Extramedullary Involvement in Acute Myeloid Leukemia. A Single Center Ten Years' Experience

The incidence, risk factors, and prognostic significance of extramedullary involvement (EMI) in adult patients with acute myeloid leukemia (AML) have not been established yet. This study analyzed clinical and biological characteristics, the impact on prognosis, and the cumulative incidence of EMI in a monocentric retrospective series. All adult patients diagnosed with AML observed in our institution between January 2010 and December 2017 were included in the analysis. Overall, 346 AMLs were analyzed. The incidence of EMI was 11% (38 patients). The involved sites were: skin (66%), central nervous system (CNS) (23%), pleura (7%), lymph nodes (5%), peritoneum (2%), spleen (2%), pancreas (2%), breasts (2%) and bones (2%). Most patients (91%) had only one EMI site, while 9% had multiple sites affected at the same time. Twenty-four (63%) patients showed signs of EMI at presentation, while extramedullary relapse occurred in 10 patients (26%); 4 patients had EMI both at presentation and relapse. EMI had a significantly higher frequency in patients with monocytic and myelo-monocytic leukemia subtypes (p<0,0001), CD117-negative (p=0,03) at flow cytometry analysis, MLL rearrangements (p=0.001), trisomy 8 (p=0,02). An analysis regarding treatment, overall survival (OS), and disease-free survival (DFS) was performed only on the 28 patients who experienced EMI at the onset of their disease; one EMI patient receiving best supportive care was excluded from OS analysis. The other 27 patients were treated with: conventional chemotherapy (21 patients), hypomethylating agents (5 patients), and low dose cytarabine (1 patient); 8 patients only (28.5%) received an allogeneic stem cell transplantation (allo-HSCT). After induction therapy, complete remission (CR) rate was 22%, with a median DFS of 7.4 months. The median OS of all 27 EMI patients was 11.6 months (range 2-79); this resulted significantly longer for the 8 EMI patients who undergone allo-HSCT than those (19 patients) who did not receive this procedure (16.7 vs. 8.2 months respectively, p=0.02). Univariate and multivariate analyses showed that undergoing allo-HSCT and achieving CR were the main positive prognostic factors for our population's survival (p<0,0001). This study confirms the poor prognosis for EMI patients. Allo-HSCT, applicable however only in some cases, seems to have a crucial role in these patients' therapeutic approach, being associated with a better prognosis.