Yttrium-90 ibritumomab tiuxetan doses calculated to deliver up to 15 Gy to critical organs may be safely combined with high-dose BEAM and autologous transplantation in relapsed or refractory B-cell non-Hodgkin's lymphoma

Radioligand Therapy in Lymphoma: Past, Present, and Future

In the1980s, radiolabeled cells helped understand the pathology of hemato-oncology. In the 1990s, preclinical trials evaluated radiolabeled immunotherapy with monoclonal antibodies (MoAbs) such as anti-CD20 agents labeled with Iodine-131 (Bexxar) or Yttrium-90 (Zevalin). Due to the safe and durable responses of radiolabeled MoAbs, the Food and Drug Administration approved these agents in the 2000s. Despite radioimmunotherapy's long journey, its application has recently decreased. This review will discuss the historical timeline of radioimmunotherapy, debate on advantages and difficulties, and explore trials. We will examine future directions of radioligand therapy in hemato-oncology, considering emerging molecules that may become the next theragnostic trend.

Dosimetric Approaches for Radioimmunotherapy of Non-Hodgkin Lymphoma in Myeloablative Setting

Radioimmunotherapy (RIT) is a safe and active treatment available for non-Hodgkin lymphomas (NHLs). In particular, two monoclonal antibodies raised against CD20, that is Zevalin (⁹⁰Y-ibritumomab-tiuxetan) and Bexxar (¹³¹I-tositumomab) received FDA approval for the treatment of relapsing/refractory indolent or transformed NHLs. RIT is likely the most effective and least toxic anticancer agent in NHLs. However, its use in the clinical setting is still debated and, in case of relapse after optimized rituximab-containing regimens, the efficacy of RIT at standard dosage is suboptimal. Thus, clinical trials were based on the hypothesis that the inclusion of RIT in myeloablative conditioning would allow to obtain improved efficacy and toxicity profiles when compared to myeloablative total-body irradiation and/or high-dose chemotherapy regimens. Standard-activity RIT has a safe toxicity profile, and the utility of pretherapeutic dosimetry in this setting can be disputed. In contrast, dose-escalation clinical protocols require the assessment of radiopharmaceutical biodistribution and dosimetry before the therapeutic injection, as dose constrains for critical organs may be exceeded when RIT is administered at high activities. The aim of the present study was to review and discuss the internal dosimetry protocols that were adopted for non-standard RIT administration in the myeloablative setting before hematopoietic stem cell transplantation in patients with NHLs.

Anti-CD25 radioimmunotherapy with BEAM autologous hematopoietic cell transplantation conditioning in Hodgkin lymphoma

High-risk relapsed or refractory (R/R) classical Hodgkin lymphoma (HL) is associated with poor outcomes after conventional salvage therapy and autologous hematopoietic cell transplantation (AHCT). Post-AHCT consolidation with brentuximab vedotin (BV) improves progression-free survival (PFS), but with increasing use of BV early in the treatment course, the utility of consolidation is unclear. CD25 is often expressed on Reed-Sternberg cells and in the tumor microenvironment in HL, and we hypothesized that the addition of 90Y-antiCD25 (aTac) to carmustine, etoposide, cytarabine, melphalan (BEAM) AHCT would be safe and result in a transplantation platform that is agnostic to prior HL-directed therapy. Twenty-five patients with high-risk R/R HL were enrolled in this phase 1 dose-escalation trial of aTac-BEAM. Following an imaging dose of 111In-antiCD25, 2 patients had altered biodistribution, and a third developed an unrelated catheter-associated bacteremia; therefore, 22 patients ultimately received therapeutic 90Y-aTac-BEAM AHCT. No dose-limiting toxicities were observed, and 0.6 mCi/kg was deemed the recommended phase 2 dose, the dose at which the heart wall would not receive >2500 cGy. Toxicities and time to engraftment were similar to those observed with standard AHCT, though 95% of patients developed stomatitis (all grade 1-2 per Bearman toxicity scale). Seven relapses (32%) were observed, most commonly in patients with ≥3 risk factors. The estimated 5-year PFS and overall survival probabilities among 22 evaluable patients were 68% and 95%, respectively, and non-relapse mortality was 0%. aTac-BEAM AHCT was tolerable in patients with high-risk R/R HL, and we are further evaluating the efficacy of this approach in a phase 2 trial. This trial was registered at www.clinicaltrials.gov as #NCT01476839.

Dosimetry in Clinical Radiopharmaceutical Therapy of Cancer: Practicality Versus Perfection in Current Practice

The use of radiopharmaceutical therapies (RPTs) in the treatment of cancers is growing rapidly, with more agents becoming available for clinical use in last few years and many new RPTs being in development. Dosimetry assessment is critical for personalized RPT, insofar as administered activity should be assessed and optimized in order to maximize tumor-absorbed dose while keeping normal organs within defined safe dosages. However, many current clinical RPTs do not require patient-specific dosimetry based on current Food and Drug Administration-labeled approvals, and overall, dosimetry for RPT in clinical practice and trials is highly varied and underutilized. Several factors impede rigorous use of dosimetry, as compared with the more convenient and less resource-intensive practice of empiric dosing. We review various approaches to applying dosimetry for the assessment of activity in RPT and key clinical trials, the extent of dosimetry use, the relative pros and cons of dosimetry-based versus fixed activity, and practical limiting factors pertaining to current clinical practice.

Prospective SPECT-CT Organ Dosimetry-Driven Radiation-Absorbed Dose Escalation Using the In-111 (111In)/Yttrium 90 (90Y) Ibritumomab Tiuxetan (Zevalin®) Theranostic Pair in Patients with Lymphoma at Myeloablative Dose Levels

Simple Summary

We prospectively evaluated the feasibility of SPECT-CT/planar organ dosimetry-based radiation dose escalation radioimmunotherapy in patients with recurrent non-Hodgkin’s lymphoma using the theranostic pair of ¹¹¹In and ⁹⁰Y anti-CD20 ibritumomab tiuxetan (Zevalin^®) at myeloablative radiation-absorbed doses with autologous stem cell support. Unlike most routine dose escalation approaches, our approach used patient-individualized measurements of organ radiation absorbed dose from the tracer study, with patient-specific adjustments of the injected therapy dose to deliver a pre-specified radiation absorbed dose to the liver. Our approach was feasible, stem cell engraftment was swift, resulted in an 89% tumor response rate in treated patients, demonstrated over 3 fold variability in liver dosimetry/injected activity among patients, allowed us to exceed the FDA approved administered activity by over 5 fold and demonstrated the normal liver maximum tolerated dose to exceed 28 Gy. Dose escalation was not continued due to lack of drug availability. With modern dosimetry approaches, patient specific dosimetry-driven radiation dose escalation is feasible, allows adjustment of administered activity for heterogeneous pharmacokinetics and allows marked dose escalation vs. non-dosimetry driven approaches.

