Clinical Utility of Radioimmunoscintigraphy of Non-Hodgkin's Lymphoma with Radiolabelled LL2 Monoclonal Antibody., Lymphoscan™: Preliminary Results

Aims and Background

Adequate clinical staging of non-Hodgkin's lymphoma patients is essential because only localized disease can be treated satisfactorily. Many imaging procedures are necessary to stage the disease accurately. The objective of this study was to evaluate the efficacy of an anti-lymphoma antibody in the Fab’ fragment form, labelled with 99mTc, to detect malignant lesions.

Methods

Radioimmunodetection (RAID) with 99mTc-labelled B-cell lymphoma monoclonal antibody IMMU-LL2-Fab’ (LymphoSCAN™; Immunomedics, Morris Plain, NJ, USA) was investigated in 10 patients (5 females and 5 males; age range, 20-72 years) with histologically proved non-Hodgkin's lymphoma. Of the 10 lymphomas, 7 were intermediate grade and 3 were low grade. Whole body images with multiple planar views were obtained at 30 min, 4-6 and 24 h after i.v. injection of 1 mg LL2-Fab’ labelled with 740-925 MBq of 99mTc. SPET of the chest or abdomen was performed in all patients 5-8 h after the immunoreagent injection.

Results

No adverse reactions were observed in any patient after Mab infusion, and no appreciable changes were seen in the blood counts, renal or liver function tests. A total of 18 of 21 (85.7%) lymphoma lesions were detected by RAID. All the tumor localizations were confirmed by clinical examination and with other imaging techniques, such as CT scan, MRI or gallium scan. In this series of patients no false-positive results were noted. As regards the biodistribution of the immunoreagent, no appreciable bone marrow activity was seen; splenic targeting was demonstrated in all patients; the tumor-to-non-tumor ratios ranged from 1.2 to 2.8 ad measured by the ROI technique; no difference in uptake was noted for different tumor grades. The images obtained 24 h after injection did not reveal new lesions, but areas of doubtful uptake were seen as positive focal areas in the delayed scan.

Conclusions

LymphoSCAN™ seems to be useful for detection, staging and follow-up of non-Hodgkin's lymphoma patients.

Radioimmunoguided Breast Surgery Using Radiolabeled Antibody NR-LU-10 FAB: A Pilot Study

Aim and Background

Radioimmunoguided surgery using radiolabeled NR-LU-10 Fab was evaluated as a method of intraoperative breast cancer detection.

Methods

Breast cancer patients were injected intravenously with 125I (74 MBq) labeled NR-LU-10 Fab (5 mg) and then underwent tumor excision 2, 4 or 7 days later, during which time the gamma detector probe was used to evaluate the primary tumor for evidence of radioactive uptake.

Results

Intraoperative probing revealed tumor localization in 7 of 10 patients (70%). Gamma probe counts of the excised tumor were elevated in all patients, although high counts in surrounding nonmalignant tissue obscured the ability to detect the tumor in vivo in 3 patients. One patient with bilateral breast cancer was found to have a separate focus of occult tumor in each breast using the gamma detector probe.

Conclusions

Radiolabeled NR-LU-10 Fab possesses favorable pharmokinetics and tumor-binding ability as a targeting agent. However, binding to nonmalignant tissue limits its role in the intraoperative evaluation of tumor margins in breast cancer patients. Its role in other malignancies should be explored.

Preliminary Study on Radioimmunodiagnosis of Experimental Tumor Models Using Technetium-99m-Labeled Anti-C-erbB-2 Monoclonal Antibody

Aims and background

One of the great challenges of oncology is to improve methods for early tumor detection. Diagnosis of premalignant lesions and early stage primary tumors is crucial for the success of cancer therapy and increased survival rates. Growth factor receptors localized to the cell membrane play a vital role in cancer. Monoclonal antibodies labeled with radioisotopes have been used extensively for radioimmunodiagnosis and radioimmunotherapy of various malignancies. A preliminary study on immunoscintigraphy was carried out on animal tumor models using 99mTc-labeled monoclonal antibody CIBCgp185 generated against the C-erbB-2 oncoprotein with a view to develop technologies for in vivo radioimmunodetection and localization of human breast cancer.

Methods

Mammary tumor xenografts induced using BT474 cells, a breast carcinoma cell line showing overexpression of C-erbB-2, were used for immunoscintigraphic studies.

Results

Scintigrams showed high radiolabel uptake by the tumor tissue of the mice belonging to the experimental group, whereas in control animals no radiolabel uptake was visualized. Biodistribution studies correlated well with scintiscans.

Conclusions

The results indicate the potential application of this monoclonal antibody for in vivo diagnosis of occult malignancies of tumors with overexpression of C-erbB-2.

Preliminary Study on Immunoscintigraphy of a Murine Lymphoma Using Technetium-99M Labeled Chicken Antibody

AIMS AND BACKGROUND

Radiolabeled antibodies generated against tumor-associated antigens are used for immunoscintigraphy to detect tumors and tumor metastases. Although successful tumor imaging has been achieved using trace-labeled murine monoclonal antibodies, such antibodies often lead to the development of human anti-murine antibodies (HAMA), which limit their subsequent administration for tumor imaging and therapy. It has been reported recently that chicken polyclonal antibodies have high affinity and specificity for the antigen against which they are raised and do not have any immunological cross-reactivity with HAMA.

METHODS

The present study deals with immunoscintigraphy of Dalton's lymphoma, an experimental tumor model using chicken antibodies generated against Dalton's lymphoma-associated antigen (DLAA) and labeled with technetium-99m ((99m)Tc).

RESULTS

Scintigrams showed specific uptake of the radiolabel resulting in clear tumor images. The radioactivity uptake of the chicken anti-DLAA antibody was about twofold higher than that of the non-specific chicken antibody.

CONCLUSIONS

The results demonstrate the potential of chicken antibody for in vivo radioimmunodetection and localization of tumors.

Pilot, Multicenter and Prospective Trials with an Anti-CEA Antibody

In this paper we summarize the investigations performed by our group utilizing an anti-CEA monoclonal antibody (F023C5) labelled with different radionuclides in humans. Since 1983 radioimmunoscintigraphy (RIS) was performed on 51 patients with 64 localizations of colorectal carcinoma (pilot study). A multicenter clinical trial in a large number of patients (509 pts of which 284 with gastrointestinal cancer) was subsequently carried out in collaboration with ten nuclear medicine centres. High sensitivity and specificity values were obtained by these studies and many unsuspected lesions were recorded. In order to better define the clinical role of RIS, a prospective study was performed on 59 patients with suspected local relapses of colorectal cancer. A comparative evaluation of RIS, CT scan, US and MRI was done. RIS and MRI had the highest accuracy (86%) followed by CT scan (68%) and US (54%).

Diagnostic Applications and Therapeutic Approaches with Different Preparations of Anti-CEA Antibodies

Various preparations of anti-CEA antibodies have shown to detect very sensitively CEA producing tumors. The development of human anti-mouse antibodies (HAMA) prevents from the widespread use of immunoscintigraphy (IS) in the follow-up of patients with colorectal carcinoma. It is, however, not yet clear if genetically reshaped antibodies will solve this problem and it is even less clear if this will change prognosis of these patients. There is certainly room for new therapeutic approaches in colorectal carcinoma. Radioimmunotherapy in combination with other techniques might advantageously complete surgery, chemotherapy and radiotherapy, but needs to be further developed.

Anti-CEA and Other Antibodies in the Study of Gastrointestinal Tumors

Localization of gastrointestinal tumors by means of labeled monoclonal antibodies is a new, sensitive and suitable technique currently used in several centers. Encouraging results have been documented with several monoclonal antibodies by different authors. This article reviews our experience with radioimmunoscintigraphy in 59 patients with colorectal cancer in follow-up, using 131I and 111In labeled B72.3, and in 16 patients with primary gastrointestinal tumors using 99mTc anti-CEA monoclonal antibody (type F023C5). The sensitivity of both B72.3 and anti-CEA was greater than 70% either for primary tumors and abdominal recurrences or distant metastases except hepatic ones. A significant gradient in antibody uptake was measured on surgical biopsies between tumors and normal tissues allowing a good in vivo contrast for gamma detection. We have defined the impact of some factors affecting in vivo tumor targeting. In fact, pharmacodynamics of MAbs, percentage of injected dose bound to tissues were measured, and in particular antigenic content in tumor nodules was quantified. Furthermore, the results of RIS were compared to those obtained by CT and other imaging modalities.

