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Durable Responses Reported With Radioimmunotherapy in Low-Grade Non-Hodgkin’s Lymphoma

Durable Responses Reported With Radioimmunotherapy in Low-Grade Non-Hodgkin’s Lymphoma

According to studies presented at the 43rd annual
meeting of the American Society of Hematology (ASH), tositumomab/iodine-131
tositumomab (Bexxar), an investigational radioimmunotherapy being evaluated for
the treatment of low-grade or transformed low-grade non-Hodgkin’s lymphoma
(NHL), produced durable, long-term responses when used alone or following
chemotherapy. Multiple presentations suggested that tositumomab/iodine-131
tositumomab may be an important new treatment option for patients with relapsed
or refractory NHL and, in particular, for patients whose prognosis is poor.

John Leonard, md, clinical director of the Center for Lymphoma and Myeloma,
Weill Medical College of Cornell University, New York, and his colleagues
analyzed data on 582 patients with relapsed, refractory low-grade or transformed
low-grade NHL who received tositumomab/iodine-131 tositumomab in clinical trials
conducted between 1990 and 2000. The analysis showed that the radioimmunotherapy
combination produced an overall response in 57% of patients, with 50% remaining
in remission for at least 14.3 months. Moreover, 28% of all patients
achieved a complete response, and 50% of those who did so remained in remission
for 4.8 years or longer. The median follow-up was 1.3 years, with a
maximum follow-up of 8.5 years.

First-Line Triple-Modality Therapy

In another trial reported by Dr. Leonard, investigators treated 35 previously
untreated NHL patients with triple-modality therapy—the combination of
fludarabine (Fludara), tositumomab, and iodine-131-labeled tositumomab. All
patients in the trial exhibited a response to treatment, with 77% achieving a
complete response. After a median follow-up of 23 months, more than half showed
no signs of disease progression.

"This novel approach produces a high response rate in initial therapy
for low-grade non-Hodgkin’s lymphoma," said Dr. Leonard. "We have
also found that by using fludarabine to debulk or reduce a patient’s tumor
burden, including tumor in the bone marrow, we can expand the number of patients
who can benefit from Bexxar therapy."

Triple-modality therapy (various chemotherapies combined with tositumomab/iodine-131
tositumomab) is being investigated for the treatment of other types of NHL as
well. Results from one such study, a phase II clinical trial of CHOP
(cyclophosphamide [Cytoxan, Neosar], doxorubicin HCl, vincristine [Oncovin],
prednisone) followed by the radioimmunotherapy combination in newly diagnosed
follicular NHL, were reported at the ASH meeting by researchers affiliated with
the Southwest Oncology Group. In this study, 80% of the 71 patients evaluated
following sequential therapy achieved an objective remission, ie, either a
complete (52%) or partial (28%) response. In 17 patients (24%), the addition of
tositumomab/iodine-131 tositumomab to CHOP improved the overall best response,
either from a partial to a complete response (15 patients, or 21%) or from an
unconfirmed to a confirmed complete response (2 patients, or 3%).

Importance of Radiation Component

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