4. Antibody therapy for malignant lymphoma

Rituximab, a genetically engineered, chimeric anti-CD20 monoclonal antibody, induces the apoptosis of B-lymphoma cells, in addition to the lyses by complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC), as shown in Fig. 1. A Japanese phase I study of rituximab in relapsed or refractory patients with B-cell non-Hodgkin's lymphoma (B-NHL) showed an overall response rate (ORR) of 64% (7/11) with minimal toxicities. Elimination half-life (T(1/2)) of serum rituximab was 445+/-361 hours, and the serum rituximab was detectable at three months. In the subsequent phase II study, 90 relapsed or refractory patients with indolent B-NHL or mantle cell lymphoma (MCL) were treated with rituximab at 375 mg/m2x4 weekly infusions. ORRs in indolent B-NHL and MCL were 61% (37/61) and 46% (6/13), respectively. In this presentation, the results of clinical trials of antibody therapy of malignant lymphoma are summarized, focusing on the two recent Japanese multicenter trials of rituximab and a Japanese feasibility study of anti-CD20 radioimmunotherapy with yttrium-90-lableled ibritumomab tiuxetan.

[Ten years since the successful introduction of the first monoclonal antibody (rituximab) into the therapy of lymphomas]

Cancer treatment is based on combination of systemic chemotherapy and radiotherapy. The new methods of therapy based on biological priniciples have been introduced within last decade. The monoclonal antibody rituximab was launched ten years ago in 1997. This antibody against CD20 antigen, which is expressed on B cell lymphocytes and on the majority of B-cell lymphoid malignancies, has revolutionized the lymphoma therapeutic strategy. The immuno-chemotherapy has dramatically improved the outcome of diffuse large B-cell lymphomas patients. The combination of rituximab and chemotherapy as first line therapy has for the first time improved the survival of follicular lymphoma patients previously considered to be incurable. Rituximab has become the inevitable part of therapeutic regimens for other B-cell lymphomas, chronic lymphocytic leukaemia as well as for some non-malignant diseases. The important milestones, the therapeutic results of rituximab and other approved monoclonal antibodies (alemtuzumab, ibritumomab tiuxetan 90Y) is reviewed in this paper as well as short compendium of new antibodies is given. The cost effectiveness of the new therapy is discussed.

Therapeutic potential of 90Y- and 131I-labeled anti-CD20 monoclonal antibody in treating non-Hodgkin's lymphoma with pulmonary involvement: a Monte Carlo-based dosimetric analysis

Pulmonary involvement is common in patients with non-Hodgkin's lymphoma (NHL). (90)Y- and (131)I-anti-CD20 antibodies (ibritumomab tiuxetan and tositumomab, respectively) have been approved for the treatment of refractory low-grade follicular NHL. In this work, we used Monte Carlo-based dosimetry to compare the potential of (90)Y and (131)I, based purely on their emission properties, in targeted therapy for NHL lung metastases of various nodule sizes and tumor burdens.

METHODS

Lung metastases were simulated as spheres, with radii ranging from 0.2 to 5.0 cm, which were randomly distributed in a voxelized adult male lung phantom. Total tumor burden was varied from 0.2 to 1,641 g. Tumor uptake and retention kinetics of the 2 radionuclides were assumed equivalent; a uniform distribution of activity within tumors was assumed. Absorbed dose to tumors and lung parenchyma per unit activity in lung tumors was calculated by a Monte Carlo-based system using the MCNP4B package. Therapeutic efficacy was defined as the ratio of mean absorbed dose in the tumor to that in normal lung. Dosimetric analysis was also performed for a lung-surface distribution of tumor nodules mimicking pleural metastatic disease.

RESULTS

The therapeutic efficacy of both (90)Y and (131)I declined with increasing tumor burden. In treating tumors with radii less than 2.0 cm, (131)I targeting was more efficacious than (90)Y targeting. (90)Y yielded a broader distribution of tumor absorbed doses, with the minimum 54.1% lower than the average dose; for (131)I, the minimum absorbed dose was 33.3% lower than the average. The absorbed dose to normal lungs was reduced when the tumors were distributed on the lung surface. For surface tumors, the reductions in normal-lung absorbed dose were greater for (90)Y than for (131)I, but (131)I continued to provide a greater therapeutic ratio across different tumor burdens and sizes.

CONCLUSION

Monte Carlo-based dosimetry was performed to compare the therapeutic potential of (90)Y and (131)I targeting of lung metastases in NHL patients. (131)I provided a therapeutic advantage over (90)Y, especially in tumors with radii less than 2.0 cm and at lower tumor burdens. For both (90)Y- and (131)I-labeled antibodies, treatment is more efficacious when applied to metastatic NHL cases with lower tumor burdens. (131)I has advantages over (90)Y in treating smaller lung metastases.

Decreased intraperitoneal disease recurrence in epithelial ovarian cancer patients receiving intraperitoneal consolidation treatment with yttrium-90-labeled murine HMFG1 without improvement in overall survival

This study analyzes the site of disease recurrence in ovarian cancer patients to assess the influence of a single intraperitoneal (IP) administration of yttrium-90-labeled murine monoclonal antibody HMFG1 ((90)Y-muHMFG1) on the pattern of disease recurrence. In a large phase III trial ovarian cancer patients in complete clinical remission with FIGO stage Ic-IV were randomized between standard treatment plus a single IP (90)Y-labeled muHMFG1 versus standard treatment alone after negative second-look laparoscopy. Case report forms of all patients with disease recurrence were reviewed to determine site and date of recurrent disease. In total 447 patients were included in the study with a median follow-up of 3.5 years. Relapse was seen in 104/224 in the active and 98/223 in the control arm. Significantly fewer IP (p < 0.05) and more extraperitoneal (p < 0.05) relapses occurred in the active treatment arm. Time to IP recurrence was significantly longer (p = 0.0019) and time to extraperitoneal recurrence was significantly shorter for the active treatment arm (p < 0.001). The impact of IP radioimmunotherapy on IP relapse-free survival could only be seen in the subgroup of patients with residual disease after primary surgery (HR, 0.31; 95% CI, 0.18 to 0.53; p = 0.002). Although, there is no survival benefit for IP radioimmunotherapy as consolidation treatment for epithelial ovarian cancer, we found an improved control of IP disease, that was offset by increased extraperitoneal recurrences.

IART: intraoperative avidination for radionuclide treatment. A new way of partial breast irradiation

A new procedure, known as Intraoperative Avidination for Radionuclide Therapy (IART), is described in breast cancer patients. In this paper, we provide proof of the principle that intraoperative injection of avidin in the tumour bed after quadrantectomy allows homing in of intravenously (IV) administered radioactive biotin to the target site. This approach of targeted therapy consists of two steps: (i) "avidination" of the anatomical area of the tumour with avidin injected by the surgeon, into and around the tumour bed; (ii) targeting the anatomical area of the tumour by IV injection of radiolabelled biotin. The scintigraphic images demonstrated fast and stable uptake of labelled biotin at the site of operated breast. The radiation dose released to the index quadrant was more than 5 Gy/GBq, consistent with a boost of 20 Gy for an activity of 3.7 GBq 90Y-biotin (100mCi). A further large clinical trial facing IART in combination with reduced external-beam radiotherapy is, in our opinion, fully justified.