Radioimmunoimaging of liver metastases with PET using a 64Cu-labeled CEA antibody in transgenic mice

Purpose

Colorectal cancer is one of the most common forms of cancer, and the development of novel tools for detection and efficient treatment of metastases is needed. One promising approach is the use of radiolabeled antibodies for positron emission tomography (PET) imaging and radioimmunotherapy. Since carcinoembryonic antigen (CEA) is an important target in colorectal cancer, the CEA-specific M5A antibody has been extensively studied in subcutaneous xenograft models; however, the M5A antibody has not yet been tested in advanced models of liver metastases. The aim of this study was to investigate the ⁶⁴Cu-DOTA-labeled M5A antibody using PET in mice bearing CEA-positive liver metastases.

Procedures

Mice were injected intrasplenically with CEA-positive C15A.3 or CEA-negative MC38 cells and underwent micro-computed tomography (micro-CT) to monitor the development of liver metastases. After metastases were detected, PET/MRI scans were performed with ⁶⁴Cu-DOTA-labeled M5A antibodies. H&E staining, immunohistology, and autoradiography were performed to confirm the micro-CT and PET/MRI findings.

Results

PET/MRI showed that M5A uptake was highest in CEA-positive metastases. The %ID/cm³ (16.5%±6.3%) was significantly increased compared to healthy liver tissue (8.6%±0.9%) and to CEA-negative metastases (5.5%±0.6%). The tumor-to-liver ratio of C15A.3 metastases and healthy liver tissue was 1.9±0.7. Autoradiography and immunostaining confirmed the micro-CT and PET/MRI findings.

Conclusion

We show here that the ⁶⁴Cu-DOTA-labeled M5A antibody imaged by PET can detect CEA positive liver metastases and is therefore a potential tool for staging cancer, stratifying the patients or radioimmunotherapy.

Preliminary radioimmunoimaging and biodistribution of ¹³¹iodine-labeled single-chain antibody fragment against progastrin-releasing peptide(₃₁₋₉₈) in small cell lung cancer xenografts

BACKGROUND

Monoclonal antibodies (mAbs) such as DD3, raised against progastrin-releasing peptide(31-98) (ProGRP (31-98)) antigen, have been used to target small cell lung cancer (SCLC). However, as an intact mAb, DD3 is cleared slowly from the body, with an optimal radioimmunoimaging time of 72 hours. More recently, a single-chain antibody fragment has demonstrated reduced excretion time in blood and normal tissues and is increasingly used in diagnostic cancer research. Thereby, it potentially increases the radioimmunoimaging efficacy. However, there have been few studies with this antibody fragment. The aim of this study was to characterize the preliminary radioimmunoimaging and biodistribution of (131)I-anti-ProGRP(31-98) scFv in nude mice bearing SCLC xenografts.

METHODS

Anti-ProGRP(31-98) scFv was used to detect ProGRP expression by flow cytometry analysis and immunohistochemistry. (131)I-anti-ProGRP(31-98) scFv was injected intravenously into healthy Kunming mice and the percentage injected dose per gram (%ID/g) in various organs was calculated. Similarly, the %ID/g and tumor/non-tumor ratio in xenograft-bearing mice was calculated. After injection of (131)I-anti-ProGRP(31-98) scFv, treated mice were imaged at 1, 24, and 30 hours. Then the tumor/base ratios were calculated.

RESULTS

ProGRP was highly expressed in NCI-H446 cells and xenograft tissue. The metabolism of (131)I-anti-ProGRP(31-98) scFv in healthy mice was consistent with a first-order and two-compartment model; T1/2α and T1/2β were 10.2 minutes and 5 hours 18 minutes, respectively. The %ID/g of (131)I-anti-ProGRP(31-98) scFv in xenografts was much higher than in healthy tissues at 12 hours after injection, reaching a maximum of (5.38±0.92) %ID/g at 24 hours. Successful imaging of xenograft tissue was achieved as early as 1 hour post-injection and persisted until 30 hours, with 24 hours proving optimal.

CONCLUSION

(131)I-anti-ProGRP(31-98) scFv shows highly selective tumor uptake with low accumulation in normal tissues and rapid blood clearance, indicating that it could be a promising agent for SCLC radioimmunoimaging.

Scintigraphic detection of colon carcinomas with iodinated monoclonal antibodies

PURPOSE

The aim of this study was to evaluate the clinical reliability of the immunoscintigraphy with iodinated monoclonal antibodies for the detection of metastases and recurrences of colon carcinomas.

METHODS

A total of 45 patients with colon carcinoma was investigated with gamma camera, after intravenous application of iodinated monoclonal antibodies.

RESULTS

The sensitivity of the method was 90%, specificity 86%, positive predictive value 93%, negative predictive value 80% and accuracy 87%. There was statistically significant relationship between immunoscintigraphic and ultrasonographic (US) findings (p=0.005). Also, there was significant relationship between immunoscintigraphy and Dukes stage (p=0.019). Tumor marker levels were not significantly correlated with immunoscintigraphic findings (p<0.05). Significant difference was noted in patients with positive findings for malignancy on US and immunoscintigraphic findings (p=0.006), i.e. patients with positive findings for malignancy had more frequently immunoscintigraphic findings of malignancy. Correlation with other diagnostic procedures (rectoscopy, colonoscopy, CT) did not show significant correlations.

CONCLUSION

We conclude that immunoscintigraphy can be helpful in the detection of metastases and recurrences of colon carcinomas.

Recognition based hormonal 95kDa monoclonal antibody on three human cancer cell lines for developing targeted radio-immuno-imaging and therapy

The present study aimed to explore the possibility of developing a immuno-imaging/therapeutic agent for hCG-expressing tumors by using antibodies raised against them. Three human cancer cell lines were selected:lung adenocarcinoma (A549), glioblastoma (U87MG) and breast cancer (MCF7). Anti-β-hCG monoclonal antibody, obtained from ascitic fluid, was purified by affinity chromatography followed by characterization and titration. Ectopic expression of hCG on these cell lines was tested by flow cytometry and in-vitro cytotoxicity with antibodies was tested by MTT assay on the cell line with the highest percentage binding. For positive and negative controls, immortalized trophoblast cells (SW71) and peripheral blood monocytes were used. Antibody was then radiolabeled with lutetium-177 ((177)Lu) and in vivo biodistribution studies were conducted in murine tumor model. Antibodies could be purified to homogeneity with a concentration 28mg/mL. Percentage receptor expression on A549, U87MG and MCF7 cells was 95%, 66% and 55% respectively. About 90% of A549 cells could be killed with antibody at 72h post-treatment. No cytotoxicity was observed on SW71 despite a high binding percentage (96%). Antibodies were radiolabeled with high efficiency (∼98%). In-vivo studies using radiolabeled antibodies showed hepato-biliary excretion route and significant uptake in A549 tumor. In conclusion, among the 3 cancer cell lines, lung adenocarcinoma significantly expresses β-hCG and shows dose dependent cytotoxicity with anti-β-hCG antibody. Radiolabeling of this antibody can aid in imaging and also has the potential of enhancing its therapeutic potential. This study provides a platform for further studies for targeted radio-immuno imaging and subsequent therapy of hCG-expressing cancers.

Sentinel lymph node biopsy techniques in thyroid pathologies--a meta-analysis

INTRODUCTION

To review different sentinel lymph node biopsy (SLNB) techniques in patients with thyroid neoplasm. We also compared the detection rates of the different detection methods in these patients.

MATERIAL AND METHODS

The Medline database from 1998 until December 2010 was searched for the following terms: thyroid cancer, thyroid neoplasm, and sentinel lymph node. Studies in which sentinel lymph nodes were detected by the blue dye technique and/or by a radiotracer in patients with suspected thyroid cancer were analysed.