Abstract

Purpose: We prospectively evaluated the feasibility of SPECT-CT/planar organ dosimetry-based radiation dose escalation radioimmunotherapy in patients with recurrent non-Hodgkin’s lymphoma using the theranostic pair of ¹¹¹In and ⁹⁰Y anti-CD20 ibritumomab tiuxetan (Zevalin^®) at myeloablative radiation-absorbed doses with autologous stem cell support. We also assessed acute non-hematopoietic toxicity and early tumor response in this two-center outpatient study. Methods: 24 patients with CD20-positive relapsed or refractory rituximab-sensitive, low-grade, mantle cell, or diffuse large-cell NHL, with normal organ function, platelet counts > 75,000/mm³, and <35% tumor involvement in the marrow were treated with Rituximab (375 mg/m²) weekly for 4 consecutive weeks, then one dose of cyclophosphamide 2.5 g/m² with filgrastim 10 mcg/kg/day until stem cell collection. Of these, 18 patients with successful stem cell collection (at least 2 × 10⁶ CD34 cells/kg) proceeded to RIT. A dosimetric administration of ¹¹¹In ibritumomab tiuxetan (185 MBq) followed by five sequential quantitative planar and one SPECT/CT scan was used to determine predicted organ radiation-absorbed dose. Two weeks later, ⁹⁰Y ibritumomab tiuxetan was administered in an outpatient setting at a cohort- and patient-specific predicted organ radiation-absorbed dose guided by a Continuous Response Assessment (CRM) methodology with the following cohorts for dose escalation: 14.8 MBq/kg, and targeted 18, 24, 28, and 30.5 Gy to the liver. Autologous stem cell infusion occurred when the estimated marrow radiation-absorbed dose rate was predicted to be <1 cGy/h. Feasibility, short-term toxicities, and tumor response were assessed. Results: Patient-specific hybrid SPECT/CT + planar organ dosimetry was feasible in all 18 cases and used to determine the patient-specific therapeutic dose and guide dose escalation (26.8 ± 7.3 MBq/kg (mean), 26.3 MBq/kg (median) of ⁹⁰Y (range: 12.1–41.4 MBq/kg)) of ibritumomab tiuxetan that was required to deliver 10 Gy to the liver. Infused stem cells engrafted rapidly. The most common treatment-related toxicities were hematological and were reversible following stem cell infusion. No significant hepatotoxicity was seen. One patient died from probable treatment-related causes—pneumonia at day 27 post-transplant. One patient at dose level 18 Gy developed myelodysplastic syndrome (MDS), 4 patients required admission post-⁹⁰Y RIT for febrile neutropenia, 16/18 patients receiving ⁹⁰Y ibritumomab tiuxetan (89%) responded to the therapy, with 13 CR (72%) and 3/18 PR (17%), at 60 days post-treatment. Two patients had progressive disease at sixty days. One patient was lost to follow-up. Median time to progression was estimated to be at least 13 months. MTD to the liver is greater than 28 Gy, but the MTD was not reached as the study was terminated due to unexpected discontinuation of availability of the therapeutic agent. Conclusions: Patient-specific outpatient ⁹⁰Y ibritumomab tiuxetan RIT with myeloablative doses of RIT up to a targeted 30.5 Gy to the liver is feasible, guided by prospective SPECT/CT + planar imaging with the theranostic pair of ¹¹¹In and ⁹⁰Y anti-CD20, with outpatient autologous stem cell transplant support. Administered activity over 5 times the standard FDA-approved activity was well-tolerated. The non-hematopoietic MTD in this study exceeds 28 Gy to the liver. Initial tumor responses were common at all dose levels. This study supports the feasibility of organ dosimetry-driven patient-specific dose escalation in the treatment of NHL with stem cell transplant and provides additional information on the radiation tolerance of the normal liver to radiopharmaceutical therapy.

Astatine-211 labelled a small molecule peptide: specific cell killing in vitro and targeted therapy in a nude-mouse model

Extensive interest in the development of α-emitting radionuclides astatine-211 (211At) stems from the potential superiority for the treatment of smaller tumors, disseminated disease, and metastatic disease. VP2, a small molecule fusion peptide, can specifically bind to the VPAC1 receptor which is over-expressed in malignant epithelial tumors. In our recent study, we performed the preparation of 211At labelled VP2 through a one-step method. In this work, we explored the targeted radionuclide therapy with [211At]At-SPC-VP2 in vitro and in vivo. The cytotoxicity and specific cell killing of [211At]At-SPC-VP2 were evaluated using the CCK-8 assay. Compared with the [211At]NaAt, the VPAC1-targeted radionuclide compound [211At]At-SPC-VP2 showed more effective cytotoxicity in vitro. Targeted radioactive therapy trial was carried out in non-small-cell lung cancer (NSCLC) xenograft mice. For the therapy experiment, 4 groups of mice were injected via the tail vein with 370 kBq, 550 kBq, 740 kBq, 3 × ∼246 kBq of [211At]At-SPC-VP2, of which the second and third injections were given 4 and 8 days after the first injection, respectively. As controls, animals were treated with saline or 550 kBq [211At]NaAt. The body weight and tumor size of mice were monitored before the administration and every 2 days thereafter. Cytotoxic radiation of partial tissue samples such as kidneys, liver and stomach of mice were assessed by immunohistochemical examination. The tumor growth was inhibited and significantly improved survival was achieved in mice treated with [211At]At-SPC-VP2, two-fold prolongation of survival compared with the control group, which received normal saline or 550 kBq [211At]NaAt. No renal or hepatic toxicity was observed in the mice receiving [211At]At-SPC-VP2, but gastric pathological sections showed 211At uptake in stomach resulting in later toxicity, highlighting the importance of further enhancing the stability of labelled compounds.

Yttrium-90 Anti-CD45 Immunotherapy Followed by Autologous Hematopoietic Cell Transplantation for Relapsed or Refractory Lymphoma

Autologous hematopoietic cell transplantation (AHCT) is a standard of care for several subtypes of high-risk lymphoma, but durable remissions are not achieved in the majority of patients. Intensified conditioning using CD45-targeted antibody-radionuclide conjugate (ARC) preceding AHCT may improve outcomes in lymphoma by permitting the delivery of curative doses of radiation to disease sites while minimizing toxicity. We performed sequential phase I trials of escalating doses of yttrium-90 (⁹⁰Y)-labeled anti-CD45 antibody with or without BEAM (carmustine, etoposide, cytarabine, melphalan) chemotherapy followed by AHCT in adults with relapsed/refractory or high-risk B cell non-Hodgkin lymphoma (NHL), T cell NHL (T-NHL), or Hodgkin lymphoma (HL). Twenty-one patients were enrolled (16 NHL, 4 HL, 1 T-NHL). Nineteen patients received BEAM concurrently. No dose-limiting toxicities were observed; therefore, the maximum tolerated dose is estimated to be ≥34 Gy to the liver. Nonhematologic toxicities and engraftment kinetics were similar to standard myeloablative AHCT. Late myeloid malignancies and 100-day nonrelapse deaths were not observed. At a median follow-up of 5 years, the estimates of progression-free and overall survival of 19 patients were 37% and 68%, respectively. Two patients did not receive BEAM; one had stable disease and the other progressive disease post-transplant. The combination of ⁹⁰Y-anti-CD45 with BEAM and AHCT was feasible and tolerable in patients with relapsed and refractory lymphoma. The use of anti-CD45 ARC as an adjunct to hematopoietic cell transplantation regimens or in combination with novel therapies/immunotherapies should be further explored based on these and other data.

A phase II trial evaluating the efficacy of high-dose Radioiodinated Tositumomab (Anti-CD20) antibody, etoposide and cyclophosphamide followed by autologous transplantation, for high-risk relapsed or refractory non-hodgkin lymphoma

Radiation is the most effective treatment for localized lymphoma, but treatment of multifocal disease is limited by toxicity. Radioimmunotherapy (RIT) delivers tumoricidal radiation to multifocal sites, further augmenting response by dose-escalation. This phase II trial evaluated high-dose RIT and chemotherapy prior to autologous stem-cell transplant (ASCT) for high-risk, relapsed or refractory (R/R) B-cell non-Hodgkin lymphoma (NHL). The primary endpoint was progression free survival (PFS). Secondary endpoints were overall survival (OS), toxicity, and tolerability. Patients age < 60 years with R/R NHL expressing CD20 were eligible. Mantle cell lymphoma (MCL) patients could proceed to transplant in first remission. Patients received I-131-tositumomab delivered at ≤25Gy to critical normal organs, followed by etoposide, cyclophosphamide and ASCT. A group of 107 patients were treated including aggressive lymphoma (N = 29), indolent lymphoma (N = 45), and MCL (N = 33). After a median follow-up of 10.1 years, the 10-year PFS for the aggressive, indolent, and MCL groups were 62%, 64%, 43% respectively. The 10-year OS for the aggressive, indolent, and MCL groups were 61%, 71%, 48% respectively. Toxicities were similar to standard conditioning regimens and non-relapse mortality at 100 days was 2.8%. Late myeloid malignancies were seen in 6% of patients. High-dose I-131-tositumomab, etoposide and cyclophosphamide followed by ASCT appeared feasible, safe, and effective in treating NHL, with estimated PFS at 10-years of 43%-64%. In light of novel cellular therapies for R/R NHL, high-dose RIT-containing regimens yield comparable efficacy and safety and could be prospectively compared.

