Impact of the tumor microenvironment on prognosis in follicular lymphoma is dependent on specific treatment protocols

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Abstract
Background The clinical behavior of follicular lymphoma is largely determined by properties of the non-malignant tumor microenvironment. The precise nature of the cell populations is still unclear and published data on their prognostic significance are highly conflicting. This may be partly due to heterogeneous composition and treatments. Design and Methods Pre-treatment biopsy samples of patients with follicular lymphoma treated in an EORTC/BNLI trial comparing fludarabine to cyclophosphamide, vincristine and prednisone (CVP) chemotherapy could be retrieved for 61 patients in five European countries. Immunohistochemical investigations were performed to evaluate tumor cell characteristics, T-cell subsets, follicular dendritic cells and macrophages and associations with clinical outcome were studied. Results Some markers showed a homogeneous prognostic impact, while others had a different and sometimes opposite effect in the treatment arms. CD69 expression on tumor cells was a poor prognostic sign and an interfollicular infiltrate of FoxP3-positive T cells was a good prognostic sign irrespective of the treatment arm. It is suggestive that a dense infiltrate of FoxP3-positive T cells, a dense and interfollicular infiltrate of CD68-positive macrophages and complete follicular dendritic meshworks were associated with a favorable time to progression in CVP-treated patients, while being a poor prognostic sign in fludarabine-treated patients. Conclusions Our results suggest that characteristic properties of the microenvironment in follicular lymphoma determines the responses to essentially different chemotherapeutic approaches. These data may provide an explanation for the highly conflicting results on immunohistochemical markers and the prognostic role of the microenvironment in follicular lymphoma reported thus far and lay the basis for the development of predictive assays to tailor treatment in patients with follicular lymphoma.