Factors associated with toxicity and response to yttrium 90-labeled ibritumomab tiuxetan in patients with indolent non-Hodgkin's lymphoma

Treatment of patients with indolent non-Hodgkin's lymphoma (NHL) is evolving. These patients usually present with advanced-stage disease. Treatment options for patients who experience relapse are limited, and no treatment has been shown to be superior to others in improving overall survival of this group of patients, with the possible exception of allogeneic stem cell transplantation. Therefore, new approaches are needed to improve outcomes in patients with relapsed or refractory disease. The anti-CD20 monoclonal antibody, rituximab, was the first monoclonal antibody approved for the treatment of indolent B-cell NHL. As a single agent in the treatment of relapsed or refractory indolent lymphoma, response rates as high as 56% have been observed. This promising new therapy was followed by development of radioimmunotherapy, a novel treatment approach that combines the targeting capability of monoclonal antibodies with the additional cytotoxic effects of radiation. Yttrium 90-labeled ibritumomab tiuxetan (Zevalin) is a radiolabeled monoclonal antibody that has been shown to produce clinically significant responses in up to 80% of patients with indolent NHL and is the first radiolabeled monoclonal antibody approved for therapeutic use in the treatment of lymphoma. This article reviews some of the safety and efficacy data for this agent in addition to examining factors that could aid in predicting response and toxicity in patients with low-grade relapsed or refractory NHL treated with 90Y ibritumomab tiuxetan.

Combining yttrium 90-labeled ibritumomab tiuxetan with high-dose chemotherapy and stem cell support in patients with relapsed non-Hodgkin's lymphoma

Targeted radioimmunotherapy, including yttrium 90-labeled ibritumomab tiuxetan (Zevalin) and iodine I 131 tositumomab (Bexxar), has the potential to increase the cure rate for patients with CD20+ B-cell malignancies who are undergoing autologous hematopoietic stem cell transplantation. The results of phase I and II trials suggest that radioimmunoconjugates can be safely combined with high-dose chemotherapy, although the optimal approach remains to be established. This review focuses on the use of 90Y ibritumomab tiuxetan combined with high-dose chemotherapy in the setting of autologous hematopoietic stem cell transplantation.

Ongoing trials with yttrium 90-labeled ibritumomab tiuxetan in patients with non-Hodgkin's lymphoma

Targeted radiation therapy or radioimmunotherapy has been an important recent advance in the treatment of patients with B-cell non-Hodgkin's lymphoma (NHL). Yttrium 90-labeled ibritumomab tiuxetan (Zevalin) comprises the murine monoclonal antibody ibritumomab, the linker chelator tiuxetan, and the radiolabeled isotope yttrium 90. Yttrium 90 ibritumomab tiuxetan has been shown to be efficacious in the treatment of B-cell NHL. Initial phase I/II trials established the therapeutic dose of ibritumomab tiuxetan for low-grade NHL to be 0.4 mCi/kg, or 0.3 mCi/kg for patients with mild thrombocytopenia. Currently, there are many ongoing trials of ibritumomab tiuxetan with different dose schedules and dose intensities in combination with chemotherapy and autologous or allogeneic stem cell transplantation in an attempt to improve response rate and duration and to study its effectiveness in other B-cell lymphomas including mantle cell lymphoma, and chronic lymphocytic leukemia. This article reviews the ongoing trials with 90Y ibritumomab tiuxetan. Radioimmunotherapy has great promise, and the safe incorporation of 90Y ibritumomab tiuxetan into treatment will hopefully result in improved survival for patients with NHL.

Immunohistochemical analysis of Hodgkin's disease in Kampala, Uganda

BACKGROUND

Histopathological examination remains crucial for diagnosis and classification of Hodgkin's disease (HD) but poses problems when characteristic features of HD are not present and hence the value of immunohistochemistry. Experience with immunohistochemistry in developing countries is limited due to cost.

OBJECTIVE

To describe the immunophenotypic and histologic types of Hodgkin's disease in Kampala, Uganda

DESIGN

A cross-sectional study.

SETTING

Makerere University Medical School, Department of Pathology.

