Myeloablative Radioimmunotherapy Research Articles

Tandem Myeloablative 131 I-rituximab Radioimmunotherapy and High-Dose Chemotherapy in Refractory/Relapsed Non-Hodgkin Lymphoma Patients

This Phase I/II study investigated myeloablative (131)I-rituximab radioimmunotherapy (RIT) and high-dose chemotherapy supported by one or two autologous stem cell transplantations in heavily pretreated patients with relapsed or refractory B cell non-Hodgkin lymphoma. Myeloablative RIT was safe and feasible when followed by autologous stem cell transplantation with low incidence of secondary late effects and could be a reasonable alternative regimen especially in elderly patients and in patients who have concerns about high-dose chemotherapy. Tandem myeloablative (131)I-rituximab RIT and high-dose chemotherapy supported by two autologous stem cell transplantations was also feasible. However, the toxicity was higher than after myeloablative RIT, therefore it might be recommended to restrict the tandem approach to lymphoma with poor prognosis.

A Phase I Study Of Myeloablative Radioimmunotherapy Using Iodine-131 Anti-CD45 Antibody Followed By Autologous Stem Cell Transplantation For High-Risk B-Cell and T-Cell Non-Hodgkin Lymphoma and Hodgkin Lymphoma

BackgroundHigh-dose therapy and autologous stem cell transplant (ASCT) remains the standard of care for many high-risk/relapsed B-cell non-Hodgkin lymphomas (B-NHL), T-cell NHL (T-NHL) and classical Hodgkin lymphoma (HL), yet most will not achieve sustained remissions. High-dose anti-CD20 radioimmunotherapy (RIT) and ASCT has been successfully employed to address this challenge in B-NHL, yet relapse still occurs potentially due to blockade of target sites by circulating rituximab (R). RIT options are limited for patients with T-NHL and HL. Preclinical data indicate that targeting the panhematopoietic antigen CD45 with RIT can successfully circumvent R blocking in B-NHL and target a variety of T-NHL histologies (Gopal, 2008 & 2009). We thus performed a phase I trial using high-dose anti-CD45 RIT and ASCT for B-NHL, T-NHL, and HL. MethodsPatients were ≥18 years old with relapsed, refractory, or high-risk B-NHL, T-NHL, or HL and had acceptable organ function with an ECOG performance status of 0-1 and no detectible human anti-mouse antibodies. They could not have received ≥20 Gy of prior radiation (RT) to critical organs or prior ASCT within 1 year, or prior allogeneic transplant at any time. All patients first received anti-CD45 antibody (BC8) trace-labeled with 131I followed by gamma camera imaging to evaluate biodistribution and estimate organ-specific absorbed doses. Patients then received 131I-BC8 at an absorbed dose determined by the following: Patients with prior RT >20 Gy or prior ASCT started at 10 Gy to the dose-limiting normal organ (Arm A), while others started dose escalation at 20 Gy (Arm B). Subsequent dose escalation/de-escalation followed a two-stage approach (Storer, 2001). ASCT occurred after sufficient radiation decay, and G-CSF was started on day 1. Dose limiting toxicity (DLT) was determined by Bearman grade III/IV events. The primary objective was to estimate the maximum tolerated dose, defined as that yielding a DLT rate of 25%. Responses were scored using standard criteria (Cheson, 2007). ResultsBetween August 2009 and March 2013, 15 patients were treated. Median age was 62 years (range 20-71); stage III/IV = 11 (73%); median prior regimens = 3 (range 2-12), including 1 prior ASCT; chemorefractory disease (i.e., <PR to the most recent chemotherapy) = 8 (53%); histologies were HL (n = 6), B-NHL (n = 6), and T-NHL (n = 3; see Table). The mean administered 131I activity was 646 mCi (range 344-1064 mCi; 23.9 GBq, range 12.7-39.4 GBq). The liver was the dose-limiting normal organ in 12 patients (2.41-3.98 cGy/mCi). The absorbed dose was escalated to 14 Gy for patients in Arm A (n = 3) and 30 Gy in Arm B (n = 12). Neutrophil (>500/μl) and platelet (>20 K/μl) engraftment occurred a median of 8 (range 10-20) and 12 (range 8-26) days after ASCT, respectively. No DLTs, non-relapse deaths, or non-hematologic toxicities > NCI-CTCAE v3 grade 3 have been observed. Currently, 11 (73%) patients are alive and 7 (47%) are progression-free with a median follow-up of 12 months. Seven (54%) of 13 patients with measurable disease at enrollment had objective disease responses, including 3 of 3 with T-NHL, 3 of 6 with HL, and 1 of 1 with follicular lymphoma (FL; see Table). ConclusionMyeloablative doses of 131I targeted to CD45 are safe and feasible in patients with lymphoma, with no DLTs observed after delivery of up to 30 Gy to the liver. Objective disease responses in heavily-treated B-NHL, T-NHL, and HL were observed. This work has led to current studies using yttrium-90 as the therapeutic radionuclide (given its longer beta pathlength and absence of gamma emission) in anti-CD45 RIT for lymphoma. Disclosures:No relevant conflicts of interest to declare.