Design, Synthesis, and Biological Evaluation of Somatostatin-Based Radiopeptides

The prototypes for tumor targeting with radiolabeled peptides are derivatives of somatostatin. Usually, they primarily have high affinity for somatostatin receptor subtype 2 (sst2), and they have moderate affinity for sst5. We aimed at developing analogs that recognize different somatostatin receptor subtypes for internal radiotherapy in order to extend the present range of accessible tumors. We synthesized DOTA-octapeptides based on octreotide by replacing Phe3 mainly with unnatural amino acids. The affinity profile was determined by using cell lines transfected with sst1-5. Internalization was determined by using AR42J, HEK-sst3, and HEK-sst5 cell lines, and biodistribution was studied in rat tumor models. Two of the derivatives thus obtained showed an improved binding affinity profile, enhanced internalization into cells expressing sst2 and sst3, respectively, and better tumor:kidney ratios in animals.

Radiopharmaceutical management of90Y/111In labeled antibodies: shielding and quantification during preparation and administration

BACKGROUND

The combined application of potent beta-emitting isotopes for therapy with remitting isotopes for scintigraphy requires a profound regimen concerning team member safety and radionuclide quantification.

METHODS

We have developed materials and methods for a proper and easy manipulation of 90Y during preparation and administration of 90Y/111In pharmaceuticals used for radioimmunotherapy.

RESULTS

The efficacy of the shielding measures is documented. Protocols for the calibration of gamma-dose calibrators with respect to 90Y are extended to the assessment of quench-corrected liquid scintillation counting of 90Y. The contribution of 90Y backscatter to 111 In counting is quantified. Newly developed shielding equipment allows an adequate administration of relatively large volumes (100 ml) of 90Y/111In labeled pharmaceuticals to patients.

CONCLUSIONS

The procedures described combine pharmaceutical (Good Manufacturing Practice) and radiation safety requirements with an accurate logging of relevant data.

Diffusion-weighted MR imaging for determination of hepatocellular carcinoma response to yttrium-90 radioembolization

Early detection of the response of hepatocellular carcinoma (HCC) to yttrium-90 radioembolization therapy may be important to permit repeat radioembolization or alternative treatment options. Water-mobility measurements with use of diffusion-weighted (DW) magnetic resonance (MR) imaging are useful for noninvasive interrogation of microstructural tissue properties. Findings of DW MR imaging may serve as an early biomarker of HCC response. This study tested the hypothesis that DW MR imaging can detect changes in tumor tissue water diffusion in response to (90)Y therapy. In each of six patients with HCC included in the study, tumor water diffusion increased significantly after therapy. DW MR imaging is a promising technique for noninvasive assessment of tumor response to (90)Y radioembolization.

Reducing renal uptake of 90Y- and 177Lu-labeled alpha-melanocyte stimulating hormone peptide analogues

OBJECTIVE

The purpose of this study was to improve the tumor-to-kidney uptake ratios of (90)Y- and (177)Lu-[1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Re-Cys(3,4,10), d-Phe(7), Arg(11)]alpha-melanocyte stimulating hormone(3-13) {DOTA-Re(Arg(11))CCMSH} through coupling a negatively charged glutamic acid (Glu) to the peptide sequence.

METHODS

A new peptide of DOTA-Re(Glu(2), Arg(11))CCMSH was designed, synthesized and labeled with (90)Y and (177)Lu. Pharmacokinetics of (90)Y- and (177)Lu-DOTA-Re(Glu(2), Arg(11))CCMSH was determined in B16/F1 murine melanoma-bearing C57 mice.

RESULTS

(90)Y- and (177)Lu-DOTA-Re(Glu(2), Arg(11))CCMSH exhibited significantly (P<.05) less renal uptake values than (90)Y- and (177)Lu-DOTA-Re(Arg(11))CCMSH at 30 min and at 2, 4 and 24 h after dose administration. The renal uptake values of (90)Y- and (177)Lu-DOTA-Re(Glu(2), Arg(11))CCMSH were 28.16% and 28.81% of those of (90)Y- and (177)Lu-DOTA-Re(Arg(11))CCMSH, respectively, at 4 h postinjection. (90)Y- and (177)Lu-DOTA-Re(Glu(2), Arg(11))CCMSH displayed higher tumor-to-kidney uptake ratios than (90)Y- and (177)Lu-DOTA-Re(Arg(11))CCMSH at 30 min and at 2, 4 and 24 h after dose administration. The tumor-to-kidney uptake ratio of (90)Y- and (177)Lu-DOTA-Re(Glu(2), Arg(11))CCMSH was 2.28 and 1.69 times of (90)Y- and (177)Lu-DOTA-Re(Arg(11))CCMSH, respectively, at 4 h postinjection. The (90)Y- and (177)Lu-DOTA-Re(Glu(2), Arg(11))CCMSH activity accumulation was low in normal organs except for kidney.

CONCLUSIONS

Coupling a negatively charged amino acid (Glu) to the CCMSH peptide sequence dramatically reduced the renal uptake values and increased the tumor-to-kidney uptake ratios of (90)Y- and (177)Lu-DOTA-Re(Glu(2), Arg(11))CCMSH, facilitating their potential applications as radiopharmaceuticals for targeted radionuclide therapy of melanoma.

Validation of a Novel CHX-A‘ ‘ Derivative Suitable for Peptide Conjugation: Small Animal PET/CT Imaging Using Yttrium-86-CHX-A‘ ‘-Octreotide

A versatile bifunctional chelating reagent based on a preorganized cyclohexyl derivative of DTPA (CHX-A'') has been developed for the convenient N-terminal labeling of peptides with metal ion radionuclides of Bi(III), In(III), Lu(III), or Y(III). This was achieved via the synthesis of a mono-N-hydroxysuccinimidyl penta-tert-butyl ester derivative of CHX-A'' (trans-cyclohexyldiethylenetriaminepenta-acetic acid) featuring a glutaric acid spacer. Commercially obtained octreotide was modified at its N-terminus by this reagent in the solution phase, and its subsequent radiolabeling with (111)In (T(1/2) = 2.8 d) and (86)Y (T(1/2) = 14.7 h) demonstrated. Small animal PET/CT imaging results of (86)Y-CHX-A''-octreotide in a somatostatin receptor-positive tumor-bearing rat model are presented for the validation of the novel agent.

Ibritumomab tiuxetan for non-Hodgkin's lymphoma

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

Radioimmunotherapy of CD22-expressing Daudi tumors in nude mice with a 90Y-labeled anti-CD22 monoclonal antibody

A study was undertaken to investigate the efficacy of a high affinity, rapidly internalizing anti-CD22 monoclonal antibody for selectively delivering high-energy (90)Y radioactivity to B lymphoma cells in vivo. The antibody, RFB4, was readily labeled with (90)Y using the highly stable chelate, 1B4M-diethylenetriaminepentaacetic acid. Labeled RFB4 selectively bound to the CD22(+) Burkitt's lymphoma cell line Daudi, but not to CD22(-) control cells in vitro as compared with a control antibody, and was more significantly bound (P = 0.03) to Daudi solid tumors growing in athymic nude mice. Biodistribution data correlated well with the antitumor effect. The therapeutic effect of (90)Y-labeled anti-CD22 (Y22) was dose-dependent, irreversible, and the best results were achieved in mice receiving a single i.p. dose of 196 microCi. These mice displayed a significantly better (P < 0.01) antitumor response than control mice and survived >200 days with no evidence of tumor. Histology studies showed no significant injury to kidney, liver, or small intestine. Importantly, tumor-bearing mice treated with Y22 had no radiologic bone marrow damage compared with tumor-bearing mice treated with the control-labeled antibody arguing that the presence of CD22(+) tumor protected mice from bone marrow damage. When anti-CD22 radioimmunotherapy was compared to radioimmunotherapy with anti-CD19 and anti-CD45 antibodies, all three antibodies distributed significantly high levels of radioisotope to flank tumors in vivo compared with controls (P < 0.05), induced complete remission, and produced long-term, tumor-free survivors. These findings indicate that anti-CD22 radioimmunotherapy with Y22 is highly effective in vivo against CD22-expressing malignancies and may be a useful therapy for drug-refractory B cell leukemia patients.

