Poor survival and younger age in patients with blast Phase chronic myeloid leukemia in a developing country: A multicenter real-world study of 138 patients.

Abstract Background: Chronic myeloid leukemia (CML) in blast phase (BP) remains a very difficult condition to treat despite current therapies. To date, there is no national data reflecting the poor prognosis of these patients, nor is there a standardized treatment guideline for this condition. Methods: A retrospective review was conducted on patients over 14 years of age with chronic myeloid leukemia in blast phase from four healthcare institutions in Lima, Peru. Clinical and laboratory data, prognostic scores, and treatments provided at each institution were collected to assess overall survival. Results: We identified a total of 138 patients from four institutions, diagnosed with BP CML between 2008 and 2025. The median age was 41 years (range, 14–84 years), and 62% were male. 71% and 5% of patients had a previous chronic and accelerated phase, respectively, before transforming into blast phase. De novo blast phase CML accounted for 23% of cases. The immunophenotype at presentation was myeloid, lymphoid, or mixed in 71%, 27%, and 2% of patients, respectively. ALL showed a higher rate of central nervous system involvement (6%), compared to AML, where extramedullary involvement was more common (7.2%). Regarding prognostic scores: 74%, 51% and 60% of patients had high risk by Sokal, EUTOS and ELTS, respectively. Of the 138 patients, 105 (76%) had available treatment data. Among them, 79 (75%) received intensive chemotherapy, including 71 in combination with a tyrosine kinase inhibitor (TKI). The most frequently used TKI was Dasatinib (64% of pts). The time from chronic phase to blast phase was 72.5 months. Complete remission was achieved in 29% of patients, 11.5% patients underwent bone marrow transplantation, and the median overall survival was 4.23 months. We observed an inferior survival in patients that progress from chronic phase compared to those with de novo blast phase (median 3.1 vs 9.4 months). Conclusion: This Peruvian cohort showed a younger age of presentation and poorer overall survival in blast phase CML. These outcomes may be related to limited healthcare resources, poor access to alternative TKIs, bone marrow transplantation, and delays in hospital care. This data shows the urgent need to improve national policies for access to innovative therapies that could improve the outcome of this dismal condition.