Comparison of Outcomes between the Cellex and Uvar-Xts Closed-System Extracorporeal Photopheresis (ECP) Devices When Used for Graft-Versus-Host Disease; A Single Center Experience
Authors: Afzal Amber , Tarbunova Maryna , Despotis George , Grossman Brenda J. 
Published: October 2019

Abstract
BACKGROUND:
Graft versus host disease (GVHD) is a significant contributor to non-relapse mortality after allogeneic stem cell transplant (SCT). Steroids are first line therapy and extracorporeal photopheresis (ECP) is used as second line therapy for steroid refractory or intolerant patients. ECP has immunomodulatory effects rather than immunosuppressive effect which decreases the risk of infection, and may decreases the risk of disease relapse.
There are two ECP instruments approved in the US for the treatment of Cutaneous T Cell Lymphoma (CTLC), however both have been used "off-label" to prevent or treat solid organ transplant rejection, acute and chronic GVHD, and other autoimmune diseases. Until recently the UVAR-XTS instrument has been the most commonly used closed system in the US until the CELLEX was approved in 2009. The CELLEX and the UVAR-XTS procedures are similar in that buffy coat is collected, exposed to methoxsalen (UVADEX®) ex vivo and then UVA light before returning the treated cells back to the patient in a closed looped system. The instruments differ in the collection of the buffy coat; collection is continuous by the CELLEX, and it is intermittent by UVAR-XTS. In addition CELLEX has been shown to be more efficient in collecting mononuclear cells when compared to the UVAR -XTS. Little clinical data is available comparing the clinical efficacy of the two instruments in the setting of GVHD. We designed a single institution retrospective study to compare the efficacy and safety of the two instruments. The primary outcomes analyzed were >/=50% reduction of steroid dose between the initial and final dose during the study period, and the number and type of adverse events that occurred during the ECP procedures.
METHODS:
Study Population:
We reviewed charts of allogeneic stem cell transplant patients who received ECP for the treatment of acute or chronic GVHD between 1/2009 and 12/2015. The patients were divided into two groups based on the type of ECP instrument that was used. One group was exclusively treated with UVAR-XTS while the second group with CELLEX. Patients who received treatments with both instruments were excluded. The frequency of steroid dose reduction by >/=50%, and toxicity was compared between the two instruments while adjusting for age, gender, GVHD severity, number of organs involved by GVHD, type of allogeneic stem cell transplant, conditioning regimen, number of other immunosuppressants, type of anticoagulants (ACDA vs heparin), type of access line, and baseline blood counts.
Statistical Analysis:
The baseline characteristics of the patients in the two groups were compared using Chi square, Fischer's exact test for categorical variables and one-way analysis of variance (ANOVA) for continuous variables. Chi square analysis was used to determine the difference in frequency of >/=50% steroid dose reduction and adverse events between the two groups. Logistic multivariate regression was used to evaluate the potential interactions of all significant covariates.
A p value of less than 0.05 was considered to be statistically significant. Statistical analyses were performed using STATA14 software (StataCorp, College Station, TX).
RESULTS:
We identified 242 allogeneic SCT recipients who received ECP for acute or chronic GVHD in the study period, 146 of whom met the selection criteria. 69 patients had all procedure performed with UVAR-XTS and 77 patients had all procedures performed with CELLEX. There was no significant difference in age, gender, percent of acute GVHD, anticoagulant used, type of transplant, number of organs involved, number of immunosuppressants, vascular access and baseline blood counts between the two treatment cohorts as shown in table 1. Although year of transplant and conditioning regimen were different between the two cohorts, neither of these covariates influenced the impact of instrument on the primary outcome. In multivariate analysis, the patients who underwent ECP with CELLEX were 3 times more likely to have >/=50% steroid dose reduction (p =0.01). The total number of adverse events was similar between the instruments (p = 0.73). (Table 2)
CONCLUSION:
More than twice as many patients with GVHD treated with the CELLEX had a steroid dose reduction by >/=50% reflecting clinical improvement when compared to the patients treated with the UVAR-XTS. Similar safety profile was observed between the two instruments based on a similar number of adverse events.

Disclosures
No relevant conflicts of interest to declare.