Enhanced efficacy of 90Y-radiolabeled anti-Lewis Y humanized monoclonal antibody hu3S193 and paclitaxel combined-modality radioimmunotherapy in a breast cancer model

Radioimmunotherapy (RIT) of solid tumor is often limited in efficacy because of restrictions in achieved tumor dose. In an effort to overcome this, the combination of RIT with other therapeutic modalities was investigated in an animal model of breast carcinoma. The rationale for this combined-modality RIT (CMRIT) was to increase the therapeutic efficacy of RIT through the use of paclitaxel to arrest cells in the radiosensitive G(2)/M phase of the cell cycle.

METHODS

In this study, the biodistribution and therapeutic efficacy of (90)Y-radiolabeled humanized anti-Lewis Y hu3S193 monoclonal antibody ((90)Y-hu3S193) RIT in combination with paclitaxel chemotherapy was explored in a Lewis Y-expressing MCF-7 tumor xenografted BALB/c nude mouse model of breast cancer.

RESULTS

Biodistribution studies demonstrated excellent tumor targeting and limited normal tissue uptake by (90)Y-hu3S193. A therapeutic study with established tumors assessed (90)Y-hu3S193 as a single agent and demonstrated significant antitumor effects in all animals receiving a single intravenous 1.85 or 3.70 MBq dose of this treatment compared with phosphate-buffered saline placebo controls (P = 0.0008 vs. P < 0.0001). Complete responses were observed in all animals in the 3.70 MBq study arm for the duration of the study. Single-dose (90)Y-hu3S193 plus paclitaxel (600 microg) CMRIT displayed improved efficacy over single-modality therapies, with a significant difference (P < 0.0001) between the mean percentage change in tumor volume in mice receiving 0.46 MBq (90)Y-hu3S193 alone and when combined with 600 mug paclitaxel.

CONCLUSION

The significant efficacy of (90)Y-hu3S193 and paclitaxel CMRIT at low radiation doses in this model of breast carcinoma indicates its therapeutic potential and warrants further investigation into this promising therapeutic approach.

Three-dimensional positron emission tomography imaging with 124I and 86Y

BACKGROUND

Impure positron emitters have physical characteristics that degrade image quality compared to conventional positron emitters like 18F. Two impure positron emitters with potentially interesting applications are 124I and 86Y. The degradation in image quality due to the imperfection of these isotopes is quantified for a human three-dimensional (3-D) positron emission tomography (PET) system. An acquisition protocol to obtain similar image quality as for 18F imaging is determined by Monte Carlo simulations.

METHODS

The effects of larger positron range, associated singles and the other decay modes on image quality are determined by extensive Monte Carlo simulations of the Allegro scanner. Spatial resolution was evaluated for both isotopes and compared to spatial resolution of 18F. The loss in sensitivity due to triple coincidences was determined as a function of the axial acceptance angle of the PET scanner. The performance of the scanner at low count rates was studied by determining the noise equivalent count (NEC) values for different upper energy thresholds. The image degrading effect of spurious coincidences is taken into account by adding another factor to the NEC calculation. This allowed the contribution of spurious coincidences to be minimized by using a setting for the appropriate energy window. For this optimal energy window the amount of spurious and scattered coincidences was quantified. Simulations of count rate performance were also done to determine the peak NEC and the activity at which the maximum occurred.

RESULTS

Spatial resolution degradation, compared to 18F, is about 0.5 mm for 86Y and 1 mm for 124I. Associated singles have a similar effect as scattered coincidences, as they also add a background to the image. The effect, however, is less important than the effect of scatter. The fraction of triple coincidences is quite small for a 3-D PET scanner used for humans as the axial acceptance angle is still moderate. For the Allegro with an energy resolution of 18% the optimal upper energy threshold was determined at 600 keV. For 124I this leads to 2.5% extra contamination that needs to be added to the scatter fraction. For 86Y this fraction is about 5.5%.

CONCLUSION

3-D PET images of 124I and 86Y have lower spatial resolution. For PET scanners used for humans the difference is not as important as for scanners used for animals. The limited positron decay fraction of both isotopes can be compensated by increasing the imaging time by a factor of 3-5 (same activity). A short coincidence window limits the contamination from other decay modes. Good energy resolution allows setting a selective upper energy threshold to limit the effect of spurious coincidences. With an appropriate setting of the energy window it should be possible to obtain good image quality in a relatively short time because of the high sensitivity of 3-D PET scanners.

Intraperitoneal pretarget radioimmunotherapy with CC49 fusion protein

PURPOSE

This study examined a pretarget radioimmunotherapy strategy for treatment of an i.p. tumor model (LS174T).

EXPERIMENTAL DESIGN

The strategy used regional administration (i.p.) of a novel targeting molecule composed of four CC49 anti-tumor-associated glycoprotein 72 (TAG-72) single-chain antibodies linked to streptavidin as a fusion protein (CC49 fusion protein); 24 hours later, a synthetic clearing agent was administered i.v. to produce hepatic clearance of unbound CC49 fusion protein/synthetic clearing agent complexes. Four hours later, a low molecular weight radiolabeled reagent composed of biotin conjugated to the chelating agent 7,10-tetra-azacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) complexed with (111)In-, (90)Y-, or (177)Lu-DOTA-biotin was injected.

RESULTS

Radiolocalization to tumor sites was superior with i.p. administration of radiolabeled DOTA-biotin as compared with i.v. administration. Imaging and biodistribution studies showed excellent tumor localization of radioactivity with (111)In- or (177)Lu-DOTA-biotin. Tumor localization of (111)In-DOTA-biotin was 43% ID/g and 44% ID/g at 4 and 24 hours with the highest normal tissue localization in the kidney with 6% ID/g at 48 and 72 hours. Therapy studies with (90)Y-DOTA-biotin at doses of 400 to 600 microCi or (177)Lu-DOTA-biotin at doses of 600 to 800 microCi produced significant prolongation of survival compared with controls (P = 0.03 and P < 0.01).

CONCLUSIONS

Pretarget radioimmunotherapy using regional administration of CC49 fusion protein and i.p. (90)Y- or (177)Lu-DOTA-biotin represents a successful therapeutic strategy in the LS174T i.p. tumor model and this strategy may be applicable to human trials in patients with i.p. ovarian cancer.

Phase III Trial of Intraperitoneal Therapy With Yttrium-90–Labeled HMFG1 Murine Monoclonal Antibody in Patients With Epithelial Ovarian Cancer After a Surgically Defined Complete Remission

Purpose

This was a multinational, open-label, randomized phase III trial comparing yttrium-90–labeled murine HMFG1 (90Y-muHMFG1) plus standard treatment versus standard treatment alone in patients with epithelial ovarian cancer (EOC) who had attained a complete clinical remission after cytoreductive surgery and platinum-based chemotherapy.

Patients and Methods

In total, 844 International Federation of Gynecology and Obstetrics stage Ic to IV patients were initially screened, of whom 447 patients with a negative second-look laparoscopy (SLL) were randomly assigned to receive either a single dose of 90Y-muHMFG1 plus standard treatment (224 patients) or standard treatment alone (223 patients). Patients in the active treatment arm received a single intraperitoneal dose of 25 mg of 90Y-muHMFG1 (target dose 666 MBq/m2). The primary end point was length of survival; secondary end points included time to relapse and safety. The study had an 80% power to detect a 15% change in survival.

