Cancer
Improved Outcomes in Certain Lymphomas With Ibritumomab Tiuxetan Radioimmunotherapy
By M.I.N.D.S.
Jun 9, 2006, 00:25

New data was presented this week at the 42nd American Society of Clinical Oncology (ASCO) Annual Meeting in Atlanta, showing that lymphoma patients with refractory and hard-to-treat disease, specifically mantle cell lymphoma (MCL), follicular non-Hodgkin's lymphoma (NHL) and primary central nervous system (CNS) lymphoma, experienced improved response and remission rates following administration of Ibritumomab Tiuxetan radio-immunotherapy as consolidation treatment after other, more standard therapies have been given. Additionally, data suggest the use of Ibritumomab Tiuxetan as a component of a transplant regimen may reduce patients' risk of relapse.

"We are pleased that the data at this year's ASCO meeting continues to explore Ibritumomab Tiuxetan's ability to impact a broad range of patients, and underscores the growing role that Ibritumomab Tiuxetan can play in the standard of care for lymphoma," said Dr. Wayne Saville, director of Medical Affairs for Biogen Idec.

Eleven abstracts were presented on Ibritumomab Tiuxetan data during the meeting. Mitchell R. Smith, M.D., Ph.D., lead study investigator and director of Lymphoma Service, Fox Chase Cancer Centre, presented data from the Eastern Cooperative Oncology Group Study E1499 on the use of Ibritumomab Tiuxetan following administration of R-CHOP in previously untreated patients with stage II-IV MCL. The study was designed to evaluate response and toxicity, with a primary endpoint of time-to-treatment failure. After four cycles of R-CHOP, seven of the 50 evaluable patients in the study (14 percent) achieved a complete response (CR/CRu) and 29 (58 percent) achieved a partial response. Following treatment with Ibritumomab Tiuxetan, responses improved in 15 of 37 patients. Twelve of the patients with a partial response exhibited a complete response after Ibritumomab Tiuxetan, two patients with stable disease exhibited a partial response, and one patient moved from stable disease to a complete response. The final response rate following Ibritumomab Tiuxetan administration was 84 percent, with a complete response rate of 45 percent, more than triple the rate following R-CHOP alone.

Oliver Weigert, M.D., University Hospital Grosshadern/LMU, Munich, Germany, presented data from two Phase 2 trials of patients with relapsed or refractory MCL. Twenty-two patients were evaluated to identify predictors or response. Seven of 14 patients with residual tumor burden after cytoreduction converted from partial to complete remission following administration of Ibritumomab Tiuxetan, and 14 of the 16 evaluable patients receiving consolidation Ibritumomab Tiuxetan therapy were in remission. Bulky disease before Ibritumomab Tiuxetan therapy was the most prominent adverse risk factor with no response in these patients. Patients with fewer prior therapies (less than 2) had significantly higher response rates.

Nicholas A. DeMonaco, M.D., University of Pittsburgh, presented data from an ongoing Phase 2 trial for the predictive value of 111In scans and PET/CT results. The proportion of patients with a negative PET scan was eight of 15 (53.3 percent) after CHOP-R compared with 100 percent after Ibritumomab Tiuxetan was added. Using IWG criteria in combination with PET scan results, the complete response rate increased from 26.7 percent after CHOP-R to 80 percent after Ibritumomab Tiuxetan. There was no difference in the complete response rate in patients� tumour uptake by 111In scan and those with a negative 111In scan. Data from this trial suggest that functional imaging with PET-CT may be a more sensitive method than CT alone in determining residual disease in follicular lymphoma (FL).

On February 19, 2002, the Ibritumomab Tiuxetan therapeutic regimen was approved by the U.S. Food and Drug Administration (FDA) for the treatment of patients with relapsed or refractory low grade, follicular or transformed B-cell non Hodgkin's lymphoma (NHL), including patients with rituximab (RITUXAN) refractory follicular non-Hodgkin's lymphoma. Determination of the effectiveness of Ibritumomab Tiuxetan in a relapsed or refractory patient population is based on overall response rates. The effects of Ibritumomab Tiuxetan on survival are not known. Radio-immunotherapy offers an option to patients with certain types of B-cell non-Hodgkin's lymphoma who have failed to adequately respond to other cancer therapies.

The Ibritumomab Tiuxetan therapeutic regimen combines a monoclonal antibody with a radioisotope. The monoclonal antibody in Ibritumomab Tiuxetan recognizes and attaches to a particular cell-surface protein on B-cells called the CD20 antigen. This allows Ibritumomab Tiuxetan to specifically target B-cells, destroying malignant NHL B-cells and also normal B-cells.

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