131I-tositumomab myeloablative radioimmunotherapy for non-Hodgkin’s lymphoma

To investigate radiation doses to the testes delivered by a radiolabeled anti-CD20 antibody and its effects on male sex hormone levels. Testicular uptake and retention of (131)I-tositumomab were measured, and testicular absorbed doses were calculated for 67 male patients (54 ± 11 years of age) with non-Hodgkin's lymphoma who had undergone myeloablative radioimmunotherapy (RIT) using (131)I-tositumomab. Time-activity curves for the major organs, testes, and whole body were generated from planar imaging studies. In a subset of patients, male sex hormones were measured before and 1 year after the therapy. The absorbed dose to the testes showed considerable variability (range = 4.4-70.2 Gy). Pretherapy levels of total testosterone were below the lower limit of the reference range, and post-therapy evaluation demonstrated further reduction [4.6 ± 1.8 nmol/l (pre-RIT) vs. 3.8 ± 2.9 nmol/l (post-RIT), P<0.05]. Patients receiving higher radiation doses to the testes (≥ 25 Gy) showed a greater reduction [4.7 ± 1.6 nmol/l (pre-RIT) vs. 3.3 ± 2.7 nmol/l (post-RIT), P<0.05] compared with patients receiving lower doses (<25 Gy), who showed no significant change in total testosterone levels. The testicular radiation absorbed dose varied highly among individual patients. Patients receiving higher doses to the testes were more likely to show post-RIT suppression of testosterone levels.

A Phase II Trial of Myeloablative I-131-Tositumomab, Etoposide and Cyclophosphamide Followed by Autologous Transplantation for B-Cell Non-Hodgkin's Lymphoma

AbstractAbstract ▪811▪This icon denotes a clinically relevant abstract Background:High-dose therapy and autologous hematopoietic stem cell transplantation (ASCT) is the standard of care for many patients (pts) with high-risk or relapsed B-cell non-Hodgkin lymphoma (B-NHL). Despite the use of transplant, relapse is likely for most with indolent or mantle cell lymphoma (MCL) as well as for aggressive B-NHL recurring after rituximab (R)-based chemotherapy. Total body irradiation (TBI) has been incorporated into ASCT regimens to overcome chemotherapy resistance and improve outcomes, but studies to date indicate that escalation of TBI is not feasible due to toxicity in non-target organs. We hypothesized that radioimmunotherapy (RIT) could supplant TBI and identified the maximally tolerated dose (MTD) of high-dose RIT using I-131-tositumomab that could be safely combined with high-dose etoposide (VP-16) and cyclophosphamide (CY) prior to ASCT (Press, Blood 2000). We now present the mature data of a large prospective phase II trial at the MTD of high-dose I-131-tositumomab, VP-16, and CY. Methods:Pts were eligible if they were <60 years of age, had MCL in first remission or any relapsed/refractory B-NHL, an ECOG PS of 0–1, acceptable organ function, >2×106 autologous CD34+ peripheral blood stem cells/kg collected, <20 Gy prior radiation to critical organs, and no human-anti-mouse-antibodies. All pts underwent outpatient biodistribution studies using tositumomab (1.7 mg/kg, n= 64 or 485mg flat dose, n= 43) labeled with ∼10mCi I-131 followed by serial quantitative gamma camera imaging to calculate individualized organ-specific absorbed dose estimates. Pts then received therapeutic infusions of I-131-tositumomab to deliver 25Gy to the critical normal organ receiving the highest radiation absorbed dose. When residual radiation was <7mR/hr at 1m (median 10 days) pts received 60mg/kg VP-16 followed 48 hours later by 100mg/kg CY. ASCT occurred when residual radiation was <2mR/hr at 1m. Toxicity was scored on the Bearman transplant scale and CTCAE 2.0. Response followed standard criteria. Results:Between June 1999 and April 2011 107 pts were transplanted on this protocol. Baseline characteristics included: median age 52 yrs (range 32–60), stage III/IV = 104 (97%), median number of prior regimens = 3 (range 1–11), prior R = 98 (92%), R refractory = 35 (33%), chemoresistant disease (defined as < a partial response [PR] to the most recent regimen) = 41 (40%), >1 extranodal site = 36 (33%), elevated LDH = 46 (42%). Histological strata: Indolent 43% (45 follicular lymphoma [FL], 1 lymphoplasmacytic lymphoma), MCL = 31%, Aggressive 27% (27 diffuse large B-cell including 12 with transformed disease, 2 Burkitt’s). Dose limiting critical normal organs receiving up to 25Gy included lung (71), liver (29), kidney (6), and heart (1) from a median administered I-131 activity of 557 mCi (range 231–1353) resulting in a median whole body dose of 4.4Gy. ASCT occurred an average of 14 days after the I-131-tositumomab infusion with a median of 5.9×106 CD34/kg (range 2–20×106 CD34/kg). An unsupported ANC>500/μL and platelets >20K/μL occurred at a median of day 12 and day 13, respectively. Bearman toxicity of grade III/IV was observed in 6 pts (5.6%) with 3 (3%) non-relapse deaths (all cardiopulmonary toxicity) by day 100. Pulmonary toxicity of ≥ grade 4 CTCAE occurred in 10 (9%) pts. Responses to therapy included: CR/CRu = 87 (81%), PR = 8 (7%), SD = 11 (10%), and PD = 1 (1%). Currently, 76 (71%) pts are alive with 59 (55%) progression-free. The estimated 5-year overall survival (OS), progression-free survival (PFS) and relapse were 72%, 56%, and 36%, respectively (figure, median follow up of 5.2 years). Five-year OS/PFS estimates for the 3 histological groups included indolent (81%/61%), aggressive (69%/51%), and MCL (57%/52%). MCL pts with relapsed/refractory disease had a 5-year OS/PFS of 55%/42%. Multivariable analysis only identified chemoresistant disease as associated with death (HR 3.07 (1.46–6.44, p=.003) and relapse or death (HR 2.12 (1.17–3.86, p=.01). Secondary AML/MDS occurred in 1 patient to-date. Conclusions:This largest prospective trial of myeloablative RIT demonstrates that I-131-tositumomab delivering 225Gy to critical organs along with high-dose VP-16 and CY prior to ASCT is feasible and effective with toxicities comparable to TBI-based regimens. These data provide the foundation for future approaches incorporating RIT into transplant conditioning regimens for lymphoma. [Display omitted] Disclosures:Gopal:GSK: Research Funding; Spectrum: Research Funding. Off Label Use: high-dose use of I-131-tositumomab. Rajendran:GSK: Research Funding. Pagel:GSK: Research Funding. Maloney:GSK: Research Funding. Press:GSK: Research Funding.