Results

After a median follow-up of 3.5 years (range, 1 to 6 years), 70 patients had died in the active treatment arm compared with 61 patients in the control arm. Cox proportional hazards analysis of survival demonstrated no difference between treatment arms. In the study drug arm, 104 patients experienced relapse compared with 98 patients in the standard treatment arm. No difference in time to relapse was observed between the two study arms. Active therapy was associated with occasional grade 3 or 4 thrombocytopenia and neutropenia and grade 1 or 2 GI symptoms, abdominal discomfort, arthralgia, and myalgia.

Conclusion

A single IP administration of 90Y-muHMFG1 to patients with EOC who had a negative SLL after primary therapy did not extend survival or time to relapse.

In vitro evaluation of no carrier added, carrier added and cross-complexed [90Y]-EDTMP provides evidence for a novel “foreign carrier theory”

The present study focused on the preparation of novel bone tracers containing yttrium as radionuclide or carrier. Moreover, these preparations were comparatively evaluated in vitro on the basis of a recently presented pre vivo model comprising binding studies on synthetic and human bone powder. It was shown that among the therapeutic radionuclides, no carrier added [(90)Y]-EDTMP exceeded [(188)Re]-EDTMP while yielding lower binding values than [(153)Sm]-EDTMP. Furthermore, the authors investigated the influence of "foreign" carriers added to [(90)Y]-EDTMP, [(99m)Tc]-EDTMP and [(111)In]-EDTMP by the method of cross-complexation. The findings reveal a new paradigm: a carrier more foreign to the complexed radionuclide causes a higher binding increase on human bone matrices in vitro than a more "related" carrier.

90Y Labeling of monoclonal antibody MOv18 and preclinical validation for radioimmunotherapy of human ovarian carcinomas

The monoclonal antibody (mAb) MOv18 binds the membrane alpha isoform of the folate receptor (FR) which is overexpressed in human ovarian carcinoma cells. Exploiting the targeting capacity of this mAb, we developed and preclinically validated a protocol for the stable labeling of the mAb with 90Y, an isotope which has shown promise in cancer radioimmunotherapy. MOv18 was derivatized with the stable macrocyclic ligand p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10- tetraacetic acid (Bz-DOTA). MOv18-Bz-DOTA conjugates were labeled with 90Y or 111In under metal-free and good laboratory practice conditions. At the optimal Bz-DOTA/mAb derivatization ratio of 4-5, conjugates maintained binding activity up to 6 months, were efficiently labeled with 90Y or 111In (mean labeling yield 85 and 64%, associated to a final mean specific activity of 74 and 37 MBq/mg) and displayed a mean immunoreactivity of 60 and 58%, respectively. The radiolabeled preparations were stable in human serum, with >97% radioactivity associated to mAb at 48 h after labeling. The ability of 90Y- and 111In-MOv18 to localize FR on tumors in vivo was analyzed in nude mice bearing tumors induced by isogenic cell lines differing only in the presence or absence of the relevant antigen [A431FR (FR-positive) and A431tMock (FR-negative)]. In vivo biodistribution in organs other than tumor was comparable in non-tumor-, A431tMock- and A431FR-bearing mice, whereas the median tumor uptake of the radiolabeled reagents, expressed as area under the curve (AUC) and maximum uptake (Umax), was significantly higher (sixfold to sevenfold) in A431FR than in A431tMock tumors (P=0.0465 and P=0.0332, respectively). Mean maximum uptake (% ID/g) for 90Y-MOv18 was 53.7 and 7.4 in A431FR and A431tMock respectively; corresponding values for 111In-Mov18 were 45.0 and 11.3. These data demonstrate the feasibility of 90Y-labeling of MOv18 without compromising antibody binding ability and the immunoreagent-specific localization in vivo on FR-expressing tumors, suggesting the suitability of 90Y-MOv18 for clinical studies.

High-precision dosimetry for radiotherapy using the optically stimulated luminescence technique and thin Al2O3:C dosimeters

The potential of using the optically stimulated luminescence (OSL) technique with aluminium oxide (Al(2)O(3):C) dosimeters for a precise and accurate estimation of absorbed doses delivered by high-energy photon beams was investigated. This study demonstrates the high reproducibility of the OSL measurements and presents a preliminary determination of the depth-dose curve in water for a 6 MV photon beam from a linear accelerator. The uncertainty of a single OSL measurement, estimated from the variance of a large sample of dosimeters irradiated with the same dose, was 0.7%. In the depth-dose curve obtained using the OSL technique, the difference between the measured and expected doses was < or =0.7% for depths between 1.5 and 10 cm, and 1.1% for a depth of 15 cm. The readout procedure includes a normalization of the response of the dosimeter with respect to a reference dose in order to eliminate variations in the dosimeter mass, dosimeter sensitivity, and the reader's sensitivity. This may be relevant for quality assurance programmes, since it simplifies the requirements in terms of personnel training to achieve the precision and accuracy necessary for radiotherapy applications. We concluded that the OSL technique has the potential to be reliably incorporated in quality assurance programmes and dose verification.

Joint aspiration and injection

Joint aspiration/injection is an invaluable procedure for the diagnosis and treatment of joint disease. The knee is the commonest site to require aspiration although any non-axial joint is accessible for obtaining synovial fluid. Septic arthritis and crystal arthritis can be readily diagnosed by aspirating synovial fluid. Intra-articular injection of long-acting insoluble corticosteroids produces rapid resolution of inflammation in most injected joints and is a well established procedure in rheumatological practice. The technique involves only a knowledge of basic anatomy and should not be unduly painful for the patient. Provided sterile equipment and a sensible, aseptic approach are used it is a safe procedure. This chapter addresses the indications, technical principals, expected benefits and risks of intra-articular corticosteroid injection. The use of other intra-articular injections including osmic acid, radioisotopes and hyaluronic acid, which are less universally utilised than intra-articular corticosteroid, will also be addressed.

Endocrine tumours of the gastrointestinal tract. Peptide receptor radionuclide therapy

Peptide receptor radionuclide therapy is a new treatment modality for patients with inoperable or metastasised neuroendocrine gastroenteropancreatic tumours. After the successful implementation of somatostatin receptor scintigraphy in daily clinical practice, the next logical step was to increase the radiation dose of the administered radiolabelled somatostatin analogue in an attempt to induce tumour shrinkage. Since then, an increasing number of patients has been successfully treated with this approach, resulting in a substantial numbers of patient with objective tumour shrinkage. Serious side-effects have been rare. This article reviews the effectiveness of the different radiolabelled somatostatin analogues used, the currently known side-effects and the survival data available. Furthermore, clinical issues, including indication and timing of therapy, are discussed. Finally, important directions for future research are briefly mentioned to illustrate that, although the currently available results already suggest a favourable outcome compared with other systemic therapies, new strategies are being developed to increase efficacy.

Imaging with radiolabelled monoclonal antibody (MUJ591) to prostate-specific membrane antigen in staging of clinically localized prostatic carcinoma: comparison with clinical, surgical and histological staging

OBJECTIVE

To evaluate the reliability of prostate scintigraphy using a radiolabelled antibody (MUJ591) raised against the external domain of prostate-specific membrane antigen (PSMA) in the staging of early prostate cancer.

