Abstract
Background: FL displays a diverse spectrum of clinical behavior as evidenced by marked variability in patient survival. Biological prognostic markers predictive of overall survival (OS) are mostly lacking. Recent work by the Leukemia Lymphoma Molecular Profiling Project (LLMPP) demonstrated that non-neoplastic cells in FL biopsy samples were important for determining outcome in FL and were integral to the design of a molecular gene expression survival predictor (Dave et al, Blood 102; #11: A617, ASH 2003, in press). We examined the role of immune cells as prognostic markers in FL.
Methods: Between 1987 and 1993, the BC Cancer Agency enrolled 126 patients with FL on a phase II study of BP-VACOP and involved region radiotherapy. All patients were treatment naïve, < 61 y of age and had advanced-stage FL. Of these cases, paraffin blocks were available for tissue microarray (TMA) construction for 105 patients. The TMAs consisted of duplicate 1.0mm cores of diagnostic biopsies and were all screened with CD20 antibodies to ensure tumor cell content. The TMAs were immunostained for CD20, CD3, CD4, CD7, CD8, CD57, MIB1, CD21, TIA1 and CD68. Immuno-architectural patterns and numbers of cells per 1,000X field (hpf) were determined. OS was determined and a Cox multivariate model was constructed.
Results: 99/105 cases were successfully arrayed and comprise the study group. The median follow-up of the 55 living patients was 12.5 y. The median OS was 16.5 y. Histologic FL grade (WHO): grade1 (n=77), grade 2 (n=15) and grade 3A (n=7). 15 patients had marginal zone differentiation. In univariate analysis the IPI was predictive of OS (p = 0.003). Of the 99 evaluable FL cases, 87 had < 15 CD68+ macrophages/hpf (median 7 [range 1–14]) and 12 had > 15 macrophages/hpf (median 20 [range 16–25]) with median OS being 16.3 y vs 5.0 y, respectively (p = 0.0003). None of the pathology variables were predictive of OS in univariate analysis with the exception of the CD68 score, equivalent to LAM. There was no relationship between proliferation and the LAM score. In accordance, the CD68+ cells did not appear to be predominantly phagocytic. The macrophages were both within and between neoplastic follicles. A Cox multivariate model showed that IPI and CD68/LAM score were independent variables (p = 0.009 and p = 0.001, respectively).
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Conclusions: The LAM score is an important independent prognostic factor in advanced-stage FL patients treated uniformly with an aggressive treatment regimen that included multi-agent chemotherapy and radiation. Numbers and distribution of T cell subsets and patterns of follicular dendritic cells were not predictive in this cohort. CD68+ macrophages/LAM may be a surrogate for an important component of the “immune response-2” gene expression signature, previously associated with inferior OS by the LLMPP consortium. LAM may allow improved stratification of FL for treatment purposes and importantly, understanding the role of macrophages in FL may provide insights into new targets for immune-based or other novel therapies.