90Y-Daclizumab (Anti-CD25), High-Dose Carmustine, Etoposide, Cytarabine, and Melphalan Chemotherapy and Autologous Hematopoietic Stem Cell Transplant Yielded Sustained Complete Remissions in 4 Patients with Recurrent Hodgkin's Lymphoma

Background: Despite advances in therapy of Hodgkin's lymphoma (HL), a proportion of patients will not respond or relapse. The authors had previously identified CD25, IL-2Rα, as a target for systemic radioimmunotherapy of HL since most normal cells do not express CD25, but it is expressed by a minority of Hodgkin/Reed-Sternberg (HRS) cells and most Tregs rosetting around HRS cells. Study Design and Treatment: This was a single institution, nonrandomized, open-label phase I/II trial of radiolabeled ⁹⁰Y-daclizumab, an anti-CD25 monoclonal antibody, BEAM (carmustine, etoposide, cytarabine, and melphalan) conditioning treatment followed by autologous hematopoietic stem cell transplant (ASCT). Four patients with refractory and relapsed HL were treated in this trial with 3 patients receiving a single dose of 564.6-574.6 MBq ⁹⁰Y-daclizumab and the fourth patient receiving two doses of 580.9-566.1 MBq ⁹⁰Y-daclizumab followed by high-dose chemotherapy and ASCT. Results: All 4 evaluable patients treated with ⁹⁰Y-daclizumab obtained complete responses (CRs) that are ongoing 4.5-7 years following their stem cell transplant. The spectrum and severity of adverse events were mild and more importantly none of the patients, including several with multiple therapies before this treatment, developed the myelodysplastic syndrome. Discussion: Targeting by daclizumab was not directed primarily at tumor cells, but rather the nonmalignant CD25-expressing T cells adjacent to the HRS cells and ⁹⁰Y-daclizumab provided strong enough β emissions to kill CD25-negative tumor cells at a distance by a crossfire effect. Furthermore, the strong β irradiation killed normal cells in the tumor microenvironment. Conclusions: ⁹⁰Y-daclizumab (anti-CD25), high-dose BEAM chemotherapy and ASCT was well tolerated and yielded sustained complete remissions in all 4 patients with recurrent HL patients who completed their treatment. Significance: Despite advances, a proportion of patients with HL will not have a CR to their initial treatment, and some with CRs will relapse. They demonstrated that the addition of ⁹⁰Y-daclizumab into the preconditioning regimen for refractory and relapsed HL patients with high-dose BEAM chemotherapy and ASCT provided sustained CRs in the 4 patients studied. Two of these patients were highly refractory to multiple prior treatments with bulky disease at entry into this study, including 1 patient who never entered a remission and had failed 6 different therapeutic regimens. Despite the small number of patients treated in this study, the sustained clinical benefit in these patients indicates a highly effective treatment. The daclizumab was directed primarily not at HRS cells themselves but toward nonmalignant T cells rosetting around malignant cells. ⁹⁰Y provided strong β emissions that killed antigen nonexpressing tumor cells at a distance by a crossfire effect. Furthermore, the strong β radiation killed normal cells in the tumor microenvironment that nurtured the malignant cells in the lymphomatous mass. The present study supports expanded analysis of ⁹⁰Y-daclizumab as part of the regimen of ASCT in patients with refractory and relapsed HL.

Radioimmunotherapy-based conditioning regimen prior to autologous stem cell transplantation in non-Hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) is the most common hematologic malignancy and the sixth cause of death from cancer in the USA. Autologous stem cell transplantation (ASCT) is a potentially curative therapeutic option for many NHL patients. Choosing the most effective conditioning regimen prior to ASCT can lead to longer survival in these patients, and, as in many cases of high risk NHL, the only potentially curative option is stem cell transplantation. Radioimmunotherapy (RIT) is based on using radiolabeled monoclonal antibodies against tumoral antigens. Since lymphoma cells are sensitive to radiation, RIT has become a potential approach in treating NHL. In this review, we have discussed the efficacy and safety of RIT as an alternative conditioning regimen prior to ASCT.

Updated Results of Rituximab Pre- and Post-BEAM with or without 90Yttrium Ibritumomab Tiuxetan during Autologous Transplant for Diffuse Large B-cell Lymphoma

Purpose: We evaluated the effect on long-term survival of adding rituximab (R) to BEAM (carmustine, etoposide, cytarabine, and melphalan) conditioning with or without yttrium-90 ibritumomab tiuxetan (90YIT) in patients with relapsed diffuse large B-cell lymphoma (DLBCL) undergoing autologous stem cell transplant (ASCT).Experimental design: Patients were enrolled on three consecutive phase II clinical trials. Patients received two doses of rituximab (375 and 1,000 mg/m2) during mobilization of stem cells, followed by 1,000 mg/m2 on days +1 and +8 after ASCT with R-BEAM or 90YIT-R-BEAM (90YIT dose of 0.4 mCi/kg) conditioning.Results: One hundred thirteen patients were enrolled, with 73 receiving R-BEAM and 40 receiving 90YIT-R-BEAM. All patients had a prior exposure to rituximab. The median follow-up intervals for survivors were 11.8, 8.1, and 4.2 years in the three trials, respectively. The 5-year disease-free survival (DFS) rates were 62% for R-BEAM and 65% for 90YIT-R-BEAM (P = 0.82). The 5-year overall survival rates were 73% and 77%, respectively (P = 0.65). In patients with de novo DLBCL, survival outcomes of the germinal center/activated b-cell histologic subtypes were similar with 5-year OS rates (P = 0.52) and DFS rates (P = 0.64), irrespective of their time of relapse (<1 vs. >1 year) after initial induction chemotherapy (P = 0.97).Conclusions: Administering ASCT with rituximab during stem cell collection and immediately after transplantation induces long-term disease remission and abolishes the negative prognostic impact of cell-of-origin in patients with relapsed DLBCL. The addition of 90YIT does not confer a further survival benefit. Clin Cancer Res; 24(10); 2304-11. ©2018 AACR.

Yttrium-90 ibritumomab tiuxetan (Zevalin) followed by BEAM (Z-BEAM) conditioning regimen and autologous stem cell transplantation (ASCT) in relapsed or refractory high-risk B-cell non-Hodgkin lymphoma (NHL): a single institution Italian experience

Chemo-refractory NHL has a very poor outcome; the addiction of RIT to salvage regiment pre ASCT had recently demonstrated promising results.We performed a retrospective sequential study to determine the feasibility of standard Zevalin with BEAM in high-risk relapse/refractory NHL. A matched cohort analysis with a group treated with standard BEAM without Zevalin was performed as secondary endpoint. Between October 2006 and January 2013, 37 NHL patients at high risk for progression or early (< 1 year) or multiple relapses were treated with Z-BEAM and ASCT after R-DHAP or R-ICE as salvage therapy. Clinical characteristics were 19 refractory and 18 early or multiple relapse; 16 patients received 1, and 21 had 2 or more previous rituximab-containing chemotherapy. At the end of treatment, response was CR 22 (59%), PR 10 (27%), PD 4 (11%), and toxic death (TD) 1 (3%). With a median follow up of 61 months, 3-year PFS was 61% and OS 61%. Fifteen patients died, 12 of lymphoma. Comparison with 21 treated with BEAM alone showed a numerical higher 3-yr PFS rate in favor of Z-BEAM but not statistically significant (57 vs 48%). With the limitation of the small sample subgroup analysis, a significant benefit was observed in relapsed patients for PFS (78% Z-BEAM vs 22% BEAM p = 0.016) and OS (83% Z-BEAM vs 22% BEAM p = 0.001). In relapsed/refractory high-risk NHL, Z-BEAM+ASCT is able to achieve a good ORR. Three-year PFS is promising for early relapsed patients but is not satisfactory for those with refractory disease.

