Impact of Day 28 Absolute Lymphocyte Count on Outcome of Adult Patients with Acute Myeloid Leukemia

Introduction: Lymphocyte recovery after induction chemotherapy (IC) predicts outcome in adult patients (pts) with acute myeloid leukemia (AML) (Behl et al. Leukemia 2006; 20: 29-34). However, it is unknown whether absolute lymphocyte count (ALC) recovery after IC predicts outcome in those pts who are then treated with allogeneic hematopoietic stem cell transplant (AHCT) in first complete remission (CR1). We hypothesized that the prognostic impact of ALC might be nullified by AHCT in CR1 due to the abrogation of normal immunologic recovery. In this study, our aims were to (1) evaluate the impact of Day 28 ALC on all AML pts receiving IC and (2) to specifically, evaluate the impact of Day 28 ALC on the subset of AML pts proceeding to AHCT in CR1.

Methods: A retrospective chart review of 180 adult AML pts (≥ 18 years of age) who were treated with IC during the years 2001- 2012 at the Cleveland Clinic was performed. Institutional Review Board approval was obtained. Pts with acute promyelocytic leukemia were excluded . Ninety-four of the 180 pts received AHCT in CR1. A total of 141 AML pts receiving IC and a total of 66 pts receiving IC and then receiving AHCT in CR1 were eligible for data analysis because Day 28 ALC was missing in the remainder of the pts. Prior studies in AML identified an ALC of < 500/ µL at Day 28 of IC as predictive of overall survival. We stratified Day 28 ALC into the following categories: (a)< 250/ µL (b) < 350/ µL (c) < 500/ µL and (d) < 500/ µL for Max ALC [Max ALC was defined as the maximum ALC value between days 26 and 30 after the initiation of IC]. Other variables collected included age at diagnosis, WBC at diagnosis, and cytogenetic (CG) risk. CG risk was ascribed by CALBG criteria. The Kaplan-Meier method was used to summarize overall survival (OS) and relapse-free survival (RFS), which were measured for all pts from the time of diagnosis. The log-rank test was used for univariate analysis of categorical factors and the Cox proportional hazards model was used for measured factors and multivariate analysis. We performed two separate analyses : one for all AML pts (n=141); and a second analysis only focusing on those receiving AHCT in CR1 (n=66).

Results: Pt characteristics for the entire AML cohort: The median age was 58.0 years (20.0-80.0); 46.1% female. The median WBC at diagnosis was 11.6 K / µL (range 0.7-220.7) and median Day 28 ALC was 400/ µL (0-2.4). Twenty-seven pts (19.7%) had favorable CG, 84 (61.3%) intermediate, and 26 (19.0%) unfavorable. Most pts (91%) received "7+3" IC and 93 (66%) also received at least 1 cycle of post-remission chemotherapy. On univariate analysis, age ≥60 (HR 2.72, p< 0.001), CG risk (HR 2.13, p < 0.001), Day 28 ALC < 250/ µL (HR 1.60, p=0.022), Day 28 ALC < 350/ µL (HR 1.57, p=0.029), and max ALC < 500/ µL (HR 1.54, p=0.035) were associated with a worse OS from the initiation of treatment. Low ALC was associated with both a higher incidence of refractory disease and death during induction (p=0.015). In our second analysis of pts undergoing AHCT in CR1, although not statistically significant, max ALC < 500/ µL (during IC) was associated with a trend towards decreased OS from the start of treatment on both univariate (HR 1.88,p= 0.13) and multivariate (HR 2.16, p=0.075) analysis.

Conclusions: Max ALC < 500/ µL is predictive of outcome in AML pts undergoing IC, and there is a suggestion that this effect may not be abrogated by AHCT. A larger study will be needed to further confirm these findings. Therapies to improve lymphocyte recovery may be important in the treatment of AML.