METHODOLOGY

Two hundred formalin fixed, paraffin- embedded biopsies, which had been previously diagnosed as Hodgkin's disease in the Makerere University, Department of Pathology from 1980--2000, were re-assessed with haematoxylin and eosin. The sections were then subjected to immunohistochemistry using monoclonal antibodies: leucocyte common antigen (CD45), antibodies to Reed-Sternberg cells (CD15, CD30) and to B cells (CD20).

RESULTS

Of the 200 biopsies, 171 (71.3%) were diagnosed as Hodgkin's disease using immunohistochemistry. The mean age of the 171 cases was 26.1(SD 16.2) years; mode 20.0; median 22.5 years. The 15-24 year age group was most affected (47.2%). There were more males (65.9%) than females and most were Baganda who are the main tribe in the central region of Uganda. Mixed cellularity (35.7 %) and lymphocyte depleted (24.6 %) HD were the commonest histological types. Classic HD (CD30, CD 15, CD20, CD45) was the most commonest (77.8%) immunophenotype.

CONCLUSION

Classic Hodgkin's disease (CD30, CD 15, CD20 and CD45) is the most commonest immunophenotype in Kampala, Uganda, and mixed cellularity and Iymphocyte depleted are the main histologic subtypes.

90Y-ibritumomab tiuxetan: Rationale for patient selection in the treatment of indolent non-Hodgkin’s lymphoma

Radioimmunotherapy with 90Y-ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, San Diego, CA, and Schering AG, Berlin, Germany) was approved in the United States in 2002 for patients with relapsed or refractory, low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma, including patients with rituximab-refractory disease, and in Europe in 2003. This agent has yielded good results in the treatment of patients with relapsed or refractory non-Hodgkin's lymphoma, for whom limited treatment options are available. Radioimmunotherapy with 90Y-ibritumomab tiuxetan is well tolerated and produces statistically and clinically significant higher overall and complete response rates than rituximab alone. Furthermore, treatment can be safely administered on an outpatient basis, with minimal disruption to patients' daily routines. The 90Y-ibritumomab tiuxetan treatment regimen, appropriate patient selection, and risk assessment are discussed in this article.

Development of 131I-tositumomab

The median survival for patients with advanced indolent non-Hodgkin's lymphoma (NHL) has remained at 7 to 8 years since the 1960s. Targeted treatment using radioimmunotherapy (RIT), radiolabeled monoclonal antibodies directed against tumor-specific antigens, is an attractive option for this patient population, combining the advantages of an active biologic therapy with low dose-rate irradiation of an inherently radiosensitive tumor. Two anti-CD20 RIT agents have now been approved for the treatment of refractory NHL: 90Y-ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, San Diego, CA, and Schering AG, Berlin, Germany) is approved in both the United States and Europe, and 131I-tositumomab (Bexxar; Corixa Corp, Seattle, WA) is approved only in the United States. This article discusses the development of 131I-tositumomab. Because 131I-labeled antibody clearance varies significantly among patients, prescription of 131I-tositumomab activity must be based on a calculated total-body dose derived from quantitative whole-body imaging. The maximum tolerated total-body dose has been established at 75 cGy in patients with adequate bone marrow reserves and less than 25% bone marrow involvement by lymphoma (65 cGy in patients with mild thrombocytopenia; 45 cGy in patients who have received stem cell transplantation). In a phase III trial, overall response rate (ORR) and complete response (CR) rate were significantly higher following 131I-tositumomab than following the patient's last qualifying chemotherapy (ORR, 65% v 28%; P <.001; CR, 20% v 3%; P <.001). 131I-tositumomab has also been shown to be effective in patients who are refractory to rituximab (ORR, 70%; CR, 32%) and as first-line therapy in patients with NHL (ORR, 97%; CR, 63%). The major side effects of 131I-tositumomab are hematologic. In the phase III study, 20% of patients experienced grade 4 neutropenia and 22% experienced grade 4 thrombocytopenia. Myelodysplastic syndromes or secondary acute myeloid leukemia have been reported in 8.4% of patients with chemotherapy-refractory disease treated with 131I-tositumomab, but have not been observed to date in patients receiving 131I-tositumomab as first-line therapy. Future progress in NHL management is likely to include RIT as part of a multi-modality approach; trials are planned or currently underway to investigate the combination of RIT with chemotherapy regimens.