Radioimmunotherapy-augmented BEAM chemotherapy vs BEAM alone as the high-dose regimen for autologous stem cell transplantation (ASCT) in relapsed follicular lymphoma (FL): a retrospective study of the EBMT Lymphoma Working Party

Relapse remains the most common cause of treatment failure in patients receiving autologous stem cell transplantation (ASCT) for follicular lymphoma (FL). The aim of this study was to evaluate the effect of adding radioimmunotherapy or rituximab (R) to BEAM (carmustine, etoposide, ara-c, melphalan) high-dose therapy for ASCT in patients with relapsed FL. Using the European Society for Blood and Marrow Transplantation registry, we conducted a cohort comparison of BEAM (n=1973), Zevalin-BEAM (Z-BEAM) (n=207) and R-BEAM (n=179) and also a matched-cohort analysis of BEAM vs Z-BEAM including 282 and 154 patients, respectively. BEAM, Z-BEAM and R-BEAM groups were well balanced for age, time from diagnosis to ASCT and disease status at ASCT. The cumulative incidences of relapse (IR) at 2 years were 34, 34 and 32% for Z-BEAM, R-BEAM and BEAM, respectively. By multivariate analysis, there were no significant differences with Z-BEAM or R-BEAM compared with BEAM for IR, non-relapse mortality, event-free survival or overall survival. With the caveat that the limitations of registry analyses have to be taken into account, this study does not support adding radioimmunotherapy or R to BEAM in ASCT for relapsed FL. However, we cannot rule out the existence a particular subset of patients who could benefit from Z-BEAM conditioning that cannot be identified in our series, and this should be tested in a randomized trial.

Y90 -Ibritumomab tiuxetan (Y90 -IT) and high-dose melphalan as conditioning regimen before autologous stem cell transplantation for elderly patients with lymphoma in relapse or resistant to chemotherapy: a feasibility trial (SAKK 37/05)

Standard conditioning regimens for autologous stem cell transplantation (ASCT) are often not tolerated by elderly patients, on one hand. Single high-dose melphalan, on the other hand, has been shown to be safe and active as a pretransplant preparative regimen in elderly patients. Y⁹⁰ -Ibritumomab tiuxetan (Y⁹⁰ -IT) is well tolerated and feasible in the transplantation setting. We therefore investigated the combination of high-dose melphalan and Y⁹⁰ -IT as a conditioning regimen for patients ≥65 years of age. Patients with relapsed or resistant CD20-positive lymphoma in remission after salvage chemotherapy could be enrolled. High-dose therapy consisted of standard dose Y⁹⁰ -IT (0.4-mCi/kg body weight) followed by melphalan at escalating doses (100, 140, 170 and 200 mg/m² ) and ASCT. The primary objective was to identify the maximum tolerated dose; secondary end points were complete response (CR) rate 100 days after transplantation and toxicity. Twenty patients (median age 72 years) were included. No DLT occurred at any dose level. Thirteen patients completed the treatment, 11 were evaluable for response. Seven patients did not complete treatment because of mobilization failure (n = 3), progressive disease (n = 2), worsening of cardiac function (n = 1), and grade 3 dyspnea (n = 1). Seven patients achieved a CR/complete remission/unconfirmed (CRu) and 2 had stable disease. Five out of 7 responding patients were still alive more than 3 years after transplantation. The 2 patients with SD had a long-term survival of 3 and 5 years, respectively. Nonhematological grade 3 or higher treatment related adverse events (AEs) were infection (n = 6), including 2 cases of febrile neutropenia, diarrhea (n = 3), mucositis, anorexia, viral hepatitis, hypokalemia, dehydration, and multiorgan failure (n = 1 for each). The combination of Y⁹⁰ -IT and high-dose melphalan is feasible before ASCT for elderly patients, with promising activity and manageable toxicity.

Comparative Analysis of Bispecific Antibody and Streptavidin-Targeted Radioimmunotherapy for B-cell Cancers

Streptavidin (SA)-biotin pretargeted radioimmunotherapy (PRIT) that targets CD20 in non-Hodgkin lymphoma (NHL) exhibits remarkable efficacy in model systems, but SA immunogenicity and interference by endogenous biotin may complicate clinical translation of this approach. In this study, we engineered a bispecific fusion protein (FP) that evades the limitations imposed by this system. Briefly, one arm of the FP was an anti-human CD20 antibody (2H7), with the other arm of the FP an anti-chelated radiometal trap for a radiolabeled ligand (yttrium[Y]-DOTA) captured by a very high-affinity anti-Y-DOTA scFv antibody (C825). Head-to-head biodistribution experiments comparing SA-biotin and bispecific FP (2H7-Fc-C825) PRIT in murine subjects bearing human lymphoma xenografts demonstrated nearly identical tumor targeting by each modality at 24 hours. However, residual radioactivity in the blood and normal organs was consistently higher following administration of 1F5-SA compared with 2H7-Fc-C825. Consequently, tumor-to-normal tissue ratios of distribution were superior for 2H7-Fc-C825 (P < 0.0001). Therapy studies in subjects bearing either Ramos or Granta subcutaneous lymphomas demonstrated that 2H7-Fc-C825 PRIT is highly effective and significantly less myelosuppressive than 1F5-SA (P < 0.0001). All animals receiving optimal doses of 2H7-Fc-C825 followed by ⁹⁰Y-DOTA were cured by 150 days, whereas the growth of tumors in control animals progressed rapidly with complete morbidity by 25 days. In addition to demonstrating reduced risk of immunogenicity and an absence of endogenous biotin interference, our findings offer a preclinical proof of concept for the preferred use of bispecific PRIT in future clinical trials, due to a slightly superior biodistribution profile, less myelosuppression, and superior efficacy. Cancer Res; 76(22); 6669-79. ©2016 AACR.

90 Y-ibritumomab tiuxetan: a nearly forgotten opportunityr

Y-ibritumomab tiuxetan (90Y-IT) combines the benefits of a monoclonal antibody with the efficacy of radiation in the treatment of B-cell non-Hodgkin lymphoma (NHL), a remarkably radiosensitive hematologic malignancy. 90Y-IT activity has been well established in the indolent setting, being approved in front-line treatment of follicular lymphoma (FL) patients as well as salvage therapy. However, no advantage in OS was observed with respect to standard treatment. Promising data are available also for aggressive B-cell lymphoma. In particular, the addition of RIT to short-course first line chemotherapy enables reduction of chemotherapy while maintaining cure rates in elderly, untreated diffuse large B-cell lymphoma (DLBCL) patients. Furthermore, 90Y-IT improves response rate and outcomes of relapsed/refractory DLBCL patients, eligible and ineligible for autologous stem cell transplantation (ASCT). Clinical results have shown a role of 90Y-IT even in mantle cell lymphoma (MCL). RIT might improve responses and treat minimal residual disease when used as consolidation after first-line chemotherapy in MCL. Moreover, 90Y-IT has demonstrated its efficacy in combination with high-dose chemotherapies as conditioning regimen for ASCT, with evidence suggesting the ability to overcome chemotherapy resistance. Herein, we review the available evidence for this approved drug and examine the recently published and ongoing trials for potential novel indication in aggressive B-cell NHL.