PATIENTS AND METHODS

This was a prospective study of 16 patients who had radical retropubic prostatectomies (median PSA 9.75 ng/mL). All patients underwent PSMA imaging using MUJ591 radiolabelled with (99m)Tc using a photo-reduction technique.

RESULTS

The findings of prostate imaging and histology were identical in seven patients. Scans showed understaging and overstaging in six and three patients, respectively.

CONCLUSIONS

PSMA scintigraphy using (99m)Tc-labelled MUJ591 identifies the presence of prostate cancer, but is not sensitive in delineating micro-invasion of the capsule, seminal vesicles or bladder neck. As in other studies it seems to be useful in detecting prostate bed recurrence and distant micrometastasis.

A special mini-extrapolation chamber for calibration of90Sr+90Y sources

90Sr+90Y applicators are commonly utilized in brachytherapy, including ophthalmic procedures. The recommended instruments for the calibration of these applicators are extrapolation chambers, which are ionization chambers that allow the variation of their sensitive volume. Using the extrapolation method, the absorbed dose rate at the applicator surface can be determined. The aim of the present work was to develop a mini-extrapolation chamber for the calibration of 90Sr+90Y beta ray applicators. The developed mini-chamber has a 3.0 cm outer diameter and is 11.3 cm in length. An aluminized polyester foil is used as the entrance window while the collecting electrode is made of graphited polymethylmethacrylate. This mini-chamber was tested in 90Sr+90Y radiation beams from a beta particle check source and with a plane ophthalmic applicator, showing adequate results.

Determination of immunoreactive fraction of radiolabeled monoclonal antibodies: what is an appropriate method?

Determination of the immunoreactive fraction (IF) of radiolabeled monoclonal antibodies (MAb) is essential to the understanding of the effects of radiolabeling and subsequent target-specific tumor localization. There has been generally no accepted method of determining the IF of MAbs. The conventional method is based on a radioimmunoassay technique in which the fraction of radiolabeled MAb bound to antigen under conditions of "antigen excess" is determined. Lindmo et al. introduced a modified method in which the IF is determined by extrapolation to conditions representing "infinite antigen excess." Although the Lindmo method, in principle, is insensitive to experimental parameters, it does not always provide a reliable estimate of IF. We, therefore, evaluated an alternate method in which percent cell bound fraction is measured under conditions of fixed antigen concentration and various dilutions of radiolabeled MAb. We developed a mathematical equation to estimate immunoreactivity. J591 MAb specific for prostate-specific membrane antigen was radiolabeled with (111)In, (90)Y and (177)Lu to specific activities of 1-20 mCi/mg. We compared the effect of several experimental conditions on the determination of IF using all three different methods. The Lindmo method requires careful optimization of experimental conditions for each radiolabeled MAb. The alternate method, based on a fixed antigen concentration, appears to be practical and may provide a more reliable measure of immunoreactivity.

Imaging of melanoma using 64Cu- and 86Y-DOTA-ReCCMSH(Arg11), a cyclized peptide analogue of alpha-MSH

Early detection of melanoma is essential, since a patient's prognosis with metastatic melanoma is poor. Previous studies showed that (111)In-DOTA-ReCCMSH(Arg(11)), a cyclic analogue of alpha-melanocyte stimulating hormone (alpha-MSH), exhibited high tumor concentration and rapid clearance from nontarget tissue. The goal of this current study was to label DOTA-ReCCMSH(Arg(11)) with beta(+)-emitting radionuclides, to determine if the high sensitivity of positron emission tomography (PET) imaging would aid in the detection of malignant melanoma. DOTA-ReCCMSH(Arg(11)) was labeled with (64)Cu and (86)Y. Biodistribution and small animal PET imaging were carried out in mice implanted with B16/F1 murine melanoma tumor and compared with data obtained in the same animal model with [(18)F]FDG. In both cases a subset of animals were co-injected with 20 microg of DOTA-ReCCMSH(Arg(11)) to determine if tumor concentration was receptor mediated. Tumor concentration for both the (86)Y- and (64)Cu-complexes reached a maximum at 30 min, while coadministering 20 microg of unlabeled complex reduced tumor uptake significantly. Nontarget organ concentration was considerably lower with (86)Y-DOTA-ReCCMSH(Arg(11)) than its (64)Cu analogue, except in the kidneys, where the (64)Cu complex had lower accumulation at all time points. Small animal PET images for both complexes showed the tumor could be visualized after 30 min, with the standardized uptake value (SUV) analysis following a similar trend as the biodistribution data. The data obtained suggests that DOTA-ReCCMSH(Arg(11)), when labeled with beta(+)-emitting radionuclides, has the potential for early detection of malignant melanoma by exploiting the sensitivity and high resolution of PET.

Report of a European consensus workshop to develop recommendations for the optimal use of 90Y-ibritumomab tiuxetan (Zevalin®) in lymphoma

BACKGROUND

Non-Hodgkin's lymphoma (NHL) comprises a group of related haematological malignancies, predominantly of B-cell origin, which have been described as indolent or aggressive according to their clinical course. Standard treatment for indolent NHL consists of conventional chemotherapy, but, although long-term remissions may occur, most patients will die of their disease. Radioimmunotherapy (RIT) is a novel modality for treating indolent NHL, using monoclonal antibodies to target tumour cells with systemic, low-dose radiation. (90)Y-Ibritumomab tiuxetan (Zevalin); Schering AG, Berlin, Germany), the first RIT approved for use in relapsed/refractory indolent NHL, comprises the murine anti-CD20 monoclonal antibody ibritumomab, covalently linked to the high-energy beta-emitter, yttrium-90, by the chelator, tiuxetan.

MATERIALS AND METHODS

A multidisciplinary consensus workshop of European clinicians who had taken part in clinical trials of (90)Y-ibritumomab tiuxetan was convened to develop recommendations for the clinical preparation and administration of (90)Y-ibritumomab tiuxetan in Europe. The workshop was held in anticipation of European Medicines Agency approval of this agent, which was gained in 2004 for adult patients with rituximab-relapsed or refractory CD20(+) follicular B-cell NHL.

RESULTS AND CONCLUSIONS

This article summarises the consensus recommendations developed for hemato-oncologists.

Evaluation of 90Y phosphate particles as a possible radiation synoviorthesis agent

BACKGROUND

90Y is one of the radioisotopes used extensively for therapy due to its favourable nuclear characteristics. Particles and colloids incorporating 90Y are being used for radiation synovectomy, especially in European countries.

METHODS

In our present work, 90Y phosphate particles were prepared and evaluated for use in radiation synovectomy. The radioactive particles were prepared by reacting carrier added 90YCl3 with phosphoric acid.

RESULTS

The radiolabelling yield obtained was >95%. The particles were found to be stable in saline for up to 7 days of study at 37 degrees C. Particle size analysis of inactive yttrium phosphate showed that most of the particles were in the size range of 2-20 microm. Biodistribution studies carried out by intra-articular injection of the particles into the knee joints of rats showed that approximately 99% of the particles were retained in the joints with negligible radioactivity in the major organs even at 48 h post-injection. Scintigraphic studies in rabbit showed that >99% of the radioactive particles were retained in the knee joint even at 96 h post-injection. No significant radioactivity above background was detected in the blood.

CONCLUSION

The promising results warrant further studies on 90Y phosphate particles for use in radiation synovectomy.

