Clinical Significance of Granulocytic Sarcoma at Relapse In Adult Patients with Acute Myeloid Leukemia
Authors: Shimizu Hiroaki , Saitoh Takayuki , Hoshino Takumi , Hatsumi Naoko , Takada Satoru , Irisawa Hiroyuki , Yokohama Akihiko , Jimbo Takahiro , Handa Hiroshi , Matsushima Takafumi , Sakura Toru , Tsukamoto Norifumi , Karasawa Masamitsu , Murakami Hirokazu , Miyawaki Shuichi 
Published: October 2019

Abstract
Abstract 4373

Background
We reported that adult AML patients with granulocytic sarcoma (GS) at diagnosis were associated with younger age, higher WBC counts, and monocytic differentiation of leukemia cells and GS adversely affected relapse rate and DFS at the 51st ASH annual meeting. However clinical impact of GS at relapse has not been clear. The objective of this study was to describe the frequency and clinical characteristics of adult AML patients with GS at relapse.

Methods
Between January, 1990 and March 2010, 517 patients (median age 57 (15-88), male/female; 313/204) diagnosed as AML were included. 58 patients (11.2%) were with GS at diagnosis and 459 patients were without GS. 480 younger patients were treated according to Japan Adult Leukemia Study Group treatment protocols (JALSG AML92, AML95, AML97, GML200, or AML201). 37 older patients were treated with low-dose Ara-C based regimen. The χ2-test was used for the binary variable comparison. The Mann-Whitney U test was used for continuous variable comparison. P < 0.05 was considered to indicate statistical significance.

Results
A total of 295 relapses was occurred in 233 patients. 32 relapses (11.0%) were with GS and 263 were without GS. 30 patients with GS at relapse had the same characteristics as patients with GS at diagnosis, including younger age (p<0.001), higher WBC counts at relapse (p=0.045), and high frequency of FAB M4 (p=0.001) and M5 (p=0.042) morphology. No significant differences in sex, the distribution of cytogenetic risk groups, and the frequency of each cytogenetic change including t(8;21), 11q23, inv(16), and the complex karyotype demonstrated. 38 relapses occurred in 34 patients with GS at diagnosis and 257 relapses in 199 patients without GS. The frequency of relapse with GS in patients with GS at diagnosis was significantly higher than that in patients without GS (29% vs 8%; p=0.0006). 41 relapses occurred in 37 patients after allogenic stem cell transplantation (allo-SCT) and 254 relapses in 196 patients after chemotherapy. 8 patients received allo-SCT from peripheral blood stem cell, 24 from bone marrow, and 6 from cord blood. 31 patients received conditioning regimen containing total body irradiation (TBI) and 6 received non-TBI regimen. The frequency of relapses with GS after allo-SCT was significantly higher than that after chemotherapy (27% vs 9%; p=0.0035). In patients after allo-SCT cell source and conditioning regimen did not affected frequency of GS. 58% of patients achieved CR with any salvage chemotherapy. Patients with GS had a trend of a lower CR rate than without GS (47% vs 63%; p=0.068).

Conclusions
Patients with GS at relapse had the same characteristics as patients with GS at diagnosis, including younger age, higher WBC counts, and monocytic differentiation of leukemia cells. This study shows the high frequency of relapse with GS in patients with GS at diagnosis and after allo-SCT independently of cell source and the conditioning regimen. As patients with GS at relapse tended to get chemotherapy-resistant we should give the attention to relapse with GS in follow-up of such AML patients.

Disclosures:
No relevant conflicts of interest to declare.