Advancing radioimmunotherapy and its future role in non-Hodgkin lymphoma

Radioimmunotherapy is an effective treatment modality with an acceptable toxicity profile in both indolent B-cell non-Hodgkin lymphoma and histologic transformation. Its ease of administration from a patient's perspective sets it apart from chemoimmunotherapy regimens. It has demonstrated efficacy in a range of different treatment scenarios. Despite its promise as a treatment modality, radioimmunotherapy has been seldom used, and one of the previously available agents is now off the market. Radioimmunotherapy has shown impressive activity in both the relapsed and upfront settings in follicular lymphoma, histologic transformation, as consolidation after chemotherapy, and in conjunction with high-dose chemotherapy and autologous stem cell support. Future efforts should focus on its optimal employment in the upfront setting for follicular lymphoma as well as further investigation of the promising activity in histologic transformation.

High-dose CD20-targeted radioimmunotherapy-based autologous transplantation improves outcomes for persistent mantle cell lymphoma

Autologous stem cell transplant (ASCT) can improve outcomes for mantle cell lymphoma (MCL) patients, yet relapses are frequent. We hypothesized that high-dose anti-CD20 radioimmunotherapy (RIT)-based conditioning could improve results in this setting. We thus assessed 162 consecutive patients with MCL at our centre undergoing ASCT following high-dose RIT-based (n = 61) or standard (n = 101) conditioning. RIT patients were less likely to be in first remission (48% vs. 72%; P = 0·002), be in complete remission (CR) (26% vs. 61%; P < 0·001) and have chemosensitive disease (84% vs. 96%; P = 0·006). RIT-based conditioning was associated with a reduced risk of treatment failure [hazard ratio (HR) 0·40; P = 0·001] and mortality (HR 0·49; P = 0·01) after adjusting for these imbalances. This difference increased as disease status worsened (from CR to partial remission to stable/progressive disease), with respective HRs of 1·14, 0·53 and 0·04 for mortality, and 0·66, 0·36 and 0·14 for treatment failure. RIT-based conditioning appears to improve outcome following ASCT for MCL patients unable to achieve CR after controlling for imbalances in important risk factors. These data support the further study of RIT and radiation-based strategies in a risk-adapted approach to ASCT for persistent MCL.

Advancement in high dose therapy and autologous stem cell rescue in lymphoma

Although advanced stage aggressive non-Hodgkin’s lymphomas and Hodgkin’s disease are thought to be chemotherapy-responsive cancers, a considerable number of patients either relapse or never attain a remission. High-dose therapy (HDT) followed by autologous stem cell transplantation (ASCT) is often the only possibility of cure for most of these patients. However, many controversial issues still remain with respect to HDT/ASCT for lymphomas, including its role for, the optimal timing of transplantation, the best conditioning regimen and the potential use of localized radiotherapy or immunologic methods to decrease post-transplant recurrence. Recently, mainly due to the unavailability of carmustine, several novel conditioning protocols have been clinically developed, with the aim of improving the overall outcome by enhancing the anti-lymphoma effect and, at the same time, by reducing short and long-term toxicity. Furthermore, the better safety profiles of novel approaches would definitively allow patients aged more than 65-70 years to benefit from this therapeutic option. In this review, we will briefly discuss the most relevant and recent data available regarding HDT/ASCT in lymphomas.

Radioimmunotherapy of human tumours

The eradication of cancer remains a vexing problem despite recent advances in our understanding of the molecular basis of neoplasia. One therapeutic approach that has demonstrated potential involves the selective targeting of radionuclides to cancer-associated cell surface antigens using monoclonal antibodies. Such radioimmunotherapy (RIT) permits the delivery of a high dose of therapeutic radiation to cancer cells, while minimizing the exposure of normal cells. Although this approach has been investigated for several decades, the cumulative advances in cancer biology, antibody engineering and radiochemistry in the past decade have markedly enhanced the ability of RIT to produce durable remissions of multiple cancer types.

Astatine-211 conjugated to an anti-CD20 monoclonal antibody eradicates disseminated B-cell lymphoma in a mouse model

α-Emitting radionuclides deposit a large amount of energy within a few cell diameters and may be particularly effective for radioimmunotherapy targeting minimal residual disease (MRD). To evaluate this hypothesis, (211)At-labeled 1F5 monoclonal antibody (mAb) (anti-CD20) was studied in both bulky lymphoma tumor xenograft and MRD animal models. Superior treatment responses to (211)At-labeled 1F5 mAb were evident in the MRD setting. Lymphoma xenograft tumor-bearing animals treated with doses of up to 48 µCi of (211)At-labeled anti-CD20 mAb ([(211)At]1F5-B10) experienced modest responses (0% cures but two- to threefold prolongation of survival compared with negative controls). In contrast, 70% of animals in the MRD lymphoma model demonstrated complete eradication of disease when treated with (211)At-B10-1F5 at a radiation dose that was less than one-third (15 µCi) of the highest dose given to xenograft animals. Tumor progression among untreated control animals in both models was uniformly lethal. After 130 days, no significant renal or hepatic toxicity was observed in the cured animals receiving 15 µCi of [(211)At]1F5-B10. These findings suggest that α-emitters are highly efficacious in MRD settings, where isolated cells and small tumor clusters prevail.

Evaluation of a semiautomated lung mass calculation technique for internal dosimetry applications

PURPOSE

The authors sought to evaluate a simple, semiautomated lung mass estimation method using computed tomography (CT) scans obtained using a variety of acquisition techniques and reconstruction parameters for mass correction of medical internal radiation dose-based internal radionuclide radiation absorbed dose estimates.

METHODS

CT scans of 27 patients with lung cancer undergoing stereotactic body radiation therapy treatment planning with PET∕CT were analyzed retrospectively. For each patient, free-breathing (FB) and respiratory-gated 4DCT scans were acquired. The 4DCT scans were sorted into ten respiratory phases, representing one complete respiratory cycle. An average CT reconstruction was derived from the ten-phase reconstructions. Mid expiration breath-hold CT scans were acquired in the same session for many patients. Deep inspiration breath-hold diagnostic CT scans of many of the patients were obtained from different scanning sessions at similar time points to evaluate the effect of contrast administration and maximum inspiration breath-hold. Lung mass estimates were obtained using all CT scan types, and intercomparisons made to assess lung mass variation according to scan type. Lung mass estimates using the FB CT scans from PET∕CT examinations of another group of ten male and ten female patients who were 21-30 years old and did not have lung disease were calculated and compared with reference lung mass values. To evaluate the effect of varying CT acquisition and reconstruction parameters on lung mass estimation, an anthropomorphic chest phantom was scanned and reconstructed with different CT parameters. CT images of the lungs were segmented using the OsiriX MD software program with a seed point of about -850 HU and an interval of 1000. Lung volume, and mean lung, tissue, and air HUs were recorded for each scan. Lung mass was calculated by assuming each voxel was a linear combination of only air and tissue. The specific gravity of lung volume was calculated using the formula (lung HU - air HU)∕(tissue HU - air HU), and mass = specific gravity × total volume × 1.04 g∕cm(3).

RESULTS

The range of calculated lung masses was 0.51-1.29 kg. The average male and female lung masses during FB CT were 0.80 and 0.71 kg, respectively. The calculated lung mass varied across the respiratory cycle but changed to a lesser degree than did lung volume measurements (7.3% versus 15.4%). Lung masses calculated using deep inspiration breath-hold and average CT were significantly larger (p < 0.05) than were some masses calculated using respiratory-phase and FB CT. Increased voxel size and smooth reconstruction kernels led to high lung mass estimates owing to partial volume effects.

CONCLUSIONS

Organ mass correction is an important component of patient-specific internal radionuclide dosimetry. Lung mass calculation necessitates scan-based density correction to account for volume changes owing to respiration. The range of lung masses in the authors' patient population represents lung doses for the same absorbed energy differing from 25% below to 64% above the dose found using reference phantom organ masses. With proper management of acquisition parameters and selection of FB or midexpiration breath hold scans, lung mass estimates with about 10% population precision may be achieved.

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.

