The Rebirth of Radioimmunotherapy of Non-Hodgkin Lymphoma: The Phoenix of Nuclear Medicine?

In Greek mythology, The Phoenix is an immortal bird that dies, but then achieves new life by rising from the ashes of its predecessor. Radioimmunotherapy (RIT) of B-cell Non-Hodgkin lymphoma (NHL) is a field which once began to fly high-with FDA approval of the anti-CD20 RITs Zevalin® and Bexxar® in 2002 and 2003 respectively, as safe and effective therapies of NHL. However, despite their therapeutic efficacy, Bexxar® was withdrawn from the market by the manufacturer in 2014 due to limited commercial demand and Zevalin® has had very limited to no availability of late. I-131 rituximab is used to a limited extent in Australia, India and other countries, as well. But has RIT of NHL been (perhaps prematurely) left for dead by many? Given the current great clinical and commercial interest in radiopharmaceutical therapies of cancer, notably PSMA and SSTR targeting agents in prostate and neuroendocrine cancers, can radioimmunotherapy of NHL-like the mythical Phoenix-now rise from its ashes in an even better form to fly higher, faster, farther and longer than before?

Changing Trends in B-Cell Non-Hodgkin Lymphoma Treatment: The Role of Novel Monoclonal Antibodies in Clinical Practice

We are currently witnessing a dramatic shift in our approach to the treatment of B-cell non-Hodgkin lymphoma (B-NHL). In the evolving clinical landscape, novel treatments for this clinically heterogeneous disease span a wide range of interventions, encompassing targeted agents, cell therapy approaches, and novel monoclonal antibodies (NMABs). Among these, the latter are likely to exert the most profound impact due to their distinctive high efficacy and versatile applicability. NMABs represent a heterogeneous group of agents, including naked antibodies, immunotoxins, and T-cell-engaging molecules. In recent times, several NMABs have either gained regulatory approval or are on the verge of introduction into clinical practice, addressing multiple therapeutic indications and treatment regimens. Their anticipated impact is expected to be broad, initially in the context of relapsed/refractory (R/R) disease and subsequently extending to early treatment lines. The scope of this review is to provide a comprehensive overview of the biological characteristics, clinical properties, efficacy, and toxicity profiles of NMABs that have recently been introduced or are nearing integration into clinical practice.

90Y-ibritumomab Tiuxetan in B-cell Non-Hodgkin Lymphomas: Real-world Data From the United Arab Emirates

Purpose

B-cell non-Hodgkin lymphomas (NHLs) are significant contributors to cancer-related mortality. In this single-arm, retrospective cohort study, we aimed to examine the outcomes of a radioimmunotherapeutic modality, ⁹⁰Y-labeled ibritumomab tiuxetan (⁹⁰YIT) in B-cell NHLs.

Methods and Materials

We conducted this study based on data from the United Arab Emirates lymphoma registry. All patients with NHL subjected to ⁹⁰YIT were eligible for inclusion. The country of research lacked a national autologous stem cell transplantation (ASCT) center, but many ASCT-eligible patients received ⁹⁰YIT. We investigated overall survival (OS) and event-free survival (EFS), as well as safety outcomes.

Results

Between 2004 and 2008, 54 of 111 patients with B-cell NHL received radioimmunotherapy. The therapy was applied as first-line treatment in 18 cases (33.3%) and second- or later-line treatment in 36 cases (66.7%). All patients were evaluable for response. The first-line group consisted mainly of follicular lymphoma cases, and 3 of 18 patients died (16.7%) during the follow-up (range, 22-67 months). Median OS was not reached. No progression occurred after treatment (median EFS, 36.5 months [Q₁-Q₃ range, 30.5-44 months]). The second- or later-line group consisted mainly of diffuse large B-cell lymphoma cases, and 3 of 36 patients died (8.3%) during the follow-up (range, 4-68 months). Median OS was not reached. One case of progression was registered (median EFS: 33 months [Q₁-Q₃ range, 30.5-44 months]). ⁹⁰YIT had acceptable short- and long-term safety profiles.

Conclusions

The findings suggest that patients with NHL may benefit from ⁹⁰YIT as salvage treatment if ASCT is not available; however, this should be validated in randomized studies.

Efficacy and safety of new anti-CD20 monoclonal antibodies versus rituximab for induction therapy of CD20+ B-cell non-Hodgkin lymphomas: a systematic review and meta-analysis

