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The inhibition of angiogenesis represents a major step toward a more selective and better-tolerated therapy of cancer. An alternative way to take advantage of a tumor's absolute dependence on a functional neovasculature is illustrated by the strategy of "antibody-based vascular tumor targeting." This technology aims at the selective delivery of bioactive molecules to the tumor site by their conjugation to a carrier antibody reactive with a tumor-associated vascular antigen. A number of high-affinity monoclonal antibodies are nowadays available which have demonstrated a remarkable ability to selectively localize to the tumor vasculature. Indeed, some of them have already progressed from preclinical animal experiments to clinical studies in patients with cancer, acting as vehicles for the site-specific pharmacodelivery of proinflammatory cytokines or radionuclides.In this chapter, we present a selection of well-characterized markers of angiogenesis which have proven to be suitable targets for antibody-based vascular targeting approaches. Furthermore, different transcriptomic and proteomic methodologies for the discovery of novel vascular tumor markers are described. In the last two sections, we focus on the discussion of antibody-based vascular tumor targeting strategies for imaging and therapy applications in oncology.

The formation of a provisional extracellular matrix represents an important step during tumor growth and angiogenesis. Proteins that participate in this process become activated and undergo conformational changes that expose biologically active cryptic sites. Activated matrix proteins express epitopes not found on their native counterparts. We hypothesized that these epitopes may have a restricted tissue distribution, rendering them suitable targets for therapeutic human monoclonal antibodies (huMabs). In this study, we exploited phage antibody display technology and subtractive phage selection to generate human monoclonal antibody fragments that discriminate between the activated and native conformation of the extracellular matrix protein vitronectin. One of the selected antibody fragments, scFv VN18, was used to construct a fully human IgG/kappa monoclonal antibody with an affinity of 9.3 nM. In immunohistochemical analysis, scFv and huMab VN18 recognized activated vitronectin in tumor tissues, whereas hardly any activated vitronectin was detectable in normal tissues. Iodine 123-radiolabeled huMabVN18 was shown to target to Rous sarcoma virus-induced tumors in chickens, an animal model in which the epitope for huMab VN18 is exposed during tumor development. Our results establish activated vitronectin as a potential target for tumor therapy in humans.

Purpose: We investigated and compared the biodistribution of Albuleukin, a human serum albumin (HSA)-interleukin-2 (IL-2) fusion protein, with those of IL-2 and HSA. The objective was to determine whether Albuleukin distributes differently to normal organs and lymphoid tissues than IL-2 by virtue of its genetic fusion with HSA., Methods: The chelating agent 2-( p-isothiocyanato-benzyl)-cyclohexyl-diethylenetriaminepentaacetic acid (CHX-A(II) was selected for radiolabeling with (111)In, and conjugation with CHX-A(II) did not alter bioactivities of IL-2 and Albuleukin on proliferation of CTLL-2 cells. The radiolabeled proteins were injected intravenously into mice, uptake in organs was measured, and whole-body autoradiography was performed., Results: Striking differences in the biodistribution of IL-2 and Albuleukin were noted. (111)In-IL-2 cleared from blood rapidly, with less than 1% ID/g (percentage of injected dose per gram of tissue) at 20 min after injection. At this time, the kidneys showed more than 120% ID/g uptake, and these high levels persisted through 6 h. (111)In-Albuleukin, by contrast, showed significantly longer circulation (14% ID/g at 6 h), lower kidney uptake (<6% ID/g), and higher localization in liver, spleen, and lymph nodes (maximal uptake approximately 22% ID/g for all three organs). Uptake in liver, spleen, and lymph nodes appears to be mediated in part by the IL-2 component of Albuleukin because (111)In-HSA showed significantly lower accumulation in those tissues despite more prolonged circulation in blood., Conclusion: These data support the hypothesis that Albuleukin targets tissues where lymphocytes reside to a much greater extent than does IL-2, and suggest that Albuleukin may exhibit improved efficacy and reduced toxicity in the treatment of solid tumors. Clinical trials underway will determine whether the improved targeting in the mice translates into a better therapeutic index in humans.

The size of a lymph node is not in principle a limitation for the detection of cancer by Nuclear Medicine techniques. A radioactive pinhead is detectable if it has enough radioactivity on it. The approach of Nuclear Medicine to the demonstration of impalpable lymph nodes or to those lymph nodes detected by radiological techniques that are under 1 cm as to whether or not they contain cancer, is to increase the activity attached to cancer cells in such a lymph node as much as possible and to use sophisticated image analysis techniques to distinguish such uptake from its environment. This may be undertaken using a non specific technique such as F-18 Deoxyglucose and Positron Emission Tomography which is highly sensitive and which has been successful. The alternative approach is to use a highly specific and sensitive agent, such as a radio-labelled peptide or a radio-labelled monoclonal antibody together with image analysis. This paper describes these approaches and in particular the use of Tc-99m SM3 monoclonal antibody in the detection of impalpable axillary nodes in patients with breast cancer before surgery, using a change detection analysis providing a probability map of the significance of uptake of this radiopharmaceutical. It is a robust approach, providing the patient and the surgeon with information as to the likely need for extensive axillary surgery well prior to operation. A negative study should be followed by a sentinel node evaluation at surgery.

A 22-year-old male with juvenile dermatomyositis presented with fever up to 40 degrees C and acute pain in his right thigh accompanied by muscle weakness, a skin rash and a tender swelling. Serum aspartate aminotransferase (AST) and aldolase were mildly elevated. C-reactive protein (CRP) and fibrinogen were markedly increased. The differential white blood cell count revealed relative lymphopenia. Radiography showed diffuse calcifications particularly around the thighs and knees of both legs. Magnetic resonance imaging (MRI) demonstrated inflammatory infiltrates in the right thigh. The lesions were identified as phlegmone by immunoszintigraphy with 99mTc-labelled antigranulocyte antibodies. On the 10th day of treatment Staphylococcus aureus was cultured from blood. Patients with juvenile dermatomyositis and calcinosis may develop bacterial infections of soft tissue which sometimes mimic a disease flare. For differential diagnosis plain radiographs, CT scans and MRI are of limited value. Immunoszintigraphy is able to differentiate between infiltrates caused by granulocytes and lymphocytes.

