Biodistribution properties of (111)indium-labeled C-functionalized trans-cyclohexyl diethylenetriaminepentaacetic acid humanized 3S193 diabody and F(ab')(2) constructs in a breast carcinoma xenograft model

The humanized complementarity determining region-grafted anti-Lewis Y (Le(y)) monoclonal antibody [humanized 3S193 (hu3S193)] was developed for targeting Le(y)-expressing epithelial tumors such as breast, colon, lung, prostate, and ovarian carcinoma. We are exploring the potential use of smaller molecular size, bivalent analogues of hu3S193, because the faster blood clearance of M(r) approximately 54,000 diabody and M(r) approximately 110,000 F(ab')(2) molecules may be advantageous in achieving optimal and rapid tumor uptake for diagnostic and potential therapeutic applications. The single-chain variable fragment-5 residue linker construct (diabody) was expressed using the bacterial secretion vector pPOW3, and soluble product was purified without refolding processes. The F(ab')(2) fragment was obtained by pepsin digest of parental hu3S193. To facilitate evaluations, the radiometal (111)In was used to label C-functionalized trans-cyclohexyl diethylenetriaminepentaacetic acid chelated diabody and F(ab')(2). The immunoreactivity of the radiolabeled constructs was 41.3 and 58.6%, and the K(a) was 1.68 x 10(6) M(-1) and 5.33 x 10(6) M(-1) for the diabody and F(ab')(2), respectively. Radioconjugates were injected into mice bearing Le(y)-positive MCF-7 tumors, and biodistribution properties were determined at various time points after injection. The uptake of radiolabeled diabody in xenografts was maximal at 1 h after injection (4.7 +/- 0.6% injected dose/g), whereas the F(ab')(2) peaked at 8 h after injection (14.2 +/- 2.4% injected dose/g). The tumor:blood ratio at 4 h for the diabody and F(ab')(2) was 5:1 and 2:1, which increased to 20:1 and 5:1, respectively, at 8 h and increased further to 40:1 and 130:1, respectively, at 48 h. These results demonstrate that the diabody construct may have applications as a diagnostic imaging reagent, whereas F(ab')(2) displayed effective tumor targeting and may have potential as a therapeutic molecule in patients with Le(y)-expressing tumors.

Population pharmacokinetics of antifibroblast activation protein monoclonal antibody F19 in cancer patients

AIMS

The population pharmacokinetics of 131I-mAbF19, a radiolabelled murine monoclonal antibody against fibroblast activation protein and a potential antitumour stroma agent, were investigated during two phase I studies in cancer patients.

METHODS

131I-mAbF19 serum concentration-time data were obtained in 16 patients from two studies involving imaging and dosimetry in colorectal carcinoma and soft tissue sarcoma. Doses of 0.2, 1 and 2 mg antibody were administered as 60 min intravenous infusions. The data were analysed by nonlinear mixed effect modelling.

RESULTS

The data were described by a two-compartment model. Population mean values were 109 ml h(-1) for total serum clearance, 3.1 l for the volume of distribution of the central compartment, and 4.9 l for the volume of distribution at steady state. Mean terminal half-life was 38 h. Intersubject variability was high, but no patient covariates could be identified that further explained this variability. In particular, there was no influence of tumour type or mAbF19 dose.

CONCLUSIONS

The pharmacokinetics of antistromal mAbF19 were well defined in these two studies with different solid tumour types, and were comparable with those of other murine monoclonal antibodies that do not bind to normal tissue antigens or blood cells.

Current status of positron emission tomography in oncology

Positron emission tomography (PET) has emerged as a powerful diagnostic tool in oncology patients. There is evidence of the superior utility over conventional imaging methods of the principal PET tracer 18F-fluoro-2-deoxy-glucose in the staging of a range of cancers and monitoring disease recurrence, as well as changing patient management to more appropriate therapy. The methods for evaluating the evidence for PET remain complex, particularly as the standard evidence-based approach of randomized controlled trials is not generally applicable to imaging technologies. PET has the potential to dramatically improve our ability to manage patients with cancer and is also making major contributions to the development of new therapies.

In vivo biodistribution of a humanized anti-Lewis Y monoclonal antibody (hu3S193) in MCF-7 xenografted BALB/c nude mice

The biodistribution characteristics of a humanized anti-Lewis(y) antibody (hu3S193) radiolabeled to three radioisotopes, 125I, 111In, and 90Y, were examined in a BALB/c nude mouse xenograft model of breast cancer. The immunoreactivity of both 125I- and 111In-bound hu3S193 exceeded 50% and was 20% for 90Y. In vivo, labeled antibody was shown by gamma camera imaging and immunohistochemical and autoradiographic techniques to localize to Lewis(y)-expressing breast xenografts with minimal normal tissue uptake. Maximal radioisotope uptake peaked at 48 h for all three isotopes; however, the percentage of injected dose/gram and tumor retention were greater for 111In- and 90Y-bound antibody than for 125I-bound antibody. Although immunoreactivity of 111In- and 125I-labeled hu3S193 in serum was stable over a 5-day period, the amount of unlabeled 111In in serum was lower than 125I, which together with higher tumor uptake indicates better retention of 111In-labeled hu3S193 and catabolites within the tumor cells. Superior tumor uptake and retention of 111In-labeled hu3S193 and similar blood clearance compared with 125I-labeled hu3S193, suggest that radiometals are the preferred radioisotope for this antibody-antigen system. Humanized 3S193 is a promising new construct for the targeting and potential therapy of Lewis(y)-expressing tumors.

Therapeutic efficacy of anti-Lewis(y) humanized 3S193 radioimmunotherapy in a breast cancer model: enhanced activity when combined with taxol chemotherapy

Monoclonal antibody therapy may provide new treatment options in the management of metastatic breast cancer by selectively targeting tumors and producing a therapeutic effect, by delivering radiation or other toxins directly to tumor cells, or by producing an intrinsic immune inflammatory response. The effect of 131I-labeled humanized anti-Lewis(y) monoclonal antibody 3S193 (hu3S193) was compared with that of placebo and radiolabeled huA33 control antibody in a series of radioimmunotherapy experiments in a MCF-7 xenografted BALB/c nude mouse breast cancer model. The maximum tolerated dose of 131I-labeled antibody occurred at 200 microCi/mouse, at which dose level three of six mice that received 131I-hu3S193 showed significant tumor growth inhibition in contrast to no responses in the comparable 131I-huA33 control treatment arm. Breast cancer is an ideal model to test the efficacy of combined modalities given its known sensitivity to both radiotherapy and chemotherapy. The synergy between radioimmunotherapy and chemotherapy was therefore also explored using a combination of 131I-labeled hu3S193 antibody and Taxol using subtherapeutic doses of each agent. The combination of Taxol and 100 microCi of 131I-hu3S193 produced significant tumor inhibition in 80% of mice, whereas no responses were seen with either treatment modality alone or the combination of Taxol and 131I-huA33. These results support a potential therapeutic role of radiolabeled hu3S193 in the treatment of breast cancer, including combination therapy with Taxol, and warrants further investigation of this promising new agent.

The fate of hypoxic tissue on 18F-fluoromisonidazole positron emission tomography after ischemic stroke

We studied 24 patients up to 51 hours after ischemic stroke using 18F-fluoromisonidazole positron emission tomography to determine the fate of hypoxic tissue likely to represent the ischemic penumbra. Areas of hypoxic tissue were detected on positron emission tomography in 15 patients, and computed tomography was available in 12 patients, allowing comparison with the infarct volume to determine the proportions of the hypoxic tissue volume that infarcted and survived. The proportion of patients with hypoxic tissue and the amount of hypoxic tissue detected declined with time. On average, 45% of the total hypoxic tissue volume survived and 55% infarcted. Up to 68% (mean, 17.5%) of the infarct volume was initially hypoxic. Most of the tissue "initially affected" proceeded to infarction. We correlated hypoxic tissue volumes with neurological and functional outcome assessed using the National Institutes of Health Stroke Scale, Barthel Index, and Rankin Score. Initial stroke severity correlated significantly with the "initially affected" volume, neurological deterioration during the first week after stroke with the proportion of the "initially affected" volume that infarcted, and functional outcome with the infarct volume. Significant reductions in the size of the infarct and improved clinical outcomes might be achieved if hypoxic tissue can be rescued.