Rituximab combined with chemotherapy is the first-line induction therapy of CD20 positive B-cell non-Hodgkin lymphomas (CD20+ B-NHL). Recently new anti-CD20 monoclonal antibodies (mAbs) have been developed, but their efficacy and safety compared with rituximab are still controversial. We searched MEDLINE, Embase, and Cochrane Library for eligible randomized controlled trials (RCTs) that compared new anti-CD20 mAbs with rituximab in induction therapy of B-NHL. The primary outcomes are progression-free survival (PFS) and overall survival (OS), additional outcomes include event-free survival (EFS), disease-free survival (DFS), overall response rate (ORR), complete response rate (CRR) and incidences of adverse events (AEs). Time-to-event data were pooled as hazard ratios (HRs) using the generic inverse-variance method and dichotomous outcomes were pooled as odds ratios (ORs) using the Mantel-Haenszel method with their respective 95% confidence interval (CI). Eleven RCTs comprising 5261 patients with CD20+ B-NHL were included. Compared with rituximab, obinutuzumab significantly prolonged PFS (HR 0.84, 95% CI 0.73-0.96, P = 0.01), had no improvement on OS, ORR, and CRR, but increased the incidences of serious AEs (OR 1.29, 95% CI 1.13-1.48, P < 0.001). Ofatumumab was inferior to rituximab in consideration of ORR (OR 0.73, 95% CI 0.55-0.96, P = 0.02), and had no significant differences with rituximab in regard to PFS, OS and CRR. 131I-tositumomab yielded similar PFS, OS, ORR and CRR with rituximab. 90Y-ibritumomab tiuxetan increased ORR (OR 3.07, 95% CI 1.47-6.43, P = 0.003), but did not improve PFS, DFS, OS and CRR compared with rituximab. In conclusion, compared with rituximab in induction therapy of CD20+ B-NHL, obinutuzumab significantly improves PFS but with higher incidence of AEs, ofatumumab decreases ORR, 90Y-ibritumomab tiuxetan increases ORR.

ImmunoPET in Multiple Myeloma-What? So What? Now What?

Despite constant progress over the past three decades, multiple myeloma (MM) is still an incurable disease, and the identification of new biomarkers to better select patients and adapt therapy is more relevant than ever. Recently, the introduction of therapeutic monoclonal antibodies (mAbs) (including direct-targeting mAbs and immune checkpoint inhibitors) appears to have changed the paradigm of MM management, emphasizing the opportunity to cure MM patients through an immunotherapeutic approach. In this context, immuno-positron emission tomography (immunoPET), combining the high sensitivity and resolution of a PET camera with the specificity of a radiolabelled mAb, holds the capability to cement this new treatment paradigm for MM patients. It has the potential to non-invasively monitor the distribution of therapeutic antibodies or directly monitor biomarkers on MM cells, and to allow direct observation of potential changes over time and in response to various therapeutic interventions. Tumor response could, in the future, be anticipated more effectively to provide individualized treatment plans tailored to patients according to their unique imaging signatures. This work explores the important role played by immunotherapeutics in the management of MM, and focuses on some of the challenges for this drug class and the significant interest of companion imaging agents such as immunoPET.

Radioimmunotherapy in Non-Hodgkin's Lymphoma: Retrospective Adverse Event Profiling of Zevalin and Bexxar

The development of monoclonal antibodies has dramatically changed the outcome of patients with non-Hodgkin’s lymphoma (NHL), the most common hematological malignancy. However, despite the satisfying results of monoclonal antibody treatment, only few NHL patients are permanently cured with single-agent therapies. In this context, radioimmunotherapy, the administration of radionuclides conjugated to monoclonal antibodies, is aimed to augment the single-agent efficacy of immunotherapy in order to deliver targeted radiation to tumors, particularly CD20+ B-cell lymphomas. Based on evidence from several trials in NHL, the radiolabeled antibodies ⁹⁰Y-ibritumomab tiuxetan (Zevalin, Spectrum Pharmaceuticals) and ¹³¹I-tositumomab (Bexxar, GlaxoSmithKline) received FDA approval in 2002 and 2003, respectively. However, none of the two radioimmunotherapeutic agents has been broadly applied in clinical practice. The main reason for the under-utilization of radioimmunotherapy includes economic and logistic considerations. However, concerns about potential side effects have also been raised. Driven by these developments, we performed retrospective analysis of adverse events reporting Zevalin or Bexxar, extracted from the FDA’s Adverse Event Reporting System (FAERS) and the World Health Organization’s VigiBase repository. Our results indicate that the two radioimmunotherapeutic agents have both related and distinct side effect profiles and confirm their known toxicological considerations. Our work also suggests that computational analysis of real-world post-marketing data can provide informative clinical insights. While more prospective studies are necessary to fully characterize the efficacy and safety of radioimmunotherapy, we expect that it has not yet reached its full therapeutic potential in modern hematological oncology.