The aim of this study was to assess the utility of a radioimmunoconjugate containing a lead radionuclide for therapy and scintigraphy applications. The radioimmunoconjugate evaluated consisted of a bifunctional DOTA ligand and monoclonal antibody (MAb) B72.3 using athymic mice bearing LS-174T tumors, human colon carcinoma xenografts. In the studies reported here, the lead-203-DOTA complex itself was first demonstrated to have in vivo stability. MAb B72.3 was then conjugated with the DOTA ligand and labeled with 203Pb, and the immunoreactivity of B72.3 was maintained. The localization of the radioimmunoconjugate to tumor tissue and other select organs paralleled that of DOTA-125I-B72.3, suggesting a similar metabolic pattern of the two radioimmunoconjugates. Thus, the DOTA-metal complex does not alter the behavior of the radioimmunoconjugate. Tumor localization of the 203Pb-DOTA-B72.3 conjugate was demonstrated with biodistribution studies as well as immunoscintigraphy studies. Such data highlight the stability of a lead radionuclide in the DOTA ligand. The suitability of this chelation chemistry for labeling radioimmunoconjugates with a lead radionuclide now makes its application in nuclear medicine a feasible proposition.

Accurate and reproducible quantification of tumor radioactivity by imaging requires definition of a region of interest (ROI) for the tumor. The use of a threshold for creating the tumor ROI based on tumor-to-background image contrast (image contrast) was examined. Quantification of iodine-131 in spheres in a phantom that simulated tumors in patients was investigated using planar imaging and geometric-mean and effective-point-source methods. Thresholds that provided the least quantitative error for spheres with different diameters (1-5 cm) and locations (0-11 cm deep in the body), 131I concentrations (0.037-3.2 MBq/ml), and sphere-to-background concentration ratios (1:0, 14:1 and 7:1) were investigated. The correlation between threshold and sphere image contrast was examined. The phantom study showed that an appropriate threshold value for quantification of tumor radioactivity could be determined using image contrast for a single view, provided that image contrast was >/=1.5. The error of quantification was less than 10% for spheres with high image contrast (>/=1.5) but was greater than 17% for spheres with low image contrast (<1.5). When image contrast-dependent thresholds were applied to patient studies, 131I concentrations determined by imaging were in good agreement with the concentrations determined by counting biopsy samples. Additionally, reproducibility was improved when compared with a visual boundary method. It is concluded that accurate and reproducible quantification of radioactivity in tumors is achievable using thresholds based on image contrast if image contrast is greater than or equal to 1.5. Optimal thresholds for quantification of tumor radioactivity were similar if image contrast was similar despite differing tumor diameters, locations and 131I concentrations. Under certain circumstances, the effective-point-source method was preferable to the geometric-mean method.

The outstanding sensitivity of pentagastrin in detecting the presence of primary, recurrent or metastatic medullary thyroid cancer (MTC) suggests widespread expression of the corresponding receptor type in human MTC. Indeed, recent autoradiographic studies have demonstrated the presence of cholecystokinin (CCK)-B (= gastrin) receptors not only in more than 90% of MTCs but also in a high percentage of small cell lung cancers, stromal ovarian cancers, astrocytomas and several other tumour types. The aim of this study was to evaluate whether radiolabelled gastrin may be suitable for targeting CCK-B receptor-expressing tumours in vivo. For this purpose, the biodistribution of the radioiodinated human heptadecapeptide gastrin-I was studied in nude mice bearing subcutaneous xenografts of the human MTC cell line, TT. Initial therapy experiments were undertaken. Finally, the biodistribution of iodine-131- labelled gastrin-I was studied in a patient with metastatic MTC. At a peptide amount of approximately 1 microg, maximum tumour uptake (8.9+/-2.9%ID/g) was observed in animals at 1 h post injection, with tumour-to-blood ratios as high as 6.3+/-1.9. Physiological CCK-B receptors in the stomach, gallbladder and pancreas of the mice were targeted as well. The major route of excretion was renal, but strong evidence for a biliary excretion pathway also exists. Pilot therapy studies with 131I-labelled gastrin showed significant anti-tumour efficacy as compared with untreated controls. In accordance with the preclinical data, good receptor targeting was observed in the tumour sites, stomach, gallbladder and pancreas of a patient with metastatic MTC. These data suggest that gastrin and its analogues may represent a useful new class of receptor binding peptides for diagnosis and therapy of a variety of tumour types, including MTC and small cell lung cancer. Future preclinical and clinical studies will address in more detail the molecular features that render CCK-B receptor binding agents potentially useful candidates for in vivo scintigraphy and radionuclide therapy.

