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| |  ICML: Bexxar Found to be Effective against Follicular Lymphoma By Tim Allmark LUGANO, SWITZERLAND -- June 19, 2002 -- Results of a five-year trial confirmed the efficacy of tositumomab (Bexxar) for patients with follicular lymphoma but was less encouraging for patients with other types of lymphoma. The study, carried out at St. Bartholomew’s Hospital, London, and Christie Hospital, Manchester, United Kingdom, was presented here Friday on June 14th at the 8th International Conference on Malignant Lymphoma (ICML). Bexxar is an investigational radioimmunoconjugate used to enhance the effect of monoclonal antibody therapy by conjugating the murine monoclonal antibody tositumomab to the CD20 protein with iodine131 radioactive isotope. Between March 1996 and March 2001, 96 patients (median age 53 years, range 27 to 90) with recurrent or refractory lymphoma were enrolled in the study, 61 as part of an open phase II trial and 35 on a compassionate basis. Of these, 64 had follicular lymphoma, five had mantle cell lymphoma, four had lymphoplasmacytic lymphoma, three had small lymphocytic lymphoma; 20 had transformed to large B cell lymphoma (19 from follicular and one from lymphoplasmacytic lymphoma). Patients had a median of two previous therapies (range one to nine); 11 had previous high-dose therapy. Following dosimetric administration of radioactive antibody, patients received individualised therapeutic doses; those with platelet counts above 150x109/L received 75 cGy; those with platelet counts of 100-149x109/L received 65 cGy; and those who had progressed after high-dose rituximab therapy received 45 cGy. Response was assessed seven weeks after therapy and subsequently every three months. Toxicity was principally haematological, with 38 percent incidence of grade 3 to 4 neutropaenia and 30 percent grade 3 to 4 thrombocytopaenia. Median neutrophil and platelet nadirs occurred at seven and six weeks, respectively. All patients recovered around 10 weeks after therapy. The overall response rate (ORR) was 59 percent at seven weeks and complete response (CR) rate was 10 percent, rising to 25 percent after subsequent assessments. "Median remission duration hasn’t yet been reached, but it looks as if it's going to be about 2.5 years," said Dr. A. Davies, of St. Bartholomew’s Hospital, London. "Included in those patients are a number of patients who had refractory disease, with a huge number of therapies between them, and have been in complete remission for over five years with chemofractious disease. That’s a very important advance." For those in partial remission, duration was far shorter at a median seven months. The ORR also declined with the number of previous therapies from 76 percent after one previous therapy to 66 percent after two and 46 percent after three. Patients with follicular lymphoma received the most benefit from treatment, achieving an ORR of 70 percent and CR of 10 percent at seven weeks. "Unfortunately the people with nonfollicular histologies did less well, and all of them have progressed by one year," Dr. Davies noted. The study was supported by the Imperial Cancer Research Fund (IRCF), Cancer Research Campaign (CRC), Corixa Corp., and National Health Service of the United Kingdom.
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