Use of 90Y-ibritumomab tiuxetan in non-Hodgkin’s lymphoma

The increase in the incidence of non-Hodgkin's lymphoma (NHL) that has occurred over recent decades is expected to continue. Therapeutic options for patients with NHL have improved over the past 20 years, but almost all patients with low-grade lymphoma and approximately 50% of patients with high-grade lymphoma eventually die of their disease, regardless of the regimen used. Thus, there is a continuing need for novel therapeutic options. One such strategy is targeted radioimmunotherapy, which is an attractive approach because lymphoma cells are inherently sensitive to radiation. 90 Y-ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, San Diego, CA, and Schering AG, Berlin, Germany) was the first radioimmunotherapy agent to be approved by the US Food and Drug Administration for the treatment of patients with relapsed, low-grade B-cell NHL. 90Y-ibritumomab tiuxetan comprises the murine IgG1 anti-CD20 antibody ibritumomab, covalently linked to the beta-emitter 90 Y by a chelator tiuxetan. A prospective trial comparing 90Y-ibritumomab tiuxetan with single-agent rituximab showed an overall response rate (ORR) to 90Y-ibritumomab tiuxetan of 80% (34% complete response [CR]/unconfirmed CR [CRu]) compared with 56% (20% CR/CRu) with rituximab (P = .002). Of patients achieving a CR/CRu, 32% were still in remission at 3 to 4 years of follow-up. Similar efficacy (83% ORR, 43% CR/CRu) has been reported with 90 Y-ibritumomab tiuxetan in patients with relapsed or refractory low-grade NHL with mild thrombocytopenia (platelet counts 100,000 to 149,000/mm3 ), and in patients with rituximab-refractory NHL (ORR 74% [CR 15%] compared with an ORR 32% to last rituximab treatment). Safety data compiled from patients entered into five studies have confirmed initial observations that the toxicities encountered with 90Y-ibritumomab tiuxetan therapy are mainly hematologic and transient. As part of a consolidated clinical approach to the ongoing development of 90Y-ibritumomab tiuxetan, studies are currently being conducted in the United States and Europe to examine the role of this agent in first-line therapy of indolent NHL, in diffuse large B-cell lymphoma, and in combination with chemotherapy with peripheral blood stem cell support.

PRDM1/Blimp-1 is expressed in human B-lymphocytes committed to the plasma cell lineage

PRDM1/Blimp-1 (in human and mouse, respectively) has a central role in determining and shaping the secretory arm of mature B-cell differentiation. In this study, a mouse monoclonal antibody that recognizes PRDM1 was used to detail its distribution in normal human lymphoid tissue and in lymphoid neoplasms that correspond to different stages of B-cell differentiation. PRDM1 was expressed in germinal centre blasts that co-express Pax5, CD19, CD20, and CD10, but not BCL6 or MTA-3. Pax5 was downregulated and full plasma cell morphology and phenotype were acquired by PRDM1+, nuclear cREL-, pre-plasma cells upon exit from the germinal centre. Activated extrafollicular B-cells (CD30+, Pax5+) were largely PRDM1-. PRDM1 was also absent in tissue histiocytes and the majority of resting T-cells and S-100+ antigen-presenting cells. PRDM1 and CD138 were expressed simultaneously in human lymphomas with plasma cell differentiation, but not in marginal zone lymphomas or chronic lymphocytic leukaemias. A minority of diffuse large B-cell lymphomas expressed PRDM1 and Hodgkin lymphomas were largely PRDM1-. Infiltrating T-cells in PRDM1- B-cell lymphomas expressed PRDM1. In conclusion, PRDM1 staining is a reliable and informative assay to define plasma cell commitment and differentiation in human normal and neoplastic B-cell lineages.

