Introduction

Follicular lymphoma (FL) is the second most common lymphoma after diffuse large B-cell lymphoma (DLBCL). It has an annual incidence of 4 per 100 000 (USA and Europe) and accounts for 22% of all cases of non-Hodgkin's lymphoma (NHL). As discussed in Chapter X the incidence changes with geography and may be up to 10-fold lower in Asia. The disease is generally characterized by the insidious onset of lymphadenopathy, usually without extranodal disease or B-symptoms. Although long-term disease-free survival (DFS) is seen in some patients treated for early-stage disease, the majority of patients are incurable with conventional therapy. Although usually readily responsive to treatment, remissions are temporary and the disease follows a relapsing and remitting course. Successive remissions become harder to achieve and of shorter duration. Most patients receive several lines of treatment before finally succumbing to refractory disease or high-grade transformation. In addition, a small proportion of patients die from complications of therapy.

The behavior of FL shows considerable variability. In some cases the disease follows an aggressive chemorefractory course while in others the disease can be controlled for 15 years or more. Studies comparing the median survival of FL patients over the past few decades suggest that patient survival is improving. A number of new therapeutic modalities have been introduced in recent years and may explain some of this improvement. In particular, the development of the anti-CD20 antibody rituximab appears to be changing the natural history of FL.