Technetium-99m labelled antigranulocyte antibodies are ready to use and are sensitive and specific in the diagnosis of infectious diseases. 99mTc-SSEA antigranulocyte antibodies have a very high affinity constant (Kd 10(-12) M) for human neutrophils (PMNs), and excellent imaging qualities with high target/background ratios. The aim of this study was to compare the diagnostic accuracy of the 99mTc-anti-SSEA-1 monoclonal antibody (Mab) with that of 99mTc-hexamethylpropylene amine oxime (HMPAO)-labelled white blood cells (WBCs). To this end, 17 patients with 23 proven infectious foci were examined with 555 MBq 99mTc-anti-SSEA-1 MAb and with 370 MBq 99mTc-HMPAO labelled autologous leucocytes within a period of 7 days. All the infections were confirmed by culture, biopsy, surgery and follow-up. Whole-body images and planar spot views with the antibody were performed at 1-h, 4-h and 24-h post injection; the biodistribution of the antibody was quantified, absorbed radiation doses were calculated and the diagnostic results were compared with the 99mTc-HMPAO WBC images. Human anti-mouse antibody (HAMA) evaluation was performed in all patients before and 3 months after antibody injection. Blood was drawn at different times after 99mTc-anti-SSEA-1 MAb injection to determine the amount of granulocyte-associated radioactivity and to calculate recovery. 99mTc-anti-SSEA-1 MAb scintigraphy detected all 23 lesions, while 21 were detected with 99mTc-HMPAO WBC scan. In this small group of patients, the sensitivity and specificity of 99mTc-anti-SSEA-1 MAb scintigraphy were 95% and 96% respectively, as compared with 91% and 82% respectively for 99mTc-HMPAO WBC scan. An increasing uptake of the injected activity in the lesion at different time points was indicative of high affinity and of specific PMN binding. There was no HAMA formation. In four of five patients investigated, a transient mild leukopenia was found at 15 min p.i.. There was increased uptake of the antibody in liver and spleen and normal uptake in kidneys and bone marrow. The estimated radiation doses for the whole body and the red bone marrow were 1.1x10(-2) cGy/37 MBq and 5.3x10(-2) cGy/37 MBq, respectively. The activity associated to the PMNs in vivo was 33.5%, 30.6%, 21.3% and 9% at 5, 15, 30 and 45 min. post-injection, respectively. It is councluded that use of 99mTc-anti-SSEA-1 antigranulocyte antibodies demonstrates promising results comparable to those obtained with 99mTc-labelled autologous WBCs. The 99mTc-labelled MAb is ready to use, has excellent image qualities and a high target/background ratio.

Elevated renal uptake and prolonged retention of radiolabeled antibody fragments and peptides is a problem in the therapeutic application of such agents. Over recent years, one of the focuses of research has therefore been to develop suitable methods to reduce this renal uptake, and to evaluate whether the resulting methodology will benefit therapy with antibody fragments and peptides. In these studies it has been shown that the kidney uptake of antibody fragments in animals can be reduced in a dose-dependent manner by almost one order of magnitude by the systemic administration of cationic amino acids and their derivatives, whereas the uptake in all other organs, as well as the tumor, remains unaffected. A similar reduction in renal retention is achieved for all intracellularly retained radionuclides (e.g., radiometals) or radioiodinated immunoconjugates, as well as for smaller peptides. Lysine is usually the preferred agent, and its d- and l-isomers are equally effective whether given intraperitoneally or orally. Amino sugars are effective, but their N-acetyl derivatives, lacking the positive charge, are not. Basic polypeptides are also effective, and their potency increases with increasing molecular weight (i.e., the amount of positive charges per molecule). Urine analysis of treated individuals shows the excretion of unmetabolized, intact fragments or peptides, in contrast to mostly low-molecular-weight metabolites in untreated controls. In therapy studies using radiometal-conjugated Fab fragments, the kidney is the first dose-limiting organ. Administration of cationic amino acids results in a substantial increase in the maximum tolerated dose of such Fab fragments. No biochemical or histological evidence of renal damage has been observed under these conditions. As was the case in animal studies, in pilot clinical trials the renal uptake in patients injected with Fab' fragments and given amino acids could be decreased significantly, whereas the uptake by all other organs remained unaffected. These recent studies indicate that a variety of basic compounds are capable of inhibiting the tubular reabsorption of peptides and proteins, thus significantly lowering the renal uptake of antibody fragments or peptides in both animals and patients. On a molecular basis, the effect seems to rely essentially on the presence of a positively charged amino group. Thus, radiation nephrotoxicity of antibody fragments and peptides can be overcome successfully; this may provide new prospects for cancer therapy with radiolabeled antibody fragments and peptides.

Chronic post-traumatic osteomyelitis (OM) represents a particular challenge for nuclear medicine and radiology since clinical and biochemical parameters are frequently unreliable. The aim of this study was to investigate the value of combined bone scan (BS) and immunoscintigraphy (IS) with technetium-99m labelled monoclonal antigranulocyte antibody (MAB) in patients with suspected chronic OM of the appendicular skeleton. Twenty-four patients (17 females and 7 males) with suspected chronic post-traumatic OM were evaluated with three-phase BS/99mTc-MAB-IS. The final diagnosis was established by means of bone culture and histology in 19 cases and clinical follow-up in five cases. The studies were reviewed by two independent and experienced observers; the interobserver agreement was calculated by kappa statistics. The sensitivity, specificity and accuracy of BS alone were 92%, 18% and 58%, respectively. Combined BS/99mTc-MAB-IS had a sensitivity, specificity and accuracy of 84%, 72% and 79%, respectively. Of 24 studies, 11 were true-positive, two false-negative, eight true-negative and three false-positive. Two patients presented with unexpected ectopic haematopoietic bone marrow in the appendicular skeleton that caused false-positive results. A high degree of interobserver agreement was found (kappa=0. 85). It is concluded that combined BS/99mTc-MAB-IS represents a very sensitive and reproducible method with an acceptable specificity for the investigation of chronic OM. Problems may occur in the differentiation of low-grade OM from aseptic inflammation. Another problem is ectopic marrow that may occur in the appendicular skeleton due to a chronic inflammatory stimulus. A former intramedullary intervention in the femur with displacement of haematopoietic marrow may also lead to an ectopic location.

Transitional cell carcinoma of the bladder is the fifth commonest cause of death from cancer in men in the United Kingdom. Most patients present early with superficial disease, though with current treatment up to 20% progress to invasive disease, which has a poor prognosis. Better local treatments are required to limit this tumour progression. The ease of access to the bladder via a catheter provides the ideal opportunity for antibody (Ab) targeted therapy. We have previously shown that indium-111 labelled anti-MUC1 mucin Ab C595 selectively localises to bladder tumours after intravesical administration. We have selected copper-67 as an alternative radiolabel with suitable physical characteristics for radioimmunotherapy. This communication demonstrates that C595 can be reproducibly labelled with 67Cu and that the radioimmunoconjugate is both stable and maintains high immunoreactivity. Pilot studies on cystectomy specimens in a novel ex vivo system and in one patient confirmed the ability of this conjugate to localise to tumour after intravesical administration. On the basis of these studies we are now in a position to study the intravesical administration of 67Cu-labelled C595 in patients with bladder cancer with a view to a therapeutic trial.

