Prolonged Lymphopenia and Infection Risk Is Mitigated By Antimicrobial Prophylaxis in Patients with Indolent Non-Hodgkin Lymphoma (iNHL) Treated with Bendamustine +/- Anti-CD20 Antibody: The Australasian Lymphoma Alliance Experience.

Background: Bendamustine +/- anti-CD20 antibody is a highly effective regimen for iNHL. Though initially favoured for its toxicity profile, subsequent analyses demonstrate profound and prolonged lymphopenia and the landmark phase III GALLIUM study showed a grade 3-5 infection rate of 20-26% in the bendamustine arms (Hiddemann JCO 2018). The relationship between severity and duration of lymphopenia and infection, and the role of antimicrobial prophylaxis (ppx), are not fully characterised. We performed a multicentre, retrospective analysis of bendamustine-treated iNHL patients (pts) to define the type and onset of infections, identify concomitant risk factors and evaluate the role of ppx. Method(s): iNHL pts aged >=18 yrs, treated with bendamustine +/- anti-CD20 in 1st-3rd line from 2011-2019, were identified from 9 Australian centres. HIV, prior transplant and long-term immunosuppression were excluded. Demographics, treatment, lymphocyte counts, infections and ppx were collected from baseline to 24 months post end of bendamustine treatment (EOT) or subsequent lymphoma therapy. Association between potential risk factors and infection was evaluated by logistic regression (odds ratio, OR) and negative binomial regression (incidence rate ratio, IRR) with Stata 16.1. Result(s): 302 pts were eligible. Baseline and treatment characteristics are summarised in Table 1. 252 infection episodes occurred across 134 pts (44%), equally divided between during therapy and after EOT (Figure 1A, Table 2). Infections on treatment occurred in 30% of pts (n=92) with 18% hospitalised (n = 54; n = 20 with febrile neutropenia (FN)) and dose delay /modification/ discontinuation in 11%. Late infections post EOT occurred in 23% of pts (n=70) with 11% hospitalised (n = 32; n = 12 with FN); infection post EOT was more common in pts on maintenance anti-CD20 (infection rate 49% v 16%, OR 5.1 p<0.001). Opportunistic infections (OI) occurred in 21 pts: VZV (n=9; 4 on treatment, 5 post EOT, 1 on ppx)