Acute leukemia in adults: novel allogeneic transplant strategies

Acute myeloid leukemia (AML) is the most common indication for hematopoietic cell transplantation (HCT). Significant improvements in histocompatibility testing have resulted in identifying better alternative donors to provide grafts; coupled with expanding use of reduced-intensity conditioning (RIC) regimens, patient outcomes have improved. Most AML patients in complete remission now can undergo allogeneic HCT procedures with an anticipated result that approaches that obtained with sibling donors and myeloablative conditioning (MAC). Treatment-related mortality (TRM), relapse, GVHD and, for umbilical cord blood (UCB) grafts, slow engraftment/engraftment failures, however, continue to plague HCT. Newer strategies include the use of double unit UCB HCT and ex vivo expansion of UCB units using: multipotent mesenchymal stromal cells (MSCs); polyamine copper chelator tetraethylenepentamine (TEPA); and Notch ligand. Haploidentical bone marrow and blood HCT are increasing in numbers given the improved outcome with post-HCT cyclophosphamide therapy. Novel chemotherapeutic preparative regimens incorporating agents such as clofarabine and treosulfan, and novel radiation preparative regimens utilizing selective radiation approaches (helical tomotherapy) and targeted myeloablative radioimmunotherapy appear to enhance the anti-AML effect. Immunological approaches with chimeric antigen receptor-redirected T lymphocytes have been added to the armamentarium. Other novel maneuvers include more sophisticated T-cell depletion of the donor graft and post-transplant immunotherapy with regulatory T cell (Treg) therapy and MSCs for GVHD prevention. These and other strategies are improving the outlook of AML HCT recipients.

A Phase I Study of Myeloablative I-131-Anti CD-20 (Tositumomab) Radioimmunotherapy with Escalating Doses of Fludarabine Followed by Autologous Hematopoietic Stem Cell Transplantation (ASCT) for Adults ≥ 60 Years of Age with High-Risk or Relapsed/Refractory B-Cell Lymphoma