Fifty-three women with clinical evidence of adenocarcinoma of the breast were studied with technetium-99m labelled monoclonal antibody (MAb) 170H.82 at protein doses of 1, 2 and 4 mg. An overall per lesion efficacy of 83.5% sensitivity and 97.7% positive predictive value was obtained. Efficacy appears higher in lesions restricted to the breast and local regional disease than systemic metastases. For the 2 mg dose the breast/local regional disease efficacy was 90% sensitivity and 90.2% positive predictive value. The biodistribution of this MAb was best represented by a two-compartment model with a distribution-phase half-life of 4.0+/-1.4 h, followed by an elimination-phase half-life of 39.6+/-6.6 h. In all six patients studied, the critical organ was the kidney, with a mean radiation absorbed dose of 37+/-6.9 mGy/GBq. The accuracy of this imaging technique allows the development of diagnostic strategies for the routine use of the compound in patients with breast cancer.

Most nuclear medicine departments possess one or more imaging apparatuses for single-photon emission tomography (SPET). Molecules of biological interest to assess metabolism and receptor function are often labelled with 123I, which allows proper SPET imaging. The various methods for radiolabelling are reviewed. As the biological integrity of these agents has been demonstrated for numerous radiopharmaceuticals, the purpose of this review is to summarize the efficacy in various fields of medicine, including the imaging of tumours, infection, myocardium and cerebrum.

Clinical studies are currently underway to assess the biodistribution and therapeutic potential of the genetically engineered human antibody hCTM01 directed against polymorphic epithelial mucin (PEM) in patients with ovarian carcinoma. The present study was undertaken to assess the effect of circulating PEM antigen on the biodistribution of the anti-PEM antibody in mice bearing MUC-1 transfected adenocarcinoma cell lines. Tumour xenografts were established from three cell lines: 413-BCR, which expressed antigen on the cell surface and also shed antigen into the circulation, E3P23, which expressed the antigen but did not shed into the circulation, and a negative control (410.4 MUCI). Groups of five mice were injected with 1.0 mg/kg antibody, imaged after 72 h and then sacrificed, followed by assay of tissue uptake. The results showed a clear difference in the tumour and liver uptake, with the non-secreting cell line showing almost twice the tumour uptake and approximately 20% of the liver uptake of the secreting cell line.

Multiple imaging methods are currently used to detect the presence, location, and extent of breast cancer, either at initial presentation or during follow-up. Even at initial diagnosis, more specific methods are needed to complement the high sensitivity of mammography in the detection and diagnosis of mammary carcinoma. Therefore, the current study evaluates the potential use of a new monoclonal antibody-based imaging agent, arcitumomab (CEA-Scan), which comprises an anti-carcinoembryonic antigen monoclonal antibody Fab' fragment labeled directly with technetium-99m, in the detection of primary, recurrent, or metastatic mammary cancer. A prospective, non-randomized, open-label, multicenter trial was conducted in 123 women 100 with primary breast cancer confirmed by histology or cytology, and 23 with a prior history and who were under evaluation for possible recurrence or metastasis. A 1-mg dose of arcitumomab labeled with 20-25 mCi Tc-99m was injected i.v., and planar images were acquired at 5-8 hr, as well as single-photon emission computed tomography. Additional planar scanning was performed optionally at 18-24 hr. The imaging studies were interpreted as positive if there was abnormal focal activity, and were correlated, wherever possible, with histopathology or conventional imaging tests. In 78 evaluable patients with primary breast carcinoma arcitumomab showed an imaging sensitivity and specificity of 82% and 88%, respectively, even detecting lesions < 1 cm in 61% of the cases. Among 58 patients evaluable for axillary node involvement, 30 were positive by histopathology, of which arcitumomab was correct in 19 with cancer (63% sensitivity) and in 25 of 28 without cancer (89% specificity). Among 88 primary operable patients, arcitumomab showed additional sites of focal uptake outside of the breasts and axillae in 10, or 11%. In a total of 19 breast cancer patients with known or suspected recurrence or metastatic disease, 13, or 68%, showed one or more focal sites of uptake, involving the typical sites of spread of mammary cancer. No significant adverse effects or induction of human antimouse antibodies were observed in these patients. Arcitumomab immunoscintigraphy is a simple, same-day, and safe new imaging modality for the detection of sites of breast cancer, including lesions < 1 cm, with a reasonably high rate of sensitivity and specificity. It may be used to complement mammography in the differentiation of malignant from benign disease.

This study presents immunoscintigraphic results in 24 patients suffering from primary colorectal cancer, recurrent or metastatic disease after the injection of 1197-1351 MBq technetium-99m labelled totally human monoclonal antibody 88BV59. Labelling efficacy of 99mTc-88BV59 ranged from 97% to 99%. Immunoscintigraphy was performed 18-20 h after injection. Scintigraphic findings were compared with those of computed tomography (CT). Patients underwent surgery in order to evaluate immunoscintigraphic findings histologically. Sera of the patients (before injection and 1 and 3 months post infusion) were analysed for the presence of human anti-human antibodies (HAHA). None of the patients showed a HAHA response as assessed by a solid-phase ELISA assay. The antibody scan detected about 25% more lesions than CT. In the detection of extrahepatic disease, the sensitivity of the antibody scan proved to be 68%, whereas the sensitivity of CT was 41%.