Construction, production, and characterization of humanized anti-Lewis Y monoclonal antibody 3S193 for targeted immunotherapy of solid tumors

The Lewis Y (Ley) antigen is a blood group-related antigen that is expressed in a high proportion of epithelial cancers (including breast, colon, ovary, and lung cancer) and is an attractive target for monoclonal antibody-directed therapy. The murine monoclonal 3S193 (IgG3) was generated in BALB/c mice by immunization with Ley-expressing cells of the MCF-7 breast carcinoma cell-line. The murine 3S193 showed high specificity for Ley in ELISA tests with synthetic Ley and Ley-containing glycoproteins and glycolipids and also reacted strongly in rosetting assays and cytotoxic tests with Ley-expressing cells. We generated a humanized form of the murine 3S193 antibody by linking cDNA sequences encoding the variable region of murine 3S913 with frameworks of the human KOL heavy chain and REI K chain. The genes for the humanized 3S193 monoclonal antibody IgG1 were transfected into mouse myeloma NS0 cells and cloned for the establishment of high antibody-producing colonies. Humanized 3S193 antibody was subsequently produced through in vitro culture and under good manufacturing practice conditions using hollow-fiber bioreactors. The purified humanized 3S193 (hu3S193) was subsequently characterized and validated for use in preliminary immunotherapy investigations. hu3S193 reacted specifically with Ley antigen, with similar avidity to the murine form. hu3S193 demonstrated potent immune effector function, with higher antibody-dependent cell-mediated cytotoxicity than its murine counterpart and potent complement-dependent cytotoxicity (ED50, 1.0 microg/ml). The in vivo immunotherapeutic potential of hu3S193 was assessed in a human breast xenograft model using MCF-7, Ley-positive cells. Six i.v. doses of up to 1 mg of hu3S193 were administered to animals bearing established tumors (120-130 mm3) with no significant effect on tumor growth. In contrast, in an MCF-7 xenograft preventive model, a 1-mg hu3S193 dosage schedule was able to significantly slow tumor growth compared with placebo and isotype-matched control IgG1 antibody. hu3S193 has promise for immunotherapy of Ley-positive tumors and is currently entering Phase I clinical trials.

Monoclonal antibodies to vascular endothelial growth factor-D block its interactions with both VEGF receptor-2 and VEGF receptor-3

Vascular endothelial growth factor-D (VEGF-D), the most recently discovered mammalian member of the VEGF family, is an angiogenic protein that activates VEGF receptor-2 (VEGFR-2/Flk1/KDR) and VEGFR-3 (Flt4). These receptor tyrosine kinases, localized on vascular and lymphatic endothelial cells, signal for angiogenesis and lymphangiogenesis. VEGF-D consists of a central receptor-binding VEGF homology domain (VHD) and N-terminal and C-terminal propeptides that are cleaved from the VHD to generate a mature, bioactive form consisting of dimers of the VHD. Here we report characterization of mAbs raised to the VHD of human VEGF-D in order to generate VEGF-D antagonists. The mAbs bind the fully processed VHD with high affinity and also bind unprocessed VEGF-D. We demonstrate, using bioassays for the binding and cross-linking of VEGFR-2 and VEGFR-3 and biosensor analysis with immobilized receptors, that one of the mAbs, designated VD1, is able to compete potently with mature VEGF-D for binding to both VEGFR-2 and VEGFR-3 for binding to mature VEGF-D. This indicates that the binding epitopes on VEGF-D for these two receptors may be in close proximity. Furthermore, VD1 blocks the mitogenic response of human microvascular endothelial cells to VEGF-D. The anti-(VEGF-D) mAbs raised to the bioactive region of this growth factor will be powerful tools for analysis of the biological functions of VEGF-D.

Psychological and sex features of delayed gut transit in functional gastrointestinal disorders

BACKGROUND

The relation of demographic and psychological factors to the presence and extent of gut transit impairment in the functional gastrointestinal disorders has received little attention.

AIMS

To compare the psychosocial and demographic features of patients with functional gastrointestinal disorders and delayed transit in one region of the gastrointestinal tract with those displaying more widespread delayed transit (that is, delay in two or three regions), and those with normal transit in all three regions.

PATIENTS

Of 110 outpatient participants who satisfied standardised criteria for functional gastrointestinal disorders, 46 had delayed transit in one region, 32 had delay in two or three regions, and 17 exhibited normal transit in all regions.

METHODS

Transit in the stomach, the small intestine, and the large intestine was assessed concurrently using a wholly scintigraphic technique; psychological status was assessed using established psychometric measures.

RESULTS

Patients with delayed transit displayed demographic and psychological features that contrasted with patients with normal transit in all regions. In particular, widespread delayed transit featured female sex, a highly depressed mood state, increased age, frequent control of anger, and more severe gastric stasis, while the features distinguishing normal transit were male sex and high levels of hypochondriasis.

CONCLUSION

These data suggest the existence of a distinct psychophysiological subgroup, defined by the presence of delayed transit, in patients with functional gastrointestinal disorders.

No evidence of hypoxic tissue on 18F-fluoromisonidazole PET after intracerebral hemorrhage

We studied six patients after intracerebral hemorrhage (ICH) and eight controls using positron emission tomography (PET) with to determine whether a zone of tissue hypoxia, possibly representing "penumbral" tissue, exists surrounding an intracerebral hemorrhage. None of the stroke patients, studied 24 to 43 hours after symptom onset, nor any of the controls exhibited areas of tissue hypoxia on 18F-fluoromisonidazole PET images. These findings may have implications for the treatment of intracerebral hemorrhage with neuroprotective strategies.

Head trauma and mid-frequency hearing loss

Numerous reports in the literature associate head trauma with high-frequency hearing losses, often mimicking "4K notches" attributed to noise exposure. We have observed that some patients with a positive history for head trauma may show midfrequency notches in their audiometric configurations.

Positron emission tomography: radioisotope and radiopharmaceutical production

A Centre for Positron Emission Tomography (PET) has been operational within the Department of Nuclear Medicine at the Austin & Repatriation Medical Centre (A&RMC) in Melbourne for seven years. PET is a non-invasive imaging technique based on the use of biologically relevant compounds labelled with short-lived positron-emitting radionuclides such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18. The basic facility consists of a medical cyclotron (10 MeV proton & 5 MeV deuteron), six lead-shielded hotcells with associated radiochemistry facilities, radiopharmacy and a whole body PET scanner. A strong radiolabelling development program, including the production of 15O-oxygen, 15O-carbon monoxide, 15O-carbon dioxide, 15O-water, 13N-ammonia, 18F-FDG, 18F-FMISO, 11C-SCH23390 and 11C-flumazenil has been pursued to support an ambitious clinical and research program in neurology, oncology, cardiology and psychiatry.

F-18 fluorodeoxyglucose positron emission tomography in the non-invasive staging of non-small cell lung cancer

OBJECTIVE

Positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG), a glucose analogue, as a metabolic tumour marker, has been proposed for the non-invasive staging of oncological disease. Tumours demonstrate increased glycolytic activity and thereby, FDG PET can differentiate benign from malignant lesions. To determine its role in the mediastinal staging of patients with suspected non-small cell lung cancer, a prospective study of FDG PET and computed tomography (CT) compared to surgery and pathology was performed. The analysis group consists of 50 patients, 37 men and 13 women, mean age 64 years (range, 41-78 years).