Phase I trial of iodine-131 tositumomab with high-dose chemotherapy and autologous stem-cell transplantation for relapsed non-Hodgkin's lymphoma

PURPOSE

To determine the maximum outpatient dose of iodine-131 tositumomab (up to 0.75 Gy) combined with high-dose carmustine, etoposide, cytarabine, and melphalan (BEAM) followed by autologous stem-cell transplantation (ASCT) for the treatment of chemotherapy-resistant relapsed or refractory B-cell non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

Twenty-three patients with chemotherapy-refractory or multiply-relapsed B-cell NHL were treated in a phase I trial combining iodine-131 tositumomab (ranging from 0.30 to 0.75 Gy total-body dose [TBD]) with high-dose BEAM followed by ASCT.

RESULTS

The complete response rate after transplantation was 57%, and the overall response rate was 65%. Short-term and long-term toxicities were similar to historical control patients treated with BEAM alone. With a median follow-up of 38 months (range, 27 to 60 months), the overall survival (OS) rate was 55%, and the event-free survival (EFS) rate was 39%.

CONCLUSION

There were no significant added toxicities apparent with the addition of iodine-131 tositumomab up to a dose of 0.75 Gy TBD to high-dose BEAM chemotherapy followed by ASCT. The EFS and OS were encouraging in this group of chemotherapy-resistant or refractory B-cell NHL patients. A follow-up phase II trial with iodine-131 tositumomab at the dose of 0.75 Gy TBD with BEAM is currently ongoing.

Radioimmunotherapy in Non-Hodgkin's Lymphoma: Trials of Yttrium 90–Labeled Ibritumomab Tiuxetan and Beyond

The treatment for non-Hodgkin's lymphoma (NHL) has improved over the past 20 years, but the natural history of the disease has not improved with conventional therapeutics. New modalities using targeted therapy based on molecular biology and immunology hold promise for better outcomes with less toxicity. Major radionuclides available (iodine I 131 and yttrium 90) are discussed and clinical trial data with the 90Y-labeled antibody ibritumomab tiuxetan are presented. Long-term toxicity questions are addressed, the use of dosimetry as a means for predicting toxicity is reviewed, and quality-of-life analyses are discussed. Radioimmunotherapy represents a safe and effective treatment modality for patients with NHL.

Efficacy and safety of radioimmunotherapy with yttrium 90 ibritumomab tiuxetan (Zevalin)

OBJECTIVES

To detail recent developments pertaining to the efficacy and safety of radioimmunotherapy with yttrium 90 (90Y) ibritumomab tiuxetan for patients with B-cell non-Hodgkin's lymphoma (NHL).

DATA SOURCES

Published clinical trials of 90Y ibritumomab tiuxetan and secondary literature on radioimmunotherapy and NHL.

CONCLUSION

Yttrium 90 ibritumomab tiuxetan is safe and effective in the indicated population. It has a good safety profile and is generally well tolerated. It is not associated with the adverse events from conventional chemotherapy and external beam radiation therapy.

IMPLICATIONS FOR NURSING PRACTICE

Nursing professionals who are aware of the efficacy and safety data associated with 90Y ibritumomab tiuxetan can optimize efficacy and educate patients and their caregivers about the regimen.

Educating patients about radioimmunotherapy with yttrium 90 ibritumomab tiuxetan (Zevalin)

OBJECTIVES

To present the relevant information for the education of patients with B-cell non-Hodgkin's lymphoma (NHL) who are about to undergo radioimmunotherapy (RIT) with yttrium 90 (90Y) ibritumomab tiuxetan.

DATA SOURCES

Published clinical trials of 90Y ibritumomab tiuxetan and secondary literature on radioimmunotherapy and NHL.

CONCLUSION

RIT is an emerging therapeutic option for patients with B-cell NHL and promises to become more prevalent in clinical use. Patients need to understand the rationale for and schedule of treatments with this regimen and the necessary ongoing laboratory tests for monitoring myelosuppression, as well as possible adverse events that might occur after treatment.

IMPLICATIONS FOR NURSING PRACTICE

Nursing professionals should be aware of the logistics of the ibritumomab tiuxetan regimen and with the data associated with it to educate patients and facilitate patient understanding and expectations.