Biodistribution and Dosimetry of Indigenously Produced 131I-Rituximab in B-Cell Lymphoma: Pilot Study Estimating Patient-Specific Dose Comparing 2 Different Dosimetric Methods

Cost containment through indigenous production of radioimmunotherapy agents for non-Hodgkin lymphoma (NHL) would be a pivotal step toward wider clinical availability, especially in developing countries. We examined the biodistribution and dosimetry of indigenously developed and radiolabeled ¹³¹I-rituximab, using the monoclonal antibody of chimeric origin, in patients with B-cell lymphoma for potential use in radioimmunotherapy. Methods: This prospective study included 13 patients with B-cell NHL who underwent low-dose diagnostic scanning for dosimetric and biodistribution studies. Soon after rituximab infusion, a diagnostic dose of radioiodinated rituximab was administered. Serial planar whole-body γ-camera images were taken soon afterward and on days 1, 2, 4, and 6. A source of ¹³¹I with known activity was used as a reference standard for dosimetry calculations. Results: The patient-specific administered dose that would give a whole-body absorbed radiation dose of 75 cGy, calculated by the MIRD schema, ranged from 3,095.42 to 6,330.33 MBq (83.66-171.09 mCi), with a mean of 3,986.01 ± 863.95 MBq (107.73 ± 23.35 mCi) and a median of 3,697.41 MBq (99.93 mCi). The mean residence time was 69.54 h. Within the first 48 h at least 50% of the injected activity was cleared, and by 144 h at least 80% was cleared. The patient-specific administered dose that would give a whole-body absorbed radiation dose of 75 cGy, calculated by mean residence time and activity-hours, ranged from 2,654.75 to 6,210.45 MBq (71.75-167.85 mCi), with a mean of 3,576.42 ± 927.59 MBq (96.66 ± 25.07 mCi) and a median of 3,421.02 MBq (92.46 mCi). With respect to organ-specific dosimetry, the mean absorbed doses to organs (apart from blood pool [3.77 Gy] and spleen [4.02 Gy]) were 0.97 Gy to the lungs, 0.69 Gy to the liver, and 0.7 Gy to the kidneys. Conclusion: The indigenous product had kinetics similar to commercial radiopharmaceuticals, with the advantage of a lower human antimouse antibody response because of the pharmaceutical's being a chimeric antibody rather than a murine antibody. Hence, clinical administration was safe. In none of the organs did dose-limiting radiation exposure occur at the proposed therapeutic dose.

90 Y-ibritumomab-tiuxetan as a therapeutic alternative for follicular lymphoma (FL): A single-center experience

BACKGROUND

Follicular lymphoma (FL) is the most frequent indolent lymphoma subtype in adults. Maintenance therapy with rituximab is frequently applied to FL patients with complete or partial response following initial chemoimmunotherapy. However, radioimmunotherapy with ⁹⁰ Y-ibritumomab-tiuxetan represents a therapeutic alternative.

METHODS

To compare the clinical and the prognostic impact of both therapies, a study collective of n = 56 patients diagnosed with indolent B-cell lymphoma was retrospectively investigated. The study collective was subdivided into two groups: n = 36 patients treated with rituximab maintenance therapy vs n = 20 patients treated with ⁹⁰ Y-ibritumomab-tiuxetan.

RESULTS

No prognostic differences for performance status, FLIPI score, gender, or B-symptoms were found for ⁹⁰ Y-ibritumomab-tiuxetan or rituximab maintenance therapy. Overall survival rates and progression-free survival did not differ between both maintenance therapies.

CONCLUSION

Our retrospective single-center analysis of two patient groups without major differences in prognostic parameters revealed similar outcome with two different maintenance therapies. Hence, ⁹⁰ Y-ibritumomab-tiuxetan therapy might offer a valuable alternative treatment option for FL patients with partial response. However, large prospective trials are needed to confirm the reported findings.

Unmet needs in the first-line treatment of follicular lymphoma

For the majority of patients with newly diagnosed follicular lymphoma (FL), current treatments, while not curative, allow for long remission durations. However, several important needs remain unaddressed. Studies have consistently shown that ∼20% of patients with FL experience disease progression within 2 years of first-line treatment, and consequently have a 50% risk of death in 5 years. Better characterization of this group of patients at diagnosis may provide insight into those in need of alternate or intensive therapies, facilitate a precision approach to inform clinical trials, and allow for improved patient counseling. Prognostic methods to date have employed clinical parameters, genomic methods, and a wide assortment of biological and biochemical markers, but none so far has been able to adequately identify this high-risk population. Advances in the first-line treatment of FL with chemoimmunotherapy have led to a median progression-free survival (PFS) of approximately 7 years; creating a challenge in the development of clinical trials where PFS is a primary end point. A surrogate end point that accurately predicts PFS would allow for new treatments to reach patients with FL sooner, or lessen toxicity, time, and expense to those patients requiring little to no therapy. Quality of response to treatment may predict PFS and overall survival in FL; as such complete response rates, either alone or in conjunction with PET imaging or minimal residual disease negativity, are being studied as surrogates, with complete response at 30 months after induction providing the strongest surrogacy evidence to date. A better understanding of how to optimize quality of life in the context of this chronic illness is another important focus deserving of further study. Ongoing efforts to address these important unmet needs are herein discussed.

Radionuclides in oncology clinical practice – review of the literature

Radionuclide therapy is a promising type of targeted therapy for cancer and its use is becoming more common in several types of malignant tumors.