Advances in the treatment of hematologic malignancies using immunoconjugates

Monoclonal antibody therapy has revolutionized cancer treatment by significantly improving patient survival both in solid tumors and hematologic malignancies. Recent technological advances have increased the effectiveness of immunotherapy leading to its broader application in diverse treatment settings. Immunoconjugates (ICs) consist of a cytotoxic effector covalently linked to a monoclonal antibody that enables the targeted delivery of its therapeutic payload to tumors based on cell-surface receptor recognition. ICs are classified into 3 groups based on their effector type: immunotoxins (protein toxin), radioimmunoconjugates (radionuclide), and antibody drug conjugates (small-molecule drug). Optimization of each individual component of an IC (antibody, linker, and effector) is essential for therapeutic efficacy. Clinical trials have been conducted to investigate the effectiveness of ICs in hematologic malignancies both as monotherapy and in multiagent regimens in relapsed/refractory disease as well as frontline settings. These studies have yielded encouraging results particularly in lymphoma. ICs comprise an exciting group of therapeutics that promise to play an increasingly important role in the management of hematologic malignancies.

Autologous stem cell transplantation after conditioning with yttrium-90 ibritumomab tiuxetan plus BEAM in refractory non-Hodgkin diffuse large B-cell lymphoma: results of a prospective, multicenter, phase II clinical trial

Lymphoma patients with persistent disease undergoing autologous transplantation have a very poor prognosis in the rituximab era. The addition of radioimmunotherapy to the conditioning regimen may improve the outcome for these patients. In a prospective, phase 2 study, we evaluated the safety and efficacy of the addition of (90)Y-ibritumomab tiuxetan to the conditioning chemotherapy in patients with refractory diffuse large B-cell lymphoma. Thirty patients with induction failure (primary refractory; n=18) or refractory to salvage immunochemotherapy at relapse (n=12) were included in the study. The median age of the patients was 53 years (range, 25-67). All patients were given (90)Y-ibritumomab tiuxetan at a fixed dose of 0.4 mCi/kg (maximum dose 32 mCi) 14 days prior to the preparative chemotherapy regimen. Histological examination showed that 22 patients had de novo diffuse large B-cell lymphoma and eight had transformed diffuse large B-cell lymphoma. All patients had persistent disease at the time of transplantation, with 25 patients considered to be chemorefractory. The median time to neutrophil recovery (>500 white blood cells/μL) was 11 days (range, 9-21), while the median time to platelet recovery (>20,000 platelets/μL) was 13 days (range, 11-35). The overall response rate at day +100 was 70% (95% CI, 53.6-86.4) with 60% (95% CI, 42.5-77.5) of patients obtaining a complete response. After a median follow-up of 31 months for alive patients (range, 16-54), the estimated 3-year overall and progression-free survival rates are 63% (95% CI, 48-82) and 61% (95% CI, 45-80), respectively. We conclude that autologous transplantation with conditioning including (90)Y-ibritumomab tiuxetan is safe and results in a very high response rate with promising survival in this group of patients with refractory diffuse large B-cell lymphoma with a very poor prognosis. Study registered at European Union Drug Regulating Authorities Clinical Trials (EudraCT) N. 2007-003198-22.

Radioimmunotherapy for hematopoietic cell transplantation

Radioimmunotherapy (RIT) represents an attractive strategy to deliver radiation selectively to tumor and other target organs while minimizing toxicity to normal tissues. RIT with β-particle-emitting isotopes targeting CD33, CD45 and CD66 can potentially allow intensification of conditioning before hematopoietic cell transplantation (HCT) in leukemia. Similarly, RIT directed against CD20 has shown promise in the setting of autologous and allogeneic HCT for B-cell lymphomas. α-particle immunotherapy with isotopes such as bismuth-213, actinium-225 and astatinine-211 offers the possibility of more selective and efficient killing of target cells while sparing the surrounding normal cells. Pretargeting strategies may further improve target:normal organ dose ratios. While RIT has demonstrated significant antitumor activity, ultimately, randomized studies will be required to determine if conditioning regimens that include this therapeutic modality can improve patient outcomes after HCT.

Biodistribution and dosimetry of (177)Lu-tetulomab, a new radioimmunoconjugate for treatment of non-Hodgkin lymphoma

The biodistribution of the anti-CD37 radioimmunoconjugate ¹⁷⁷Lu-tetraxetan-tetulomab (¹⁷⁷Lu-DOTA-HH1) was evaluated. Biodistribution of ¹⁷⁷Lu-tetraxetan-tetulomab was compared with ¹⁷⁷Lu-tetraxetan-rituximab and free ¹⁷⁷Lu in nude mice implanted with Daudi lymphoma xenografts. The data showed that ¹⁷⁷Lu-tetulomab had a relevant stability and tumor targeting properties in the human lymphoma model. The half-life of ¹⁷⁷Lu allowed significant tumor to normal tissue ratios to be obtained indicating that ¹⁷⁷Lu-tetraxetan-tetulomab could be suitable for clinical testing. The biological and effective half-life in blood was higher for ¹⁷⁷Lu-tetraxetan-tetulomab than for ¹⁷⁷Lu-tetraxetan-rituximab. The biodistribution of ¹⁷⁷Lu-tetraxetan-tetulomab did not change significantly when the protein dose was varied from 0.01 to 1 mg/kg. Dosimetry calculations showed that the absorbed radiation doses to normal tissues and tumor in mice were not significantly different for ¹⁷⁷Lu-tetraxetan-tetuloma b and ¹⁷⁷Lu-tetraxetan-rituximab. The absorbed radiation doses were extrapolated to human absorbed radiation doses. These extrapolated absorbed radiation doses to normal tissues for ¹⁷⁷Lu-tetraxetan-tetulomab at an injection of 40 MBq/kg were significantly lower than the absorbed radiation doses for 15 MBq/kg Zevalin, suggesting that higher tumor radiation dose can be reached with ¹⁷⁷Lu-tetraxetan-tetulomab in the clinic.

Radiobiologic optimization of combination radiopharmaceutical therapy applied to myeloablative treatment of non-Hodgkin lymphoma

Combination treatment is a hallmark of cancer therapy. Although the rationale for combination radiopharmaceutical therapy was described in the mid-1990s, such treatment strategies have only been implemented clinically recently and without a rigorous methodology for treatment optimization. Radiobiologic and quantitative imaging-based dosimetry tools are now available that enable rational implementation of combined targeted radiopharmaceutical therapy. Optimal implementation should simultaneously account for radiobiologic normal-organ tolerance while optimizing the ratio of 2 different radiopharmaceuticals required to maximize tumor control. We have developed such a methodology and applied it to hypothetical myeloablative treatment of non-Hodgkin lymphoma (NHL) patients using (131)I-tositumomab and (90)Y-ibritumomab tiuxetan.

METHODS

The range of potential administered activities (AAs) is limited by the normal-organ maximum-tolerated biologic effective doses (MTBEDs) arising from the combined radiopharmaceuticals. Dose-limiting normal organs are expected to be the lungs for (131)I-tositumomab and the liver for (90)Y-ibritumomab tiuxetan in myeloablative NHL treatment regimens. By plotting the limiting normal-organ constraints as a function of the AAs and calculating tumor biologic effective dose (BED) along the normal-organ MTBED limits, we obtained the optimal combination of activities. The model was tested using previously acquired patient normal-organ and tumor kinetic data and MTBED values taken from the literature.

RESULTS

The average AA value based solely on normal-organ constraints was 19.0 ± 8.2 GBq (range, 3.9-36.9 GBq) for (131)I-tositumomab and 2.77 ± 1.64 GBq (range, 0.42-7.54 GBq) for (90)Y-ibritumomab tiuxetan. Tumor BED optimization results were calculated and plotted as a function of AA for 5 different cases, established using patient normal-organ kinetics for the 2 radiopharmaceuticals. Results included AA ranges that would deliver 95% of the maximum tumor BED, allowing for informed inclusion of clinical considerations, such as a maximum-allowable (131)I administration.