The conjugate Rituximab/saporin-S6 completely inhibits clonogenic growth of CD20-expressing cells and produces a synergistic toxic effect with Fludarabine

Immunotoxins are chimeric proteins consisting of a toxin coupled to an antibody. To date, several clinical trials have been conducted, and some are still ongoing, to evaluate their anti-tumor efficacy. In this view, we chemically constructed an anti-CD20 immunotoxin with the mAb Rituximab and the type 1 ribosome-inactivating protein (RIP) saporin-S6, designed for B cells non-Hodgkin's lymphoma (NHL) therapy. This immunotoxin showed a specific cytotoxicity for the CD20+ cell lines Raji and D430B, evidenced by inhibition of protein synthesis, evaluation of apoptosis and clonogenic assay. Upon conjugation, saporin-S6 increased its toxicity on target cells by at least 2 logs, with IC(50) values of 0.1-0.3 nM. The percentage of AnnexinV+ cells was over 95% in both cell lines treated with 10 nM immunotoxin. A complete elimination of Raji clones was reached with the 10 nM immunotoxin, whereas a mixture of free RIP and mAb gave about 90% of clonogenic growth. Rituximab/saporin-S6, at 10 nM concentration, also induced apoptosis in 80% of lymphoma cells from NHL patients. Moreover, sensitivity of Raji to Rituximab/saporin-S6 was augmented when cells were coincubated with Fludarabine. The synergistic toxic effect of the two drugs led to a total elimination of the neoplastic population.

History of antibody therapy for non-Hodgkin's lymphoma

Monoclonal antibodies (mAbs) were the first successful targeted therapy for cancer. In contrast to the nonspecific nature of most chemotherapy, antibodies bind with high specificity to cell-surface antigens, resulting in targeted killing of malignant cells, relative sparing of normal tissues, and low toxicity. Antibody therapy has undergone substantial development since Ehrlich's notion of a "magic bullet," in 1890. It was not until the 1970s, however, that mAbs became viable as therapeutic tools and clinical studies showed them to be effective. The results were most impressive in hematologic malignancies, especially B-cell non-Hodgkin's lymphoma. In 1997, rituximab (Rituxan; Genentech Inc, South San Francisco, CA, and Biogen Idec Inc, Cambridge, MA) became the first mAb approved by the US Food and Drug Administration for use in the treatment of cancer. The first approval for a radiolabeled antibody to treat cancer was in 2002 for (90)Y ibritumomab tiuxetan (Zevalin; Biogen Idec). This is a conjugate of an anti-CD20 mAb (ibritumomab, the murine parent of rituximab) with the beta-emitter radionuclide (90)Y. (90)Y ibritumomab tiuxetan has been shown to be safe and effective in the indicated patient population. Other radioimmunoconjugates are being investigated for the treatment of non-Hodgkin's lymphoma, as are several immunotoxins. This article reviews important events in the development of mAb therapy and radioimmunotherapy for B-cell non-Hodgkin's lymphoma.

Radiation safety with Yttrium 90 ibritumomab tiuxetan (Zevalin) radioimmunotherapy

OBJECTIVES

To present pertinent issues involved in radiation safety in radioimmunotherapy with 90Y ibritumomab tiuxetan.

DATA SOURCES

Published clinical trials of 90Y ibritumomab tiuxetan and secondary literature on radiation safety and radioimmunotherapy.

CONCLUSION

Radioimmunotherapy with 90Y ibritumomab tiuxetan is safe and effective in the indicated population, and radiation safety requirements for caregivers and patients are minimal. Yttrium 90 ibritumomab is routinely and safety administered as an outpatient procedure; safety precautions are universal precautions, with the addition of acrylic shielding for the preparation and administration of the radiolabeled dose.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses play a key role in the multidisciplinary team. By observing universal precautions, and advising patients to do the same, oncology nurses may facilitate the safe and effective administration of the ibritumomab tiuxetan regimen.