RESULTS

Twenty five studies were included in the meta-analysis. Based on the technique used for sentinel lymph node (SLN) detection, the included studies were divided into three groups. Group 1 consisted of studies in which only the blue dye technique was used to detect SLNs. Group 2 was made up of studies in which the radioisotope technique was used. Studies in which both techniques were used were grouped into Group 3. There were 18 studies in which the blue dye technique was used to detect SLNs (Group 1), four studies in which only the radioisotope technique was used to detect SLNs (Group 2), and only two studies where both techniques were used (Group 3). Among 891 patients from Group 1, SLN was found in 740 (83.1%) patients. Detection rates in these studies were very different and varied from 0% to 95.5%. Among 160 patients from Group 2, SLN was detected in 158 (98.8%). In the third group of patients, in which both methods were performed, SLN was found in 48 (98%) of 49 patients. Detection rates in those studies were very high (100% and 97.8%).

CONCLUSIONS

The analysis proved that SLNB is, technically, fairly easy to perform. However, nodal metastases are of debatable prognostic value in thyroid cancer, so the clinical value of SLNB remains to be proven. It seems reasonable to perform further, prospective studies on larger groups of patients, in which both techniques would be used. They should compare the efficiency of SLNB with elective or selective central lymphadenectomy in reducing local recurrence rates.

Application of labeled radioimmunoimaging tracing in detecting pulmonary embolism in rabbits after bone cement perfusion and relevant treatment effects

BACKGROUND

During the process of bone cement joint replacement, some patients show a series of complications, such as a sudden drop in blood pressure or dyspnea. The cause of the complication is considered to be due to emboli caused by the femur prosthesis insertion. The purpose of the present study was to detect the pulmonary embolism in rabbits after bone cement perfusion by radioimmunoimaging, and to explore its protective measures.

METHODS

Forty rabbits, 2.5 - 3.0 kg weight, were randomly assigned to four groups, with ten rabbits in each group. Group I (no intervention): Bone cement perfusion was done after medullary cavity reaming and pressurizing. Group II (epinephrine hydrochloride intervention): The medullary cavity was rinsed with a 1:10 000 normal saline-diluted epinephrine hydrochloride solution followed by bone cement perfusion after medullary cavity reaming and pressurizing. Group III (fibrin sealant intervention): The medullary cavity was precoated with fibrin sealant followed by bone cement perfusion after medullary cavity reaming and pressurizing. Group IV (blank control group): The medullary cavity was not perfused with bone cement after reaming. In each group, the rabbits underwent femoral head resection and medullary cavity reaming. Before bone cement perfusion, 2 ml of developing tracer was injected through the ear vein. Radionuclide imaging was performed at 60, 120, and 180 minutes after bone cement perfusion, and the pulmonary radioactivity in vivo was measured. The rabbits were immediately sacrificed, and the pulmonary tissue was removed and its radioactivity was measured in vitro. Pulmonary tissue was then fixed and the pulmonary embolism and the associated pathological changes were observed.

RESULTS

The pulmonary radioactivity in vivo was measured at 60, 120, and 180 minutes after bone cement perfusion. The radioactivities of the four groups were 11.67 ± 2.16, 14.59 ± 2.92 and 18.43 ± 4.83 in group I; 8.37 ± 3.05, 10.35 ± 2.24 and 11.48 ± 2.96 in group II; 3.91 ± 1.19, 5.53 ± 2.95 and 7.25 ± 1.26 in group III; 1.04 ± 0.35, 1.14 ± 0.87 and 1.43 ± 0.97 in group IV. The radioactivities of groups I, II, III at 60, 120 and 180 minutes were significantly higher than group IV (P < 0.05). The pulmonary embolism could be detected. Pretreatment with epinephrine hydrochloride and fibrin sealant significantly decreased the pulmonary radioactivity in group II and group III, but it was still higher than in the group IV.

CONCLUSIONS

Radioimmunoimaging is an alternative method for the dynamic observation of rabbit pulmonary embolism after bone cement perfusion. Radioimmunoimaging is the optional way to evaluate the effect of pretreatment with epinephrine hydrochloride or fibrin sealant on pulmonary embolism after bone cement perfusion.

Radioimmunoimaging with longer-lived positron-emitting radionuclides: potentials and challenges

Radioimmunoimaging and therapy has been an area of interest for several decades. Steady progress has been made toward clinical translation of radiolabeled monoclonal antibodies for diagnosis and treatment of diseases. Tremendous advances have been made in imaging technologies such as positron emission tomography (PET). However, these advances have so far eluded routine translation into clinical radioimmunoimaging applications due to the mismatch between the short half-lives of routinely used positron-emitting radionuclides such as (18)F versus the pharmacokinetics of most intact monoclonal antibodies of interest. The lack of suitable positron-emitting radionuclides that match the pharmacokinetics of intact antibodies has generated interest in exploring the use of longer-lived positron emitters that are more suitable for radioimmunoimaging and dosimetry applications with intact monoclonal antibodies. In this review, we examine the opportunities and challenges of radioimmunoimaging with select longer-lived positron-emitting radionuclides such as (124)I, (89)Zr, and (86)Y with respect to radionuclide production, ease of radiolabeling intact antibodies, imaging characteristics, radiation dosimetry, and clinical translation potential.

Molecular imaging of Bcr-Abl phosphokinase in a xenograft model

The purpose of this study was to determine whether the Bcr-Abl tyrosine kinase can be assessed by gamma-imaging using an 111In-labeled anti-phosphotyrosine (APT) antibody, and if the response to treatment with imatinib could be detected using this imaging technique. APT antibody was labeled with 111In using ethylenedicysteine (EC) as a chelator. To determine if 111In-EC-APT could assess a nonreceptor tyrosine kinase, xenografts of the human chronic myelogenous leukemia cell line K562 were used. gamma-Scintigraphy of the tumor-bearing mice, before and after imatinib treatment, was obtained 1, 24, and 48 h after they were given 111In-EC-APT (100 microCi/mouse i.v.). 111In-EC-APT is preferentially taken up by Bcr-Abl-bearing tumor cells when compared with 111In-EC-BSA or 111In-EC-IgG1 controls and comparable with the level of uptake of 111In-EC-Bcr-Abl. Imatinib treatment resulted in decreased expression of phospho-Bcr-Abl by Western blot analysis, which correlated with early (4 days after starting imatinib) kinase down-regulation as assessed by imaging using 111In-EC-APT. The optimal time to imaging was 24 and 48 h after injection of 111In-EC-APT. Although tumor regression was insignificant on day 4 after starting imatinib treatment, it was marked by day 14. 111In-EC-APT can assess intracellular phosphokinase activity, and down-regulation of phosphokinase activity predates tumor regression. This technique may therefore be useful in the clinic to detect the presence of phosphokinase activity and for early prediction of response.

Preclinical radioimmunotargeting of folate receptor alpha using the monoclonal antibody conjugate DOTA-MORAb-003

INTRODUCTION

The in vitro and in vivo behavior of the radiolabeled monoclonal antibody MORAb-003 was investigated as a prelude to a clinical trial.

METHODS

The cellular retention of 111In- and 131I-labeled MORAb-003 was investigated using IGROV1 and SW620 cells. Biodistribution studies in tumor-bearing mice were performed with the more favorable agent.

RESULTS

Five 1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetraacetic acid (DOTA) molecules were conjugated to MORAb-003 with no apparent loss of immunoreactivity. Radiolabeled MORAb-003 had a high affinity for the folate receptor alpha (FRA) expressed by both IGROV1 and SW620 cells and was found to bind to around 8 x 10(5) and 7 x 10(5) sites/cell, respectively. Both cancer cell lines were found to internalize both 131I- and 111In-labeled MORAb-003, but 111In was retained and 131I was released as iodide. In athymic mice, 111In-DOTA-MORAb-003 was cleared from the blood with a single exponential biological clearance rate of 110 h. The uptake in SW620 tumors was 32+/-5%ID/g after 4 days. The clearance rate of activity from normal organs such as liver, kidney and spleen was similar to the blood clearance and was 5.36%ID/g, 4.03%ID/g and 4.36%ID/g at 1 day postinjection and 2.14%ID/g, 1.65%ID/g and 3.74%ID/g after 8 days, respectively. In a pilot clinical study, the biodistribution and tumor targeting of 111In-MORAb-003 was assessed in three patients undergoing treatment with cold MORAb-003.