Anti-CEA-scintigraphy turned out very reliable in detecting primary and recurrent colorectal cancer, its overall accuracy being more than 90 p.c. The intraoperative application of this technology should provide similar results when focussing at extrahepatic tumor deposits, for example in lymph nodes, thus allowing accurate staging of the underlying disease. To test this hypothesis we lauched the following feasibility-study the results of which are compared to those reported in the recent literature. We investigated 20 patients-six with rectum-, 14 with colon cancer, 24 hours before surgery they were intravenously given 1 ml of an fab-fragment-antibody to CEA, labeled with 25mCi of 99mTc (CEA-Scan). During surgery the radioactivity in lymph glands regionary for the tumors was measured and compared to the-much lower-activity in healthy nodes. For this we used a scintillation-probe (C-Trak). All lymph nodes of interest were-then excised and submitted to frozen section pathology. In 7/20 cases scintimetry led to an up-staging of the disease. In addition we found metastatic spread to lymph nodes that were basically not regionary for the primary tumor. Our results are confirmed by those of other investigators. Scintimetry can precisely identify even very small tumor deposits. So it leads to accurate staging when surgery is still on-going. In a next step the concept of sentinel-node-diagnosis, which is right now being clinically evaluated, may be applied is colorectal surgical oncology.

Variant isoforms of CD44, a family of cell-surface glycoproteins generated by alternative splicing and post-translational modifications, are expressed in a variety of human tumors and play important roles in tumor progression and metastasis formation. The murine monoclonal IgG1 antibody VFF18, specific for an epitope encoded by human CD44 variant exon 6, binds with high affinity to the recombinant protein (Kd = 1.7 x 10(-10) M) as well as to tumor cell lines in vitro, and is suitable for immunohistochemical analysis of human tumors. Screening of more than 500 tumor samples of different histogenesis showed that VFF18 most strongly and uniformly reacts with squamous cell carcinomas (SCC). Detailed analysis of 185 SCC (head and neck, lung, skin) confirmed reactivity of the antibody with 99% of the samples, with intense and homogeneous staining of the tumor cells in the majority of cases, whereas reactivity of VFF18 with normal tissues is limited to certain epithelia and activated lymphocytes. When radiolabelled VFF18 was administered to nude mice bearing human epidermoid carcinoma (A-431) xenograft, fast and selective tumor uptake of the radioimmunoconjugate with a maximum of 18% of the injected dose per gram of tissue was observed. Taken together, these data suggest that mAb VFF18 is a promising targeting vehicle for radioimmunotherapy of squamous cell carcinomas in humans.

This study was undertaken as part of a Coordinated Research Programme initiated by the International Atomic Energy Agency to evaluate the usefulness of radioimmunoscintigraphy (RIS) in the management of patients with colorectal cancer. Technetium-99m labelled BW431/26, a monoclonal antibody against carcinoembryonic antigen (CEA), was used. The study included 73 patients (31 females and 42 males). Sixty-eight patients were suspected of having recurrent colorectal adenocarcinoma while another five were suspected to have primary colorectal cancer. Images were acquired at 10 min and 4 and 24 h following the injection of radioantibody. The efficacy of RIS in tumour detection was evaluated by the findings at surgery, histological investigation and/or other diagnostic modalities and clinical follow-up. Four of five patients with suspected primary colorectal cancer gave true-positive results (three at primary sites, one at the site of a metastatic lesion) while one was false-positive. The overall accuracy of RIS in the diagnosis of recurrent colorectal cancer was 87%. Its sensitivity in the detection of locoregional or abdominal recurrence and liver metastases was 97% and 89% respectively. RIS was more accurate than computed tomography (CT) scan in the detection of pelvic recurrence and liver metastases while CT scan was far superior to RIS in detecting lung metastases. RIS proved most useful in patents who had rising CEA levels on clinical follow-up but in whom other work-up, including CT scan, was negative. The advantages of RIS include the ability to detect tumour recurrence prior to other investigations and to identify tumour recurrence in areas such as the pelvis, where CT and magnetic resonance imaging have their greatest weaknesses in diagnosing recurrent disease. The imaging accuracy is significantly increased when combined CT and antibody imaging is performed.

In this study we investigated the applicability of 99mTc-labeled CD19 monoclonal antibody (mAb) for tumor imaging in patients with B cell non-Hodgkin's lymphoma. A 1-mg sample of murine CD19 mAb was labeled with approximately 550 MBq [99mTc]pertechnetate. The labeled mAb was administered i.v. to seven patients, four without and three with pretreatment with 10 mg unlabeled CD19 mAb. The number of circulating B cells was decreased by 44 +/- 5% 1 h after injection of the radiolabeled mAb. Peripheral B cells were coated with CD19, resulting in partial modulation of CD19, most pronounced in the three pretreated patients. Whole-body images were obtained with a gamma camera and compared with results obtained by conventional imaging techniques. Initially, blood-pool activity dominated, whereas 24 h after injection the radioactivity was mainly located in the spleen, kidneys and liver. In two patients, a lesion in the spleen appeared as an unlabeled spot. In one patient, a lesion in the femur, which was detected by computed tomography (CT) and gallium-67 scans, was also seen on the CD19 scan from 1 h after administration of the radioimmunoconjugate onwards. Good imaging of bone marrow infiltration was observed in one of three patients. Lymph node involvement was not observed in any of the patients in whom affected lymph nodes were detected by CT or gallium-67 scan. In conclusion, in the present study radioimmunodetection with 99mTc-labeled CD19 mAb was found to be inferior to CT and gallium-67 scanning in the diagnosis of patients with B cell non-Hodgkin's lymphoma.

Radiopharmaceuticals have been used as investigative tools for the detection and treatment of arthritis activity in rheumatoid arthritis (RA) since the 1950s. Against the background of the pathophysiology of RA, the current status of joint scintigraphy and possible future developments are reviewed. Both non-specific (radiolabelled leucocytes and technetium-99m labelled human immunoglobulin) and specific targeting radiopharmaceuticals (including radiolabelled antibodies) are considered. The use of radiopharmaceuticals in the detection of arthritis activity has the advantages of allowing direct imaging of joints by means of whole-body scintigraphy and of joints that are difficult to assess clinically or radiographically. Promising results have been obtained with radiolabelled anti-CD4 and anti-E-selectin antibodies and with somatostatin receptor imaging, but more data are available regarding 99mTc-IgG scintigraphy, which differentiates between the various degrees of arthritis activity and thus facilitates the choice of antirheumatic drug. Newer promising approaches to the imaging of RA include the use of radiolabelled J001 and cytokines, though studies on these are limited at present.