Safety and efficacy of radioimmunotherapy (RIT) in treatment of non-Hodgkin's lymphoma in the community setting

INTRODUCTION

Radioimmunotherapy (RIT) is a unique therapeutic modality that combines biologic and radiolytic mechanisms to induce tumor kill. RIT is underutilized in the community outpatient setting.

METHODS

This is an institutional review of patients treated with RIT at St. John Hospital and Medical Center (SJH&MC) 2003-2011. RIT agents were dosed according to recommended guidelines. Response was assessed using the Revised Response Criteria for Malignant Lymphoma and toxicity was assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events. The primary aim was to assess overall response rate (ORR) and overall survival (OS). The secondary aim was to assess the impact of variable host and disease factors on the ORR to RIT and OS.

RESULTS

Forty-eight patients were treated with RIT within the specified period at SJH&MC; of which 52% with follicular lymphoma (FL) and 46% with diffuse large B cell lymphoma (DLBCL). The majority of patients had relapsed or refractory disease (98%). Median duration of follow-up was 17 months. The ORR was 73% with 44% complete remission (CR) rate and OS of 48 months. The ORR was 79% with 58% CR rate and OS of 82 months among FL patients. Among DLBCL patients, the ORR was 65% with 30% CR rate and OS of 39 months. Response to last therapy before RIT was the only significant predictor of response to RIT and a significant predictor of OS in multivariate analyses. Prior exposure to EBRT did not predict response or survival in multivariate analyses. Toxicity was manageable and predominantly hematologic.

CONCLUSIONS

RIT is effective and feasible for use in the community outpatient setting.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Patients with B-cell NHL can safely receive RIT close to home. With some coordination of effort, it is not difficult for community-based cancer centers to implement this treatment modality.

Are we nearing an era of chemotherapy-free management of indolent lymphoma?

Indolent B-cell lymphomas are heterogeneous, comprising three grades of follicular lymphoma, small lymphocytic lymphoma, Waldenstöm macroglobulinemia, marginal zone lymphoma, and most recently, possibly low proliferative mantle cell lymphoma. These lymphomas are characterized by a high responsiveness to chemotherapy or immunochemotherapy; however, in most cases, conventional therapy might not offer a cure. Furthermore, the patient's age at diagnosis, at time to first or subsequent relapses, as well as potential comorbidities often preclude the use of chemotherapy. Recent progress has been made in our understanding of dysregulated pathways and immunologic antitumor responses in indolent lymphoma. Major therapeutic advances have been achieved in the development of nonchemotherapeutic agents, making "chemo-free" treatment a near-future reality. In this article, we highlight these promising approaches, such as the combination of anti-CD20 antibodies with immunomodulatory drugs, with mAbs directed against other surface antigens such as CD22, with immunomodulatory antibodies such as PD-1, or with inhibitors of key steps in the B-cell receptor pathway signaling. However, the cost of such therapies and potential, albeit manageable, toxicity should be considered. Phase III trials will confirm the benefit of these new treatment strategies that do not require a chemotherapeutic drug and help us identify their exact place in the therapeutic armamentarium for indolent lymphoma. Here we focus on follicular lymphoma, which is the most frequent subtype of indolent lymphoma and for which an increasing body of evidence has emerged that supports the dawn of a new era of chemotherapy-free treatment. See all articles in this CCR Focus section, "Paradigm Shifts in Lymphoma."

Comparing the cost-effectiveness of rituximab maintenance and radioimmunotherapy consolidation versus observation following first-line therapy in patients with follicular lymphoma

BACKGROUND

Phase 3 randomized trials have shown that maintenance rituximab (MR) therapy or radioimmunotherapy (RIT) consolidation following frontline therapy can improve progression-free survival for patients with follicular lymphoma (FL), but the cost-effectiveness of these approaches with respect to observation has not been examined using a common modeling framework.

OBJECTIVES

To evaluate and compare the economic impact of MR and RIT consolidation versus observation, respectively, following the first-line induction therapy for patients with advanced-stage FL.

METHODS

We developed Markov models to estimate patients' lifetime costs, quality-adjusted life-years (QALYs), and life-years (LYs) after MR, RIT, and observation following frontline FL treatment from the US payer's perspective. Progression risks, adverse event probabilities, costs, and utilities were estimated from clinical data of Primary RItuximab and MAintenance (PRIMA) trial, Eastern Cooperative Oncology Group (ECOG) trial (for MR), and First-line Indolent Trial (for RIT) and the published literature. We evaluated the incremental cost-effectiveness ratio for direct comparisons between MR/RIT and observation. Model robustness was addressed by one-way and probabilistic sensitivity analyses.

RESULTS

Compared with observation, MR provided an additional 1.089 QALYs (1.099 LYs) and 1.399 QALYs (1.391 LYs) on the basis of the PRIMA trial and the ECOG trial, respectively, and RIT provided an additional 1.026 QALYs (1.034 LYs). The incremental cost per QALY gained was $40,335 (PRIMA) or $37,412 (ECOG) for MR and $40,851 for RIT. MR and RIT had comparable incremental QALYs before first progression, whereas RIT had higher incremental costs of adverse events due to higher incidences of cytopenias.

