DR. BOLLARD: Thank you, Dr. Gross. Again, another very comprehensive answer to a difficult question. I'm actually going to push this back to Dr. Cairo and then impose the same soon to be 18-year-old patient to you. This time, he's coming to you with relapsed diffuse large B-cell lymphoma. What are you going to tell him? Are you going to treat him today on pediatric protocols, or will you wait until tomorrow when he could have access to adult protocols?
DR. CAIRO: I think the results are relatively similar, but, in part, the answer to the question is of course based on what their original therapy was. If the original therapy was the pediatric-inspired type of treatment, I think there's a world of experience of what are some of the best pediatric-inspired regimens to use for retrieval. If, however, the original therapy was an adult-inspired regimen, then I think the options are open because the disease may not be as resistant in that setting; therefore, one would want to consider all the adult type of retrieval regimens in that case, because that group of patients—at least in the adult experience—tend to have disease that may be more responsive because they're not as resistant to the higher dose and multi-agent therapy that a pediatric-inspired regimen would have given them had they been treated that way.
DR. BOLLARD: I was also trying to ask you to speak to the access that an 18-year-old might have to novel therapies that a 17-year-old might not. How do you address that issue?
DR. CAIRO: That's an excellent question. I think that for first relapse or first induction failure most of the retrieval regimens, the first line regimens, that are available, either pediatric inspired or adult inspired, probably don't require an investigational agent that an 18-year-old might have access to if he was being treated on an adult type of regimen. However, I would strongly encourage an 18-year-old who failed one retrieval regimen to consider experimental therapy. There I think the access to new agents—if you're 18 or over—are so much greater that I would encourage them to be treated on an adult retrieval regimen, where some of the newer agents may be investigational, are not available to a pediatric program.
DR. BOLLARD: Thank you very much, Dr. Cairo. I have one last question on the B-cell diseases before I move to Dr. Lowe, and the last question goes to Dr. Gross. Would you recommend that a patient with relapsed Burkitt lymphoma—now increasingly rare—be treated with salvage chemotherapy and then autologous transplant or allogeneic stem cell transplant?
DR. GROSS: As the others on this discussion know, we performed an analysis from data in the Center for International Blood and Marrow Transplant Research (CIBMTR), and the problem is that Burkitt lymphoma tends to reoccur so rapidly after transplant. The median time to relapse is 3 months after transplant. We could not find a difference in the outcome between autografts and allografts because of its early reoccurrence. That said, my personal opinion is, since we know that Burkitt lymphoma is a hematologically spread disease, that I always prefer a donor source where I know they're not going to have tumor cells in them, which is an allogeneic donor. I always prefer an allogeneic donor, because I know it's tumor-free, but also it gives us an opportunity, if the disease will stay under control long enough, to potentially get an immune response against any residual tumor. For that reason, I recommend an allogeneic donor if it can be found readily.
DR. BOLLARD: Thank you very much, Dr. Gross. Now, on to Dr. Lowe, and Dr. Lowe's particular area of expertise is in anaplastic large cell lymphoma (ALCL) and T-cell diseases. I was wondering if you could explain to me the difference between T-cell lymphoblastic lymphoma and T-cell acute lymphoblastic leukemia (ALL), specifically since the World Health Organization (WHO) groups these two disease entities together as T-lymphoblastic leukemia/lymphoma. If you could clarify that classification that would be very helpful.
DR. LOWE: As you well know, many physicians believe that T-cell lymphoblastic leukemia and T-cell lymphoblastic lymphoma are very similar diseases, but they are not exactly the same disease although we sometimes treat them very similar. We know that T-cells do not mature in bone marrow but rather they are thymic driven cells. Because of this, there are distinct differences between the leukemia and lymphoma. For example, we know that the genetics between the two—although in limited samples—are not always the same, including in prognostic. Just one example, loss of heterozygosity at 6Q has been shown to be prognostically important in lymphoblastic lymphoma but not in T-cell ALL. I think the real challenge is to figure out what the differences are. I think we could argue that potentially, T-ALL is stage four T-cell lymphoblastic lymphoma.
I think that the WHO classifying the two diseases as one entity with T-lymphoblastic leukemia/lymphoma has hindered a little in the advancement of recognizing the differences in that many people assume that they're the same disease. When you look up from a pathological standpoint and you say, well, they're clearly the same disease because they're listed as a single entity, and when you look up treatment, you say, well they're treated very similar, so they must be the same disease. I think that does us a little disservice in trying to advance the field forward, because I think getting lymphoblastic lymphoma samples, which is challenging, is extremely important to determine the genetic drivers of this disease.