Transformation of follicular lymphoma - Why does it happen and can it be prevented?

Follicular lymphoma is a clinical disease with a multitude of presentations and behaviors. Although infrequent, transformation of follicular lymphoma to a more aggressive behaving subtype - prototypically diffuse large B-cell lymphoma - confers a substantially adverse prognosis. There is no consensus for optimal management after transformation is recognized. Historically considered a distinct clinical event, this review highlights the multiple subclinical transformational events that either variably or cumulatively result in clinical recognition of transformed follicular lymphoma. Known and suspected events include genetic and epigenetic perturbations, metabolomic changes, and alterations in the microenvironment. This diverse spectrum of pathways leads to heterogeneous clinical presentations and outcomes of transformed follicular lymphoma. Current options for prevention of transformation are limited to known strategies of managing follicular lymphoma before the transformation is recognized. Although most retrospectively analyzed studies suggest an association of lower transformation rates with early systemic therapy, specific components of therapy such as anti-CD20 antibodies, anthracyclines, or purine analogues are less strongly associated with "preventative' value. Thus, the goal of preventing transformation is of limited value among all factors that go into decisions on early management of follicular lymphoma. Future opportunities to prevent clinical evidence of transformation will benefit from early detection of markers of subclinical transformation and development of therapies to specifically target the biology implied by those markers.