Non-Hodgkin’s lymphoma (NHL) patients with cancer progression after treatment with Bexxar® (Tositumomab and Iodine I-131 Tositumomab) generally have adequate bone marrow reserves at the time of progression and are able to receive additional NHL therapy. These results were published in the journal Cancer.
Non-Hodgkin’s lymphoma (NHL) is a form of cancer that begins in the cells of the lymph system. The lymph system includes the spleen, thymus, tonsils, bone marrow, lymph nodes, and circulating immune cells. The main cells in the lymph system are lymphocytes, of which there are two types: B and T-cells. Each of these cells has a specific function in aiding the body fight infection.
NHL is characterized by the excessive accumulation of atypical (cancerous) lymphocytes. These lymphocytes can crowd the lymph system and suppress the formation and function of other immune and blood cells.
NHL is categorized by the type of lymphocyte it involves and is further defined by the rate at which the cancer grows; growth rate is determined by the appearance of the cells under a microscope. Low-grade or indolent lymphoma refers to NHL that is slow growing.
Due to the side effects associated with chemotherapy and radiation, researchers have been investigating novel therapeutic strategies, including radioimmunotherapy.
Radioimmunotherapy involves treatment with a radioactive substance that is linked to an antibody. When injected into the body, the radioactive substance and antibody will attach to cancer cells. By delivering the radiation directly to the cancer, more normal tissue is spared from radiation and there are fewer side effects.
Bexxar is an antibody with radioactive iodine 131 attached. The monoclonal antibody portion of the drug attaches to a protein (CD20) found only on the surface of B-lymphocytes, such as cancerous B-cells found in many forms of NHL. The radioactivity that is spontaneously emitted targets the B-cell and destroys it.
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A potential concern about use of radioimmunotherapy is that the radiation may deplete bone marrow reserves. If this occurs, it may limit the patient’s ability to receive subsequent treatment, such as chemotherapy and stem cell transplantation. Subsequent treatment may be important for patients who do not respond to radioimmunotherapy, or who develop progressive NHL after radioimmunotherapy.
To explore the treatment of progressive NHL in patients who had received Bexxar, researchers reviewed the records of 155 Bexxar-treated NHL patients. Sixty-eight of the patients included in the analysis either failed to respond to Bexxar or developed progressive disease after treatment with Bexxar. A majority of these patients had follicular NHL, and all had received at least one chemotherapy regimen before treatment with Bexxar.
- 44 of the 68 patients (65%) received chemotherapy after disease progression, and 24 (35%) did not receive chemotherapy.
- The decision not to use chemotherapy appeared to be based on factors other than blood counts in all but three of the 24 patients who did not receive chemotherapy.
- Of the 44 patients who received chemotherapy, roughly 50% either completed chemotherapy and experienced a reduction in detectable disease or were still receiving chemotherapy.
- 30% of patients who received subsequent chemotherapy underwent a stem cell transplant.
The researchers conclude that NHL patients with disease progression after treatment with Bexxar generally have acceptable blood counts and are able to receive subsequent therapy, including chemotherapy and stem cell transplantation.
Reference: Dosik AD, Coleman M, Kostakoglu L et al. Subsequent Therapy Can Be Administered after Tositumomab and Iodine I-131 Tositumomab for Non-Hodgkin Lymphoma. Cancer. 2006;106:616-22.
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