Nuclear medicine imaging of infection has two major indications: (a) the localization of a focus of infection in patients with fever of unknown origin; in this context the radio-pharmaceutical should be highly sensitive whereas specificity is not so important because subsequent biopsy or morphologically based imaging can be performed; (b) the diagnosis of an infection in patients with localized symptoms, for example after surgery, when normal anatomy is absent or when metal implants prevent computed tomography or magnetic resonance imaging. In these latter cases high sensitivity and to an even greater extent high specificity are mandatory to guide further clinical management (conservative or surgical). All radiopharmaceuticals available to date, such as technetium-99m nanocolloids, gallium-67 citrate, indium-111- and 99mTc-labelled white blood cells, 99mTc-antigranulocyte antibodies, and 99mTc-or 111In-labelled unspecific human immunoglobulin, have different biodistributions and different physical characteristics. The absence of physiological uptake in an organ and the radiation exposure of a patient are reasons to use different radiopharmaceuticals in different clinical situations, adapted to the individual circumstances of the patient.

The recently developed technetium-99m-labelled monoclonal antibody-170 (MAb-170) was designed for diagnostic use in patients suffering from gynaecological adenocarcinoma. Following in vitro studies which showed immunoreactivity of this antibody to more than 90% of human adenocarcinomas, the present investigation was initiated to verify its usefulness for radioimmunoscintigraphy of ovarian tumours. Most of the 30 patients participating in this study underwent immunoscintigraphy prior to first-look surgery. Biokinetic evaluation in two patients showed a plasma half-time of 18.9 h (mean value, n = 2, r = 0.98) and a biexponential total body curve with values of 7.7 h and 17 days (r = 0.98). The mean 24-h urinary excretion was 12% of the injected dose. Radioimmunoscintigraphy using the MAb-170 recognised 12 of 13 cases of adenocarcinoma of the ovaries, corresponding to an overall sensitivity of 92.3%. Specificity was 94.1% (16/17). The calculation of accuracy yielded a figure of 93.3% (28/30). Of 33 known lesions, 26 were visualised successfully; thus the locoregional sensitivity was 78.8%. Of 29 benign tumour sites, 28 showed no evidence of tracer accumulation, corresponding to a locoregional specificity of 96.6%. The smallest lesion visualised was an adenocarcinoma of the corpus uteri with a diameter of 1.5 cm. Technetium-99m labelled MAb-170 is a promising new radiopharmaceutical for immunoscintigraphy of ovarian adenocarcinoma.

Iodine-131 3F8, a murine IgG3 monoclonal antibody that targets to GD2-bearing tumors, was administered intravenously to 12 patients with brain tumors. Six patients received 2 mCi (0.74 Bq) of 131I-3F8, five patients 10 mCi (3.7 Bq)/1.73 m2 of 131I-3F8, and one patient 2.6 mCi (0.96 Bq) of 124I-3F8, with no side-effects. Nine of 11 malignant gliomas and the single metastatic melanoma showed antibody localization, with the best tumor delineation on single-photon emission tomography (SPET) following 10 mCi (3.7 Bq)/1.73 m2 dose. No nonspecific uptake in the normal craniospinal axis was detected. There was no difference in the pharmacokinetics of low-dose versus the higher-dose antibody groups; plasma and total-body half-lives were 18 h and 49 h, respectively. Surgical sampling and time-activity curves based on quantitative imaging showed peak uptake in high-grade glioma at 39 h, with a half-life of 62 h. Tumor uptake at time of surgery averaged 3.5 x 10(-3) %ID/g and peak activity by the conjugate view method averaged 9.2 x 10(-3) %ID/g (3.5-17.8). Mean radiation absorption dose was 3.9 rad per mCi injected (range 0.7-9.6) or 10.5 cGy/Bq (range 1.9-26). There was agreement on positive sites when immunoscintigraphy was compared with technetium-99m glucoheptonate/diethylene triamine penta-acetic acid planar imaging, thallium-201 SPET, and fluorine-18 fluorodeoxyglucose positron emission tomography. Taken together, these data suggest that quantitative estimates of antibody targeting to intracranial tumors can be made using the modified conjugate view method.

From April 1, 1992 to December 31, 1993 we investigated 30 patients with suspected primary colorectal carcinoma or questionable tumor relapse by immunoscintigraphy prospective with the monoclonal antibody MAb B72.3 in order to detect the tumor and especially regional lymph node metastases. All the patients underwent surgical treatment. The diagnosis was based on surgery and biopsy. The diagnostic sensitivity of immunoscintigraphy in detecting the tumor was 76%, the specificity 94% (predictive value positive [PVP] 95%) and 43%, respectively 85% in detecting lymph node metastases (PVP 60%). The diagnostic sensitivity in detecting rectosigmoid tumors was 79 and 60% in detecting lymph node metastases of rectosigmoid carcinoma (PVP 60%). The specificity was 90%. It could be shown, that the detection of metastases in singularly lymph nodes smaller than 1 cm was not possible and often a final decision could not be done. We conclude, that the benefit of this method in detection of lymph node metastases compared to basic diagnostic, expenses and costs is doubtfully.

A patient with suspected recurrent cancer of the colon underwent a variety of imaging procedures for the differential diagnosis of a hepatic mass lesion. Computed tomography (CT) showed a low-density lesion in the left hepatic lobe, and the initial CT-guided biopsy of the liver mass was reported to demonstrate a benign lesion. Ultrasonography (US) showed a hypoechoic lesion, and technetium-99m red blood cell (RBC) scan failed to suggest a hemangioma. However, radioimmunoscintigraphy (RIS) using 99mTc- labeled anti-carcinoembryonic antigen (CEA) monoclonal antibody clearly demonstrated increase uptake of antibody in the liver lesion. Scheduled hepatic angiography was canceled and subsequent exploratory laparotomy confirmed liver metastasis. RIS appears most helpful in the diagnosis of hepatic metastasis in patients with colorectal cancer and a rising CEA level. CT, US, and 99mTc-RBC studies for the investigation of hepatic masses are briefly discussed.