The rationale for and background of radioimmunotherapy: an emerging therapy for B-cell non-hodgkin’s lymphoma

OBJECTIVES

To present the rationale for and development of radioimmunotherapy (RIT) for non-Hodgkin's lymphoma (NHL), which culminated in the FDA's approval of yttrium 90 (90Y) ibritumomab tiuxetan in February 2002.

DATA SOURCES

Published clinical trials of 90Y ibritumomab tiuxetan and secondary literature on immunotherapy, RIT, and NHL.

CONCLUSION

Monoclonal antibodies to the CD20 antigen have become an accepted therapy for NHL. Factors such as the poor vascularization of some tumors and the variable expression of the antigen can mitigate the efficacy of monoclonal antibodies, which prompted the development of a new strategy, RIT.

IMPLICATIONS FOR NURSING PRACTICE

Knowledge of the background and development of RIT is essential for nurses to educate and manage patients with NHL.

Practical considerations and radiation safety in radioimmunotherapy with yttrium 90 ibritumomab tiuxetan (zevalin)

90Y ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, Cambridge, MA), the first radioimmunotherapeutic agent approved by the US Food and Drug Administration, is a promising treatment option in patients with relapsed or refractory low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma, including patients with rituximab-refractory follicular non-Hodgkin's lymphoma. The ibritumomab tiuxetan regimen is administered on an outpatient basis over approximately 1 week and with the simplicity of weight-based dosing (ie, calculation of whole body clearance is unnecessary). Other than acrylic shielding, only universal precautions are required to administer (90)Y ibritumomab tiuxetan, and patient isolation is unnecessary. This treatment regimen requires a coordinated multidisciplinary approach. Oncologists play a leading role in selecting patients for (90)Y ibritumomab tiuxetan therapy and in prescribing and overseeing the treatment.

Radiobiology of radioimmunotherapy with 90Y ibritumomab tiuxetan (zevalin)

Radioimmunotherapy represents a significant advance over unlabeled immunotherapy for the treatment of patients with B-cell non-Hodgkin's lymphoma. The efficacy of radioimmunotherapeutic agents depends in large part on the basic biological effects associated with their components, monoclonal antibodies and radionuclides, separately and in combination. The radiobiological effects associated with yttrium 90-labeled ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, Cambridge, MA) include the induction of apoptosis and cell-cycle redistribution (eg, arrest of cells in the G(2)/M phase of the cell cycle). Because of dose-rate effects, tumor cells may, in some cases, be more susceptible to the low-dose-rate radiation used in radioimmunotherapy than to the high-dose-rate radiation used in external beam radiotherapy. The efficacy of radioimmunotherapy may potentially be optimized through a variety of approaches, including the use of agents that increase the expression of certain tumor antigens (thus facilitating improved biodistribution of radiolabeled monoclonal antibodies) or that sensitize tumor cells to radiation.

Selecting patients for treatment with 90Y ibritumomab tiuxetan (zevalin)

Yttrium 90 ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, Cambridge, MA) was the first radioimmunotherapeutic agent approved by the US Food and Drug Administration. It is indicated for treating patients with relapsed or refractory low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma, including patients with rituximab-refractory follicular non-Hodgkin's lymphoma. Proper patient selection is essential for optimizing the efficacy and safety of treatment with (90)Y ibritumomab tiuxetan. It may be advisable to use (90)Y ibritumomab tiuxetan relatively early in a patient's course of treatment because overall and complete response rates, and the estimated median duration of response, are higher among patients who have had fewer median prior antineoplastic regimens than among those who have had a greater median number of such regimens. Furthermore, the myeloablative effect of multiple courses of chemotherapy can preclude the later use of (90)Y ibritumomab tiuxetan. In contrast, other therapies, including chemotherapy and rituximab, can be used safely and successfully after (90)Y ibritumomab tiuxetan without concerns about increased hematologic toxicity from the previous radioimmunotherapy. The main adverse event associated with (90)Y ibritumomab tiuxetan therapy is hematologic toxicity and, as a result, only patients with adequate bone marrow reserves and less than 25% lymphoma marrow involvement should currently be considered for clinical therapy.

