John Leonard, M.D., specializes in medical oncology at Weill Cornell Medicine. Over several years, chemotherapy and radiation therapy have been the main treatments for patients with lymphoma and other hematologic malignancies. While some patients with certain disorders may be cured, others could benefit from improvements in available treatments either by improving efficacy against the tumor and/or reducing toxicity. More recently, a new category of treatment called immunotherapy has demonstrated effectiveness against many of these diseases. Within this class, monoclonal antibodies are the furthest along in development. Rituximab, a monoclonal antibody directed against the CD20 molecule commonly present on the surface of lymphoma cells, was the first antibody approved for the treatment of cancer. When administered to patients, these molecules can specifically target tumor cells, while relatively sparing normal cells, and can kill them via both direct and indirect mechanisms, including activation of the immune system. In the past few years, this type of treatment has made a major impact in the lives of patients with lymphoma, causing tumor shrinkage and improvement in symptoms, and potentially improving survival.