CONCLUSION

MORAb-003 is an attractive antibody for radioimmunoscintigraphy and possibly radioimmunotherapy of FRA-expressing cancers in addition to its potential direct therapeutic effects.

The emergence of imaging technology in advanced prostate cancer

Rapid advances in imaging technology have whetted our collective appetites for practical clinical applications to assist the physician and patient in therapeutic decisions. Current limitations of imaging technology are being addressed by the convergence of technology in materials science, the computer industry, and biology which have led to improvements of diagnostic imaging. Refinements in image acquisition, fusion of images, and outcomes data now suggest use for image-guided therapy. Novel imaging agents and technologies appear to provide improved capabilities to detect malignant lymph nodes. Future applications of optical coherence tomography, electron paramagnetic resonance imaging, nanotechnology, and other forms of molecular imaging promise further refinements to enhance our diagnostic armamentarium.

Operative probe scintimetry with indium and technetium for colorectal cancer

Surgeons introduced the hand-held gamma detection probe in combination with tumor-directed monoclonal antibodies in patients with colorectal cancer. The clinicians conducted innovative research involving antibody chemistry and variation as well as radioactive dosimetry and decay. The results of these studies represented an era when surgeons began reporting on specific lesion detection and the impact of the antibody administration on the management of the patient. The summary of the important early trials involving monoclonal antibodies and probe scintimetry provides a valuable look into the early development of the antibody technology and a glimpse of potential future applications using the gamma detection probe.

Tumor radioimmunolocalization in nude mice by mono- and divalent- single-chain Fv antiplacental alkaline phosphatase antibodies

One single-chain Fv antibody fragment (scFv) and a new recombinant covalently linked dimeric scFv antibody (sc(Fv)(2)) against placental alkaline phosphatase (PLAP) were investigated for selective tumor targeting. The biological behavior of these new antibodies was compared to that of the original native antibody, H7 MAb. The sc(Fv)(2)) antibody displayed convincing tumor localization properties with a rapid excretion pattern comparable to the scFv, but with a longer retention time in the tumor, and higher tumor-to-nontumor ratio (27:1), compared to the scFv (15:1), at 48 hours. For the sc(Fv)(2) antibody, more than 50% of the remaining activity in the mouse was present in the tumor between 24 and 48 hours after the injection. With this antibody, scintigraphic visualization of the tumor was also possible 1 week after the injection. It is concluded that this sc(Fv)(2) antibody fragment, with two binding sites, displays properties suitable for in vivo targeting of PLAP expressing tumors.

Quantitative radioimmunoPET imaging of EphA2 in tumor-bearing mice

PURPOSE

EphA2 receptor tyrosine kinase is significantly overexpressed in a wide variety of cancer types. High EphA2 expression has been correlated with increased metastatic potential and poor patient survival. Although many recent reports have focused on blocking the EphA2 signaling pathway in cancer, the in vivo imaging of EphA2 has not yet been investigated.

METHODS

We labeled 1C1, a humanized monoclonal antibody against both human and murine EphA2, with (64)Cu through the chelating agent 1,4,7,10-tetraazacyclododecane N,N',N'',N'''-tetraacetic acid (DOTA) and carried out positron emission tomography (PET) imaging of eight tumor models with different EphA2 expression levels. Western blotting of tumor tissue lysate was performed to correlate the EphA2 expression level with (64)Cu-DOTA-1C1 uptake in the tumors. Immunofluorescence staining and biodistribution studies were also carried out to validate the in vivo results.

RESULTS

The radiolabeling yield was 88.9 +/- 9.5% (n = 7) and the specific activity of (64)Cu-DOTA-1C1 was 1.32 +/- 0.14 GBq/mg of 1C1 mAb. The antibody retained antigen-binding affinity/specificity after DOTA conjugation as measured by FACS analysis. The uptake of (64)Cu-DOTA-1C1 in CT-26 tumors was as high as 25.1 +/- 2.5 %ID/g (n = 3) at 18 h post injection. (64)Cu-DOTA-IgG, an isotype-matched control, exhibited minimal non-specific uptake in all eight tumor models. In vivo EphA2 specificity of (64)Cu-DOTA-1C1 was confirmed by successful blocking of CT-26 tumor uptake by unlabeled 1C1. Most importantly, the tumor uptake value obtained from PET imaging had excellent linear correlation with the relative tumor tissue EphA2 expression level measured by Western blot, where r (2) equals 0.90 and 0.92 at 18 h and 42 h post injection, respectively.

CONCLUSION

The tumor uptake of (64)Cu-DOTA-1C1 measured by microPET imaging reflects tumor EphA2 expression level in vivo. This is, to our knowledge, the first report of quantitative radioimmunoPET imaging of EphA2 in living subjects. Future clinical investigation of (64)Cu-DOTA-1C1 is warranted.

Immunoscintigraphy of local recurrent rectal cancer with 99mTc-labeled anti-CEA monoclonal antibody CL58

AIM: To explore a specific diagnostic method for local recurrent rectal cancer.

METHODS: Immunoscintigraphy with ^99mTc-labeled anti-CEA monoclonal antibody (MoAb) CL-58 was performed for patients suspected of having a postoperative local recurrent rectal cancer and the findings were compared with the results of conventional imaging and pathology.

RESULTS: A total of 36 patients with a suspected local recurrent rectal cancer underwent immunoscintigraphy with ^99mTc-conjugated CL58. Local recurrence of rectal cancer was identified in 31 patients and established in 30 during operation, endoscopy and pathological examination. No local recurrence was found in 5 patients without specific accumulation of ^99mTc during the follow-up. Immunoscintigraphy had a positive rate of 86.11%, a specificity of 83.33%, and a sensitivity of 100%.

CONCLUSION: Immunoscintigraphy has a highly specific and predictive value for detecting local recurrent rectal cancer, especially after abdominal perineal resection (APR).

Radiolabeled anti-claudin 4 and anti-prostate stem cell antigen: initial imaging in experimental models of pancreatic cancer

Global expression profiling of pancreatic cancers has identified two cell surface molecules, claudin 4 and prostate stem cell antigen (PSCA), as being overexpressed in the vast majority of cases. Two antibodies, anti-claudin 4 and anti-PSCA, were radiolabeled with iodine 125 ((125)I) for imaging pancreatic cancer xenografts in mice using gamma scintigraphy and single-photon emission computed tomography-computed tomography (SPECT-CT). Immunofluorescence staining of intact and permeabilized Colo357 human pancreatic cancer cells showed strong extracellular staining by both anti-PSCA and anti-claudin 4. Biodistribution studies in claudin 4 and PSCA-expressing Colo357 and PANC-1 subcutaneous xenograft models in mice showed that [(125)I]anti-claudin 4 tumor to muscle ratio uptake was 4.3 in Colo357 at 6 days postinjection and 6.3 in PANC-1 xenografts at 4 days postinjection. Biodistribution of [(125)I]anti-PSCA showed tumor to muscle ratio uptake of 4.9 in Colo357 at 6 days postinjection. Planar gamma scintigraphic imaging in Colo357 xenograft-bearing mice showed clear tumor uptake of [(125)I]anti-claudin 4 by 24 hours postinjection and by 48 hours postinjection for [(125)I]anti-PSCA. SPECT-CT imaging with [(125)I]anti-claudin 4 and [(125)I]anti-PSCA in an L3.6PL orthotopic xenograft model showed strong tumor and spleen uptake at 5 days postinjection. Both anti-claudin 4 and anti-PSCA demonstrate promise as radiodiagnostic and possibly radiotherapeutic agents for human pancreatic cancers.