Abstract 663 Background:The majority of patients with relapsed or refractory B-cell, non-Hodgkin's lymphoma (NHL) are over 60 years of age, yet many are denied potentially curative high-dose regimens due to concerns of excessive toxicity. We have shown that myeloablative anti-CD20 radioimmunotherapy (RIT) can safely deliver effective radiation doses to tumor sites while limiting exposure to normal organs in older adults requiring high-dose therapy, however, not all patients in this series remained progression-free (Gopal, JCO 2007). Preclinical data suggest that improved anti-tumor activity may be attained by the concurrent administration of nucleoside analogs (fludarabine, cytarabine) which synergize with RIT (Johnson, Int J Cancer; Gopal, BBMT, 2006). We hypothesized that a prolonged regimen of fludarabine could be administered concurrently with myeloablative RIT and ASCT to safely augment the efficacy of this approach. We present the phase I data evaluating this strategy. Methods:Patients were eligible if they were 60 years of age or older, had mantle cell lymphoma (MCL) in first remission or relapsed/refractory B-NHL, an ECOG PS of 0–1, acceptable organ function, >2×106 autologous CD34+ peripheral blood stem cells/kg collected, <20 Gy prior radiation to critical organs, and no human-anti-mouse-antibodies (HAMA). All patients underwent outpatient biodistribution studies for dosimetry using tositumomab (1.7 mg/kg, n=3 or 485mg flat dose, n=33) labeled with ∼10mCi I-131 followed by serial quantitative gamma camera imaging to calculate individualized organ-specific absorbed dose estimates. Patients then received therapeutic infusions of I-131-tositumomab to deliver 27Gy to the critical normal organ receiving the highest radiation exposure. Forty-eight hours later fludarabine was administered in escalating doses to patients (Table) to define a regimen associated with a dose limiting toxicity (DLT = grade III/IV Bearman toxicity) rate of <25%. ASCT occurred when radiation exposure was estimated to be <2mR/hr at 1meter. Filgrastim at 5μg/kg/day or pegfilgrastim at 6mg × 1 was started on day 1. Response was scored using standard criteria. Results:Between July 2005 and May 2011 36 patients were treated. Baseline characteristics included: median age 65 yrs (range 60–76), stage III/IV = 34 (94%), median number of prior regimens = 2 (range 1–9), chemoresistant disease (defined as < a partial response [PR] to the most recent regimen) = 12 (33%), >1 extranodal site = 14 (39%), elevated LDH at treatment = 13 (36%), IPI score at transplant 3–5 = 53%. Histology: MCL = 23, diffuse large B-cell = 8 (with 5 transformed from follicular lymphoma [FL]), FL=3, and marginal zone = 1, Waldenstrom’s = 1. Dose limiting organs receiving up to 27Gy included lung (30), kidney (4), and liver (2) with a median administered I-131 activity of 471 mCi (range 260–1620). Fludarabine was escalated from 10 mg/m2/day × 5 days to 30 mg/m2 × 7 days without observation of a DLT (Table). The median CD34 dose was 5.42 ×106/kg with neutrophil (ANC>500μl) and platelet (>20 K/μl) engraftment occurring a median on 10 and 12 days after ASCT, respectively. Only 2 patients developed grade 4 NCI-CTC grade 4 non-hematologic toxicities (hypokalemia/hypophosphatemia, depression), 25 (69%) remained outpatients after discharge from radiation isolation, and there were no non-relapse deaths in the first 100 days after transplant. Responses to therapy were as follows: CR/CRu = 26 (79%), PR = 2 (6%), SD = 4 (11%), and PD = 4 (11%). Currently, 23 (64%) patients are alive with 22 (61%) progression free. The estimated 3 yr overall survival, progression-free survival, relapse, and non-relapse mortality are 54%, 53%, 41%, and 7%, respectively (median follow up of 2.5yrs after ASCT, Figure). Improved survival was associated with <2 prior regimens (HR=.08, p=.02) and chemosensitive disease (HR=.35, p=.07).Table:Dose escalation schema and dose limiting toxicities (DLT) of High-dose (27Gy) I-131 tositumomab + fludarabine + ASCTDose levelnFludarabine daily dose (mg/m2)# of dosesTotal dose (mg/m2)# DLT0710550015155750252051000352551250463051500553061800633072100 [Display omitted] Conclusions:High-dose (27 Gy) I-131 tositumomab can safely be administered concurrently with up to 210 mg/m2 fludarabine in an older, high-risk patient population. This strategy warrants further investigation as a method to safely augment the antitumor activity of myeloablative RIT. Disclosures:Gopal:GSK: Research Funding; Spectrum: Research Funding; Seattle Genetics: Consultancy, Research Funding; Merck: Research Funding; Piramal: Research Funding; Cephalon: Research Funding; Millenium: Speakers Bureau; Abbott: Research Funding; Pfizer: Research Funding; SBio: Research Funding; Bio Marin: Research Funding; Biogen-Idec: Research Funding. Off Label Use: High-dose use of I-131-tositumomab. Maloney:GSK: Consultancy, Honoraria.

Myeloablative doses of yttrium‐90‐ibritumomab tiuxetan and the risk of secondary myelodysplasia/acute myelogenous leukemia

Because the long-term toxicity of myeloablative radioimmunotherapy remains a matter of concern, the authors evaluated the hematopoietic damage and incidence of secondary myelodysplastic syndrome and acute myelogenous leukemia (sMDS/AML) in patients who received myeloablative doses of the radiolabeled antibody yttrium-90 (⁹⁰Y)-ibritumomab tiuxetan. The occurrence of sMDS/AML was investigated prospectively in 53 elderly patients with non-Hodgkin lymphoma (NHL) who underwent an autograft after high-dose radioimmunotherapy (HD-RIT) myeloablative conditioning with ⁹⁰Y-ibritumomab tiuxetan. Bone marrow (BM) hematopoietic progenitors and telomere length (TL) also were investigated. At a median follow-up of 49 months, 4 patients developed sMDS/AML at 6 months, 12 months, 27 months, and 36 months after HD-RIT, and the 5-year cumulative incidence of sMDS/AML was 8.29%. A significant but transient decrease in BM granulocyte-macrophage progenitors was observed; whereas multilineage, erythroid, and fibroblast progenitors were unaffected. A significant and persistent shortening of BM TL also was detected. A matched-pair analysis comparing the study patients with 55 NHL patients who underwent autografts after chemotherapy-based myeloablative conditioning demonstrated a 8.05% 5-year cumulative incidence of sMDS/AML. HD-RIT for patients with NHL was associated with 1) limited toxicity on hematopoietic progenitors, 2) accelerated TL shortening, and 3) non-negligible incidence of sMDS/AML, which nevertheless was comparable to the incidence observed in a matched group of patients who received chemotherapy-based conditioning. Thus, in the current series of elderly patients with NHL, the development of sMDS/AML was not influenced substantially by HD-RIT.

Tandem high-dose therapy in relapsed and refractory B-cell lymphoma: results of a prospective phase II trial of myeloablative chemotherapy, followed by escalated radioimmunotherapy with 131I-anti-CD20 antibody and stem cell rescue

A phase II trial evaluated safety, feasibility and efficacy of a sequential tandem approach combining myeloablative BEAM chemotherapy and autologous stem cell transplantation (ASCT) with myeloablative radioimmunotherapy (HD-RIT), with (131)I-anti-CD20 antibody ((131)I-rituximab), followed by a second ASCT in patients with relapsed or refractory CD20+ B-cell lymphoma. According to protocol, 16 patients with relapsed (n = 14) and refractory (n = 2) CD20+ B-cell lymphoma received salvage therapy with rituximab and Dexa-BEAM, followed by BEAM (HD chemotherapy) and high-dose myeloablative radioimmunotherapy 2-6 months after BEAM. Nine of 16 patients received HD-RIT; seven patients were excluded before HD-RIT because of toxicity or progressive disease. Disease histologies were follicular lymphoma (FL) grades 1 and 2 (n = 4), transformed follicular (FL 3b; n = 6), diffuse large B-cell (DLBCL; n = 4), mantle cell (n = 1) and marginal zone lymphoma (n = 1). After a median follow-up of 50.4 months for OS and 39.7 months for progression-free survival (PFS), estimated 4-year OS and PFS were 67% and 64%, respectively. The estimated 4-year OS and PFS for patients with FL were 80% and 78%, respectively. Toxicity was significant, including one fatal outcome due to pneumonitis. Tandem transplants consisting of HD chemotherapy followed by HD-RIT with (131)I-coupled anti-CD20 are manageable and effective but toxic treatment modalities for relapsed poor prognosis CD20+ B-NHL.