CONCLUSIONS

MR and RIT following frontline FL therapy demonstrated favorable and similar cost-effectiveness profiles. The model results should be interpreted within the specific clinical settings of each trial. Selection of MR, RIT, or observation should be based on patient characteristics and expected trade-offs for these alternatives.

Role of consolidation with yttrium-90 ibritumomab tiuxetan in patients with advanced-stage follicular lymphoma

Non-Hodgkin's lymphoma (NHL) accounts for 4% of all cancers diagnosed in the United States. Follicular lymphoma (FL) is the most common type of indolent NHL with a survival from 5 to 15 years. Although it is very sensitive to chemotherapy and radiotherapy, relapses are the main cause of therapeutic failure, and currently there is no consensus on the first-line treatment and optimal therapeutic strategies for patients with FL. Immediate treatment offers any survival benefit for asymptomatic and more indolent disease. In order to improve outcomes in FL, extend the remission, postpone the need for chemotherapy and improve OS, maintenance therapies with rituximab and consolidation treatments represent very attractive strategies. (90)Y-ibritumomab tiuxetan ((90)Y-IT, Zevalin®) is approval as consolidation therapy in previously untreated FL patients who achieve response to first-line chemotherapy. Consolidation therapy with (90)Y-IT after initial induction treatment has shown improved activity compared with induction chemotherapy alone, even in patients previously treated with rituximab, in one phase III and several phase II trials, improving progression-free survival (PFS) and rate of conversion from partial response (PR) to complete response (CR). The phase III international FIT trial shows an improvement in PFS that is maintained after a median follow up of 7.3 years. Several phase II trials show high rate of conversion from PR to CR and a significant improvement in PFS. Treatment is feasible and well tolerated although myelodysplastic syndrome cases has been observed in some trials. (90)Y-IT should be considered for the initial treatment of FL in patients who are unable to tolerate standard chemotherapy, e.g., elderly or frail patients and otherwise in high-risk patients who achieve a PR or CR due to improvements in CR rate and PFS.

Myeloablative anti-CD20 radioimmunotherapy +/- high-dose chemotherapy followed by autologous stem cell support for relapsed/refractory B-cell lymphoma results in excellent long-term survival

Background

Radioimmunotherapy (RIT) has been used to treat relapsed/refractory CD20+ Non-Hodgkin lymphoma (NHL). Myeloablative anti-CD20 RIT followed by autologous stem cell infusion (ASCT) enables high radiation doses to lymphoma sites. We performed a phase I/II trial to assess feasibility and survival.

Methods

Twenty-three patients with relapsed/refractory NHL without complete remission (CR) to salvage chemotherapy were enrolled to evaluate RIT with Iodine-131 labelled rituximab (¹³¹I-rituximab) in a myeloablative setting. Biodistribution and dosimetric studies were performed to determine ¹³¹I activity required to induce a total body dose of 21-27Gy to critical organs. In 6/23 patients RIT was combined with high-dose chemotherapy. 8/23 patients received a sequential high-dose chemotherapy with a second ASCT. The median follow-up is 9.5 years.

Results

6.956-19.425GBq of ¹³¹I was delivered to achieve the limiting organ dose to lungs or kidneys. No grade III/IV non-hematologic toxicity was seen with RIT alone. Significant grade III/IV toxicity (mucositis, fever, infection, one therapy related death) was observed in patients treated with RIT combined with high-dose chemotherapy. The overall response rate was 87% (64% CR). The median progression-free (PFS) and overall survival (OS) is 47.5 and 101.5 months. An international prognostic index score >1 was predictive for OS.

Conclusion

Myeloablative RIT with ¹³¹I-rituximab followed by ASCT is feasible, well-tolerated and effective in high risk CD20+ NHL. Combination of RIT and high-dose chemotherapy increased toxicity significantly. Long-term results for PFS and OS are encouraging.

Radioimmunotherapy for first-line and relapse treatment of aggressive B-cell non-Hodgkin lymphoma: an analysis of 215 patients registered in the international RIT-Network

PURPOSE

Very few reliable clinical data about the use of radioimmunotherapy in aggressive B-cell lymphoma exist.

METHODS

Patients with aggressive B-cell lymphoma registered in the international RIT-Network were analysed with regard to prior treatment, response and side effects. The RIT-Network is a web-based registry that collects observational data from radioimmunotherapy-treated patients with malignant lymphoma across 13 countries.

RESULTS

This analysis included 215 with aggressive B-cell lymphoma out of 232 patients registered in the RIT-Network. Histological subtypes were as follows: 190 diffuse large B-cell, 15 primary mediastinal, 9 anaplastic large cell, and 1 intravascular lymphoma. The median age of the patients was 62 years (range 17 - 88), with 27% above the age of 70 years. Radioimmunotherapy was mainly used as consolidation after first-line or second-line chemotherapy (56.1%), as part of third-line to eighth-line therapy for relapse (16.4%), and in refractory disease (12.2%). Grade IV neutropenia and thrombopenia and grade III anaemia were observed. The median time to recovery of blood count was 81 days (range 0 - 600 days). The overall response rate was 63.3%. The complete response rate was 76.4 % in patients treated as part of first-line therapy, and 44.3% in patients with relapse. Mean overall survival in first-line therapy patients was 32.7 months and 14.0 months in patients with relapse or refractory disease, respectively.