Synergistic Value of Single-Photon Emission Computed Tomography/Computed Tomography Fusion to Radioimmunoscintigraphic Imaging of Prostate Cancer

The rationale on which positron emission tomography/computed tomography (PET/CT) imaging is based, combining the functional features of PET with the anatomic detail of CT, provides many advantages that are easily transferable to single-photon emission computed tomography (SPECT)/CT imaging. Our efforts have focused on applying fused SPECT/CT imaging to identify prostate cancer and its metastasis and recurrence through radioimmunoscintigraphy (RIS). This application of RIS to imaging prostate cancer requires 2 key components: (1) a well-defined target associated with the cancer and (2) a "magic bullet" to seek that target. A well-characterized RIS target for prostate cancer is prostate-specific membrane antigen, or PSMA, and finding the bullet to seek this target with high sensitivity and specificity has been the focus of intensive study for nearly two decades. One of the candidate bullets developed is capromab pendetide, which is a monoclonal antibody that seeks PSMA. This antibody is commercially available as ProstaScint, which can be labeled with indium-111 to localize prostate cancer via SPECT imaging. In the course of applying fused SPECT/CT ProstaScint imaging to more than 800 prostate cancer cases, numerous refinements to our protocol have evolved that are aimed at staging the cancer with utmost accuracy. In addition to optimizing the localization of prostate cancer and its metastasis, these refinements also have been extended toward guiding both the implantation of radioactive seeds in brachytherapy and in other types of radiation therapy which is illustrated through 5 case reports. Progress in the therapeutic targeting of PSMA is also being actively explored, which has more universal ramifications because PSMA is found in the neovasculature of other types of cancers.

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.

Immunoscintigraphy of colorectal carcinomas with radiolabeled monoclonal antibody fragments

BACKGROUND/AIMS

The aim was evaluation of the accuracy and clinical impact of the immunoscintigraphy for the detection of metastases and recurrences of colorectal carcinomas using two different radiolabeled antibody fragments.

METHODOLOGY

The study was performed in 5 patients with IMACIS 1 containing the cocktail of 111MBq 131I MoAb 19-9 F(ab')2 and MoAb anti-CEA F(ab')2 and 8 patients with INDIMACIS 19-9 containing 150MBq of 111In-labeled MoAb 19-9 F(ab')2.

RESULTS

With IMACIS 1, in all the patients, both tumor marker values were elevated. The number of TN was 3/5 and TP 2/5. From 2 TP, one had recurrence of the diseases with peritoneal carcinosis and one with liver metastases. In one patient, the results influenced the therapeutical management. With INDIMACIS 19-9, there were 2/8 TN, with borderline value of CEA and CA 19-9. TP were 6/8 (all with elevated tumor marker values, five of them many times; 3 with recurrences, 1 with recurrence and liver metastases and two with only liver metastases. In three patients, immunoscintigraphy influenced patient management.

CONCLUSIONS

With both radiopharmaceuticals, immunoscintigraphy significantly influenced the patient management or it was complementary. It would be performed in the detection of recurrence, assessment of viability and follow-up of the therapy.

Postprostatectomy target-normal structure overlap volume differences using computed tomography and radioimmunoscintigraphy images for radiotherapy treatment planning

PURPOSE

The purpose of this study was to analyze regions of uptake in normal structures on postprostatectomy radioimmunoscintigraphy (RIS) images by evaluating differences in the overlap volumes of prostate fossa clinical target volume (CTV) and planning target volume (PTV) using correlative computed tomography (CT) images.

MATERIALS AND METHODS

The electronic records of 13 patients who received external beam radiotherapy postprostatectomy and who underwent a vessel-based RIS/CT registration were reviewed. For each patient, the RIS-defined CTV (CTV(RIS)) was compared (in terms of the overlap volume with the surrounding bladder, rectum, pubic symphysis, and penile bulb) with the CT-defined CTV(pre) before this registration and also with CTV(post) (the final target volume used for treatment). Similar analyses were done for PTV(RIS), PTV(pre), and PTV(post) defined in each case to be the corresponding CTV + 1-cm margin.

RESULTS

CTV(RIS) overlapped significantly more with the bladder, rectum, and symphysis, but not with the penile bulb, than did either the CTV(pre) or CTV(post). However, the corresponding PTV analyses revealed no significant differences between any of the overlap volumes of any of the PTVs with the bladder, rectum, and penile bulb, but did reveal a significant difference between the PTV(RIS) and PTV(post) overlap volumes with the symphysis compared with PTV(pre) overlap volumes with the symphysis.

CONCLUSIONS

On RIS images, there appear to be areas of uptake in the bladder, rectum, and pubic symphysis but not the penile bulb; however, the dosimetric consequences of this uptake for radiation treatment planning are minimal on the bladder, rectum, and penile bulb, but require segmentation for dose reduction to the pubic symphysis.

Phase I/II clinical trial of the humanized anti-EGF-r monoclonal antibody h-R3 labelled with 99mTc in patients with tumour of epithelial origin

AIM

To evaluate the biodistribution, internal radiation dosimetry and toxicity of the humanized MAb h-R3 labelled with Tc in humans.

METHODS

Twenty-five patients with suspected epithelial-derived tumours were included in this study and divided into two groups: group I consisted of 10 patients who received 3 mg/1110 MBq (3 mg/30 mCi); and group II consisted of 15 patients who received 6 mg/2220 MBq (6 mg/60 mCi). Single photon emission computed tomography (SPECT) and planar images, and multiple blood and urine samples were collected up to 24 h after injection. Haematological parameters and adverse effects were classified according to the WHO criteria. Biodistribution, human anti-mouse antibody (HAMA) response and absorbed doses were estimated and reported.

RESULTS

Liver, spleen, kidneys and heart were identified as source organs. Their higher uptakes were 53.3+/-6.4%ID, 2.0+/-1.4%ID, 9.8+/-4.3%ID and 2.8+/-0.9%ID, respectively. The urinary bladder and large intestine also had a significant uptake. The mean urinary excretion was around 22%ID. The liver received the highest absorbed doses followed by the kidneys and the urinary bladder wall. There were no haematological or biochemical abnormalities with clinical significance related to the product. No patient developed HAMA response. Preliminary analysis of clinical results showed a sensitivity of 76.5% and a specificity of 100%.

CONCLUSIONS

The results of this study suggest that Tc-h-R3 could be used in patients in a safe and effective way, for the diagnosis of epithelial-derived tumours at the two evaluated dose levels.

Radiobromination of humanized anti-HER2 monoclonal antibody trastuzumab using N-succinimidyl 5-bromo-3-pyridinecarboxylate, a potential label for immunoPET

Combining the specificity of radioimmunoscintigraphy and the high sensitivity of PET in an in vivo detection technique could improve the quality of nuclear diagnostics. Positron-emitting nuclide (76)Br (T(1/2)=16.2 h) might be a possible candidate for labeling monoclonal antibodies (mAbs) and their fragments, provided that the appropriate labeling chemistry has been established. For internalizing antibodies, such as the humanized anti-HER2 monoclonal antibody, trastuzumab, radiobromine label should be residualizing, i.e., ensuring that radiocatabolites are trapped intracellularly after the proteolytic degradation of antibody. This study evaluated the chemistry of indirect radiobromination of trastuzumab using N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate. Literature data indicated that the use of this method provided residualizing properties for iodine and astatine labels on some antibodies. An optimized "one-pot" procedure produced an overall labeling efficiency of 45.5+/-1.2% over 15 min. The bromine label was stable under physiological and denaturing conditions. The labeled trastuzumab retained its capacity to bind specifically to HER2-expressing SKOV-3 ovarian carcinoma cells in vitro (immunoreactivity more than 75%). However, in vitro cell test did not demonstrate that the radiobromination of trastuzumab using N-succinimidyl 5-bromo-3-pyridinecarboxylate improves cellular retention of radioactivity in comparison with the use of N-succinimidyl 4-bromobenzoate.