La radio-immunothérapie

Radioimmunotherapy (RIT) is a new modality of targeted therapy in which irradiation from radionuclides is delivered to tumor targets using monoclonal antibodies (MAb) directed to tumor-associated antigen. RIT has been developed for more than 20 years. Today, RIT can be used in clinical practice using non-ablative activity of murine anti-CD20 90Y-ibritumomab tiuxetan (ZevalinÒ) for treatment of patients with relapsed or refractory FL, with overall response rate of 70 to 80% and 20 to 30% of complete response. Different approaches are explored to improve efficacy of RIT in NHL: myeloablative RIT or HD treatment, RIT as consolidation after chemotherapy to target MRD, RIT in first-line treatment, fractionated RIT, RIT using other Ag targets. For solid tumors, interesting results have been obtained using anti-CEA RIT delivered as consolidation treatment or using pretargeting system.

Myeloablative radioimmunotherapy in conditioning prior to haematological stem cell transplantation: closing the gap between benefit and toxicity?

High-dose radio-/chemotherapy in the context of autologous and allogeneic haematopoietic stem cell transplantation is a double-edged sword. The requirement for dose intensification is linked to an increase in toxicity to noninvolved organs. Particularly for older patients and patients with comorbidities, efficient but toxicity-reduced schemes are needed. Myeloablative radioimmunotherapy is a targeted, internal radiotherapy that uses radiolabelled monoclonal antibodies (mAb) with affinity to the bone marrow. It involves the administration of high radiation doses (up to 30 Gy) to the bone marrow and spleen but without exposing radiosensitive organs to doses higher than 1-7 Gy. Added to conventional or intensity-reduced conditioning, myeloablative radioimmunotherapy may achieve a pronounced antileukaemic effect with tolerable toxicities. A rational and individual design of the ideal nuclide-antibody combination optimizes therapy. The anti-CD33, anti-CD45 and anti-CD66 mAbs appear to be ideal tracers so far. The beta-emitter (90)Y is coupled by DTPA and is the best nuclide for myeloablation. Approval trials for DTPA anti-CD66 mAb are underway in Europe, and in the near future these therapies may become applicable in practice. This review gives an overview of current myeloablative conditioning radioimmunotherapy. We discuss the selection of the optimal radioimmunoconjugate and discuss how radioimmunotherapy might be optimized in the future by individualization of therapy protocols. We also highlight the potential advantages of combination therapies.

Myeloablative Radioimmuntherapien zur Konditionierung bei Patienten mit AML, MDS und multiplem Myelom vor Stammzelltransplantation

Aggressive consolidation chemotherapy and hematopoietic stem cell transplantation have improved the prognosis of patients with acute myeloid leukemia (AML), myelodyplastic syndrome (MDS) and multiple myeloma. Nevertheless, only a minor fraction of patients achieve long-term disease-free survival after stem cell transplantation with disease recurrence being the most common cause of treatment failure. In addition, therapy-related effects such as toxicity of chemotherapy and complications of stem cell transplantation increase mortality rates significantly. Myeloablative radioimmunotherapy uses radiolabeled monoclonal antibodies (mAb) with affinity for the hematopoietic marrow. It applies high radiation doses in the bone marrow but spares normal organs. Adding myeloablative radioimmunotherapy to the conditioning schemes of AML, MDS and multiple myeloma before stem cell transplantation allows for the achievement of a pronounced antileukemic / antimyeloma effect for the reduction of relapse rates without significant increase of acute organ toxicity and therapy-related mortality. In order to optimise therapy, a rational design of the nuclide-antibody combination is necessary. 90 Y, 188 Re and 131 I are the most frequently used β - -particles. Of these, 90 Y is the most qualified nuclide for myeloablation. Backbone stabilised DTPA are ideal chelators to stably conjugate 90 Y to antibodies so far. For myeloablative conditioning, anti-CD66-, -45- and -33-mAb are used. The anti-CD66-antibody BW250 / 183 binds to normal hematopoietic cells but not to leukemic blasts and myeloma cells. The 90 Y-2B3M-DTPA-BW250 / 183 is the most suited radioimmunoconjugate for patients with an infiltration grade of leukemic blasts in the bone marrow < 25 %. The specific doses (Gy / GBq) are 10.2 ± 1.8 (bone marrow), 2.7 ± 2 (liver) and < 1 (kidneys). In contrast, radiolabeled anti-CD33- and anti-CD45-antibodies bind to both, most of white blood cells and leukemic blasts. They enable the treatment of leukemia patients with a high medullar tumor load or extramedullar leukemic blast infiltration. Specific doses (Gy / GBq) for the 90 Y-anti-CD45-mAb YAML568 are 6.4 ± 1.2 (bone marrow), 3.9 ± 1.4 (liver) and 1.1 ± 0.4 (kidneys). CD45 is expressed also on the extramedullar clonogenic myeloma progenitor cell that circulates in the peripheral blood. Thus, the conditioning of patients with multiple myeloma may markedly be improved using a combination of α- and β-anti-CD45-mAbs. This review provides a systematic and critical overview of the currently used radionuclides and antibodies for the treatment of AML, MDS and multiple myeloma and summarizes the present literature on clinical trials of myeloablative radioimmunotherapies for conditioning before both, autologous and allogeneic stem cell transplantation.