CONCLUSION

Most patients with aggressive B-cell lymphoma in the RIT-Network received radioimmunotherapy as consolidation after first-line therapy with excellent complete remission and overall survival rates compared to published data. In relapsed aggressive B-cell lymphoma, radioimmunotherapy is a safe and feasible treatment leading to satisfactory response rates with acceptable toxicity.

Radioimmunotherapy of B-Cell Non-Hodgkin's Lymphoma

This manuscript reviews current advances in the use of radioimmunotherapy (RIT) for the treatment of B-cell non-Hodgkin's lymphoma (NHL). RIT has been in use for more than 20 years and has progressed significantly with the discovery of new molecular targets, the development of new stable chelates, the humanization of monoclonal antibodies (MAbs), and the use of pretargeting techniques. Today, two products targeting the CD20 antigen are approved: (131)I-tositumomab (Bexxar(®)), and (90)Y-ibritumomab tiuxetan (Zevalin(®)). (131)I-tositumomab is available in the United States, and (90)Y-ibritumumab tiuxetan in Europe, the United States, Asia, and Africa. RIT can be integrated in clinical practice using non-ablative activities for treatment of patients with relapsed or refractory follicular lymphoma (FL) or as consolidation after induction chemotherapy in front-line treatment in FL patients. Despite the lack of phase III studies to clearly define the efficacy of RIT in the management of B lymphoma in the era of rituximab-based therapy, RIT efficacy in NHL has been demonstrated. In relapsing refractory FL and transformed NHL, RIT as a monotherapy induces around 30% complete response with a possibility of durable remissions. RIT consolidation after induction therapy significantly improves the quality of the response. Dose-limiting toxicity of RIT is hematological, depending on bone marrow involvement and prior treatment. Non-hematological toxicity is generally low. Different studies have been published assessing innovative protocols of RIT or new indications, in particular treatment in patients with aggressive lymphomas. High-dose treatment, RIT as consolidation after different therapeutic induction modalities, RIT in first-line treatment or fractionated RIT showed promising results. New MAbs, in particular humanized MAbs, or combinations of naked and radiolabeled MAbs, also appear promising. Personalized dosimetry protocols should be developed to determine injected activity.

Assessment of acquisition protocols for routine imaging of Y-90 using PET/CT

BACKGROUND

Despite the early theoretical prediction of the 0+-0+ transition of 90Zr, 90Y-PET underwent only recently a growing interest for the development of imaging radioembolization of liver tumors. The aim of this work was to determine the minimum detectable activity (MDA) of 90Y by PET imaging and the impact of time-of-flight (TOF) reconstruction on detectability and quantitative accuracy according to the lesion size.

METHODS

The study was conducted using a Siemens Biograph® mCT with a 22 cm large axial field of view. An IEC torso-shaped phantom containing five coplanar spheres was uniformly filled to achieve sphere-to-background ratios of 40:1. The phantom was imaged nine times in 14 days over 30 min. Sinograms were reconstructed with and without TOF information. A contrast-to-noise ratio (CNR) index was calculated using the Rose criterion, taking partial volume effects into account. The impact of reconstruction parameters on quantification accuracy, detectability, and spatial localization of the signal was investigated. Finally, six patients with hepatocellular carcinoma and four patients included in different 90Y-based radioimmunotherapy protocols were enrolled for the evaluation of the imaging parameters in a clinical situation.

RESULTS

The highest CNR was achieved with one iteration for both TOF and non-TOF reconstructions. The MDA, however, was found to be lower with TOF than with non-TOF reconstruction. There was no gain by adding TOF information in terms of CNR for concentrations higher than 2 to 3 MBq mL-1, except for infra-centimetric lesions. Recovered activity was highly underestimated when a single iteration or non-TOF reconstruction was used (10% to 150% less depending on the lesion size). The MDA was estimated at 1 MBq mL-1 for a TOF reconstruction and infra-centimetric lesions. Images from patients treated with microspheres were clinically relevant, unlike those of patients who received systemic injections of 90Y.

CONCLUSIONS

Only one iteration and TOF were necessary to achieve an MDA around 1 MBq mL-1 and the most accurate localization of lesions. For precise quantification, at least three iterations gave the best performance, using TOF reconstruction and keeping an MDA of roughly 1 MBq mL-1. One and three iterations were mandatory to prevent false positive results for quantitative analysis of clinical data.

TRIAL REGISTRATION

http://IDRCB 2011-A00043-38 P101103.