Modulated expression of a nuclear-associated glycoprotein during normal rat liver development and in various hepatoma cells

Liver plays a major role in systemic detoxification and drug metabolism. NF-164, a protein of 164 kDa predominantly localized in hepatocyte nuclei, was found to be present in increasing amounts during liver maturation. In addition, fetal rat hepatocytes had ten times, and neonatal five times less of this protein than adult hepatocytes. It was also detected in an albumin producing hepatoma cell line, but not in three other lines that have lost several differentiated functions. These data suggest that NF-164 expression is development-dependent and that it may be a marker for both normal and malignant hepatocyte differentiation. NF-164 seems to be liver-specific, since it was not detected in rat brain, spleen, kidney, lung and bovine thymus. It was purified from adult rat hepatocyte nuclei. Its estimated pI is 6.8. Its total amino acid composition and partial amino acid sequence is also being reported. Despite major differences between their respective contents in amino acids, partial sequences showed homologies with carbamyl phosphate synthetase I (CPSI). These observations may suggest that NF-164 also shares some functional features with this enzyme.

Radioimmunoscintigraphy of colorectal carcinomas with three different radiopharmaceuticals

The aim of the study was evaluation of the clinical reliability of the immunoscintigraphy for the detection of metastases and recurrences of colorectal carcinomas using three different radiopharmaceutical substances. With IMACIS 1, the number of true negative findings (TN) was 4/7 and true positive (TP) 3/7, while in one patient, the results of immunoscintigraphy significantly influenced the therapeutical management. With INDIMACIS 19-9, there were 2/8 TN and 6/8 TP. In three patients, immunoscintigraphy results influenced patient further management. With ONCOSCINT in 2 patients findings were TN, in one FN and in one FP. In 3 patients, immunoscintigraphy influenced the management of the patient. Other imaging methods (CT, US, MRI) have advantage in detection of liver metastases, while immunoscintigraphy is more specific for the assessment of reccurences of the abdominal tumors. Thus immunoscintigraphy should be applied in patients with suggested recurrences and inconclusive outcome of routine diagnostic workup.

Antibody pretargeting advances cancer radioimmunodetection and radioimmunotherapy

This article reviews the methods of pretargeting, which involve separating the targeting antibody from the subsequent delivery of an imaging or therapeutic agent that binds to the tumor-localized antibody. This provides enhanced tumor:background ratios and the delivery of a higher therapeutic dose than when antibodies are directly conjugated with radionuclides, as currently practiced in cancer radioimmunotherapy. We describe initial promising clinical results using streptavidin-antibody constructs with biotin-radionuclide conjugates in the treatment of patients with malignant gliomas, and of bispecific antibodies with hapten-radionuclides in the therapy of tumors expressing carcinoembryonic antigen, such as medullary thyroid and small-cell lung cancers.

Tailoring antibodies for radionuclide delivery

Therapeutic antibodies are well established as an important class of drugs in modern medicine. The exquisite specificity and affinity for a specific target offered by antibodies has also encouraged their development as delivery vehicles for agents such as radionuclides to target tissues, for radioimmunoimaging and radioimmunotherapy. Specifically, in nuclear medicine, radionuclide-conjugated antibody molecules make it possible to image diseased loci with greater sensitivity than other imaging modalities such as magnetic resonance imaging. Furthermore, two radionuclide-conjugated antibodies have recently been approved for the therapy of non-Hodgkin's lymphoma. However, optimal implementation of antibodies has been limited by the extended circulation persistence that is characteristic of native antibodies, which is responsible for increased background activity in radioimmunoimaging applications and dose-related normal organ toxicities in radioimmunotherapy. In this article the current status of radiolabelled intact antibodies is reviewed, focusing on strategies to improve their pharmacokinetic properties to suit a desired application. Examples from the literature that represent different approaches to accomplishing this task in terms of their successes as well as limitations, and perspectives for the future are discussed.

Improved Tumor Targeting by Combined Use of Two Antitenascin Antibodies

PURPOSE

In the pretargeted antibody-guided radioimmunotherapy (PAGRIT) system, the combined use of two different antibodies directed against the same tumor antigen could represent a valid approach for improving tumor targeting and therapeutic efficacy. We developed a novel monoclonal antitenascin antibody, ST2485, and studied its biochemical and functional properties by in vitro and in vivo assays. We then investigated the first of the three-step therapy combining ST2485 with another antitenascin antibody, ST2146, previously described, to increase accumulation of biotinylated antibodies at the tumor site.

EXPERIMENTAL DESIGN

Studies of immunoreactivity, affinity, immunohistochemistry, and biodistribution in xenograft model were carried out on ST2485. Analysis of the ST2485 and ST2146 combination was preliminary carried out by ELISA and BiaCore tests and then by in vivo distribution studies after administration of the radiolabeled biotinylated antibodies, followed by a chase with avidin as clearing agent.

RESULTS

ST2485 was found to be a suitable antibody for therapeutic applications. Indeed, for its behavior in all tests, it was comparable with ST2146 and better than BC2, an antibody already used for clinical trials. The additivity of ST2146 and ST2485 in tenascin C binding, shown by in vitro tests, was confirmed by biodistribution studies in a xenograft model where tumor localization of the antibodies was near the sum of each antibody alone, with a tumor-to-blood ratio higher than 24.

CONCLUSION

The results reported in this study suggest that a monoclonal antitenascin antibody mixture can improve tumor targeting. This strategy could represent progress for therapeutic approaches such as PAGRIT.

Management of Central Nervous System Lymphomas Using Monoclonal Antibodies: Challenges and Opportunities

Monoclonal antibodies (mAb) may change the management of central nervous system (CNS) lymphomas. This is due to the fact that traditional chemotherapies lack specificity for B-lymphoma cells and blood-brain barrier prevents adequate chemotherapy dosing in the CNS without significant systemic side effects. But in the past 5 years, the emergence of mAbs against specific receptors on B-lymphoma cells, either as a single agent or in combination with cytotoxic chemotherapies, may offer a better therapeutic index than conventional chemotherapies. The advantages of mAbs include high affinity to targets on lymphoma cells, their lack of pharmacodynamic or pharmacokinetic interactions with other drugs, and a potential for a synergistic therapeutic response when combined with conventional chemotherapies. Our review summarizes the biological behaviors of CNS lymphomas and the challenges and opportunities in using mAbs for CNS lymphomas.

Pretargeting of Carcinoembryonic Antigen–Expressing Cancers with a Trivalent Bispecific Fusion Protein Produced in Myeloma Cells

PURPOSE

To characterize a novel trivalent bispecific fusion protein and evaluate its potential utility for pretargeted delivery of radionuclides to tumors.

EXPERIMENTAL DESIGN

hBS14, a recombinant fusion protein that binds bispecifically to carcinoembryonic antigen (CEA) and the hapten, histamine-succinyl-glycine (HSG), was produced by transgenic myeloma cells and purified to near homogeneity in a single step using a novel HSG-based affinity chromatography system. Biochemical characterization included size-exclusion high-performance liquid chromatography (SE-HPLC), SDS-PAGE, and isoelectric focusing. Functional characterization was provided by BIAcore and SE-HPLC. The efficacy of hBS14 for tumor pretargeting was evaluated in CEA-expressing GW-39 human colon tumor-bearing nude mice using a bivalent HSG hapten (IMP-241) labeled with (111)In.

RESULTS

Biochemical analysis showed that single-step affinity chromatography provided highly purified material. SE-HPLC shows a single protein peak consistent with the predicted molecular size of hBS14. SDS-PAGE analysis shows only two polypeptide bands, which are consistent with the calculated molecular weights of the hBS14 polypeptides. BIAcore showed the bispecific binding properties and suggested that hBS14 possesses two functional CEA-binding sites. This was supported by SE-HPLC immunoreactivity experiments. All of the data suggest that the structure of hBS14 is an 80 kDa heterodimer with one HSG and two CEA binding sites. Pretargeting experiments in the mouse model showed high uptake of radiopeptide in the tumor, with favorable tumor-to-nontumor ratios as early as 3 hours postinjection.

CONCLUSIONS

The results indicate that hBS14 is an attractive candidate for use in a variety of pretargeting applications, particularly tumor therapy with radionuclides and drugs.

