Medical Health Encyclopedia

Rituximab is used for patients with relapsed indolent lymphomas and is proving to be very useful as first-line and maintenance therapy for patients with low-grade indolent NHL. It is also being investigated in combination with CHOP for these lymphomas. Rituximab in combination with standard chemotherapy is also showing promise as a first-line treatment for mantle cell lymphoma.

In any case, rituximab in combination with CHOP is now considered for first-line treatment for aggressive lymphomas, with studies reporting three-year event-free survival of 53% compared to 35% with CHOP alone. To date, however, studies are not finding survival advantages for maintenance treatments of aggressive lymphomas. Rituximab is also being studied for lymphomas in the central nervous system. Combinations with other immunotherapies, such as interferon, are also promising.

The treatment has mild to moderate short-term side effects, including nausea, fever, chills, hives, dizziness, and headache. Uncommon and more serious side effects are severe allergic reactions, very low blood pressure, blood abnormalities, wheezing, infections, and sudden heart events. Patients who have previously had hepatitis B, or who are at high-risk for this viral infection, should be tested before taking rituximab because the drugs has been linked to reactivation of the hepatitis B virus. Fatalities associated with a first infusion of the drug occur in 4 to 7 out of 10,000 people.  Patients who are HIV-positive may experience more adverse effects from rituximab than with CHOP. Early studies are also investigating combinations of rituximab with conjugated MAbs, or other biologic modifiers.

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Conjugated Monoclonal Antibodies with Radioimmunotherapy. Conjugated MAbs with radioimmunotherapy contain tiny amounts of radioactive materials. When the drug is injected, the monoclonal antibody targets an antigen (protein) on the surface of the tumor. The radioisotope is then delivered directly into the tumor where it kills the cancer. Ibritumomab and tositumomab both target the CD-20 antigen. Treatment with these drugs takes about 7 to 9 days to complete, compared to several months for traditional chemotherapy treatments.

• Ibritumomab (Zevalin) is approved for patients with relapsed or refractory low-grade, follicular or transformed B-cell NHL. It is also approved for patients with follicular NHL who have not responded to rituximab (Rituxan). Research indicates it may also be safe for patients with advanced NHL who have had stem cell transplantation. Zevalin uses an yttrium-90 (90-Y) radioactive isotope.
• Tositumomab and Iodine I-131 (Bexxar) combines the monoclonal antibody tositumomab with the radioisotope I-131. The Bexxar treatment is approved for treatment of relapsed or refractory low-grade, follicular, or transformed B-cell NHL. Overall response rates of 56% have been reported with Bexxar, with up to 30% being complete responses (no evidence of cancer). Recent studies suggest that when Bexxar is used as a first treatment, it may produce long-term complete remission in patients with advanced stage follicular lymphoma. In a 2005 New England Journal of Medicine study, 95% of previously untreated patients with advanced follicular lymphoma responded to Bexxar, and 75% had complete responses. Seventy percent who had complete responses from Bexxar treatment were still disease-free 4 to 7 years later.