Efficacy and safety of 90Y ibritumomab tiuxetan (zevalin) radioimmunotherapy for non-Hodgkin’s lymphoma

Radioimmunotherapy, an emerging treatment option for certain patients with non-Hodgkin's lymphoma (NHL), enables the targeting of cytotoxic radiation to tumor cells with minimal irradiation of normal cells. Yttrium 90 ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, Cambridge, MA) was approved in February 2002 for the treatment of patients with relapsed or refractory low-grade, follicular, or transformed B-cell NHL, including patients with rituximab-refractory NHL. Yttrium 90 ibritumomab tiuxetan is an effective treatment with a consistent overall response rate of 73% to 83%. It has a good safety profile and is generally well tolerated in the indicated population. The results of clinical trials show that (90)Y ibritumomab tiuxetan can be used effectively and safely in many patients with NHL, including those with mild thrombocytopenia and those with disease that is refractory to rituximab, without the adverse events associated with conventional chemotherapy and external beam radiation therapy. The use of (90)Y ibritumomab tiuxetan does not preclude subsequent therapy with other conventional treatment options.

Future directions in radioimmunotherapy for B-cell lymphoma

Rituximab has become a staple in the management of B-cell non-Hodgkin's lymphoma, but it has limited activity as a single agent, with responses in about half of patients with recurrent follicular and low-grade lymphoma. Radioimmunotherapy (RIT) may surmount inherent or acquired antibody resistance by targeting a radionuclide to tumor cells. This strategy is particularly appealing for B-cell lymphoma because CD20 affords an outstanding target and lymphomas are inherently radiosensitive. The efficacy and safety of RIT have been established in the treatment of relapsed or refractory indolent non-Hodgkin's lymphoma, and yttrium 90 ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, Cambridge, MA) was the first RIT agent to be approved by the US Food and Drug Administration. This supplement to Seminars in Oncology seeks to present hematologists and medical oncologists with the most recent developments in RIT with (90)Y ibritumomab tiuxetan for non-Hodgkin's lymphoma, to clarify the role of the medical oncologist in the administration of the ibritumomab tiuxetan regimen, to indicate how and when RIT with (90)Y ibritumomab tiuxetan may most successfully be integrated into the continuum of treatment for patients with B-cell lymphoma, and to describe ongoing clinical trials with (90)Y ibritumomab tiuxetan in B-cell lymphomas.

Successful treatment of refractory low grade duodenal lymphoma with rituximab, an anti-CD20 monoclonal antibody

Duodenal lymphoma accounts for a small percentage of gastrointestinal tumors and has a very poor prognosis. The majority of patients have little or no cure with limited time of remission. Median survival is 5 to 10 years, and most patients die of lymphoma, its complications, or complications of therapy. We report a patient with lymphoma refractory to treatment with cyclophosphamide, vincristine, and prednisone, who was successfully treated with rituximab, a CD-20 monoclonal antibody.

Monoclonal antibody therapy of non-Hodgkin's lymphoma: the Rituximab story

The advent of monoclonal antibodies targeted at tumor associated or tumor specific antigens provides a novel approach for the treatment of a broad range of malignancies. Such targeting agents can either be used as unlabeled molecules to induced antibody dependent cytotoxicity, or complement mediated lysis and/or apoptosis, or be conjugated with cytotoxic moieties such as toxins and/or radioactive nucleids. The applicability of this strategy has been expanded beyond the treatment of NHL as demonstrated by the clinical application of the chimeric monoclonal antibody directed at the Her2/neu receptor in breast cancer, the epidermal growth factor receptor in colon and head/neck cancer, and the vascular endothelial growth factor in lung and colon cancer, among others. In a variety of settings this strategy demonstrates clinical anti-tumor activity in patients who have failed to respond to or are refractory to conventional cytotoxic chemotherapy. Furthermore, given the modest toxicity of these naked antibodies, they avail themselves as ideal partners for combining with conventional chemotherapy to produce results that often appear to be greater than additive. With the discovery of newer targets and means to manipulate the immunoglobulin molecule to generate tailor made antibody fragments, the field of antibody based targeted therapy of cancer appears to be on the threshold of making major strides in the fight against cancer.