Radioimmunotherapy (RIT) is a type of targeted therapy that delivers radiation directly to cancer cells. It combines a monoclonal antibody—a type of protein that recognizes and binds to certain parts of cancer cells—with radioactive material. When the monoclonal antibody binds to the cancer cell, the radiation kills the cell.
Currently, RIT is used for the treatment of B-cell non-Hodgkin lymphomas (see examples below). RIT is also being evaluated for the treatment of other types of cancer, including prostate cancer and glioblastoma.
RIT is given on an outpatient basis, is generally completed in 10 days (as opposed to the longer duration of conventional chemotherapy), and avoids many of the side effects of chemotherapy. Because RIT may result in a temporary reduction in blood cell counts, patients typically need to have their blood cell levels monitored after treatment.
Examples of RIT
Zevalin® (ibritumomab tiuxetan): Zevalin therapy combines the monoclonal antibody Rituxan® (rituximab) with Zevalin, which is comprised of an anti-CD20 monoclonal antibody and Yttrium-90, a radioisotope that delivers the radiation. When injected into the body, Zevalin attaches to a protein (CD20) found only on the surface of B-lymphocytes, such as cancerous B-cells found in many forms of non-Hodgkin’s lymphoma. The radioactivity that is spontaneously emitted targets the B-cell and destroys it. This approach protects healthy tissue. To learn more about Zevalin and view stories from other patients living with follicular lymphoma go to www.Zevalin.com. To locate a Zevalin-experienced oncologist click here.
Bexxar® (tositumomab and iodine I 131 tositumomab): Bexxar also targets B lymphocytes, and is comprised of an anti-CD20 monoclonal antibody and radioactive iodine 131. Bexxar is used for the treatment of certain patients with CD20-positive relapsed or refractory non-Hodgkin lymphoma.
Zevalin and Advanced Follicular Lymphoma
Researchers conducted a study that included 414 patients with CD20-positive stage III or IV follicular lymphoma who achieved a complete or partial response after first-line induction treatment. Patients were randomly assigned to receive Zevalin or no further treatment.
After a median follow-up of 3.5 years, the results indicated that Zevalin significantly prolonged median progression-free survival (PFS) in all patients, regardless of whether they had achieved a partial or complete response. Median PFS in patients treated with Zevalin was 36.5 months, compared to 13.3 months for patients in the control group. For patients who achieved a partial response after induction treatment, those who received Zevalin had a median PFS of 29.3 months compared to 6.2 months for those in the control group. Among patients who achieved complete response after induction, those who received Zevalin had a median PFS of 53.9 months compared to 29.5 months in the control group. What’s more, 77 percent of patients who experienced a partial response after induction converted to a complete response, which resulted in a final complete response rate of 87 percent.
The researchers concluded that Zevalin significantly prolonged PFS and resulted in a high conversion rate from partial to complete response, regardless of the type of first-line induction treatment.
Morschhauser F, Radford J, Van Hoof A, et al. Phase III trial of consolidation therapy with yttrium-90-ibritumomab tiuxetan compared with no additional therapy after first remission in advanced follicular lymphoma. Journal of Clinical Oncology. 2008; 26: 5156-5164.