Tumor Infiltrating Lymphocytes Predict Survival in Solid Organ Transplant Recipients With Monomorphic Post-transplant Lymphoproliferative Disorders.

INTRODUCTION:The tumor microenvironment (TME) in post-transplant lymphoproliferative disorders (PTLDs) remains unexplored. Tumor infiltrating lymphocytes (TILs) are prognostic in other lymphomas. We assessed the prognostic impact of TILs in monomorphic B-cell PTLD. METHODS:TIL density (CD3+ cells/mm2) was determined by CD3 immunohistochemistry in archived diagnostic biopsies from patients diagnosed with monomorphic B-cell PTLD. RESULTS:Amongst monomorphic PTLDs (N = 107), low TIL-count was associated with inferior 2-year progression-free survival (PFS) (41% versus 86%, P = .003) and 2-year overall survival (OS) (52% versus 93%, P = .003) by Kaplan-Meier analysis. Low TIL-count was significant on Cox univariate regression for inferior PFS (HR 4.5, 95% CI 2.0-9.9, P < .001) and OS (HR 4.6, 95% CI 1.8-11.8, P < .001). Multivariate analysis with clinical variables (age ≥60 years, high LDH, stage III/IV, CNS involvement) and TIL-count showed significance for PFS (HR 3.3, 95% CI 1.3-8.3, P = .010) and a non-significant trend for OS (HR 2.6, 95% CI 0.9-7.3, P = .064). A composite score including TILs and clinical variables (age ≥60 years, high LDH, stage III/IV, CNS involvement) effectively stratified monomorphic PTLD patients by PFS and OS (2-year OS: low-risk 93%, intermediate-risk 61%, high-risk 23%, P < .001). CONCLUSIONS:The TME and TILs are prognostically relevant in monomorphic PTLD. Prognostic models including measures of the TME may improve risk stratification for patients with monomorphic PTLDs.