To determine the value of immunoscintigraphy (IS) with antigranulocyte monoclonal antibodies (Mab) in the diagnosis of subacute or chronic infection of hip prostheses, we prospectively studied 57 patients (23 women and 34 men; age 29-92 years, mean 72.7 years) sent to our institution in the past 6 years for clinical suspicion of septic loosening of a hip prosthesis. Nineteen patients had bilateral prostheses and one of them was studied twice. A total of 78 prostheses were examined. All patients had three-phase bone scans followed by IS with technetium-99m antigranulocyte Mab BW 250/183. Intervals between bone scans and IS varied from 2 days to 4 weeks. Final diagnosis was assessed by culture in 48 cases (articular puncture or intraoperative sampling) and by clinical follow-up of at least 8 months in 30 cases. Twelve prostheses were considered septic and 66 non-septic. The overall sensitivity and specificity were 92% and 64% respectively for bone scans, 67% and 75% for IS and 67% and 84% for both modalities together. In three cases, IS was doubtful and the final clinical diagnosis was negative for infection. False-positive results were observed in the presence of massive loosening of the prosthesis or in association with metaplastic peri-articular bone formation. In three of the four false-negative results, infection was proven only after enrichment of the culture, and the bacterium was Staphylococcus epidermidis. In 12/33 (36%) positive bone scans IS allowed the diagnosis of infection to be excluded. Overall accuracy of both modalities together was 81% and the negative predictive value was 93%, which compares favourably with the results reported for other non-invasive methods.

The effect of the size of the tumour and the amount of antibody injected on the biodistribution of a family of radioiodinated antibodies was studied. The intact mouse anti-(carcinoembryonic antigen) (anti-CEA) monoclonal antibody CE-25, its F(ab')2 fragment and the intact human-mouse chimeric from CE 4-8-13 were evaluated in a model system using the human CEA-producing colon xenograft T 380 grown in nude mice. The relative retention (the percentage of the injected dose per gram of tissue), of mouse mAb and F(ab')2 in tumour and most normal tissues 1 day after injection was independent of the antibody dose; after 4 days the mAb values increased with increasing antibody dose. The relative retention of chimeric mAb increased with increasing antibody dose 1 day after injection and also slightly after 4 days. The relative retention in tumour tissue was lower in bigger xenografts for all antibodies. The relative retention of mouse mAb in small tumours increased from day 1 to day 4; for chimeric mAb this value decreased. In normal tissues the relative retention of mouse mAb decreased from day 1 to day 4, but the relative retention of chimeric mAb in normal tissue dropped rapidly and changed little afterwards. Thus the biokinetics of antibodies is "species"-dependent: foreign, mainly human, chimeric antibody clears faster from normal mouse tissue than mouse antibody and reaches lower concentrations.

Uptake of indium-111 in bone marrow is seen in patients who have received 111In-labelled antibody. We report a case in which 111In uptake was not seen in the area of previous irradiation whereas fairly high uptake was noted in other bone marrow areas. 111In-labelled monoclonal antibody, which reacts with mucin, was injected into a patient with cancer of the sigmoid colon who had received radiotherapy for uterine cervical cancer 5 years previously. Marked accumulation of the antibody was observed in the tumour. Uptake of 111In in bone marrow was also seen except in the previously irradiated pelvic region. This phenomenon supports the idea that bone marrow uptake of 111In is the result of transchelation of 111In from antibody to transferrin.

Twenty-one patients with squamous cell carcinomas of the head and neck were studied by immunoscintigraphy and immunoemission, computed tomography (ECT) using monoclonal antibody 174H.64 (Biomira Edminton) labelled with 99Tcm (Schwartz Method). Immunoscintigraphic results were compared with routine clinical assessments, including CT and ultrasonography, and were controlled by histopathological examination after surgery. All primary localizations (pT1 = 3, pT2 = 3, pT3 = 7, pT4 = 5; oropharynx 7, larynx 5, hypopharynx 3, oral cavity 3, lymph nodes 3) could be visualized, while 15 out of 18 neck lesions from tumor metastases could also be visualized (pN1 = 8, pN2 = 8, pN3 = 2). In one case with micrometastases in lymph nodes that could not be demonstrated by other methods, staging was upgraded by the immunoscintigraphic results. Three other micrometastases in lymph nodes could not be visualized. Distant metastases were suspected in 5 cases, three of which were confirmed either histologically or by radiography. Two of the cases with distant metastases were detected by the immunoscintigraphy. The present results indicate that immunoscintigraphy in combination with immuno-ECT can improve preoperative staging of head and neck carcinomas, especially with regard to metastatic neck disease, tumor recurrences and some cases of distant metastases.

We have evaluated whether interleukin-2 (IL-2) at low doses can enhance delivery of radionuclides to tumour sites by improving the access of the radio-labelled antibody. The effects of 1000 or 2000 units of IL-2 on the biodistribution of technetium-99m-labelled anticarcinoembryonic antigen (CEA) monoclonal antibody, ZCE025, in athymic mice bearing human CEA-positive tumour (MKN45) xenografts were investigated. Treatment with IL-2 resulted in a significantly higher tumour uptake (1.2-1.5-fold) compared with the control group. Some normal organs, such as heart, lung, liver, spleen and kidneys, showed increased 99mTc uptake following the IL-2 treatment. Pretreatment with IL-2 also induced an enhancement of the permeability index for mouse IgG in tumours and in normal organs, whereas the blood flow in both normal organs and tumours remained at control levels. The effects of IL-2 were found to be dose-dependent. The IL-2 treatment increased the plasma CEA levels but not the CEA content in tumour tissues, suggesting that IL-2 enhanced the leakage of CEA from tumour to blood. The enhancement ratios of the tumour 99mTc-ZCE025 uptake following treatment with IL-2 were 1.4 and 1.8 in mice bearing small and large tumours, respectively. Our experimental results indicated that the low dose of IL-2 enhanced the vascular permeability sufficiently to increase the amount of antibody delivered to the tumour target. Administration of IL-2 would render radioimmunotherapy more effective, especially in patients with large tumour burdens.

