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Tositumomab May Help Elderly With Non-Hodgkin's Lymphoma: Presented at ASH

By Mike Fillon

ATLANTA, GA -- December 15, 2005 -- A phase 2 trial found that tositumomab can deliver beneficial radiation doses to tumors while limiting exposure to normal organs, which is ideal for older adults requiring high-dose therapy, as well as other highly compromised patients.

Results of the study were presented here December 12^th at the 47^th Annual Meeting of the American Society of Hematology (ASH).

Elderly patients with advanced acute myeloid leukemia, high-risk myelodysplastic syndrome, or relapsed/refractory non-Hodgkin's lymphoma (NHL) generally do not undergo intense, high-dose therapy due to perceived age-related risk. The majority of patients with relapsed or refractory B-cell NHL are older than 60 years of age. Many of these patients are denied potentially curative high-dose regimens due to concerns about the excessive toxicity associated with stem cell transplantation.

However, innovative therapies that combine cancer-fighting antibodies and radiation may provide hope for this patient population, said researcher Ajay K. Gopal, MD, assistant professor of medicine, division of medical oncology, University of Washington, and assistant member, Fred Hutchinson Cancer Research Center, Seattle, Washington.

Myeloablative I-131-anti CD-20 (tositumomab) is a monoclonal antibody that contains a radioactive substance (iodine-131). The radioimmunotherapy agent is directed to the CD-20 receptor located on B lymphocyte cells. This receptor is found on some normal lymphocytes, as well as those that are cancerous. Tositumomab attaches to the CD-20 receptor and kills the cells by exposing them to a radioactive agent. Although the drug targets both normal and cancerous cells, B-cells can eventually be repopulated by stem cell transplantation.

In this trial, conducted at the University of Washington and Fred Hutchinson Cancer Research Center, Seattle, Washington, 24 patients with relapsed or refractory B-cell NHL aged 60 years or older were treated with high-dose tositumomab and autologous hematopoietic stem cell transplantation (ASCT).

Patients with an enlarged spleen or large tumor bulk were required to undergo further treatment in order to optimize radiation efficacy. Patients were followed after ASCT for a median of 2.2 years, ranging from 1 month to 4.9 years.

The estimated 4-year survival rate was 55%, while the estimated 4-year progression-free survival rate was 37%.

Overall, the therapy was well tolerated with no treatment-related deaths and no grade 3/4 life-threatening or fatal toxicity occurring within 100 days of ASCT.

"Tositumomab can deliver potentially curative radiation doses to tumor sites while limiting exposure to normal organs," Dr. Gopal said.

"When used with autologous hematopoietic stem cell transplantation, it is a well tolerated and effective transplant option for older adults requiring high-dose therapy for B-cell non-Hodgkin's lymphoma," he added. "Further follow-up and additional patients will help confirm the durability of these findings."


[Presentation title: A Phase II Study of Myeloablative I-131-Anti CD-20 (Tositumomab) Radioimmunotherapy and Autologous Hematopoietic Stem Cell Transplantation (ASCT) for Adults >/=60 Years of Age With High-Risk Relapsed or Refractory B-Cell Lymphoma. Abstract 487]

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