METHODS

A nuclear physician, blind to the clinical and CT data, graded the FDG PET studies qualitatively on a five-point scale, based on the intensity of glucose uptake, for the presence of mediastinal nodal tumour involvement. Scores of four or greater were considered positive for tumour. An experienced radiologist interpreted the patients' CT scans blind to the other data. The CT criterion for tumour involvement was a nodal long axis diameter of 10 mm or greater. All patients underwent either thoracotomy or mediastinoscopy to obtain surgical specimens. The PET, CT, surgery and pathology were mapped according to the American Thoracic Society nodal classification resulting in 201 nodal stations evaluated. The imaging studies were analysed for N2 or N3 tumour involvement compared to histology or dissection of nodal stations.

RESULTS

All patients had proven non-small cell lung carcinoma. PET excluded tumour in 175 of 181 nodal stations (specificity 97%) compared to 162 of 181 (specificity 90%) by CT. PET correctly identified 16 of 20 (sensitivity 80%) nodal stations with tumour compared to 13 of 20 by CT (sensitivity 65%). Overall, PET correctly staged 191 of 201 nodal stations (accuracy 95%) compared to 175 of 201 by CT (accuracy 87%). By the McNemar test, PET was significantly more specific than CT in excluding nodal tumour involvement (X2 = 5.5, P < 0.05).

CONCLUSIONS

FDG PET is more specific than computed tomography in the non-invasive mediastinal staging of non-small cell lung cancer and has an important clinical role in the pre-operative staging of lung cancer patients.

Clinical Applications of [15O] H2O PET Activation Studies

Localization of eloquent cortical regions is an important aspect of neurosurgical practice. When lesions lie close to or within areas such as somatosensory, motor or language cortex, the goal of surgical treatment is maximal resection without causing neurological deficit. Hence precise functional mapping combined with accurate delineation of the extent of pathology is important for deciding whether surgery is feasible at all and defining the safe limit of resection and the optimal operative approach. In addition, when the electroclinical pattern of intractable seizures suggests a specific localization in sensorimotor cortex (e.g., seizures originating in the face area), functional mapping may be of use in directing the surgical treatment at the seizure focus. Activation studies using positron emission tomography (PET) and the tracer [(15)O] labeled water ([(15)O]H(2)O) can be used in presurgical planning and in intraoperative surgical guidance in individual patients. The use of PET technology for these purposes is critically dependent on advances in registration or alignment of images acquired using different modalities; the development of neurosurgical guidance devices; and the development of methods of statistical analysis suitable for use in single subjects.

Identifying hypoxic tissue after acute ischemic stroke using PET and 18F-fluoromisonidazole

OBJECTIVE

To show that PET with 18F-fluoromisonidazole (18F-FMISO) can detect peri-infarct hypoxic tissue in patients after ischemic stroke.

BACKGROUND

PET with (15)O-labeled oxygen and water is the only established method for identifying the ischemic penumbra in humans. We used PET with 18F-FMISO in patients after ischemic stroke to identify hypoxic but viable peri-infarct tissue likely to represent the ischemic penumbra, and to determine how long hypoxic tissues persist after stroke.

METHODS

Patients with acute hemispheric ischemic stroke were studied using PET with 18F-FMISO either within 48 hours or 6 to 11 days after stroke onset. The final infarct was defined by CT performed 6 to 11 days after stroke. Tracer uptake was assessed objectively by calculating the mean activity in the contralateral (normal) hemisphere, then identifying pixels with activity greater than 3 SDs above the mean in both hemispheres. Positive studies were those with high-activity pixels ipsilateral to the infarct.

RESULTS

Fifteen patients were studied; 13 within 48 hours of stroke, 8 at 6 to 11 days, and 6 during both time periods. Hypoxic tissue was detected in 9 of the 13 patients studied within 48 hours of stroke, generally distributed in the peripheries of the infarct and adjacent peri-infarct tissues. None of the 8 patients studied 6 to 11 days after stroke exhibited increased 18F-FMISO activity. All 6 patients studied both early and late exhibited areas of increased activity during the early but not the late study.

CONCLUSIONS

PET with 18F-FMISO can detect peri-infarct hypoxic tissue after acute ischemic stroke. The distribution of hypoxic tissue suggests that it may represent the ischemic penumbra. Hypoxic tissues do not persist to the subacute phase of stroke (6 to 11 days).

Phase I/II radioimmunotherapy trial with iodine-131-labeled monoclonal antibody G250 in metastatic renal cell carcinoma

This Phase I/II radioimmunotherapy study was carried out to determine the maximum tolerated dose (MTD) and therapeutic potential of 131I-G250. Thirty-three patients with measurable metastatic renal cell carcinoma were treated. Groups of at least three patients received escalating amounts of 1311I (30, 45, 60, 75, and 90 mCi/m2) labeled to 10 mg of mouse monoclonal antibody G250, administered as a single i.v. infusion. Fifteen patients were studied at the MTD of activity. No patient had received prior significant radiotherapy; one had received prior G250. Whole-body scintigrams and single-photon emission computed tomography images were obtained in all patients. There was targeting of radioactivity to all known tumor sites that were > or =2 cm. Reversible liver function test abnormalities were observed in the majority of patients (27 of 33 patients). There was no correlation between the amount of 131I administered or hepatic absorbed radiation dose (median, 0.073 Gy/mCi) and the extent or nature of hepatic toxicity. Two of the first six patients at 90 mCi/m2 had grade > or =3 thrombocytopenia; the MTD was determined to be 90 mCi/m2 131I. Hematological toxicity was correlated with whole-body absorbed radiation dose. All patients developed human antimouse antibodies within 4 weeks posttherapy; retreatment was, therefore, not possible. Seventeen of 33 evaluable patients had stable disease. There were no major responses. On the basis of external imaging, 131I-labeled mouse monoclonal antibody G250 showed excellent localization to all tumors that were > or =2 cm. Seventeen of 33 patients had stable disease, with tumor shrinkage observed in two patients. Antibody immunogenicity restricted therapy to a single infusion. Studies with a nonimmunogenic G250 antibody are warranted.

Direct immobilization of gangliosides onto gold-carboxymethyldextran sensor surfaces by hydrophobic interaction: applications to antibody characterization

We describe a novel immobilization technique to investigate interactions between immobilized gangliosides (GD3, GM1, and GM2) and their respective antibodies, antibody fragments, or binding partners using an optical biosensor. Immobilization was performed by direct injection onto a carboxymethyldextran sensor chip and did not require derivatization of the sensor surface or the ganglioside. The ganglioside appeared to bind to the sensor surface by hydrophobic interaction, leaving the carbohydrate epitope available for antibody or, in the case of GM1, cholera toxin binding. The carboxyl group of the dextran chains on the sensor surface did not appear to be involved in the immobilization as evidenced by equivalent levels of immobilization following conversion of the carboxyl groups into acyl amino esters, but rather the dextran layer provided a hydrophilic coverage of the sensor chip which was essential to prevent nonspecific binding. This technique gave better reactivity and specificity for anti-ganglioside monoclonal antibodies (anti-GD3: KM871, KM641, R24; and anti-GM2: KM966) than immobilization by hydrophobic interaction onto a gold sensor surface or photoactivated cross-linking onto carboxymethydextran. This rapid immobilization procedure has facilitated detailed kinetic analysis of ganglioside/antibody interactions, with the surface remaining viable for a large number of cycles (>125). Kinetic constants were determined from the biosensor data using linear regression, nonlinear least squares and equilibrium analysis. The values of kd, ka, and KAobtained by nonlinear analysis (KAKM871 = 1.05, KM641 = 1.66, R24 = 0.14, and KM966 = 0.65 x 10(7) M-1) were essentially independent of concentration and showed good agreement with data obtained by other analytical methods.

