Acute Myeloid Leukemia in Puerto Rico: A 10-Year Retrospective Study

Introduction:

Acute myeloid leukemia (AML) is a cancer notorious for being quite challenging to manage clinically and having a high death rate among adults. In Puerto Rico (PR), the University Hospital (UH) is the major referral center for adults diagnosed with AML. However, a comprehensive study of this population is lacking, representing a knowledge gap. The objective of this retrospective study was to assess the clinical aspects, presentations and outcomes of the AML patients treated at this single institution, thus, filling a clinical and scientific need.

Methods: This study evaluated patients ≥18 years of age, diagnosed with AML between January 2004 and December 2013 and treated at the UH within the Medical Center in San Juan, PR. Data regarding socio-demographics, bone marrow aspiration and biopsy, flow cytometry, cytogenetics, treatment and survival were obtained from medical records. Univariate and bivariate analyses were performed.

Results: Of a total of 319 AML cases where the majority of the necessary data was obtained, the patients were mostly females (54.5%), between 41-64 y/o (43.9%), and living in the greater metropolitan area of San Juan or adjacent municipalities. Flow cytometry results mostly expressed the myeloid markers: CD13 (82%), CD117 (74%) and CD33 (68%), followed by the lineage independent antigens HLA-DR (59%) and CD34 (57%). Monoblastic expression were mostly CD64 (34%) and CD11c (31%), and the most frequent lymphoid markers were CD7 (14%) and CD4 (11%). Cytogenetic abnormalities were present in 68% of the patients, which were then sub-classified as simple (only 1) in 54%, double in 19% or complex (≥3) in 27%, and mostly involved chromosomes 17 (27%), 15 (26%), 8 (12%), 21 (10%) and 6 (6%). Of note, acute promyelocytic leukemia (APL) was diagnosed in 17% of the patients having available cytogenetics data. Regarding treatment, the predominant induction regimen was the standard 7+3, with idarubicin as the most frequent anthracycline used; 25% of patients that received treatment required a re-induction, consisting mostly of a 5+2 regimen with the same drugs used initially. Subsequently, 48% of the initially treated patients received their first consolidation therapy. Although limited by unknown values, evidence of leukemia relapse was noted in at least 12% of all treated patients, occurring on average within 51.6 weeks, where 50% of the data resulted within 41.9 weeks. Excluding the APLs, leukemia relapse was noted in 25% of the patients. By the end of the study in 2016, 75.7% of the patients had died, and were more likely to be ≥65 of age than 41-64 or 18-40 (85% vs. 71% vs. 69%, respectively; p=0.02); or having complex cytogenetics than simple/double or normal (85% vs. 67%, vs. 77%, respectively; p=0.048). Among those that died, the average life span was about 40 weeks since diagnosis. On the other hand, those remaining alive at the end of the study have an average life span of 70.7 weeks from diagnosis till their last known visit.

Conclusion: This first analysis presentation of our 10-year retrospective study provides valuable clinical information about the AMLs being treated at the UH. The most significant clinical factors impacting survival were: age at diagnosis and amount of cytogenetic abnormalities. A necessary sub-analysis regarding the impact of the cytogenetic abnormality type will follow, as the data was not readily available at this time. Since the UH is the major referral center on the island, we can safely say it represents the AMLs of Puerto Rico, an underrepresented Latino population from the Caribbean area. In spite of limitations in data collection, especially from earlier years (2004-2007), the numbers are still robust enough (in light of being an infrequent cancer type) to consider this study as the first comprehensive assessment of the AMLs in PR. Our findings provide insight into the clinical presentation and outcomes of AMLs in PR, and may serve as a platform for future comparison studies regarding race/ethnicity and disparities. Further identification of clinical factors and genetic/epigenetic abnormalities is important in order to individualize therapy and hopefully improve outcomes in our AML population.