Measurements of finger doses in x-ray guided surgery, nuclear medicine and research

The Norwegian Radiation Protection Authority has performed measurements of finger doses to nuclear medicine staff exposed to 99Tc(m), researchers handling 32P, surgeons performing X-ray guided orthopaedic surgery and surgeons and radiologists performing X-ray guided endovascular treatment of abdominal aortic aneurysms (AAA). Calibrations were done with X-ray qualities N-40, N-60 and N-300 and with the beta source 90Sr + 90Y. Annual doses were estimated for the nuclear medicine staff and the orthopaedic surgeons. The mean annual finger dose to nuclear medicine staff exposed to 99Tc(m) was estimated to be 18.8 mSv, and the mean annual finger dose to surgeons performing X-ray guided orthopaedic surgery was 13.7 mSv. The surgeons and radiologists performing X-ray guided endovascular treatment of AAA received a mean finger dose of 0.35 mSv per treatment. The majority of researchers handling 32P received no finger dose at all, and the maximum reading was 1.65 mSv. All occupational groups received finger doses well below the annual finger dose limit of 500 mSv.

Mass Spectral Analyses of Labile DOTA-NHS and Heterogeneity Determination of DOTA or DM1 Conjugated Anti-PSMA Antibody for Prostate Cancer Therapy

Prostate specific membrane antigen (PSMA) is a well-characterized glycoprotein overexpressed on the surface of prostate cancer cells. The novel radiopharmaceutical 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) radiolabeled with Yttrium (90Y) or Indium (111In) conjugated with anti-PSMA genetically engineered humanized monoclonal antibody (huJ591) has been investigated to target prostate cancer cells. The immunoconjugate of huJ591 with the analog of the cytotoxic drug maytansine, DM1 (N2'-deacetyl-N2'-(3-mercapto-1-oxopropyl)-maytansine) has also been developed at Millennium Pharmaceuticals. Activation of the DOTA molecule, resulting in 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid mono-(N-hydroxysuccinimidyl) ester (DOTA-NHS), allows conjugation with the anti-PSMA antibody through lysine residues in the antibody. The objectives of the study were to characterize the unstable chemical properties of DOTA-NHS before bioconjugation with huJ591, evaluate the binding profiles of DOTA to huJ591, and calculate trace metal elements (which may disturb 90Y or 111In labeling efficacy to the DOTA-huJ591 conjugate). A novel LC/MS/MS (Liquid Chromatography/Mass Spectrometry/Mass Spectrometry) quantitation method was developed to monitor the stability of DOTA-NHS in solid form and its bioconjugation chemistry reactions. Meanwhile, metal analysis was quantified by Inductively Coupled Plasma Mass Spectrometry (ICP/MS) to estimate the amounts of trace metals in DOTA-NHS and ensure radiolabeling efficiency of the conjugate at the radiopharmacy. MALDI-TOF MS (Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry) was used to identify levels of DOTA or DM1conjugation in DOTA-huJ591 and DM1-huJ591 conjugates, respectively.

90Y microsphere treatment of unresectable liver metastases: changes in 18F-FDG uptake and tumour size on PET/CT

PURPOSE

The intra-arterial administration of 90Y microspheres is a new palliative treatment option for unresectable liver metastases. The aim of this study was to quantitatively assess changes in FDG uptake and tumour size following 90Y microsphere treatment (SIR-Spheres) using 18F-fluorodeoxyglucose (FDG) PET/CT imaging.

METHODS

Five patients with unresectable liver metastases who had failed multiple prior chemotherapy regimens received seven 90Y microsphere treatments to a single liver lobe. All patients underwent a baseline PET/CT scan prior to treatment, as well as up to four follow-up PET/CT scans. The tumour area of 30 liver metastases was measured on CT and the FDG uptake was semiquantitatively assessed by calculation of standardised uptake values (SUVs). A total of 18 FDG-PET/CT scans were performed.

RESULTS

The SUVs in the 30 treated liver metastases decreased from 6.5+/-2.3 at baseline to 4.2+/-1.8 after the first follow-up PET/CT scan (p=0.001). In contrast, the SUVs of untreated metastases increased slightly from 7.2+/-2.3 to 8.0+/-0.8. There was no difference in FDG uptake in treated versus untreated normal liver tissue. Using a previously defined threshold of 20% decrease in SUV from baseline to determine response, 20 out of 30 liver metastases were considered to have responded at the first follow-up PET/CT scan approximately 1 month after treatment. In these metastases, the SUV decreased by 47+/-12%, compared with a slight increase by 5.9+/-19% in ten non-responding metastases (p=0.0001). The changes in tumour size did not correlate with changes in FDG uptake. On the first follow-up PET/CT scan, the tumour area on CT increased by 3.1+/-57% in treated metastases compared with 23.3+/-32% in untreated metastases. A wide range of post-treatment changes of target lesions was observed on CT, including an increase in the size of hypodense lesions, necrotic features and complete resolution of CT abnormalities.

CONCLUSION

The metabolic information obtained from FDG-PET/CT seems to provide a more accurate and earlier assessment of therapy response following 90Y microsphere treatment than does the anatomical CT information.

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

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

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

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

Quantitative Imaging Of Yttrium-86 Pet with the Ecat Exact Hr+ In 2D Mode

The radionuclide 86Y potentially allows for the precise assessment of tissue radioactivity biodistribution and, thus, extrapolation of a therapeutic dose of 90Y-labeled compounds. A method to obtain quantitative images from 86Y-PET measurements after a background correction and a recalibration is presented. Cylinder and body phantom measurements with 18 F and 86Y using an ECAT EXACT HR+ tomograph were performed in 2D mode. A second-order series expansion is used to correct for the background of spurious coincidences in the sinogram. A recalibration of the positron emission tomography (PET) system, depending on the ratio of true coincidences and singles, is implemented. The correction for the nonannihilation coincidences with a second-order series expansion significantly improves the accuracy of quantitation: The lesion-to-background ratio is reproduced, and the variation of the activity concentration in the homogeneous background regions of the phantoms is smaller than 5%. The apparent activities in cold inserts of various densities is reduced to less than 15% of the concentration in the active region. The recalibration of the system works with a relative error of 0.2% +/- 2.4%. In conclusion, the used approximations lead to improved uniformity and quantitative accuracy in 86Y-PET measurements with the ECAT EXACT HR+.

Emergency localization of radioactive seeds lost during intracoronary brachytherapy

Recently, it has been reported that brachytherapy catheters ruptured in vivo. Localization of lost beta-radiation-emitting seeds is a problem because no appropriate technique is available that is rapid and precise. We developed a technique to localize beta-emitting seeds utilizing the effect that beta-radiation induces bremsstrahlung. The loss of a single radioactive source was simulated in an Alderson Phantom representing a human body. The beta-induced bremsstrahlung could be detected selectively by a gamma-camera. The position of the radioactive seed could be located within 5 min with an accuracy of +/- 0.5 cm. The result of this study suggests that in an emergency case of loss of a brachytherapy source, a commercially available gamma-camera can be a valuable tool to detect lost beta-radiation-emitting seeds rapidly and precisely. In addition, the technique minimizes the patient's as well as the surgeon's exposure to radiation and reduces the extent of surgical trauma.