The contribution of 18F-fluoro-2-deoxy-glucose positron emission tomographic imaging to radiotherapy planning in lung cancer

A retrospective analysis was performed to determine whether coronal thoracic [18F]fluoro-2-deoxy-glucose positron emission tomography (FDG-PET) scans, if viewed at the time of radiotherapy (RT) planning, would have influenced the anterior-posterior (AP) RT volumes that were administered to a group of unoperated lung cancer patients. Viewing of PET and diagnostic images enabled a qualitative assessment of whether abnormal thoracic PET activity was present in areas regarded as normal by diagnostic imaging; this would, therefore, have influenced the RT volume if done prospectively. Additionally a method of graphical co-registration was devised to quantitate the adequacy of coverage of each patient's abnormal PET activity by his/her actual RT field. Of 15 patients analyzed, 26.7% (four patients) would have had their RT volume influenced by PET findings, highlighting the potential value of PET in treatment planning.

Rapid and specific targeting of monoclonal antibody A33 to a colon cancer xenograft in nude mice

Monoclonal antibody (mAb) A33 detects a glycoprotein homogeneously expressed by > 95% of human colon cancers and by normal colon cells. The A33 antigen is not secreted or shed and after mAb A33 binds to antigen on the cell membrane, a fraction of membrane-bound mAb A33 is internalized into endosomes. Phase I 131I-mAb A33 biodistribution studies have shown consistent, specific tumor-targeting, and phase I radioimmunotherapy trials with 131I- or 125I-mAb A33 have demonstrated antitumor effects. Here we describe a nude mouse model that was established using a human colon cancer cell line, SW1222, which grows as a relatively hypovascular, invasive heterotransplant when injected i.m. Peak uptake of 131I-labeled or 111In-chelated mAb A33 was observed at 48-96 h, with a mean of 34% (SE +/- 5.0) and 46.7% (SE +/- 1.7) injected dose per gram of tumor tissue, respectively. 111In-mAb A33 was retained in tumor tissue longer than halide radioimmunoconjugates. The specificity of antibody localization was assessed using a control antibody (tumor uptake and pharmacokinetics), a control tumor, corrections for vascular antibody blood-pooling in tumor tissue, and blocking of radiolabeled mAb A33 localization by pretreating mice with excess unlabeled mAb A33. These experiments demonstrate that mAb A33 localization in tumor was specific, and they emphasize the unexpected rapidity with which the antibody localizes. Our conclusions were confirmed by immunohistochemical techniques which allowed direct visualization of localization and distribution of the humanized version of mAb A33 in tumor tissue. Furthermore, antibody doses approximating tumor-saturating doses demonstrated that a homogeneous distribution of antibody in tumor is possible. This model will be valuable for studies focusing on general physiologic aspects of antibody-to-tumor cell localization and critical as a guide to the evaluation of various A33 antibody constructs and combinations with other therapies for the treatment of colon cancer.

Construction and characterisation of a functional CD19 specific single chain Fv fragment for immunotherapy of B lineage leukaemia and lymphoma

The B cell specific antigen CD19 is a target for the immunotherapy of B lineage leukaemias and lymphomas. We have engineered a single chain Fv (scFv) fragment from the mouse hybridoma cell line FMC63 which produces monoclonal antibody specific for CD19. The genes encoding the FMC63 heavy and light chain variable regions were amplified from cDNA and a scFv was constructed by splice overlap extension PCR. Analysis of staining of lymphoblastoid cell lines, peripheral blood lymphocytes and tonsil sections demonstrated that the monovalent scFv fragment has the same cellular specificity as the parent hybridoma antibody. Kinetic studies with radiolabelled material showed that the scFv binds target cells with a Ka of 2.3 x 10(-9), compared with 4.2 x 10(-9) for the parent antibody. This CD19 scFv will be used in experimental models to test its therapeutic efficacy and immunogenicity, with a view to application in the diagnosis and treatment of human B cell cancers.

Antibody-based immunological therapies

Clinical research in the area of antibody-based tumor-targeted therapy has been driven for many years by the prospect of identifying cell surface antigens with sufficient restrictive tissue expression patterns to allow for the selective and specific accumulation of antibody in tumor tissue. Few, if any, such antibody-antigen systems have been identified which can effectively deliver a large fraction of an administered therapeutic agent to metastatic cancer. Despite this limitation, however, a greater understanding of the biological and physiological principles of tumor-targeted therapy has resulted in successful antibody-based therapy of lymphoma, colon cancer and breast cancer in recent clinical trials.

Pneumocystis carinii pneumonia postrestorative proctocolectomy for ulcerative colitis: a role for perioperative prophylaxis in the cyclosporine era? Report of a case and review of the literature

PURPOSE

Medical management of severe ulcerative colitis has used cyclosporine with increasing frequency as an adjuvant to systemic steroids and mercaptopurine. However, the effects of combined management with cyclosporine and prednisone may lead to significant immune compromise and adversely affect operative morbidity in the event urgent surgery is required.

METHODS

A case is reported of a 43-year-old white male who presented with severe ulcerative colitis. The patient had been initially treated with prednisone and cyclosporine for six weeks before surgical intervention. The intractability of his ulcerative colitis caused the patient to present to surgery, where he underwent restorative proctocolectomy.

RESULTS

On initial presentation, the patient manifested systemic signs of severe ulcerative colitis with hypoalbuminemia, anemia, and weight loss, despite continuous prednisone and cyclosporine management. Before surgical intervention, a chest x-ray and the patient's respiratory status were normal. A total abdominal colectomy with ileal pouch reconstruction and temporary loop ileostomy were performed without incident. On the fifth postoperative day, the patient developed respiratory failure, which was subsequently diagnosed as Pneumocystis carinii pneumonia. Although ventilator support and both aggressive medical and surgical management eventually resulted in successful outcome, significant perioperative morbidity occurred.

CONCLUSIONS

In the era of aggressive medical management for ulcerative colitis with both steroids and cyclosporine, the complications of immunosuppression may be significant, including opportunistic pneumonia. Prophylaxis against P. carinii pneumonia with sulfa antibiotics should be considered, especially in patients for whom proctocolectomy is a potential end point.

Kinetic analysis of the interaction between the monoclonal antibody A33 and its colonic epithelial antigen by the use of an optical biosensor. A comparison of immobilisation strategies

The interaction between the humanised A33 monoclonal antibody and the corresponding F(ab)'2 or Fab' fragments with the colonic epithelial A33 antigen, purified by micropreparative HPLC from membrane extracts of the colonic carcinoma cell line LIM 1215, has been studied with the BIAcore 2000 biosensor using surface plasmon resonance detection. The surface orientation of immobilised antibody and the Fab' fragment onto the biosensor surface was controlled using alternative immobilisation chemistries. This resulted in significantly higher molar binding activities compared with the conventional N-hydroxysuccinimide (NHS)/N-ethyl-N'-dimethylaminopropylcarbodiimide (EDC) chemistry. This increase in signal resulted in a concomitant increase in sensitivity of detection, which facilitates analysis of low levels of A33 antigen. The apparent association rate (ka) and dissociation rate (kd) constants obtained with the different immobilisation chemistries were determined. These analyses showed that the kinetic constants obtained for the IgG were not significantly affected by the method of immobilisation. F(ab)'2 and Fab' fragments immobilised using NHS/EDC chemistry showed significantly lower apparent affinity. By contrast the use of the thiol coupling chemistry with the Fab' fragment gave a five fold increase in observed KA, resulting in a similar affinity to that observed with the intact IgG molecule.

Resuscitation from hemorrhagic shock with diaspirin cross-linked hemoglobin, blood, or hetastarch

BACKGROUND

An oxygen-transporting hemoglobin solution should be more effective than a nonhemoglobin solution for resuscitation from hemorrhagic shock. A way to evaluate this effectiveness is to determine whether a hemoglobin solution can reverse the base deficit accumulated during hemorrhage at a faster rate than a nonhemoglobin solution. Using this criterion, we compared the resuscitative powers of autologous blood, hetastarch (Het), and diaspirin cross-linked hemoglobin (DCLHb).

METHODS

Fifteen sedated, spontaneously breathing sheep (37.5 +/- 10.2 kg) were bled until base deficits fell to -5 to -10 mEq/L, and plasma lactate concentrations rose to 6 to 9 mg/L. The animals were resuscitated with autologous blood (n = 5), Het (n = 5), or DCLHb (n = 5) (3.5-4.0 mL/kg every 15 minutes) until base deficits returned to prehemorrhage baseline.