Myeloablative 131I-Tositumomab Radioimmunotherapy in Treating Non-Hodgkin's Lymphoma: Comparison of Dosimetry Based on Whole-Body Retention and Dose to Critical Organ Receiving the Highest Dose

Myeloablative radioimmunotherapy using (131)I-tositumomab (anti-CD20) monoclonal antibodies is an effective therapy for B-cell non-Hodgkin's lymphoma. The amount of radioactivity for radioimmunotherapy may be determined by several methods, including those based on whole-body retention and on dose to a limiting normal organ. The goal of each approach is to deliver maximal myeloablative amounts of radioactivity within the tolerance of critical normal organs. Records of 100 consecutive patients who underwent biodistribution and dosimetry evaluation after tracer infusion of (131)I-tositumomab before radioimmunotherapy were reviewed. We assessed organ and tissue activities over time by serial gamma-camera imaging to calculate radiation-absorbed doses. Organ volumes were determined from CT scans for organ-specific dosimetry. These dose estimates helped us to determine therapy on the basis of projected dose to the critical normal organ receiving a maximum tolerable radiation dose. We compared organ-specific dosimetry for treatment planning with the whole-body dose-assessment method by retrospectively analyzing the differences in projected organ-absorbed doses and their ratios. Mean organ doses per unit of administered activity (mGy/MBq) estimated by both methods were 0.33 for liver and 0.33 for lungs by the whole-body method and 1.52 for liver and 1.74 for lungs by the organ-specific method (P=0.0001). The median differences between methods were 0.92 mGy/MBq (range, 0.36-2.2 mGy/MBq) for lungs, 0.82 mGy/MBq (range, 0.28-1.67 mGy/MBq) for liver, and -0.01 mGy/MBq (range, -0.18-0.16 mGy/MBq) for whole body. The median ratios of the treatment activities based on limiting normal-organ dose were 5.12 (range, 2.33-10.01) for lungs, 4.14 (range, 2.16-6.67) for liver, and 0.94 (range, 0.79-1.22) for whole body. We found substantial differences between the dose estimated by the 2 methods for liver and lungs (P=0.0001). Dosimetry based on whole-body retention will underestimate the organ doses, and a preferable approach is to evaluate organ-specific doses by accounting for actual radionuclide biodistribution. Myeloablative treatments based on the latter approach allow administration of the maximum amount of radioactivity while minimizing toxicity.

Radioimmunotherapy-Based Conditioning Regimens for Stem Cell Transplantation

Radioimmunotherapy (RIT) combines the mechanism of action and targeting capability of monoclonal antibodies with the tumoricidal effect of radiation and has shown promising results in the treatment of various hematologic malignancies. Based on RIT's efficacy and safety profile, many investigators have evaluated its use in transplant conditioning regimens with the goal of improving long-term disease control with limited toxicity. In lymphoma, two basic transplant approaches targeting CD20 have emerged: (1) myeloablative doses of RIT with or without chemotherapy, and (2) standard nonmyeloablative doses of RIT combined with high-dose chemotherapy. Myeloablative RIT has been shown to be feasible and efficacious using escalated doses of iodine 131-tositumomab, yttrium 90-ibritumomab tiuxetan, and (131)I-rituximab with or without chemotherapy followed by autologous stem cell transplant (ASCT). The second approach predominantly has used standard doses of (90)Y-ibritumomab tiuxetan or (131)I-tositumomab plus BEAM chemotherapy (carmustine [BCNU], etoposide, cytarabine, melphalan) followed by ASCT. RIT targeting CD45, CD33, and CD66 prior to allogeneic transplantation also has been evaluated for the treatment of acute leukemia. Overall RIT-based transplant conditioning for lymphoma and leukemia has been shown to be safe, effective, and feasible with ongoing randomized trials currently underway to definitively establish its place in the treatment of hematologic malignancies.

High-Dose [131I]Tositumomab (anti-CD20) Radioimmunotherapy and Autologous Hematopoietic Stem-Cell Transplantation for Adults ≥ 60 Years Old With Relapsed or Refractory B-Cell Lymphoma