Dosimetry ofin situactivated dysprosium microspheres

This paper presents the results of a study aimed at investigating the dosimetry of stable dysprosium microspheres activated, in situ, by a linac generated photon beam. In phantom measurements of the neutron flux within an 18 MV photon beam were performed using CR-39 detectors and gold activation. The results were used in conjunction with a Monte Carlo computer simulation to investigate the dose distribution resulting from the activation of dysprosium (Dy) microspheres using an 18 MV photon beam. Different depths, lesion volumes and volume concentrations of microspheres are investigated. The linac lower collimator jaws are assumed completely closed to shield the tumour volume from the photon dose. Using a single AP field with 0 x 0 cm2 field size (closed jaws), a photon dose rate of 600 MU min(-1) and 80 cm SSD for 10 min, an average dose exceeding 1 Gy can be delivered to spherical lesions of 0.5 cm and higher diameter. The variation of the average dose with the size of the lesion reaches saturation for tumour volumes exceeding 1 cm in diameter. This report shows that the photon beam of a high-energy linac can be used to activate Dy microspheres in situ and, as a result, deliver a significant dose of beta radiation. Non-radioactive Dy microspheres do not have the toxicity and imaging problems associated with commercially available yttrium-90 based products.

Technology evaluation: cT84.66, City of Hope

Chimeric T84.66 (cT84.66) is a high affinity anti-carcinoembryonic antigen (CEA) immunoglobulin G1, that is being developed by City of Hope for the potential treatment of CEA-expressing malignancies.

Yttrium-90-ibritumomab tiuxetan radioimmunotherapy: A new treatment approach for B-cell non-Hodgkin's lymphoma

This article will review the clinical development of ibritumomab tiuxetan, a yttrium-90-conjugated monoclonal antibody to CD20, for patients with relapsed B-cell non-Hodgkin's lymphomas. Ibritumomab is the murine parent anti-CD20 antibody that was engineered to make the human chimeric antibody rituximab. Tiuxetan is an MX-DTPA chelator that is linked to ibritumomab to form ibritumomab tiuxetan. Since yttrium-90 ((90)Y) is a pure beta emitter and cannot be used for patient imaging, indium-111 ((111)In) is chelated to ibritumomab tiuxetan for tumor and normal organ imaging in clinical practice and for dosimetry in clinical trials. (90)Y-ibritumomab tiuxetan is the form used for therapy. This review discusses the clinical trials that have demonstrated the efficacy of ibritumomab tiuxetan and summarizes the safety data in patients with relapsed B-cell non-Hodgkin's lymphomas. Two phase I trials of (90)Y-ibritumomab tiuxetan were conducted to establish the toxicity profile and the maximum tolerated single dose that could be administered to outpatients without the use of stem cells or prophylactic growth factors. In the first trial, cold ibritumomab was used prior to ibritumomab tiuxetan; the second trial used the human chimeric antibody rituximab. The phase I trials determined that in patients with a platelet count of greater than or equal to 150 x 10(9)/l, a schedule of intravenous rituximab 250 mg/m(2) on days 1 and 8, and 0.4 mCi/ kg of intravenous (90)Y-ibritumomab tiuxetan on day 8 was safe and efficacious and did not require stem cells. A dose of 0.3 mCi/kg was recommended for patients with a baseline platelet count of 100,000- 149,000 x 10(6)/l. Adverse events were primarily hematologic, and nonhematologic adverse events were primarily due to rituximab. There was no normal organ toxicity. The overall response rate was 67% for all patients and 82% in patients with low-grade non-Hodgkin's lymphomas. A subsequent phase III trial randomized 143 eligible patients to either rituximab or ibritumomab tiuxetan. The aim was to demonstrate that the addition of the yttrium-90 radioisotope to the antibody provided additional efficacy over the unconjugated ("cold") rituximab alone. The results of this study showed an overall response rate of 80% with (90)Y-ibritumomab tiuxetan versus 56% for rituximab (p = 0.002). An additional trial enrolled 54 patients who were nonresponsive or refractory to rituximab and treated the patients with a single dose of 0.4 mCi/kg (90)Y-ibritumomab tiuxetan. An overall response rate of 74% was found in these rituximab-refractory patients. These data provide further evidence of the added value of the yttrium-90. Finally, a fifth trial treated 30 patients with mild thrombocytopenia using 0.3 mCi/kg (90)Y-ibritumomab tiuxetan and found an overall response rate of 83%. (90)Y-ibritumomab tiuxetan radioimmunotherapy is a new treatment modality for patients with relapsed B-cell non-Hodgkin's lymphoma. The advantages of this therapy are that it utilizes targeted radiation in a single-dose, outpatient schedule that is well tolerated and accepted by the patient. Future trials will build on these results and determine at what point in the disease course this modality can best be utilized to maximize the benefits to the patient.

Intraoperative dural irradiation by customized 192iridium and 90yttrium brachytherapy plaques

PURPOSE

After vertebral or paravertebral tumor resection, tumor cells may remain on the dura. Because a tumoricidal dose is difficult to achieve using external beam radiotherapy without exceeding the spinal cord tolerance, we developed intraoperative applicators to deliver additional dose to the dura.

METHODS AND MATERIALS

Eight patients with vertebral or paravertebral tumor underwent conformal external beam radiotherapy, tumor resection, and intraoperative radiotherapy to the dura involved by tumor. At surgery, vertebra, soft tissue, and epidural tumor were resected. A radioactive applicator plaque was placed on the dura to deliver 7.5-15 Gy, and then removed. Vertebral reconstruction and stabilization was completed. Chemotherapy was administered for large, high-grade sarcomas.

RESULTS

We progressed through three plaque designs, initially (192)Ir, subsequently liquid (90)Y, and finally (90)Y foil in a semicylindrical polycarbonate plaque, in the treatment of 8 patients. The low-energy (90)Y beta-emissions provided a more attractive depth dose profile than that achievable with iridium and gave negligible staff radiation exposure. The (90)Y depth dose measured 29% at 2 mm and 9% at 4 mm from the surface of the foil plaque, with acceptable surface dose homogeneity. The average surface dose rate ranged from 18.7 to 47.6 cGy/min for the iridium plaques and 45.2 to 187.5 cGy/min for the (90)Y plaques. The treatments have been without acute or late neurologic complications. The disease of 6 of 8 patients was locally controlled at median potential follow-up of 24 months.

CONCLUSIONS

The (90)Y foil applicator is technically elegant, easy to use, and superior to the earlier models. It has been incorporated into a protocol for spinal tumor treatment.

Long-Lived Positron Emitters Zirconium-89 and Iodine-124 for Scouting of Therapeutic Radioimmunoconjugates with PET

Antibody-PET imaging might be of value for the selection of radioimmunotherapy (RIT) candidates to confirm tumor targeting and to estimate radiation doses to tumor and normal tissues. One of the requirements to be set for such a scouting procedure is that the biodistributions of the diagnostic and therapeutic radioimmunoconjugates should be similar. In the present study we evaluated the potential of the positron emitters zirconium-89 ((89)Zr) and iodine-124 ((124)I) for this approach, as these radionuclides have a relatively long half-life that matches with the kinetics of MAbs in vivo (t(1/2) 3.27 and 4.18 days, respectively). After radiolabeling of the head and neck squamous cell carcinoma (HNSCC)-selective chimeric antibody (cMAb) U36, the biodistribution of two diagnostic (cMAb U36-N-sucDf-(89)Zr and cMAb U36-(124)I) and three therapeutic radioimmunoconjugates (cMAb U36-p-SCN-Bz-DOTA-(88)Y-with (88)Y being substitute for (90)Y, cMAb U36-(131)I, and cMAb U36-MAG3-(186)Re) was assessed in mice with HNSCC-xenografts, at 24, 48, and 72 hours after injection. Two patterns of biodistribution were observed, one pattern matching for (89)Zr- and (88)Y-labeled cMAb U36 and one pattern matching for (124)I-, (131)I-, and (186)Re-cMAb U36. The most remarkable differences between both patterns were observed for uptake in tumor and liver. Tumor uptake levels were 23.2 +/- 0.5 and 24.1 +/- 0.7%ID/g for the (89)Zr- and (88)Y-cMAb U36 and 16.0 +/- 0.8, 15.7 +/- 0.79 and 17.1 +/- 1.6%ID/g for (124)I-, (131)I-, and (186)Re-cMAb U36-conjugates, respectively, at 72 hours after injection. For liver these values were 6.9 +/- 0.8 ((89)Zr), 6.2 +/- 0.8 ((88)Y), 1.7 +/- 0.1 ((124)I), 1.6 +/- 0.1 ((131)I), and 2.3 +/- 0.1 ((186)Re), respectively. These preliminary data justify the further development of antibody-PET with (89)Zr-labeled MAbs for scouting of therapeutic doses of (90)Y-labeled MAbs. In such approach (124)I-labeled MAbs are most suitable for scouting of (131)I- and (186)Re-labeled MAbs.