RESULTS

Exsanguination to target base deficits required removal of an average of 41.4 +/- 5.5 mL blood/kg (estimated total blood volume, 80 mL/kg). Resuscitation required 18 +/- 3, 38 +/- 2 (different from blood), and 35 +/- 1 (different from blood) mL/kg of autologous blood, Het and DCLHb, respectively, over periods of 78 +/- 8, 163 +/- 10 (different from blood), and 129 +/- 9 minutes (different from blood and different from Het (p < or = 0.05)). Based on regression analysis, autologous blood, Het, and DCLHb corrected the base deficit at rates of, respectively, 0.074 (different from Het (p < or = 0.05)), 0.016, and 0.056 (different from Het (P < or = 0.05)) mEq/L/min.

CONCLUSIONS

Based on the rate of base deficit correction and the volume of solution required, autologous blood was the most effective resuscitation solution. However, DCLHb was more effective than Het. DCLHb may be an attractive alternative to blood for resuscitation from hemorrhagic shock.

Implementation and evaluation of patient-specific three-dimensional internal dosimetry

Current methods for calculating the absorbed dose in a target region from a source region rely on a standard "reference man" geometry and assume an uniform distribution of radiolabel. While this approach is acceptable at the low levels of radioisotope administered for most diagnostic purposes, the generality of the calculations is not adequate for doses at the higher levels required for therapy and is not easily extendible to tumor dosimetry.

METHODS

We have developed an integrated system which utilizes patient anatomy and radionuclide distribution in the calculation of absorbed dose rate or total dose to any user-defined target region. Images of radionuclide distribution (PET/SPECT) are registered to anatomic images (CT/ MRI) and then entered into a three-dimensional internal dosimetry software system (3D-ID) where regions of interest are defined. Dose calculations are performed by the mathematical convolution between a user-specified, dose-point kernel with the activity in the source volume over the target volume. The resulting dose rate distribution may be scaled by cumulated activity to yield absorbed dose. In addition to calculating the mean dose, dose-volume histograms may be generated which plot absorbed dose with respect to percent of volume. The method was evaluated using selected standard man phantom organs.

RESULTS

Dose estimates for two patient studies are included to illustrate differences between patient-specific and MIRD-based calculations. The package provides an alternative approach to image display and three-dimensional internal dose calculations.

CONCLUSION

The dose-volume histogram representation of absorbed dose to a target volume provides valuable information in assessing tumor control probability and normal tissue toxicity.

The human A33 antigen is a transmembrane glycoprotein and a novel member of the immunoglobulin superfamily

The mAb A33 detects a membrane antigen that is expressed in normal human colonic and small bowel epithelium and > 95% of human colon cancers. It is absent from most other human tissues and tumor types. The murine A33 mAb has been shown to target colon cancer in clinical trials, and the therapeutic potential of a humanized antibody is currently being evaluated. Using detergent extracts of the human colon carcinoma cell lines LIM1215 and SW1222, in which the antigen is highly expressed, the molecule was purified, yielding a 43-kDa protein. The N-terminal sequence was determined and further internal peptide sequence obtained following enzymatic cleavage. Degenerate primers were used in PCRs to produce a probe to screen a LIM1215 cDNA library, yielding clones that enabled us to deduce the complete amino acid sequence of the A33 antigen and express the protein. The available data bases have been searched and reveal no overall sequence similarities with known proteins. Based on a hydrophilicity plot, the A33 protein has three distinct structural domains: an extracellular region of 213 amino acids (which, by sequence alignment of conserved residues, contains two putative immunoglobulin-like domains), a single hydrophobic transmembrane domain, and a highly polar intracellular tail containing four consecutive cysteine residues. These data indicate that the A33 antigen is a novel cell surface receptor or cell adhesion molecule in the immunoglobulin superfamily.

Comparison of optimised planar scintigraphy with SPECT thallium, exercise ECG and angiography in the detection of coronary artery disease

BACKGROUND

Thallium SPECT has been shown to be more sensitive than planar imaging in the detection of coronary heart disease (CAD) in a number of reported series. Early (< 10 minutes) redistribution on planar imaging has been demonstrated in clinical studies and this may partly contribute to its lower sensitivity.

AIM

To determine whether thallium SPECT is superior to planar scintigraphy (with the timing of imaging performed optimally so that it was commenced within five minutes of injection) in the detection of CAD.

METHODS

Planar and SPECT studies were performed in 44 patients with significant (> 70% stenosis) CAD, seven patients with borderline stenoses (50-69%) and in 18 patients with no significant CAD.

RESULTS

The sensitivity of planar imaging was 66% which was higher than exercise ECG 54% (ns) but significantly lower than SPECT 86% (p < 0.005). The specificity of planar thallium scintigraphy was 100% which was higher than SPECT (83%) and significantly higher than exercise ECG 72% (p < 0.05). SPECT had a significantly higher sensitivity for LAD and single vessel disease than planar imaging and this was unrelated to a history of prior myocardial infarction.

CONCLUSION

Even when planar imaging is timed optimally to minimise the impact of early redistribution, SPECT is more sensitive than either planar imaging or exercise ECG in the detection of CAD, but its specificity is lower.

Purification and characterization of a novel restricted antigen expressed by normal and transformed human colonic epithelium

A cell surface antigen that is expressed by normal and 95% of transformed colonic epithelium and is recognized by the monoclonal antibody A33 (Welt, S., Divgi, C. R., Real, F. X., Yeh, S. D., Garin-Chesa, P., Finstad, C. L., Sakamoto, J., Cohen, A., Sigurdson, E. R., Kemeny, N., Carswell, E. A., Oettgen, H. F., and Old, L. J. (1990) J. Clin. Oncol. 8, 1894-1906) has been purified to homogeneity from the human colonic carcinoma cell line LIM1215. The A33 protein was purified from Triton X-114 extracts of LIM1215 cells under nondenaturing conditions. These extracts were applied sequentially to Green-Sepharose HE-4BD, Mono-Q HR 10/10, Superose 12 HR 10/30, and micropreparative Brownlee Aquapore RP 300. The purification was monitored by biosensor analysis using surface plasmon resonance detection with a F(ab')2 fragment of the humanized A33 monoclonal antibody immobilized on the sensor surface and Western blot analysis following SDS-polyacrylamide gel electrophoresis (PAGE) under nonreducing conditions using humanized A33 monoclonal antibody. The purified A33 antigen has a Mr on SDS-PAGE of 43,000 under nonreducing conditions. By contrast, the purified protein displayed a Mr of approximately 180,000 under native conditions on both size exclusion chromatography and native PAGE, possibly due to the formation of a homotetramer. N-terminal amino acid sequence analysis of the purified protein identified 34 amino acid residues of a unique sequence: ISVETPQDVLRASQGKSVTLPXTYHTSXXXREGLIQWD. A polyclonal antibody was raised against a synthetic peptide corresponding to residues 2-20 of this sequence. The antipeptide serum recognized the purified protein using Western blot analysis under both nonreducing (Mr 43,000) and reducing (Mr 49,000) conditions.

Thoracic versus lumbar epidural anesthesia's effect on pain control and ileus resolution after restorative proctocolectomy

BACKGROUND

Epidural anesthesia as a perioperative adjunct has been shown to provide superior pain control and has been implicated in more rapid ileus resolution after major abdominal surgery, possibly through a sympatholytic mechanism. Studies suggest that the vertebral level of epidural administration influences these parameters.

METHODS

One hundred seventy-nine patients (120 male, 59 female; average age, 36 years) underwent restorative proctocolectomy for ulcerative colitis or familial polyposis between 1989 and 1995. Patients were grouped according to type of anesthesia. Group THO (n = 53) received thoracic (T6 to T10) epidurals. Group LUM (n = 51) received lumbar (L2 to L4) epidurals, and group PCA (n = 75) received patient-controlled intravenous narcotic analgesia. Patients were compared for complications, perioperative risk factors, postoperative pain, and ileus resolution.

