FCgammaRIIa Polymorphism Is Not Associated with Overall Response, Progression Free Survival and Overall Survival In Diffuse Large B-Cell Lymphoma Treated with Rituximab
Authors: Bellesso Marcelo , Bydlowski Sergio Paulo , Costa Renata Oliveira , Rodrigues Maciel Felipe Vieira , Levy Debora , Pereira Juliana 
Published: October 2019

Abstract
Abstract 5078

Background:
Low-affinity receptor for the Fcγ region of immunoglobulin G (IgG) (FcγR) is constitutively expressed on resting human neutrophils. These receptor, termed FcγRIIa display biallelic polymorphism which have functional consequences with respect to binding and/or ingestion of targets opsonized by human IgG subclass antibodies. Rituximab is a chimeric monoclonal antibody directed against CD20, an antigen found in most B-cell malignancies. Multiple mechanisms have been proposed for the activity of Rituximab, including antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC) and a direct proapoptotic effect. F(ab′)2 Rituximab homodimers were shown to be effective in inducing apoptosis of B-cell lymphoma cell lines in vitro. Recently, it have been established that ADCC is important as predominant mechanism of lymphoma cell clearance and that Fcγ receptors (FcγRs) are critical for the in vivo actions of Rituximab in non-Hodgkin lymphoma (NHL). A genomic polymorphism at amino acid 131 of FcγRIIA has been described whereby the presence of Histidine (H) rather than Arginine is associated with responses to the CD20-directed immunoglobulin G1 (IgG1) Rituximab among patients with indolent lymphoma. FcγRIIA genotype have been associated with a better clinical and molecular response in follicular lymphoma patients treated as first line therapy with Rituximab alone and in patients with diffuse large B-cell lymphoma (DLBCL) treated with the concomitant administration of Rituximab and CHOP (R-CHOP).

Methods:
Here we analyzed the role of specific polymorphism of activating FcγRIIA in 64 patients with DLBCL treated with R-CHOP concerning prediction complete response (CR), Progression Free Survival (PFS) and Overall Survival (OS) using a polymerase chain reaction-restriction fragment length polymorphism method.

Results:
The median age of the patients was 48.6 years. Out of the 64 patients (32%), were stage III-IV and 27 (42.5%) had more than 2 factors of the International Prognostic Index. Fity-six (89%) had CR and 7 (9.5%) had refractory disease (RD). Seven (11%) of the patients presented relapses. Deaths occurred in 6 (9.3%) patients with follow up of 19,5 months (range 21,3-50,1). The distribution of FcγRIIA polymorphism genotypes was: 15 (23,4%) HH, 30(46,9%) HR and 19(29,7%) RR, while considering only two groups (HH and R allele (HR and RR) was 15 (23,4%) and 49 (76,6%). There were no statistically significant differences in the genotypes groups according prognostic factors. In addition, there were not differences between response rate and FcγRIIA genotypes polymorphism: the CR in HH and HR/ RR were respectively 80% and 89%, p=0,377. It was not found differences regarding FcγRIIa. HH genotype presented a median PFS and OS. Thus, PFS HH genotype presented a median PFS 20,96 ± 10,49 months versus HR/RR median PFS 12,03 ± 7,71 months, p = 0,765, and OS 23,26 ± 10,42 months versus HR/ RR median OS 12,7 ± 7,42 months, p =0,98.

Conclusions:
Contrary to recent report we showed that FcγRIIA polymorphism is not associated to overall response, PFS and OS in patients with DLBCL treated with R-CHOP.

Disclosures:
No relevant conflicts of interest to declare.