mexico and other Latin American countries; advances in its treatment have turned this once very aggressive type of leukemia into the most curable. The development of APL is attributed to a chromosomal translocation involving chromosomes 15 and 17 leading to a genetic recombination event that merges the retinoic acid receptor alpha (RAR-a) gene with the PML gene, a putative transcription factor, resulting in the PML/RAR-a fusion.
Prompt diagnosis and treatment of the disease have resulted in a significant decrease in its early mortality, thus conferring a superior long-term prognosis, even in underprivileged circumstances; the prognosis of APL has evolved significantly as a result of the use of both all-trans retinoic acid (ATRA) and arsenic trioxide (ATO).
Due to the suboptimal hospital facilities in our country, our interest has focused for many years on managing anti-leukemic chemotherapy, autologous hematopoietic stem cell transplantation (HSCT), allogeneic HSCT, and even haploidentical HSCT on an outpatient basis.
Methods
All consecutive patients with APL studied, treated, and followed for more than 30 consecutive days in the Centro de Hematología y Medicina Interna de Puebla of the Clínica Ruiz. Patients were started on ATRA (Hoffman-La Roche AG) 45 mg / m 2 po daily, and prednisone (50 mg / m 2 po, daily for 21 days); drugs were administered on an outpatient basis, and if the white WBC increased above 30 x 10 9 / L, ATRA was reduced to 20 mg / m 2 po; intravenous myelosuppressive chemotherapy (CT), in one or two doses (adriamycin 45 mg/Kg per week x 3) was delivered until the WBC count was 10 x 10 9 / L WBC. ATRA was given until complete remission (CR), as defined by the standard criteria.
Results
A complete hematological and molecular remission (CR) was obtained in 16/17 patients (94%); ATRA was fully administered to all patients as outpatients; two presented a white blood cell count above 30 x 10 9 /L, and four, a differentiation syndrome: three during the first weeks of treatment, but they had a subsequent good outcome and achieved molecular remission; one patient developed differentiation syndrome during the first week after relapse.
All patients began treatment as outpatients, and 15/17 (88%) individuals completed it fully on an outpatient basis. Two patients required hospitalization, with one experiencing a relapse one year after CR remission and the other, during CR; the former was due to differentiation syndrome, while the latter was a result of iatrogenic neutropenic enterocolitis; both individuals died 20 and 2 months after starting treatment, respectively.
Conclusion
Since the introduction of ATRA and ATO, there has been a significant shift in the treatment approach to APL, leading to notable improvements in the management strategies and overall prognosis. Despite the relatively limited sample size of this study population, we have shown that most APL patients can be treated as outpatients, this could pave the path to begin exploring the possibility of providing out-of-hospital care for other types of leukemias, thereby decreasing the risk of contracting nosocomial infections and in turn, those expenses associated with hospitalization.