Application of shock waves as a treatment modality in the vicinity of the brain and skull

OBJECT

Shock waves have not previously been used as a treatment modality for lesions in the brain and skull because of the lack of a suitable shock wave source and concerns about safety. Therefore, the authors have performed experiments aimed at developing both a new, compact shock wave generator with a holmium:yttrium-aluminum-garnet (Ho:YAG) laser and a safe method for exposing the surface of the brain to these shock waves.

METHODS

Twenty male Sprague-Dawley rats were used in this study. In 10 rats, a single shock wave was delivered directly to the brain, whereas the protective effect of inserting a 0.7-mm-thick expanded polytetrafluoroethylene (ePTFE) dural substitute between the dura mater and skull before applying the shock wave was investigated in the other 10 rats. Visualizations on shadowgraphy along with pressure measurements were obtained to confirm that the shock wave generator was capable of conveying waves in a limited volume without harmful effects to the target. The attenuation rates of shock waves administered through a 0.7-mm-thick ePTFE dural substitute and a surgical cottonoid were measured to determine which of these materials was suitable for avoiding propagation of the shock wave beyond the target.

CONCLUSIONS

Using the shock wave generator with the Ho:YAG laser, a localized shock wave (with a maximum overpressure of 50 bar) can be generated from a small device (external diameter 15 mm, weight 20 g). The placement of a 0.7-mm-thick ePTFE dural substitute over the dura mater reduces the overpressure of the shock wave by 96% and eliminates damage to surrounding tissue in the rat brain. These findings indicate possibilities for applying shock waves in various neurosurgical treatments such as cranioplasty, local drug delivery, embolysis, and pain management.

GAF film dosimetry of a tandem positioned beta-emitting intravascular brachytherapy source train

Coronary artery brachytherapy may require treatment of lesions longer than a single source length. A treatment option is tandem positioning of the single source. This study presents relative dosimetric measurements of a cardiovascular brachytherapy source and the dosimetric characteristics in the junction region of tandem treatments. Measurements were carried out using a Novoste Beta Cath 90Sr/90Y 40 mm beta source in a plastic water phantom. Radiochromic MD-55-2 film, calibrated using both 6 MV photon and 6 MeV electron beams from a linear accelerator, was used as the dosimeter. Dose distributions around a single source and in the junction region of tandem irradiation were measured. Measurements of the near field dose as close as 1.2 mm from the source are presented. Significant over- or underdoses in the junction region of tandem irradiation were quantified. At a radial distance of 2 mm from the longitudinal axis of the source, the dose value in the middle of the junction region, normalized to the dose at 2 mm midline single source, was about 182% for a 2-seed overlap and 16% for a 2-seed gap, respectively. Dose distributions in the junction region as a function of source overlap and radial distance have fairly high gradients and exhibit characteristic patterns. The fraction of prescription dose was found to have a sigmoidal dependence on overlap size, for radial distances ranging between 1.2 and 3 mm. The parameters of these sigmoids, quantified as functions of radial distance, could be used to provide quick and reasonable over/underdose estimates, given any potential overlap or gap in the junction area, with an uncertainty within 10%.

Labeling anti-HER2/neu monoclonal antibodies with 111In and 90Y using a bifunctional DTPA chelating agent

The goal of this investigation was to develop stable radioimmunoconjugates (RICs) of anti-HER2/neu monoclonal antibodies (MoAbs) for imaging and therapy in an animal model bearing human breast tumor xenografts that express normal (MCF-7 cells) and increased amounts of HER2/neu receptors (HCC-1954, BT-474, SKBR-3 cells) on their cell surface membranes. Pharmacy-grade Herceptin, a murine anti-HER2/neu MoAb, and nonspecific mouse IgG protein were conjugated with the recently developed DTPA linker known as CHX-A"-DTPA. These immunoconjugates were labeled with (111)InCl(3) and (90)YCl(3). Using a molar excess of 10:1 CHX-A"-DTPA to immunoglobulin, average specific activities of 1.87 microCi (111)In/microg RIC and 2.71 microCi (90)Y/microg RIC were obtained. The purity of RICs was 96%+ for (111)In and 99%+ for (90)Y. Stability in human plasma at 37 degrees C for both RICs ranged from 98% at 24 h to 85% at 96 h. Binding capacity of the RICs was tested with human cancer cell lines MCF-7, HCC-1954, BT-474, and SKBR-3. Using (111)In-labeled nonspecific IgG protein as a control, (111)In-Herceptin RIC was found to bind to MCF-7 cells with a ratio of 2.5:1 and to SKBR-3 cells with a ratio of 85:1 after 3 h of incubation. (111)In anti-HER2/neu RIC bound to MCF-7 cells with a ratio of 6:1 and to SKBR-3 cells with a ratio of 115:1 after 3 h of incubation. (90)Y-anti-HER2/neu RIC bound 10-times greater to BT-474 cells than to MCF-7 cells. Thus, these MoAbs can be labeled with (111)In and (90)Y using the CHX-A"-DTPA linker. The resulting RICs ((111)In- and (90)Y-anti HER2/neu antibodies) are stable and bind significantly to HER2 overexpressing tumor cell lines.

Locoregional radioimmunotherapy in selected patients with malignant glioma: experiences, side effects and survival times

Prognosis of malignant glioma is very unfavourable mainly due to minimal tumour remnants in the peritumoural tissue. Intralesionally applied radioimmunotherapy is a possible therapeutical option with the potential to improve survival of patients with malignant glioma. We investigated side effects and survival after surgery, conventional radiotherapy and additional radioimmunotherapy with labelled tenascin-antibodies in patients with malignant glioma.

METHODS

Since 1995, 37 patients were treated with radioimmunotherapy after resection and radiotherapy of a malignant glioma. Patients received antibodies labelled with yttrium-90 and iodine-131 in different doses into the tumour cavity via a previously implanted ommaya-reservoir. Treatment was applied in up to 8 cycles (mean 2.96 cycles) in time intervals of 6-8 weeks. Mean age was 46 years, histology was anaplastic astrocytoma in 13 patients and glioblastoma in 24 patients.

RESULTS

For the whole group median survival time has not yet been reached. For glioblastoma the median survival time is 17 months, 5-year survival probability for anaplastic astrocytoma is 85% approximately. Quality of life was acceptable. Acute side effects following treatment were headache, seizures and worsening of pre-existing neurological symptoms. Late side effects were skin necrosis and, in 1 case, a delayed aphasia probably due to a vascular lesion.

CONCLUSION

Radioimmunotherapy prolonged survival time in a selected group of patients with malignant gliomas as compared to a historical control group. Patients with anaplastic astrocytomas seem to have more benefit from this therapy than patients with glioblastomas.