RESULTS

Epidural narcotics, alone or combined with local anesthetics, were administered for an average of 2 (LUM) to 4 (THO) days without significant complications. Infrequent problems related to the epidural catheters included self-limited headaches or back pain (four) and site infections (two). Epidural failure, as measured by conversion to PCA for inadequate pain control, was not significantly greater for LUM (25%) than THO (23%). Average pain scores, rated daily on a visual analog scale, were significantly higher (indicating more pain) for PCA patients (4.2) during postoperative days 1 through 5 than for LUM (3.5) (p < 0.05) and for THO (2.4) (p < 0.05). Ileus resolution, as determined by stool output and return of bowel sounds, was significantly faster in THO than in LUM or PCA (p < 0.05). Resolution of ileus was not significantly different between PCA and LUM (p > 0.05).

CONCLUSIONS

Thoracic epidural analgesia has distinct advantages over both lumbar epidural or traditional patient-controlled analgesia in shortening parameters measuring postoperative ileus and in reducing surgical pain. The procedure is safe and associated with low morbidity. Thoracic epidural anesthesia is also economically justifiable and may prove to impact significantly on future postoperative management by reducing length of hospitalization. Our data and those of others are most striking in these regards for patients with thoracic catheters, indicating the importance of vertebral level in epidural drug administration.

Abnormal colonic accumulation of fluorine-18-FDG in pseudomembranous colitis

A 51-yr-old man with a history of pancreatic carcinoma was studied with [18F]fluorodeoxyglucose ([18F]FDG) and PET as part of staging for residual disease after chemotherapy. The PET study was performed during a clostridium difficile-associated diarrheal illness. Striking [18F]FDG uptake was demonstrated in the wall of the colon over its entire length. Clostridium difficile associated diarrhea and mechanisms of [18F]FDG uptake in normal and abnormal tissues are briefly reviewed and a mechanism for FDG uptake in this patient is postulated.

Phase I/II study of iodine 125-labeled monoclonal antibody A33 in patients with advanced colon cancer

PURPOSE

A phase I/II study was designed to determine the maximum-tolerated dose (MTD) of iodine 125-labeled monoclonal antibody A33 (125I-mAb A33), its limiting organ toxicity, and the uptake and retention of radioactivity in tumor lesions.

PATIENTS AND METHODS

Patients (N = 21) with advanced chemotherapy-resistant colon cancer who had not received prior radiotherapy were treated with a single 125I-mAb A33 dose. 125I doses were escalated from 50 to 350 mCi/m2 in 50-mCi/m2 increments. Radioimmunoscintigrams were performed for up to 6 weeks after 125I-mAb A33 administration.

RESULTS

All 20 patients with radiologic evidence of disease showed localization of 125I to sites of disease. Twelve of 14 patients, who underwent imaging studies 4 to 6 weeks after antibody administration, had sufficient isotope retention in tumor lesions to make external imaging possible. No major toxicity was observed, except in one patient with prior exposure to mitomycin who developed transient grade 3 thrombocytopenia. Although the isotope showed variable uptake in the normal bowel, gastrointestinal symptoms were mild or absent, and in no case did stools become guaiac-positive. The MTD was not reached at 125I doses up to 350 mCi/m2. However, cytotoxicity assays demonstrated that patients treated with the highest dose had sufficiently high serum levels of 125I-mAb A33 to lyse colon cancer cells in vitro. Among 21 patients, carcinoembryonic antigen (CEA) levels returned to normal in one patient and decreased by 35% and 23%, respectively, in two patients; one additional patient had a mixed response on computed tomography. Additional, significant responses were observed in those patients treated with chemotherapy [carmustine [BCNU], vincristine, flourouracil, and streptozocin [BOF-Strep]) after completion of the 125I-mAb A33 study.

CONCLUSION

Low-energy emission radioimmunotherapy with doses of up to 350 mCi/m2 of 125I-mAb A33 did not cause bowel or bone marrow toxicity. The modest antitumor activity in these heavily pretreated patients is encouraging because of lack of toxicity at the doses studied. The long radioactivity retention in tumors suggests that isotopes with a long half-life may have a therapeutic advantage, based on calculated dose delivery to tumor versus normal tissue. Due to the low bone marrow dose, further 125I trials with humanized mAb A33 are warranted, and controlled studies must be conducted to evaluate the combination of radioimmunotherapy and chemotherapy.

Bone marrow dosimetry: regional variability of marrow-localizing antibody

In radiolabeled antibody therapy, imaging and biopsy-based methods are used to estimate marrow activity concentration when the administered antibody localizes to the marrow. Absorbed dose estimates obtained using such measurements may be subject to large variability due to the potential for regional differences in marrow activity concentration. This variability was examined in ten patients with leukemia after administration of 131I-labeled HuM195 antibody.

METHODS

Regions of interest were drawn around the head and neck of the humerus and femur (both sides) and around lumbar vertebra 3 (L3) and 4 (L4) on a series of planar images collected at multiple times postadministration of the antibody. A single exponential fit to each attenuation-corrected, time-activity curve was obtained to estimate clearance half-life and the back-extrapolated percent injected activity.

RESULTS

The activity concentration in the femoral head and neck (mean and s.d. = 0.04 +/- 0.02 %ID/g) was not significantly different than that measured in L3 and L4 (0.06 +/- 0.02% ID/g) but was not significantly lower than the concentrations measured in the humeral head and neck regions (0.07 +/- 0.03 %ID/g, p < 0.05). Although half-life estimates differing by more than a factor of 2 were observed in half-life between regions overall. S-factors were used for individual marrow regions to determine the mean absorbed dose to marrow in the femoral and humeral heads and the lumbar vertebrae (L3 and L4) which were 0.66 +/- 0.3, 1.0 +/- 0.3 and 2.2 +/- 0.5 mGy/MBq (2.4, 3.8 and 8.3 rad/mCi), respectively.

CONCLUSION

A single value is generally quoted for the absorbed dose delivered to the red marrow following marrow-localizing radiolabeled antibody administration. These results suggest that the regional marrow dose may differ significantly from the mean.

Pilot radioimmunotherapy trial with 131I-labeled murine monoclonal antibody CC49 and deoxyspergualin in metastatic colon carcinoma

An antimouse immune response is invariable following administration of murine monoclonal antibody (mAb), precluding effective multidose therapy. In advanced colorectal cancer patients, we carried out a pilot study with multiple doses of 131I-labeled CC49 administered with deoxyspergualin (DSG), an immunomodulator, to determine its effect on immune response. Cumulative toxicity and efficacy were also evaluated. Six patients with tumor-associated glycoprotein 72-expressing colorectal cancer were treated i.v. with 15 mCi/m2 131I-labeled to 20 mg mAb CC49 biweekly, along with concurrent DSG 200 mg/m2 daily for 5 days, for a maximum of four courses. None had received prior murine mAbs. All patients had targeting of radioactivity to known tumor sites following initial infusion. Four of six patients received all four courses of therapy, three without any acute side effects. In these patients, there was no change in serum clearance with variable tumor targeting following repeat infusions. Two patients had </= grade II anaphylactoid reactions, which were treated without sequelae. One of these had faster serum clearance of radioactivity following repeat infusions of 131I-labeled CC49. Human antimouse antibody titers in all patients were significantly less compared to concurrent times in patients receiving CC49 without DSG (P < 0.05). There was no correlation between the human antimouse antibody titer and serum clearance or tumor targeting of 131I-labeled CC49. There were no clinical responses. We concluded that multiple doses of murine antibody 131I-labeled CC49 can be safely administered with no change in serum or whole-body kinetics in 50% of patients treated biweekly. DSG may reduce the human immune response to the murine mAb.

