ROBERT MARCUS, MD: Well, that's a complex question which I'll try and simplify as much as I can. The majority of patients will fall into two main categories either diffuse large cell lymphoma which pursues an aggressive course untreated or follicular indolent lymphoma which pursues a comparatively nonaggressive course. In terms of staging, the classic staging supply a single group of glands, more than one group of glands which would be stages I and II. The disease on both sides of the diaphragm would be stage III and disseminated disease would be stage IV. There are other prognostic measures which can be used to assess the outcome of the patient.
BRETT SCOTT: Are these less common types of NHL traditionally more difficult to treat?
ROBERT MARCUS, MD: Not necessarily. Not by definition. But a certain subtype such as mantle cell lymphoma which are often quite resistant to treatment, but other rarer types such as small lymphocytic lymphomas aren't necessarily more difficult.
Lymphomas arising from T cells obviously aren't amenable to antibody therapy but aren't necessarily as a consequence more difficult to treat with chemotherapy.
BRETT SCOTT: Dr. Press, why is Rituxan being used in these different types of NHL?
OLIVER PRESS, MD: It's being used predominantly in lymphomas that express a lot of the CD20 antigen. There is a molecular target on the surface of these lymphomas which the antibody binds to and fortunately, about 85% of lymphomas express this target very well. Those lymphomas which don't -- predominantly T cells lymphomas aren't really amenable to therapy to Rituxan as is mentioned.
And other diseases such as chronic lymphocytic leukemia which express a small amount of CD20 can be treated with Rituxan, but it hasn't been as dramatic a success there as it has been with the lymphomas that express more of the antigen.
BRETT SCOTT: Let's take a couple of specific examples. Dr. Marcus, can you comment on the use of monoclonal antibodies to treat aggressive NHL? What is the recent news being communicated this weekend?