CONCLUSION

A rational approach for combination radiopharmaceutical treatment has been developed within the framework of a proven 3-dimensional (3D) personalized dosimetry software, 3D-RD, and applied to the myeloablative treatment of NHL. We anticipate that combined radioisotope therapy will ultimately supplant single radioisotope therapy, much as combination chemotherapy has substantially replaced single-agent chemotherapy.

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.

A phase I trial of immunostimulatory CpG 7909 oligodeoxynucleotide and 90 yttrium ibritumomab tiuxetan radioimmunotherapy for relapsed B-cell non-Hodgkin lymphoma

Radioimmunotherapy (RIT) for relapsed indolent non-Hodgkin lymphoma produces overall response rates (ORR) of 80% with mostly partial remissions. Synthetic CpG oligonucleotides change the phenotype of malignant B-cells, are immunostimulatory, and can produce responses when injected intratumorally and combined with conventional radiation. In this phase I trial, we tested systemic administration of both CpG and RIT. Eligible patients had biopsy-proven previously treated CD20+ B-cell NHL and met criteria for RIT. Patients received rituximab 250 mg/m(2) days 1,8, and 15; (111) In-ibritumomab tiuxetan days 1, 8; CpG 7909 days 6, 13, 20, 27; and 0.4 mCi/kg of (90) Y-ibritumomab tiuxetan day 15. The doses of CpG 7909 tested were 0.08, 0.16, 0.32 (six patients each) and 0.48 mg/kg (12 patients) IV over 2 hr without dose limiting toxicity. The ORR was 93% (28/30) with 63% (19/30) complete remission (CR); median progression free survival of 42.7 months (95% CI 18-NR); and median duration of response (DR) of 35 months (4.6-76+). Correlative studies demonstrated a decrease in IL10 and TNFα, and an increase in IL1β, in response to therapy. CpG 7909 at a dose of 0.48 mg/kg is safe with standard RIT and produces a high CR rate and long DR; these results warrant confirmation.

Allogeneic hematopoietic cell transplantation for diffuse large B cell lymphoma: who, when and how?

Despite overall improvements in outcomes of patients with diffuse large B cell lymphoma (DLBCL), ∼30-40% of patients develop relapsed or refractory disease. For patients with chemo refractory disease, or recurrent disease following autologous hematopoietic SCT (auto-HCT), the prognosis is poor, with no consensus on the optimal therapy. Currently, owing to the graft vs lymphoma effect, hematopoietic allogeneic hematopoietic cell transplantation (allo-HCT) is the only potentially curative option for such patients. In addition, many patients who are considered today for auto-HCT actually have a low likelihood of benefit. For example, a patient with prior rituximab exposure who relapses within 1 year of diagnosis and has a second-line age-adjusted International Prognosis Index of 2 or 3 at relapse has a <25% chance of being cured by auto-HCT. It is possible that such patients may be better served with an allo-HCT. Unfortunately, in many cases, allo-HCT applicability is limited by patient age, comorbidities, performance status and treatment-related toxicities. Recent attempts to improve the efficacy of auto-HCT, such as incorporating radio-immunotherapy into the conditioning regimen, have not resulted in improved outcomes. However, incorporation of novel agents such as anti-programmed death-1 antibodies as maintenance therapy after auto-HCT show promise. Allo-HCT in relapsed/refractory DLBCL patients can result in a 30-40% PFS rate at 3 years, in part due to a graft vs DLBCL effect. While reduced-intensity/non-myeloablative conditioning is increasingly being used, certain patients may benefit from myeloablative conditioning. We present an algorithm intended to discriminate which relapsed and refractory DLBCL patients are most likely to benefit from auto-HCT vs allo-HCT. New approaches, using novel agents that target the molecular heterogeneity in DLBCL, will be an essential component of moving the field forward. Lastly, we propose a prospective registry-based study as the only feasible mechanism to define the optimal position of allo-HCT in the overall treatment strategy for DLBCL. It is hoped that this review will promote the development of prospective multicenter efforts to determine whether such patients do, in fact, benefit from earlier and/or more effective implementation of allo-HCT.

Monoclonal antibodies in conditioning regimens for hematopoietic cell transplantation

Monoclonal antibodies are increasingly being incorporated in conditioning regimens for autologous or allogeneic hematopoietic cell transplantation (HCT). The benefit of adding rituximab to autologous HCT regimens is purportedly related to in vivo purging of clonal B cells. Randomized trials comparing the addition (or not) of rituximab to high-dose therapy regimens are lacking. No benefit of standard-dose radioimmunotherapy-based regimens for autografting in aggressive lymphomas was seen in a randomized controlled study. The incorporation of rituximab into allogeneic HCT regimens aims to improve responses while reducing nonrelapse mortality resulting from acute graft-versus-host disease. The optimal dose and administration schedule of rituximab in this setting are unknown, and potentially serious complications from increased infections owing to prolonged (and profound) cytopenias or persistent hypogammaglobulinemia are of concern. Radioimmunotherapy-based conditioning for allografting holds promise as a modality to optimize tumor control and synergize adoptive immunotherapy effects, but it remains experimental at this time. The addition of alemtuzumab to allogeneic HCT regimens is associated with prolonged lymphopenia and impaired immune reconstitution, high relapse rates, and serious infections. The optimal dose and schedule of alemtuzumab to avoid prolonged immune paresis remain elusive. It is anticipated that additional monoclonal antibodies will soon become available that can be incorporated into HCT regimens after safety and clinical efficacy are demonstrated.

Autotransplantation for mantle cell lymphoma

Mantle cell lymphoma (MCL) represents about 5% to 9% of all non-Hodgkin lymphomas according to the World Health Organization. The clinical presentation typically consists of diffuse lymphadenopathy and frequent extranodal involvement of the gastrointestinal tract, blood, and bone marrow, as well as frequent splenomegaly. The median survival with standard immunochemotherapy is approximately 3 to 5 years. High-dose chemotherapy and autologous stem cell transplantation (ASCT) have been used either in first partial or complete remission or at the time of relapse in an attempt to prolong the survival for patients with MCL. Autologous SCT has had disappointing results in patients with relapsed MCL with the expected progression-free survival approximately 20% to 40% in most trials. Therefore, most centers now consider ASCT for eligible MCL patients during first remission. If a complete remission can be obtained with the induction chemotherapy, the clinical results following ASCT in complete remission 1 are improved to 60% to 80% progression-free survival greater than 5 years. However, the median age of patients with MCL is older than 60 years, which does not allow ASCT to be used in all patients with MCL. Research is now focused on reducing the relapse rate after transplantation.

An update on radioimmunotherapy for lymphoma

SUMMARY Radioimmunotherapy is a promising treatment for B-cell lymphoma. 90Y-ibritumomab tiuxetan (Zevalin®) and 131I-tositumomab (Bexxar®) combine the potent antilymphoma effect of radiation with the specificity of antibody targeting. They have shown efficacy in follicular lymphoma in the setting of relapsed or refractory disease as consolidation regimens after first-line therapy, and in the front-line setting as single agents. Given their tolerability, they are actively being investigated as therapies or adjuncts for elderly patients with relapsed or high-risk diffuse large B-cell lymphoma. They have been added to autologous and allogeneic stem cell transplant preparatory regimens in early clinical trials with acceptable safety and efficacy. Early concerns over excess rates of treatment-related myelodysplastic syndrome and acute myelogenous leukemia have not come to fruition, but these questions remain to be fully answered. Ultimately, these are promising treatments for a variety of B-cell lymphomas. They are also models for the development of new radioimmunotherapies.

Phase III randomized study of rituximab/carmustine, etoposide, cytarabine, and melphalan (BEAM) compared with iodine-131 tositumomab/BEAM with autologous hematopoietic cell transplantation for relapsed diffuse large B-cell lymphoma: results from the BMT CTN 0401 trial

PURPOSE

This clinical trial evaluated standard-dose radioimmunotherapy with a chemotherapy-based transplantation regimen followed by autologous hematopoietic cell transplantation versus rituximab with the same regimen in patients with relapsed diffuse large B-cell lymphoma (DLBCL).

