Lymphocyte Recovery Following Autologous Hematopoietic Stem Cell Transplant in Classical Hodgkin Lymphoma

Introduction: The standard of care for relapsed/refractory (R/R) classical Hodgkin lymphoma (cHL) is salvage therapy followed by autologous hematopoietic stem cell transplant (auto-HCT). Pre-apheresis absolute lymphocyte count (PA-ALC) is an independent prognostic factor for overall survival (OS) after transplant. We aimed to evaluate the effect of absolute lymphocyte count following auto-HCT and hypothesized that a higher post-transplant ALC at day +15 (PT-ALC) correlates with improved OS.

Methods: A retrospective review was performed on patients with R/R cHL who underwent auto-HCT at Moffitt Cancer Center from 2000-2020. The following patient characteristics were collected: age at diagnosis, gender, initial stage and presence of B symptoms. Pretransplant variables including chemotherapy, number of cycles, response to therapy, and time from last chemo to apheresis were collected. Receiver-operator characteristics (ROC) curve was used to identify the ideal PT-ALC to predict overall survival. Patients were then identified as high ALC versus low ALC. Mann-Whitney, Pearson Chi-square, and Fisher exact test were used to compare baseline characteristics between the two groups. Univariate analysis of overall survival was done using Log-rank testing and Kaplan-Meier curve. Cox-regression analysis was used to evaluate the factors affecting OS.

Results: A total of 259 patients were included in the study, with a median age of 35 years (range 14-76). ROC curve was used to identify the ideal PT-ALC affecting OS, and a cutoff value of 300/uL was determined (AUC 0.60; 95% CI: 0.52-0.68, Figure 1). In this cohort, 52 patients (16.6%) had low PT-ALC and 207 patients (65.9%) had high PT-ALC. There was no significant difference between the two groups in regards to patient age, gender, histology type, stage at presentation, number of salvage cycles, number of CD34 cells collected, or number of days required for apheresis. Patients with a high PT-ALC had higher pre-apheresis ALC (p<0.001). There was a trend toward significance with patients with high PT-ALC receiving non-chemotherapy salvage regimens (p=0.07, Table 1). However, PA-ALC was significantly higher in non-chemotherapy regimen (p=0.007). Patients with high PT-ALC had a longer OS after transplant than those with low PT-ALC, with median OS 11.8 years and 7.7 years, respectively (p=0.012, Figure 2). On multivariate analysis, the only factor associated with improved OS was high PT-ALC (p=0.015, Table 2).

Conclusions: High PA-ALC and high PT-ALC are both independent prognostic factors for longer OS in patients with relapsed/refractory Hodgkin lymphoma after auto-HCT. High PA-ALC lead to higher PT-ALC. Although most of our patients received chemotherapy as salvage therapy prior to transplant, there was a trend toward higher PT-ALC in patients who received non-chemotherapy regimens. Future studies are required to determine the role of non-chemotherapy salvage regimens in improving lymphocyte counts during the peri-transplant period and, hence, improved survival.

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