RIT with Y90-Ibritumomab Tiuxetan in Follicular Non-Hodgkin Lymphoma: Evaluation of Recent Outcomes in a Single Institution

Background. Based on historical data we reviewed our hospital clinical database to analyse our updated information and therapy outcomes of follicular non-Hodgkin lymphoma (F-NHL) patients treated with ⁹⁰Y-Ibritumomab tiuxetan. Patients and Methods. Between 2005 and 2011, 56 F-NHL patients were included in a clinical protocol conducted by a multidisciplinary team and treated in the same centre. All patients received 0.3 or 0.4 mCi/kg IV (88%) of ⁹⁰Y-IT; response evaluation was performed 12 weeks after. Results. M/F 44.6%/55.4%, mean age 61.45 years (30–85); ECOG 0-1 96.9%. According to FLIPI score, distribution were good: 58.5%, intermediate: 29.2%, and poor: 12.3%. Previous therapies: >2: 40% (26). ORR was 94.6% (53/56). CR: 85.7%; CR according to previous disease: relapsed disease: 90% (27/30), refractory disease: 42.85% (3/7), consolidation with CR: 92.85% (13/14), and consolidation with PR: 100% (5/5). Global PR and NR were 8.9% (5) and 5.3% (3), respectively. Mean OS 63.86 months with a mean follow-up time of 57 months (2–73). Mean TTP: 52.65 months (95% CI: 43.83–61.48). Median OS and TTP were not achieved. No hospital submissions or deaths were registered. Conclusions. This study confirms the safety and high efficacy of ⁹⁰Y-IT in F-NHL patients, RIT in early stage of disease could improve outcomes.

Radioimmunotherapy in non-Hodgkin lymphoma: opinions of nuclear medicine physicians and radiation oncologists

Despite approval by the Food and Drug Administration and consistent reports of the efficacy and safety of (90)Y-ibritumomab tiuxetan and (131)I-tositumomab, these therapies are infrequently used. This study investigates the opinions and patterns of the use of radioimmunotherapy by nuclear physicians, affiliated researchers, nuclear medicine technologists, and radiation oncologists and aims to identify possible barriers to the use of this promising therapy.

METHODS

An e-mail-based survey with 13 broad questions related to radioimmunotherapy was sent electronically to 13,221 Society of Nuclear Medicine members and radiation oncologists throughout the United States.

RESULTS

Six hundred thirteen individuals (4.6%) responded to the electronic survey. Two hundred fifty-one responders (40.9%) had treated patients with non-Hodgkin lymphoma (NHL) with radioimmunotherapy in the last 24 mo. Of the responders, 29.5% used only (90)Y-ibritumomab tiuxetan, 7.6% used only (131)I-tositumomab, and 24.9% used both radiopharmaceuticals; 37.9% did not treat NHL with radioimmunotherapy. Most responders said their patients came from university hospitals (33.9%) or private offices (25.6%), and they mainly treated in a second-line (42.9%), third-line (35.6%), or consolidation (23.5%) setting. Major concerns were that referring oncologists and hematologists wanted to treat by themselves with nonradioactive compounds (mean ± SD, 3.418 ± 1.49) and that (90)Y-ibritumomab tiuxetan and (131)I-tositumomab were expensive (mean ± SD, 3.413 ± 1.35). Of the responders and involved physicians, 40.4% and 35.2%, respectively, did not know if their institution accepted Medicare patients for radioimmunotherapy. Almost 30% (29.6%) of the responders thought radioimmunotherapy would probably grow and 38.0% thought it would grow in importance in the future. Responders who did not administer radioimmunotherapy for NHL thought it took too much time to administer radioimmunotherapy (P < 0.01) and had concerns about the dosimetry procedure (P < 0.01) and radiation safety (P < 0.01). Individuals who perceived a negative future for radioimmunotherapy had significantly more concerns about the time-consuming administration process (P < 0.05) and the high cost of radioimmunotherapy (P < 0.05). Responders from academic centers had significantly fewer concerns about payment (P < 0.01), dosimetry (P < 0.01), and radiation safety (P < 0.01).

CONCLUSION

Radioimmunotherapy was generally viewed positively by the surveyed population. However, limited referrals due to alternative nonradioactive therapies and logistic, educational, and economic concerns played an important role for subgroups in the perception of radioimmunotherapy for NHL.

Radioimmunotherapy consolidation and rituximab maintenance in the initial treatment of follicular lymphoma

Several reports have documented similar efficacies and tolerable toxicities of radioimmunotherapy (RIT) consolidation and rituximab maintenance after initial R-chemotherapy of follicular lymphoma. The relative merits of these two interventions are currently under discussion. We now raise the question whether both RIT consolidation and rituximab maintenance should be used together aiming to augment the results achievable with R-chemotherapy.

Outcomes of patients with non-Hodgkin's lymphoma treated with Bexxar with or without external-beam radiotherapy

PURPOSE

To compare the efficacy and toxicity of external-beam radiotherapy (EBRT) to sites of bulky lymphadenopathy in patients with chemotherapy-refractory low-grade non-Hodgkin's lymphoma (NHL) immediately before receiving Bexxar (tositumomab and (131)I) vs. in patients receiving Bexxar alone for nonbulky disease.