Systemic administration of lysine to mice injected with indium-111-labelled Fab fragment of a monoclonal antibody has been shown to reduce renal uptake/retention of the radiometal. This treatment should be applicable to clinical immunoscintigraphy and radioimmunotherapy with radiometal-labelled antibody fragments.

Inflammatory diseases of the heart encompass myocarditis, endocarditis and pericarditis. This paper discusses the diagnostic potential of scintigraphy in these entities. In myocarditis, indium-111 antimyosin Fab imaging can visualize active myocyte damage and thus contribute substantially to the diagnosis. Antimyosin uptake is also seen in a large subset of patients with dilated cardiomyopathy, indicating ongoing myocyte injury in these cases. In endocarditis, immunoscintigraphy using monoclonal technetium-99m-labelled antigranulocyte antibodies provides useful diagnostic information in patients with equivocal echocardiographic findings. Immunoscintigraphy seems to indicate the floridity of the inflammatory process in endocarditis and may be used to monitor antibiotic therapy. In pericarditis, the clinical value of scintigraphy has not been convincingly demonstrated.

The imaging of cerebral gliomas with radiolabelled monoclonal antibodies (MoAbs) has been previously reported. However, previous studies have been hampered by the drawback of a low tumour to non-tumour ratio. In order to overcome this problem we have developed a three-step pre-targeting method using the avidin-biotin system. The rationale of this technique consists in vivo labelling of biotinylated MoAbs targeted onto tumour deposits, when most of the unbound antibodies have been cleared from the bloodstream as avidin-bound complexes. The anti-tenascin MoAb BC2, specific for the majority of gliomas, was biotinylated and 1 mg was administered i.v. in 20 patients with histologically documented cerebral lesions. After 24-36 h, 5 mg avidin was injected i.v. followed 24 h later by a third i.v. injection of 0.2 mg PnAO-biotin labelled with 15-20 mCi technetium-99m. No evidence of toxicity was observed. Whole-body biodistribution was measured at 20 min, 3 h and 5 h post-injection. [99mTc]PnAO-biotin had a fast blood clearance and was primarily excreted through the biliary system. A dedicated single-photon emission tomography system was used to acquire brain tomographic images 1-2 h after the administration of [99mTc]PnAO-biotin. Tumours were detected in 15/18 glioma patients with a tumour to non-tumour ratio of up 14:1. This three-step method, based on the sequential administration of anti-tenascin MoAb BC2, avidin and [99mTc]PnAO-biotin, can support computed tomography or magnetic resonance imaging for the diagnosis and follow-up of patients with glioma. Further studies are required to evaluate the potential of this technique for therapeutic application.

A direct comparison of the joint-imaging properties of inflammation-specific- and non-specific monoclonal antibodies (Mabs) was possible in a patient suffering from long-standing, severe rheumatoid arthritis (RA). This patient received an anti-CD4- and an anticarcinoembryonic antigen (anti-CEA) Mab, both labelled with technetium-99m, 9 days apart from each other. The anti-CD4 Mab was superior to the isotype-matched anti-CEA Mab in imaging inflamed joints. In the knee joint, the target-to-background ratio of the synovial membrane (SM) activity in comparison to that of adjacent large vessels was 1.22 (SM/muscle 1.55) for the anti-CD4 Mab and 0.53 (SM/muscle 0.92) for the anti-CEA Mab, in both cases 4 h after injection of the immunoglobulin. Since the CD4 antigen is present on the surface of T-helper lymphocytes and macrophages infiltrating the inflamed synovial membrane, imaging with the anti-CD4 Mab may allow more specific detection of inflammatory infiltrates in RA.

Lung cancer is the leading cause of death from cancer in males. Adequate staging is essential if proper treatment is to be administered. Current morphological imaging modalities are confronted with problems in the staging of lung cancer, in the evaluation of treatment response, and in establishing whether a residual mass is due to fibrosis, residual tumors or local recurrence. Nuclear medicine imaging techniques have advanced from planar gallium-67 citrate scans in the 1970s to multihead-detector single-photon emission tomography for 67Ga, Thallium-201 chloride, technetium-99m SestaMIBI, monoclonal antibodies, and octreotide compounds. Results of positron emission tomography (PET) with fluorine-18 deoxyglucose or carbon-11 methionine are very promising. PET units are now employed in centers all over the world and the recently introduced whole-body PET units will be ideal for the correct staging of malignant diseases. The current status of various nuclear medicine imaging procedures is reviewed. The problems and advantages of each scintigraphic procedure are discussed. It appears that many of the problems that confront morphological imaging will be solved by nuclear medicine techniques in the future.

The influence of human anti-OC125 antibodies formed after multiple infusions of OC125 F(ab')2 fragments on the apparent levels of CA 125 measured with four different tests were examined in two ovarian cancer patients. With the homologous Assay 1, involving only OC125 antibodies, false increases of CA 125 values were observed after infusion of OC125 fragments, which completely covered real CA 125. In contrast, with Assay 2, 3 and 4, which involve no OC125 antibodies as capture antibodies, only slight false increases occurred in the presence of very high anti-OC125 antibody concentrations. Interference was eliminated by addition of non-specific murine IgG in Assay 2 and 4, but not in Assay 1 and 3 indicating that the false increases in Assay 1 and 3 were caused by anti-idiotypic anti-OC125 antibodies. In the presence of elevated real CA 125, with Assay 2 and to a considerably lesser degree with Assay 4, an inhibitory effect of anti-OC125 antibodies became evident leading to false decreases of CA 125 values. In Assay 4 reduction of assay response was eliminated by addition of nonspecific murine IgG. The results confirm that all available CA 125 tests are influenced by interference with human anti-OC125 antibodies. Thus, CA 125 levels in patients who have been treated with OC125 fragments should be interpreted with care.