In vivo imaging and specific targeting of P-glycoprotein expression in multidrug resistant nude mice xenografts with [125I]MRK-16 monoclonal antibody

Multidrug resistance (MDR) in tumors is associated with P-glycoprotein (Pgp) expression. In vivo quantitation of Pgp may allow MDR to be evaluated noninvasively prior to treatment planning. The purpose of this study was to radiolabel MRK-16, a monoclonal antibody that targets an external epitope of P-glycoprotein, and perform in vivo quantitation of P-glycoprotein in a MDR xenograft nude mouse model. MRK-16 was labeled with 125I by the iodogen method, with subsequent purification by size exclusion chromatography. Groups of 10 Balb c mice were each xenografted with colchicine-resistant or sensitive neuroblastoma cell lines, respectively. Whole body clearance and tumor uptake over time was quantitated by gamma camera imaging, and biodistribution studies were performed with [125I]MRK-16 and an isotype matched control antibody, A33. Quantitative autoradiography and immunohistochemistry analysis of tumors was also evaluated to confirm specific targetting of [125I]MRK-16. Peak tumor uptake was at 2-3 days post-injection, and was significantly greater in resistance compared to sensitive tumors (mean % injected dose/g +/- SD) (18.76 +/- 2.94 vs 10.93 +/- 0.96; p < 0.05). Quantitative autoradiography verified these findings (19.13 +/- 0.622 vs 12.08 +/- 0.38, p < 0.05). Specific binding of [125I]MRK-16 was confirmed by comparison to [131I]A33 in biodistribution studies, and localized to cellular components of tissue stroma by comparison of histologic and autoradiographic sections of sensitive and resistant tumors. Immunoblot analysis demonstrated a 4.5-fold difference in P-glycoprotein expression between sensitive and resistant cell lines without colchicine selective pressure. We conclude that in vivo quantitation of P-glycoprotein in MDR tumors can be performed with [125I]MRK-16.(ABSTRACT TRUNCATED AT 250 WORDS)

Phase I radioimmunotherapy trial with iodine-131-CC49 in metastatic colon carcinoma

CC49 is a murine monoclonal antibody (MAb) that reacts against the TAG-72 antigen. We carried out a Phase I study with escalating doses of 131I-CC49 in patients with advanced colorectal cancer expressing the TAG-72 antigen to determine the dose-limiting toxicity and therapeutic efficacy, if any, of the radioimmunoconjugate.

METHODS

Twenty-four patients with TAG-72- expressing colorectal cancer were treated with escalating doses of 131I-CC49 starting at 15 mCi/m2 and going up to 90 mCi/m2 of 131I labeled to 20 mg MAb CC49. Patients were selected if TAG-72 was expressed in > or = 50% of cells in previously resected tumor and at least one metastasis was demonstratable on standard imaging such as CT. All patients had failed conventional chemotherapy and had not received prior radiotherapy or murine MAb. Patients were under radiation isolation precautions until whole-body radioactivity decreased to < or = 5 mR/hr at 1 m. Whole-body scintigrams were obtained prior to discharge and 1 and 2 wk after infusion in all patients. SPECT imaging was carried out at least once in all patients.

RESULTS

All patients had excellent targeting of radioactivity to known tumor sites. There was no nonhematologic toxicity. Hematologic toxicity was more pronounced in those patients who had received extensive prior chemotherapy. There were no major responses. All patients developed an immune response (HAMA) within 4 wk of therapy.

CONCLUSION

Radioimmunotherapy with 131I-CC49 is safe and there is significant therapeutic efficacy in this Phase I trial at the doses studied. There is excellent targeting of radioactivity to antigen-positive tumors. Dose-limiting toxicity is hematopoietic, with the maximum tolerated dose in this group of heavily pretreated patients being 75 mCi/m2.

Response of a Brillouin amplifier and four-wave mixing mirror to a spectrally broadened signal beam

We show that, when the input signal to a Brillouin amplifier and a phase-conjugate mirror is spectrally broadened, the Brillouin interaction can still efficiently amplify and conjugate the input.

Image registration of SPECT and CT images using an external fiduciary band and three-dimensional surface fitting in metastatic thyroid cancer

Image registration of 131I SPECT with CT scans was performed in a patient with metastatic thyroid carcinoma using an external fiduciary band and a three-dimensional surface-fitting algorithim. Areas of metastatic disease taking up 131I were accurately localized to the liver, lungs and vertebral bodies; providing information that could not be obtained by planar or SPECT images alone. Based on these findings, further invasive diagnostic procedures were not performed, therefore considerably altering management in this patient. This approach to image registration has immediate clinical utility in the registration and interpretation of SPECT studies with corresponding CT or MRI scans.

Calculated and TLD-based absorbed dose estimates for I-131-labeled 3F8 monoclonal antibody in a human neuroblastoma xenograft nude mouse model

Preclinical evaluation of the therapeutic potential of radiolabeled antibodies is commonly performed in a xenografted nude mouse model. To assess therapeutic efficacy it is important to estimate the absorbed dose to the tumor and normal tissues of the nude mouse. The current study was designed to accurately measure radiation does to human neuroblastoma xenografts and normal organs in nude mice treated with I-131-labeled 3F8 monoclonal antibody (MoAb) against disialoganglioside GD2 antigen. Absorbed dose estimates were obtained using two different approaches: (1) measurement with teflon-imbedded CaSO4:Dy mini-thermoluminescent dosimeters (TLDs) and (2) calculations using mouse S-factors. The calculated total dose to tumor one week after i.v. injection of the 50 microCi I-131-3F8 MoAb was 604 cGy. The corresponding decay corrected and not corrected TLD measurements were 109 +/- 9 and 48.7 +/- 3.4 cGy respectively. The calculated to TLD-derived dose ratios for tumor ranged from 6.1 at 24 h to 5.5 at 1 week. The light output fading rate was found to depend upon the tissue type within which the TLDs were implanted. The decay rate in tumor, muscle, subcutaneous tissue and in vitro, were 9.5, 5.0, 3.7 and 0.67% per day, respectively. We have demonstrated that the type of tissue in which the TLD was implanted strongly influenced the in vivo decay of light output. Even with decay correction, a significant discrepancy was observed between MIRD-based calculated and CaSO4:Dy mini-TLD measured absorbed doses. Batch dependence, pH of the tumor or other variables associated with TLDs which are not as yet well known may account for this discrepancy.

The identification of polymorphic microsatellite loci in the horse and their use in thoroughbred parentage testing

Six new horse microsatellite loci were identified by sequencing M13 clones containing horse genomic inserts which gave positive signals when probed with a CA/GT repeat probe. Oligonucleotide primer pairs were synthesized for these loci and for two previously described horse microsatellites, HTG4 and HTG6. Polymerase chain reaction assays were then carried out on a panel of 20 different unrelated Thoroughbred horse DNAs. DNAs from eight cases of double covering which could not be solved by conventional blood typing were also examined. Several of the loci amplified were found to be polymorphic and, using a limited subset of primers, a clear exclusion could be established for one of the stallions in five of the cases. DNA typing is therefore a useful adjunct to blood typing in the horse and indeed, in the future will probably replace it.

Clinical validation of SPECT and CT/MRI image registration in radiolabeled monoclonal antibody studies of colorectal carcinoma

Registration methods combine the anatomic localizing ability of CT or MRI with SPECT images of radiolabeled monoclonal antibodies (Mabs), allowing the accurate staging of patients prior to surgery or following treatment.

METHODS

Twenty-four patients (15 males and 9 females, mean age 55 yr, range 29-70 yr) were studied with this technique. Ten patients had suspected colorectal cancer recurrence and were infused with 10 mCi of 131I-CC49 prior to staging laparotomy. Fourteen patients treated in a Phase I radioimmunotherapy study with 131I-CC49 were also studied. All patients underwent SPECT imaging of the abdomen and pelvis 5-7 days following infusion of Mab.