PATIENTS AND METHODS

Patients with chemotherapy-sensitive persistent or relapsed DLBCL were randomly assigned to receive iodine-131 tositumomab (dosimetric dose of 5 mCi on day -19 and therapeutic dose of 0.75 Gy on day -12), carmustine 300 mg/m(2) (day -6), etoposide 100 mg/m(2) twice daily (days -5 to -2), cytarabine 100 mg/m(2) twice daily (days -5 to -2), and melphalan 140 mg/m(2) (day -1; B-BEAM) or rituximab 375 mg/m(2) on days -19 and -12 and the same chemotherapy regimen (R-BEAM).

RESULTS

Two hundred twenty-four patients were enrolled, with 113 patients randomly assigned to R-BEAM and 111 patients assigned to B-BEAM. Two-year progression-free survival (PFS) rates, the primary end point, were 48.6% (95% CI, 38.6% to 57.8%) for R-BEAM and 47.9% (95% CI, 38.2% to 57%; P = .94) for B-BEAM, and the 2-year overall survival (OS) rates were 65.6% (95% CI, 55.3% to 74.1%) for R-BEAM and 61% (95% CI, 50.9% to 69.9%; P = .38) for B-BEAM. The 100-day treatment-related mortality rates were 4.1% (95% CI, 0.2% to 8.0%) for R-BEAM and 4.9% (95% CI, 0.8% to 9.0%; P = .97) for B-BEAM. The maximum mucositis score was higher in the B-BEAM arm (0.72) compared with the R-BEAM arm (0.31; P < .001).

CONCLUSION

The B-BEAM and R-BEAM regimens produced similar 2-year PFS and OS rates for patients with chemotherapy-sensitive relapsed DLBCL. No differences in toxicities other than mucositis were noted.

The role of allogeneic haematopoietic progenitor cell transplantation in patients with diffuse large B-cell non-Hodgkin lymphomas (DLBCL)

Despite the undoubted improvement in the prognosis of patients with diffuse large B-cell lymphomas (DLBCLs) with the addition of rituximab in the front-line treatment, a significant proportion of patients still relapse. Salvage immune-chemotherapy followed by high-dose therapy with autologous haematopoietic cell transplantation (auto-HCT) remains the treatment of choice for such patients, especially in those who demonstrate chemosensitive disease. In recent years, allogeneic haematopoietic cell transplantation (allo-HCT) has increasingly been used for patients who are resistant to salvage treatment or relapse after an auto-HCT. Strategies using reduced intensity conditioning regimens have allowed application of this approach to a broader range of patients. PFS is up to 55% with a risk of relapse up to 80% depending on different studies. In multivariate analysis, several factors have been associated with favourable outcome including chemosensitivity of the disease, younger age and Karnofsky performance status at the time of the transplant being the strongest ones. DLIs have shown to induce durable responses in relapsed or progressed disease; however, its role remains controversial as the results are inferior to the responses seen in other haematological malignancies. More recently, the addition of MoAbs in the non-myeloablative conditioning regimens has shown encouraging results. In conclusion, allo-HCT is a feasible option in selective patients with chemosensitive DBCL, as it reduces the risk of relapse; however, this is achieved at the cost of significant non-relapse mortality.

Is there any role for transplantation in the rituximab era for diffuse large B-cell lymphoma?

Salvage chemotherapy followed by high-dose therapy and autologous stem cell transplantation is the standard of treatment for chemosensitive relapses in diffuse large B-cell lymphoma. The addition of rituximab to chemotherapy has improved the response rate and failure-free survival after first-line treatment and relapses. Fewer relapses are expected, although there is no consensus on the best salvage regimen. The intergroup Collaborative Trial in Relapsed Aggressive Lymphoma (CORAL) set the limits for this standard of treatment after first comparing 2 salvage regimens: rituximab, ifosfamide, etoposide, and carboplatin (R-ICE) and rituximab, dexamethasone, aracytine, and cisplatin (R-DHAP). There was no difference in response rates or survivals between these salvage regimens. Several factors affected survival: prior treatment with rituximab, early relapse (< 12 months), and a secondary International Prognostic Index score of 2-3. For patients with 2 factors, the response rate to salvage was only 46%, which identified easily a group with poor outcome. Moreover, patients with an ABC subtype or c-MYC translocation responded poorly to treatment. More than 70% of patients will not benefit from standard salvage therapy, and continued progress is needed. Studies evaluating immunotherapy after transplantation, including allotransplantation, new conditioning regimens with radioimmunotherapy and other combinations of chemotherapy based on diffuse large B-cell lymphoma subtype, are discussed herein. Early relapses and/or patients refractory to upfront rituximab-based chemotherapy have a poor response rate and prognosis. A better biological understanding of these patients and new approaches are warranted.

Autologous stem cell transplantation for aggressive lymphomas

The role of high-dose therapy (HDT) followed by autologous stem cell transplantation (ASCT) in the treatment armamentarium of aggressive B- and T-cell non-Hodgkin lymphoma (NHL) is still a matter of debate. In the pre-Rituximab era, the PARMA study demonstrated the superiority of HDT/ASCT over conventional salvage chemotherapy in chemosensitive, relapsed patients. Subsequently, HDT/ASCT has become a standard approach for relapsed NHL. With the advent of Rituximab in the landscape of NHL, transplantation as part of first-line therapy has been challenged. However, no benefit in terms of disease-free or overall survival of HDT/ASCT over standard therapy was shown when Rituximab was added to both arms. Moreover, the superiority of HDT/ASCT over conventional salvage therapy in patients relapsing from first-line therapy including Rituximab was not confirmed. From these disappointing results, novel strategies, which can enhance the anti-lymphoma effect, at the same time reducing toxicity have been developed, with the aim of improving the outcome of HDT/ASCT in aggressive NHL. In T-cell lymphoma, few publications demonstrated that consolidation of complete remission with HDT/ASCT is safe and feasible. However, up to one-third of patients may never receive transplant, mostly due to progressive disease, and relapse still remains a major concern even after transplant.

Iodine-131 rituximab radioimmunotherapy with BEAM conditioning and autologous stem cell transplant salvage therapy for relapsed/refractory aggressive non-Hodgkin lymphoma

A standard salvage therapy of relapsed/refractory aggressive non-Hodgkin lymphoma (NHL) comprises autologous stem cell transplantation (ASCT) after chemotherapy conditioning with carmustine, etoposide, cytarabine, and melphalan (BEAM) regimen. However, the achievement of long-term disease-free survival remains challenging. We have introduced concomitant (131)I-rituximab radioimmunotherapy (RIT) in an attempt to effect the elimination of lymphoma cells. Our phase II physician-sponsored study of 16 consecutive patients with relapsed, refractory, aggressive B-cell NHL reports a median 44 month follow-up after (131)I-rituximab-BEAM conditioning therapy and ASCT. Prospective personalized dosimetry performed in each patient limited the whole body radiation absorbed dose to 0.75 Gy. RIT (131)I-rituximab was administered on an outpatient basis on day -15 before ASCT. The BEAM conditioning regimen was commenced on day -6. Evaluable engraftment data are available for 15 patients who had 16 ASCTs. Engraftment was achieved in all patients, 15 out of 16 ASCTs achieved a complete response, and 1 out of 15 ASCTs achieved a partial response. Twelve out of sixteen patients remained alive and disease free at a median of 44 months (range 4-108 months) post-ASCT. This study suggests that the addition of (131)I-rituximab RIT to BEAM conditioning, before ASCT, for relapsed or primary refractory B-cell NHL improves disease eradication, compared with BEAM conditioning alone, without significant additional toxicity. In particular, there is an impression of improved disease control in the subset of patients with transformed follicular and mantle cell lymphomas.