The majority of patients with relapsed or refractory B-cell non-Hodgkin's lymphoma (NHL) are older than 60 years, yet they are often denied potentially curative high-dose therapy and autologous stem-cell transplantations (ASCT) because of the risk of excessive treatment-related morbidity and mortality. Myeloablative anti-CD20 radioimmunotherapy (RIT) can deliver curative radiation doses to tumor sites while limiting exposure to normal organs and may be particularly suited for older adults requiring high-dose therapy. Patients older than 60 years with relapsed B-cell NHL (B-NHL) received infusions of tositumomab anti-CD20 antibody labeled with 185 to 370 Mbq (5 to 10 mCi) [131I]-tracer for dosimetry purposes followed 10 days later by individualized therapeutic infusions of [131I]tositumomab (median, 19.4 Gbq [525 mCi]; range, 12.1 to 42.7 Gbq [328 to 1,154 mCi]) to deliver 25 to 27 Gy to the critical normal organ receiving the highest radiation dose. ASCT was performed approximately 2 weeks after therapy. Twenty-four patients with a median age of 64 years (range, 60 to 76 years), who had received a median of four prior regimens (range, two to 14 regimens), were treated. Thirteen patients (54%) had chemotherapy-resistant disease. The estimated 3-year overall and progression-free survival rates were 59% and 51%, respectively, with a median follow-up of 2.9 years (range, 1 to 6 years). All patients experienced expected myeloablation with engraftment of platelets (> or = 20 K/microL) and neutrophils ( 500/microL), occurring at a median of 9 and 15 days after ASCT, respectively. There were no treatment-related deaths, and only two patients experienced grade 4 nonhematologic toxicity. Myeloablative RIT and ASCT is a safe and effective therapeutic option for older adults with relapsed B-NHL.

Preparation and evaluation of 89Zr-Zevalin for monitoring of 90Y-Zevalin biodistribution with positron emission tomography

To evaluate whether (89)Zr can be used as a PET surrogate label for quantification of (90)Y-ibritumomab tiuxetan ((90)Y-Zevalin) biodistribution and dosimetry before myeloablative radioimmunotherapy. Zevalin was labelled with (89)Zr by introducing N-succinyldesferal (N-sucDf) as a second chelate. For comparison of the in vitro stability of (89)Zr-Zevalin and (88)Y-Zevalin (as a substitute for (90)Y), samples were incubated in human serum at 37 degrees C up to 6 days. Biodistribution of (89)Zr-Zevalin and (88)Y-Zevalin was assessed at 24, 48, 72 and 144 h p.i. by co-injection in nude mice bearing the non-Hodgkin's lymphoma (NHL) xenograft line Ramos. The clinical performance of (89)Zr-Zevalin-PET was evaluated via a pilot imaging study in a patient with NHL, who had undergone [(18)F]FDG-PET 2 weeks previously. Modification of Zevalin with N-sucDf resulted in an N-sucDf-to-antibody molar ratio of 0.83+/-0.04. After radiolabelling and purification, the radiochemical purity and immunoreactivity of (89)Zr-Zevalin always exceeded 95% and 80%, respectively. (89)Zr-Zevalin showed the same stability in serum as (88)Y-Zevalin, with a radiochemical purity >95% during a period of 6 days. The co-injected (89)Zr-Zevalin and (88)Y-Zevalin conjugates showed a very similar biodistribution, except for liver and bone accumulation at 72 and 144 h p.i., which was significantly higher for (89)Zr than for (88)Y. PET images obtained after injection of (89)Zr-Zevalin showed clear targeting of all known tumour lesions. (89)Zr-Zevalin and (88)Y-Zevalin showed a very similar biodistribution in mice, implying that (89)Zr-Zevalin-PET might be well suited for prediction of (90)Y-Zevalin biodistribution in a myeloablative setting.

Tandem HD-chemotherapy and myeloablative radioimmunotherapy with 131I-anti-CD20 rituximab in relapsed and refractory B-cell lymphoma: Results of a phase II study of the German RAIT Study Group

13007 Background: Radioimmunotherapy has been shown to be effective in CD20 + B-cell lymphomas. Both non-myeloablative as well as myeloablative regimens have been employed for low grade and high grade lymphomas with impressive response rates and remission durations. Recently, the Press group and our group published data on myeloablative 131-I-anti-CD20 RAIT with high response rates and favourable long term survival especially in follicular lymphomas and transformed FL. Therefore, a phase II study is currently being done within the German Radioimmunotherapy Group, interim analysis data are presented. Methods: Patients were to receive R-Dexa-BEAM, followed by BEAM and HD-RAIT 2–6 months after BEAM. 131-I-Rituximab was administered with a maximum kidney and lung dose of 25 Gy. Sample size was calculated to be 16 to evaluate toxicity and feasibility of the tandem approach as primary endpoint. Results: 16 pts with relapsed (14) or primary refractory (2) B-cell lymphomas (FLI,II: 4pts; DLBCL: 4pts (all early relapses); transformed FL: 6 pts; MCL:1 pt, marginal zone lymphoma: 1 pt) were treated with 1 (15 pts) or 2 cycles (1 pt) of R-Dexa-BEAM. 13/16 pts achieving PR (5) or CRu (8) were treated with BEAM, 2 pts with PD and 1 with subdural hematoma were drop outs. After BEAM, 9/13 pts were in CR, 3/13 PR, 1/13 PD. Of 12 responding pts, 6 received HD-RAIT (1 pancytopenia, 1 hepatic, 2 pulmonary toxicity, 3 too early). After HD RAIT, 5/6 pts were in CR, 1 in PR. 4/6 pts (3 CR, 1 PR) are alive for 22–31 months, 2 pts died in CR, 1 of interstitial lung disease 2 months after HD-RAIT, 1 pt of pneumonia 8 months after HD-RAIT. Conclusions: Myeloablative RAIT is a feasible and effective treatment modality for relapsed poor prognosis CD20+ B-NHL not having severe toxicity due to the salvage regimen and HD-chemotherapy. HD RAIT offers the potential for long term relapse free survival. Final analysis of toxicity and outcome of this phase II study will be presented at the meeting. No significant financial relationships to disclose.