Preclinical application of radioimmunoguided surgery using anti-carcinoembryonic antigen biparatopic antibody in the colon cancer

Radioimmunoguided surgery (RIGS) has been known as a sophisticated tool to detect micrometastasis intraoperatively. A preclinical model of RIGS was designed to test the possible clinical applicability of the biparatopic antibody in detecting colorectal cancer. The biparatopic antibody was constructed using two anti-carcinoembryonic antigen (CEA)-specific antibodies, T84.66 and PR1A3, reacting against two different epitopes. (125)I-labeled biparatopic antibody was introduced via the principal colonic arteries at the end of operation in 10 operable patients with colon cancer. After 24 h, the radioactivities of the tumors and lymph nodes were counted using the gamma-detecting probe. The radioactivity count was performed ex vivo. The accurate detection in the primary tumors and metastatic lymph nodes were 100 and 88.7% respectively. False-positive detections occurred in 24 of 256 lymph nodes (9.4%), whereas false-negative detections occurred in 5 of them (2%). The most frequent cause of false-positive detection was dissociated radionuclides trapped in the lymphatic tissues. False-negative detections occurred mainly from weak targeting by radiolabeled antibody, probably due to weak expression of tumor CEA. Conclusively, as most detection errors appear to be reduced within 3 days in vivo, the biparatopic antibody can efficiently be applied to the clinical RIGS, thereby facilitating accurate detection and removal of occult cancer foci in colorectal cancer.

Recent advances in the treatment of childhood brain tumors

Pediatric brain tumors are the commonest cause of cancer-related death in children. The last four decades have seen only a 35% increase in 5-year survival rate of children with these tumors. The therapeutic successes achieved are due to advances in neuroimaging, surgical techniques, radiotherapy, and induction of newer chemotherapeutic agents along with molecular targeted therapy. Neuroimaging advances include the use of MRA, MRS, DSA, and PET scans. With the use of stereotactic surgery, intraoperative mapping, and imaging, surgical resection has improved with significant decrease in morbidity. A major development has been the use of precision guided radiotherapy utilizing technologies like 3D-CRT, SRS, and IMRT, thereby decreasing radiation to normal tissues. Induction of newer drugs and high-dose chemotherapy with peripheral stem cell support has improved survival and delayed radiation in younger children and infants with brain tumors. Intense ongoing research is profiling novel molecular targets for therapeutic intervention. Newer therapeutic strategies like blood brain barrier disruption, immunotherapy, and gene therapy are in clinical trials. This review article intends to give the reader an overview of current therapeutic strategies and research involved in the treatment of children with brain tumors.

Radioimmunodetection and therapy of breast cancer

Breast cancer is the second most-common cause of cancer death in women in the United States. Although more than 60% of patients can now be cured by initial treatment, the rest, although perhaps receiving palliation with currently available therapy, will die of their disease. Early detection of micrometastasis and improved treatment strategies are needed. Monoclonal antibody (mAb)-based imaging and tumor targeted therapy holds the potential to impact these problems. The most significant results of systemically administered antibody-based radiopharmaceuticals for detection and targeted therapy (radioimmunotherapy [RIT]) of breast cancer give strong evidence that this potential can be realized. Interest in immunoimaging recently has focused on small mAb modules used with 18F, 64Cu, or 124I to detect minimal disease in breast cancer by positron emission tomography or single-photon emission computed tomography. Reported therapy trials in advanced breast cancer have yielded objective responses and minimal toxicity. These studies have spanned several radionuclides as well as several mAb, fragments and approaches, including dose intensification with bone marrow support; combined therapy with other modalities (ie, CM-RIT); biodegradable peptide linkers; and pretargeting. RIT evaluated in clinical breast cancer trials has delivered as much as 4000 cGy to metastatic breast cancer per therapy dose with marrow stem cell support. Preclinical studies have demonstrated further promising strategies for breast cancer. RIT studies must address the key issue: enhancing the therapeutic index (tumor effect verses most sensitive normal tissue (bone marrow) effect). Approaches now include newly engineered mAb, scFv modular constructs, blood clearance on demand, enhanced pretargeting, applications of both alpha and beta emitting radionuclides, and combination therapy using molecular triggers for therapeutic synergy. These strategies for detection and treatment of metastatic breast cancer should lead to notable clinical impact on management and cure of breast cancer.

Experimental radioimmunoguided surgery for peritoneal metastases of gastric cancer using anticarcinoembryonic antigen-specific T84.66 F(ab')2

PURPOSE

In gastric cancer, peritoneal dissemination is the most frequent cause of the noncurative resection and recurrence after curative resection. We therefore evaluated the feasibility of radioimmunoguided surgery (RIGS) in the treatment of peritoneal metastases of gastric cancer and the use of anti-CEA-specific T84.66 F(ab')2 as an efficient immune agent.

METHODS

Two human gastric cancer cell lines, MKN45 and RF48, were intraperitoneally xenografted into nude mice, which were later injected with 125I-labeled T84.66 F(ab')2. Peritoneal tumors were localized by RIGS 5 days after antibody injection. The minimum number of cells detected by a gamma probe was assayed by in vitro tumor cell localization.

RESULTS

We observed 37 peritoneal metastases: 8 invisible (long diameter, <1 mm), 6 small (1- < 5 mm), and 23 large (> or =5 mm) tumors. The accuracy, sensitivity and specificity of RIGS in detecting peritoneal metastasis were 82% (69/84), 76% (28/37), and 87% (41/47), respectively. RIGS accuracy did not differ with respect to tumor diameter. Mean labeling indices over minimal and maximal normal counts were 6.1+/-1.2 (mean +/- SEM) and 4.7+/-1, respectively. Mean scores of CEA immunostaining and silver grains in tumors were significantly higher than those in the nontumor-bearing peritoneum (P < 0.001). There was a close correlation among radioactivity, immunostaining and microautoradiography (P < 0.001-0.005). We observed six false-positive and nine false-negatives which may have been due to high blood background and negative radioimmune reactivity, respectively.

CONCLUSIONS

125I-labeled T84.66 F(ab')2 efficiently targeted peritoneally disseminated gastric cancer cells, suggesting that RIGS using this immune agent may accurately detect occult peritoneal metastases in patients with gastric cancer.

Monoclonal antibodies: old and new trends in breast cancer imaging and therapeutic approach

Over the last two decades, various research protocols were applied for scintigraphic imaging, prognosis and treatment of breast cancer, using monoclonal antibodies. Monoclonal antibodies approved by the United States Food and Drug Administration (FDA) include the anti-carcinoembryonic antigen (CEA), and B72.3, prepared against the tumour-associated glycoprotein, TAG-72. The recombinant humanized "cold" anti-HER2 monoclonal antibody (trastuzumab), which targets oncogene receptor HER2 has hitherto been the only monoclonal antibody widely used for the treatment of breast cancer in the USA, with or without chemotherapy. Trastuzumab is constructed against the HER2 oncogene receptor (also known as neu or c-erb-B2), which is overexpressed in 25%-30% of breast cancer cell lines and is associated with poor prognosis. Immuno-lymphoscintigraphy is also applied to guide and monitor the effect of treatment regimes. Radiolabelled, "hot" monoclonal antibodies are currently being applied for the treatment of primary or metastatic breast cancer, in experimental, pre-clinical, or clinical trials, in combination with traditional external beam radiotherapy and/or chemotherapy. Radioimmunotherapy comprises systemically administered monoclonal antibodies, linked to high-energy, beta-emitting radionuclides. Radioactive antibodies, in the form of yttrium-90 (90Y)-BrE-3, 90Y- m170 and 131I- or 90Y- labelled L6 antibody, are applied with adjuvant autologous peripheral blood stem cells transfusion, to prevent myelotoxicity. Partial or rarely complete responses to "hot" antibody treatment, of breast cancer have been reported. Innovative strategies using this combined-modality treatment hold promise for better disease-free and survival rates.

