Eric D. Jacobsen, MD, Editor

The last decade has witnessed an increase in drug development for T-cell lymphomas, with four agents (pralatrexate, romidepsin, belinostat, and brentuximab) now approved by the US Food and Drug Administration for the treatment of relapsed or refractory disease. This compares quite favorably, at least in pure numbers if not clinical impact, to the one agent (rituximab) approved for the treatment of diffuse large B-cell lymphoma in the last 20 years. We have also witnessed the advent of randomized trials in T-cell lymphomas—something that was nearly unheard of even a few years ago. Although the approval of these agents and the existence of randomized trials represent a significant step forward, the reality remains that the treatment outcome for most patients with peripheral T-cell lymphoma remains poor, and our understanding of the biology of these diseases is still inadequate. In order to complete clinical trials in a meaningful timeframe, we must lump together varied T-cell histologies that often share limited biological or clinical characteristics. The fact that the most common histology is called peripheral T-cell lymphoma, not otherwise specified, speaks volumes to the amount of work that still needs to be done to better understand the pathogenesis of these disorders.

The utility of chemotherapy remains and is likely to remain limited in most subtypes of peripheral T-cell lymphoma. Therefore, further elucidation of the genetics and molecular biology of these disorders will be critical to move the field forward. In this issue of Hematology/Oncology Clinics of North America , we present a broad-ranging discussion on the current status of the peripheral T-cell lymphomas. Most articles focus on a specific histology and review current treatment paradigms as well as key emerging data on biological and therapeutic advances. Other articles focus more broadly on experimental therapeutics and stem cell transplantation. Regardless of the focus, each article represents a cutting-edge, up-to-date discussion by a renowned expert in the field.

Peripheral T-cell lymphomas remain one of the great areas of unmet need in hematologic malignancies. Paradoxically, advances in the understanding of the biology of these diseases may make the conduct of clinical trials more challenging. For instance, completing a trial specific to angioimmunoblastic T-cell lymphoma is already daunting, but finding sufficient numbers of patients with angioimmunoblastic T-cell lymphoma who harbor an IDH2 mutation may discourage even the most stalwart clinical investigator. Yet such trials can and should be done. In order to meet this challenge, we must put personal and institutional aspirations aside and collaborate on a global scale to conduct trials based upon rationale targets, not histology or expediency. I hope this issue gives you an appreciation for the challenges we face but, more important, a deeper understanding of how those challenges are slowly but inexorably being confronted.