Retraction: Behr TM, Griesinger F, Riggert J, et al. High-dose myeloablative radioimmunotherapy of mantle cell non-hodgkin lymphoma with the iodine-131-labeled chimeric anti-CD20 antibody C2B8 and autologous stem cell support: results of a pilot study. Cancer. (2002) 94(4 Suppl):1363-72.

The original article to which this Retraction refers was published in Cancer (2002) 94(4 Suppl):1363-72.

Transplantation strategies for patients with follicular lymphoma

This review summarizes the current status and new developments in autologous and allogeneic transplantation strategies for patients with follicular lymphoma including novel concepts of myeloablative radioimmunotherapy, allogeneic transplantation with dose-reduced conditioning, and in-vivo purging strategies using B-cell-specific antibodies. Substantial progress has been made in the clinical management of follicular lymphoma. Besides immunochemotherapeutic approaches combining the B-cell antibody rituximab with conventional chemotherapy regimens, myeloablative chemotherapy or radiochemotherapy supported by autologous peripheral blood stem cell transplantation has been shown to be a highly effective treatment for advanced-stage disease. Dose-reduced conditioning regimens followed by allogeneic transplantation have substantially reduced treatment-related mortality of this approach and ongoing studies are evaluating whether the therapeutic benefit outweighs morbidity and mortality of this potentially curative treatment. Emerging concepts include the use of rituximab for in-vivo purging before reinfusion of autologous stem cells or the application of myeloablative radioimmunotherapy as part of myeloablative consolidation. The data on myeloablative therapy followed by autologous stem cell transplantation or allogeneic transplantation are encouraging. Allogeneic transplantation with dose-reduced conditioning should be further evaluated within clinical trials, however, in particular for patients with relapsed or refractory lymphoma. Future prospective randomized clinical trials should reevaluate the role of autologous stem cell transplantation in the era of antibody-based therapy and define the role of radioimmunotherapy and of reduced-intensity allogeneic transplantation.

Comparison of Radiation Dose Estimation for Myeloablative Radioimmunotherapy for Relapsed or Recurrent Mantle Cell Lymphoma Using131I Tositumomab to That of Other Types of Non-Hodgkin's Lymphoma

Patients with relapsed or refractory mantle cell lymphoma (MCL) demonstrate poor survival after standard treatment. Myeloablative radioimmunotherapy (RIT) using (131)I tositumomab (anti-CD20) has the ability to deliver specific radiation-absorbed dose to antigen-bearing tumor. We reviewed normal organ radiation- absorbed doses in MCL patients. Records of patients with MCL (n =25), who received myeloablative RIT between January 1996 and December 2003 were reviewed. Individual patient radiation dosimetry was performed on all patients after a trace-labeled infusion of (131)I tositumomab (mean = 348 MBq), to calculate the required amount of radioactivity for therapy, based on medical internal radiation dose (MIRD) schema. Mean organ residence times (hour) corrected for computed tomography (CT) derived organ volumes for MCL, were as follows: Lungs: 9.0; Liver: 12.4; Kidneys: 1.7; Spleen: 2.17; Whole Body: 62.4 and mean radiation absorbed doses mGy/Mbq were: Lungs: 1.2; Liver: 1.1; Kidneys: 0.85; Spleen: 1.7; Whole Body: 0.21. This is similar to patients with other non-Hodgkin's lymphoma (NHL). Patients received a mean activity of 21 GBq of (131)I (range, 11.5-41.4) for therapy estimated to deliver 25 Gy to the normal organ receiving the highest radiation-absorbed dose. Myeloablative RIT using (131)I tositumomab results in normal organ radiation-absorbed doses similar to those in patients with other non-Hodgkin's lymphoma, and is suitable for treating patients with relapsed or refractory MCL.

Quantitation of GD2 synthase mRNA by real‐time reverse transcription‐polymerase chain reaction

Antigen ganglioside GD2 is expressed abundantly on neuroblastoma (NB) cells. Anti-GD2 monoclonal antibody (MoAb) 3F8 kills NB cells by complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity. Its utility in bone marrow (BM) purging is evaluated by a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay to quantify the mRNA of GD2 synthase, the key enzyme in GD2 synthesis. From 1990 to 1993, 10 patients with relapsed/refractory Stage 4 NB participated in a pilot study. In these patients, MoAb 3F8 was used to purge tumor cells from harvested BM that had 5% or less tumor content by immunofluorescence (IF). Subsequently, 31 Stage 4 NB patients who underwent treatment on the N7 protocol (1994-1999) had their BM, which was in remission, purged by 3F8 before (131)I-3F8 myeloablative radioimmunotherapy. GD2-positive tumor cells before and after purging were quantified by real-time quantitative RT-PCR of GD2 synthase. GD2 positivity by IF was found before purging in six of eight patients in the pilot study. Five of six patients became negative postpurging. Of 31 patients on the N7 protocol, the more sensitive real-time quantitative RT-PCR detected GD2 synthase mRNA in the BM samples of 7 patients even though the prepurge BM samples were negative by histology and IF. Six of the seven BM samples became negative after 3F8 purging. Marker positivity before purging was statistically significant in predicting overall survival (P = 0.04), but not progression-free survival (P = 0.1). In vitro hematopoietic stem cell recovery and the median time to engraftment were acceptable. Tumor cell depletion quantified by real-time RT-PCR demonstrated efficacy of MoAb 3F8 in BM purging.