RESULTS

Phantom studies demonstrated a 3.6-mm surface fitting mean accuracy of datasets for the liver and 1.8 mm for an intrahepatic tumor. In the presurgical group, SPECT and CT/MRI registration allowed more accurate identification of uptake abnormal sites. Areas of metastatic disease > 1 cm confirmed at surgery were found in six of nine patients with liver lesions and in two patients with extrahepatic (including one patient with pelvic) disease. In patients imaged following radioimmunotherapy, all lesions > 1.5 cm seen on CT/MRI were identified, and activity distribution in tumor and normal tissue could be more accurately assessed.

CONCLUSIONS

Routine registration of SPECT and CT/MRI images is feasible and allows more accurate anatomic assessment of sites of abnormal uptake in radiolabeled Mab studies.

Flare on bone scintigraphy following Taxol chemotherapy for metastatic breast cancer

Our goal was to determine if a healing flare response seen on bone scintigraphy occurs following chemotherapy with Taxol (paclitaxel; Bristol-Myers Squibb Co., Princeton, NJ), a novel antimicrotubule agent for metastatic breast cancer.

METHODS

We performed 74 bone scans on 21 females with breast cancer and bone metastases entering a Phase II trial of Taxol chemotherapy with granulocyte colony stimulating factor (G-CSF). All patients had baseline scans within 6 wk prior to therapy, after the second cycle (4-6 wk) of Taxol, and then after 6-12 mo. All bone scans were reviewed by two nuclear medicine physicians, without knowledge of the patients' clinical history. Skeletal radiographs, CT and MRI scans, as well as clinical history were compared with scan findings.

RESULTS

Seven of the 21 patients showed improvement in bone scan findings. Of these seven, three had a flare response following two cycles (4-6 wk) of Taxol, characterized by increased activity in baseline lesions and the appearance of new lesions, followed by improvement on follow-up scans. Evidence of clinical response (> or = 50% reduction in tumor mass) was seen in all of these patients. Seven patients showed no change in baseline findings on follow-up bone scans. Seven patients had post-Taxol scans showing new lesions, with no overall improvement on later follow-up.

CONCLUSION

Flare on bone scintigraphy may be seen shortly after commencing Taxol chemotherapy. Bone scans done within the first 3 mo must be interpreted with caution and should be correlated with clinical and radiological findings to avoid inappropriate discontinuation of Taxol chemotherapy.

Imaging of brain tumor proliferative activity with iodine-131-iododeoxyuridine

METHODS

Iodine-131-iododeoxyuridine (IUdR) uptake and retention was imaged with SPECT at 2 and 24 hr after administering a 10-mCi dose to six patients with primary brain tumors. The SPECT images were directly compared to gadolinium contrast-enhanced MR images as well as to [18F]fluorodeoxyglucose (FDG) PET scans and 201Tl SPECT scans.

RESULTS

Localized uptake and retention of IUdR-derived radioactivity was observed in five of six patients. The plasma half-life of [131I]IUdR was short (1.6 min) in comparison to the half-life of total plasma radioactivity (6.4 hr). The pattern of [131I]IUdR-derived radioactivity was markedly different in the 2-hr compared to 24-hr images. Radioactivity was localized along the periphery of the tumor and extended beyond the margin of tumor identified by contrast enhancement on MRI. The estimated levels of tumor radioactivity at 24 hr, based on semiquantitative phantom studies, ranged between < 0.1 and 0.2 microCi/cc (< 0.001% and 0.002% dose/cc); brain levels were not measurable.

CONCLUSIONS

Iodine-131-IUdR SPECT imaging of brain tumor proliferation has low (marginal) sensitivity due to low count rates and can detect only the most active regions of tumor growth. Imaging at 24 hr represents a washout strategy to reduce 131I-labeled metabolites contributing to background activity in the tumors, and is more likely to show the pattern of [131I]IUdR-DNA incorporation and thereby increase image specificity. Iodine-123-IUdR SPECT imaging at 12 hr and the use of [124I]IUdR and PET will improve count acquisition and image quality.

Phase I/II study of iodine 131-labeled monoclonal antibody A33 in patients with advanced colon cancer

PURPOSE

A phase I/II study was designed to determine the maximum-tolerated dose (MTD) of iodine 131-labeled monoclonal antibody (mAb) A33 (131I-mAb A33) administered intravenously, its limiting organ toxicity, and its radioisotope retention in tumors, and to develop preliminary evidence of antitumor activity.

PATIENTS AND METHODS

Patients (N = 23) with colorectal cancer who had failed to respond to conventional chemotherapy but had not received prior radiotherapy were treated with escalating doses of 131I-mAb A33. Three or more patients were entered at each dose level, starting at 30 mCi/m2, with increments of 15 mCi/m2 to a maximal dose of 90 mCi/m2. Radiolabeling was performed to maintain a specific activity of 30 mCi/m2/4 mg mAb A33 (projected maximum, 15 mCi/mg). Patients were under strict isolation precautions until whole-body radiation levels decreased to less than 5 mrem/h at 1 m. Serial radioimmunoscintigrams were performed in some cases for up to 3 weeks after 131I-mAb A33 administration.

RESULTS

All 20 patients with radiologic evidence of disease showed localization of radioisotope to sites of disease. Two patients with elevated carcinoembryonic antigen (CEA) levels and negative radiologic tests did not have positive antibody scans. One patient with a small-bowel cancer also had a negative antibody scan. The major toxicity was hematologic and was more pronounced in patients with compromised bone marrow due to prior chemotherapy. Of five patients who received 78 to 84 mCi/m2 131I-mAb A33, one had grade 3 and one grade 4 toxicity; of six patients treated with 86 to 94 mCi/m2 131I-mAb A33, two had grade 4 and one grade 1 toxicity. The MTD was determined to be 75 mCi/m2 in these heavily pretreated patients. Although the isotope showed variable uptake in the normal bowel, gastrointestinal symptoms were mild (n = 8) or absent. No major responses were observed; however, three patients had evidence of mixed responses, and CEA levels decreased in two patients without clinical or radiologic measurable disease. Immunoreactivity of radiolabeled mAb A33 decreased at the highest dose levels in preparations in which specific activity exceeded 18 mCi/mg.

CONCLUSION

The A33 antigen appears to be a promising target for radioimmunotherapy of colon cancer. The modest antitumor activity of 131I-mAb A33 in heavily pretreated patients is encouraging because of its lack of toxicity in the bowel, the only antigen-positive normal tissue.

Clinical applications of fusion imaging in oncology

Recent developments in tumor imaging, made possible by advances in instrumentation and radiopharmaceuticals, has led to an increasing need for accurate anatomic correlation of single photon emission computed tomography (SPECT) and positron emission tomography (PET) images. Fusion imaging permits the functional strengths of SPECT and PET to be combined with the anatomic resolution of computed tomography (CT) and magnetic resonance imaging (MRI). Clinical applications of fusion imaging include the evaluation of brain tumors, lymphoma, hepatic lesions and monoclonal antibody studies. The continued development of these techniques will eventually allow fusion imaging to become a routine part of nuclear medicine practice.

Gallium-67-citrate imaging in nuclear oncology

Gallium-67-citrate is one of the most useful radiopharmaceuticals to detect tumors, stage extent of the disease, monitor response to treatment and distinguish recurrent disease from post-treatment changes. Gallium is likewise very sensitive to detect and locate infections and inflammatory foci. This application is extremely important in the management of immunocompromised cancer patients. Image interpretation should be tempered with full knowledge of the patients clinical condition, anatomic alterations due to prior surgery and correct timing of image acquisition. Early imaging at 4-6 h is useful to detect gastrointestinal infections, whereas 24 h imaging is used to evaluate chest infections. Although gallium-67 is a non-specific agent, the identification of the etiology of the inflammation may be improved by adequate clinical and laboratory information as well as correlation with other imaging modalities such as sonography and computerized x-ray tomography (CT). High dose (10 mCi) gallium-67 single photon emission computed tomography (SPECT) imaging with image co-registration is important for accurate uptake localization.