In situ immunoradiographic method for quantification of specific proteins in normal and ischemic brain regions

This study tested the application of an immunoisotopic assay for immunohistochemical localization and quantification of proteins in brain sections from rats without or with transient focal ischemia. We assessed the hypothesis that measurements of protein levels in injured brain determined by an isotopic assay using [(125)I]-protein A have greater reliability than those made by conventional immunoperoxidase labeling using diaminobenzidine. Quantification of immunoreactivities for glial fibrillary acidic protein (GFAP), glutamate transporter-1 (GLT-1) and heat shock protein-70 (HSP-70) was determined by optical density signal in the immunoisotopic and immunoperoxidase assays. In ischemic brain, the immunoisotopic assay detected protein increases (cortical penumbra HSP-70, 151+/-6%), protein decreases (cortical ischemic core GLT-1, 61+/-6%) and no changes in GFAP levels compared to controls animals. These results differed from the protein levels found by the immunoperoxidase assay, which showed elevated HSP-70, GLT-1 and GFAP in all ischemic regions. We conclude that nonspecific immunosignal confounds assessments of protein expression in injured brain and that the immunoisotopic method is a valid approach to regionally localize and quantify proteins after brain injury. The disadvantage of the falsely positive overestimation of protein immunoreactivity after stroke with the immunoperoxidase method has to be weighted with the advantage of the cellular resolution.

The Potential Use of 99mTc-MDP Bone Scans to Plan High-Activity 186Re-HEDP Targeted Therapy of Bony Metastases from Prostate Cancer

Patients with skeletal metastases from hormone-refractory prostate cancer have shown variable responses to high-activity therapy with (186)Re-HEDP and peripheral stem cell support. In this paper, we report on the use of a novel technique to compare sequential planar images acquired post-(186)Re-HEDP therapy administration with pretherapy diagnostic (99m)Tc-MDP scans, to evaluate the turnover of the radiopharmaceutical in normal and abnormal bone. It was found that the activity in normal (i.e., disease-free) segments of the spine demonstrates a faster effective decay than that of the metastases, with the latter showing only physical decay. This study showed, for the first time, a detailed correlation in the behavior of the (99m)Tc-MDP and (186)Re-HEDP images, encouraging the possibility of using the pretherapy 99mTc-MDP scan for estimations of absorbed doses to be delivered by prescribed activities of (186)Re-HEDP.

Effects of sleep deprivation, nicotine, and selenium on wound healing in rats

Effects of sleep deprivation (SD), nicotine, and selenium (Se) on wound healing were studied in 50 male rats (Sprague-Dawley strain). Full-skin-thickness burns were produced in animals. Then, SD, nicotine, and Se administrations were applied to animals in different groups. Wound healing was assessed by pathological analysis of wound by counting fibroblasts, capillary vessels, polymorphonuclear leucocytes (PNLs), and by measuring radiolabeled immunoglobulin G (IgG) amount in wound area by radio-pharmaceutical and immunoscintigraphic procedures. The number of fibroblasts and capillary vessels were higher in control and Se groups than in sleep deprivation and nicotine groups, and the number of PNLs and the radiolabeled polyvalent IgG levels were higher in SD and nicotine groups than in control and Se groups. The results suggest that SD and nicotine may delay wound healing and that Se supplementation may accelerate wound healing by preventing nicotine-induced oxidative stress and lipid peroxidation.

Tc-99m labelled anti CD 66 antigranulocyte antibody imaging for assessment of bone marrow reserve

Patients with metastatic disease to the bone marrow are at risk of significant hematologic toxicity, if they undergo myelotoxic chemotherapy. Tc-99m labelled Anti CD 66 monoclonal antibody imaging is a useful, noninvasive approach to the assessment of bone marrow reserve under such circumstances.

Improved targeting of pancreatic cancer: experimental studies of a new bispecific antibody, pretargeting enhancement system for immunoscintigraphy

PURPOSE

The early detection and diagnosis of pancreatic cancer remains a major clinical challenge in which imaging procedures have a central role. The purpose of this study was to evaluate a pretargeting method with a bispecific PAM4 (bsPAM4; anti-MUC1) antibody for radioimmunoscintigraphy of experimental human pancreatic cancer.

EXPERIMENTAL DESIGN

A bispecific F(ab')(2) antibody was generated from chimeric PAM4 Fab' and murine 734 (anti-indium-diethylenetriaminepentaacetic acid) Fab' fragments and then used in conjunction with 2 peptide haptens ((111)In-IMP-156 and (99m)Tc-IMP-192). Biodistribution studies and radioimmunoscintigraphic imaging properties of the radiolabeled bsPAM4, and pretargeted, radiolabeled peptides were examined in the CaPan1 human pancreatic tumor grown as s.c. xenografts in athymic nude mice. Tumor uptake and tumor:nontumor ratios were compared with a nontargeting irrelevant anti-CD20, bispecific rituximab, radiolabeled peptides alone, and with directly labeled PAM4.

RESULTS

Biodistribution results indicated significantly greater tumor uptake of radiolabeled peptides at 3 h after injection when pretargeting was performed with bsPAM4 as compared with the bispecific rituximab [20.2 +/- 5.5 percentage of injected dose per gram of tissue (%ID/g) versus 0.9 +/- 0.1%ID/g, respectively, for (111)In-IMP-156, and 16.8 +/- 4.8%ID/g versus 1.1 +/- 0.2%ID/g, respectively, for (99m)Tc-IMP-192]. Similar results were obtained at the 24-h time point. Tumor:nontumor ratios were >30 for all of the tissues except the kidneys, where a ratio of 7.8 +/- 2.8 was observed. By immunoscintigraphy, tumors could be visualized as early as 30 min after injection of the radiolabeled peptide.

CONCLUSIONS

These studies demonstrate the feasibility of using the pretargeted, bispecific antibody technology for nuclear imaging of pancreatic cancer. The advantage of pretargeted bsPAM4 antibody as an imaging platform is the high specificity for pancreatic cancer as compared with the physicochemical parameters identified by current imaging technologies.

Radioimmunoimaging. Advances and prospects

The advent of biotechnology has made it possible to overcome the undesired host antiglobulin response evidenced following the injection of rodent antibodies for radioimmunoimaging; initially through the construction of chimeric and CDR-grafted antibodies and more recently through the derivation of completely human antibodies. Available platforms for derivation of completely human antibodies include phage- and ribosome-display techniques and transgenic mice that are deleted in their own antibody genes and reconstituted with large parts of the genes encoding for human antibodies. Additionally, biotechnology has made it possible to tailor affinity, respectively through CDR-walking or chain schuffling, and avidity, respectively through manifold engineering, of antibodies and derivatives. More recent developments include the development of highly stable single domain binders based on the use of a conserved framework region and a highly variable antigen-binding site, using other proteins or molecules that are smaller in size and easier to manufacture than antibodies. Finally, novel technologies have been and are being developed optimizing the concept of pretargeting.

Reduced In Vivo Aortic Uptake of Radiolabeled Oxidation-Specific Antibodies Reflects Changes in Plaque Composition Consistent With Plaque Stabilization

OBJECTIVE

Labeled oxidation-specific antibodies (Ox-AB) detect, quantify, and noninvasively image lipid-rich atherosclerotic lesions. However, it is unknown whether Ox-AB detect plaque stabilization.

METHODS AND RESULTS

The aortic uptake of intravenously injected 125I-MDA2 (Ox-AB to malondialdehyde [MDA]-low-density lipoprotein [LDL]) was quantitated in: (1) LDL receptor-/- mice with established atherosclerosis continued on Western diet (Progression) or switched to chow (Regression) or chow+vitamins E and C (Regression-VIT) for 6 months; and (2) Watanabe rabbits (3- to 57-months old) with naturally evolved atherosclerotic lesions. In mice, the Progression group had more extensive atherosclerosis, higher 125I-MDA2 uptake, high concordance of Sudan (lipid)-staining and 125I-MDA2 uptake, and stronger oxidized LDL (OxLDL) and macrophage immunostaining than both Regression groups. In contrast, the Regression groups showed Sudan-positive lesions with focally diminished 125I-MDA2 uptake, which coincided with reduced OxLDL and macrophages but more smooth muscle cells (SMCs) and collagen. In rabbits, areas of increased 125I-MDA2 uptake were associated with high Sudan concordance and strong immunostaining for OxLDL and macrophages. Interestingly, advanced lesions with focally diminished 125I-MDA2 uptake showed stronger immunostaining for SMCs and collagen, particularly at the fibrous cap.

CONCLUSIONS

Ox-AB uptake is focally diminished in plaques displaying accepted features of plaque stability. Imaging techniques to detect the presence and depletion of OxLDL may be useful in assessing plaque stabilization.