METHODS AND MATERIALS

Nineteen patients with chemotherapy-refractory NHL were treated with Bexxar at our institution (University of Florida, Gainesville, FL) from 2005 to 2008. Seventeen patients had Grade 1-2 follicular lymphoma. Ten patients received a median of 20 Gy in 10 fractions to the areas of clinical involvement, immediately followed by Bexxar (EBRT + Bexxar); 9 patients received Bexxar alone. The median tumor sizes before EBRT + Bexxar and Bexxar alone were 4.8 cm and 3.3 cm, respectively. All 5 patients with a tumor diameter >5 cm were treated with EBRT + Bexxar. A univariate analysis of prognostic factors for progression-free survival (PFS) was performed.

RESULTS

The median follow-up was 2.3 years for all patients and 3.1 years for 12 patients alive at last follow-up. Of all patients, 79% had a partial or complete response; 4 of the 8 responders in the EBRT + Bexxar group achieved a durable response of over 2 years, including 3 of the 5 with tumors >5 cm. Three of 9 patients treated with Bexxar alone achieved a durable response over 2 years. Actuarial estimates of 3-year overall survival and PFS for EBRT + Bexxar and Bexxar alone were 69% and 38% and 62% and 33%, respectively. The median time to recurrence after EBRT + Bexxar and Bexxar alone was 9 months. Having fewer than 4 involved lymph-node regions was associated with superior PFS at 3 years (63% vs. 18%). There was no Grade 4 or 5 complications.

CONCLUSIONS

Adding EBRT immediately before Bexxar produced PFS equivalent to that with Bexxar alone, despite bulkier disease. Hematologic toxicity was not worsened. EBRT combined with Bexxar adds a safe and effective therapeutic treatment for managing recurrent low-grade follicular NHL.

New antibody drug treatments for lymphoma

INTRODUCTION

The advent of anti-CD20 monoclonal antibody (mAb) rituximab heralded a new era in the treatment of non-Hodgkin's lymphoma leading to significant improvements in outcome for patients. This unprecedented success has changed the mindset of the clinical community and catalyzed the interest in the pharmaceutical industry to develop the next-generation of antibodies and antibody conjugates in cancer.

AREAS COVERED

There are an ever increasing number of newer generation anti-CD20 and rituximab 'bio-similars' undergoing early phase clinical development. In addition emerging novel therapies including antibody drug conjugates (brentuximab vedotin, SGN-35) and mAb against T-cell lymphomas antigens (e.g., zanolimumab) offer hope of improved outcome for other lymphomas. Bispecific T-cell-engaging antibodies and combination immunotherapy, also provide the promise of further improvements. Radiolabelled antibodies or radioimmunotherapy (RIT) has also demonstrated high clinical activity and two drugs namely 131I-tositumomab (Bexxar) and 90Y-ibritumomab (Zevalin) are licensed.

EXPERT OPINION

Despite the large numbers of new anti-CD20 mAb currently undergoing clinical testing, improving on clinical efficacy of rituximab is a substantial challenge. Further improvements in outcome for patients will require rigorous testing in well designed clinical trials alongside the translation of new insights into mechanism of mAb action that lead to improvements in clinical efficacy.

Radioimmunotherapy of relapsed indolent non-Hodgkin lymphoma with 131I-rituximab in routine clinical practice: 10-year single-institution experience of 142 consecutive patients

Radioimmunotherapy of indolent non-Hodgkin lymphoma (NHL) has achieved objective response rates in clinical trials comparable with standard rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy, but is relatively underused in routine practice. In this article, we report our clinical experience in 142 consecutive patients who received iodine-131 rituximab radioimmunotherapy for low-grade, predominantly follicular, relapsed NHL. Objective response rates of 67%, with complete response (CR) in 50% and median overall survival of 32 months, matched the response rates in a phase 2 clinical trial of 131I-rituximab radioimmunotherapy and compares favorably with those reported for 131I-tositumomab or 90Y-ibritumomab tiuxetan. Progression-free survival was 18 months overall and 32 months in CR or CR-unconfirmed patients. Our patients comprised 107 (75%) follicular lymphoma, 21 (15%) small lymphocytic lymphoma, 6 (4%) mucosa-associated lymphoid tissue/marginal zone lymphoma, and 8 (6%) mantle-cell lymphoma, with median follow-up of 32 months and 8-year overall survival of 48%. Toxicity was limited to hematologic grade 4 neutropenia, occurring in 10% and thrombocytopenia in 6%. There were no episodes of bleeding or infection requiring hospital admission. Radioimmunotherapy with 131I-rituximab in routine clinical outpatient practice provides cost-effective, safe treatment of relapsed/refractory indolent NHL, with half of patients achieving durable, complete remission with potential for repeat radioimmunotherapy on relapse.