Incidence, risk factors, and outcome of asymptomatic central nervous system involvement in adult patients with acute myeloid leukemia

Examination of central nervous system (CNS) involvement is not routine diagnostic practice in adult patients with acute myeloid leukemia (AML). Therefore, many asymptomatic patients with CNS involvement might go undetected. The effect of CNS involvement on the AML disease course is not well defined, with conflicting results regarding clinical outcome. This study aimed to determine the incidence of asymptomatic CNS involvement in AML estimated by multiparametric flow cytometry of cerebrospinal fluid (MFC-CSF) at diagnosis, the related potential risk factors, and prognosis. In total, 645 patients with de novo AML were screened; 183 (28.4%) of them fulfilled institutional practice for MFC-CSF analysis based on presence of CNS symptoms and/or clinical features. CNS symptoms and signs were observed in 8/183 (4.4%) patients, but most patients (175/183, 95.6%) were asymptomatic. In the asymptomatic group, 73/175 (41.7%) patients had positive or suspicious cerebrospinal fluid (CSF) findings categorized as CNS positive (CNS^pos) and 102/175 (58.3%) had normal CNS findings categorized as CNS negative (CNS^neg). The presence of leukemic blasts was confirmed in 81/183 (44.3%) patients; the total incidence of CNS involvement in the whole AML group was 12.6% (81/645). Compared with asymptomatic patients with CNS^neg, those with CNS^pos had a significantly higher frequency of lymphadenopathy, white blood cell count ≥30 × 10⁹/L, presence of the monocytic phenotype, and a high percentage of bone marrow (BM) blasts. The multivariate logistic regression model identified monocytic phenotype (p = 0.047) and high percentage of BM blasts (p = 0.042) as predictors for CNS^pos. CNS^pos did not affect overall survival in patients with AML. There was a higher incidence of CNS involvement in asymptomatic adult patients with de novo AML, emphasizing possible undervalued rates of CNS disease at diagnosis. Prospective studies should determine whether diagnostic lumbar puncture for MFC-CSF analysis and CNS prophylaxis could contribute to better selection and prognosis in this patient population.