Detection of occult tumor using indium 111-labeled anticarcinoembryonic antigen antibodies.

Even with the advancement of radiologic techniques, metastatic cancers can still be difficult to detect. In this study, 48 patients suspected of having occult metastases were studied by radioimmunodetection following the administration of 92.5 to 181.3 MBq of indium 111-labeled monoclonal anticarcinoembryonic antigen antibody. All but seven patients were thought to have metastatic colorectal carcinoma. In the majority of cases, physical examinations and computed tomographic scans had failed to detect a lesion. At least one lesion that was later proved to exist was detected in 34 of the 50 studies performed on these patients. Seven of eight patients with normal radioimmunodetection scans remain free of disease. One hundred one sites were detected overall; 60 were considered true-positive sites and 27 false-positive sites. Fourteen sites remained in question. Nineteen false-negative sites occurred. Radioimmunoimaging appears valuable for the detection of occult cancer where standard, noninterventional techniques have failed to detect the suspected disease.

Effect of acetylation on monoclonal antibody ZCE-025 Fab': distribution in normal and tumor-bearing mice.

Studies were performed to determine in vitro and in vivo effects of acetylation on Fab' fragments of ZCE-025, a monoclonal anti-CEA antibody. Isoelectric focusing revealed a drop in isoelectric point of 1.7 pI units following acetylation. Biodistribution studies of acetylated and nonacetylated [111In]Fab' were performed in normal BALB/c mice and in nude mice bearing the T-380 CEA-producing human colon tumor. The acetylated fragments remained in the vascular compartment longer and had significantly diminished renal uptake of 111In compared to controls. While acetylation itself effected a 50% drop in immunoreactivity, tumor uptake of the acetylated and nonacetylated 111In-labeled Fab' fragments was comparable, with the exception of one data point, through 72 h.

Distribution of radiolabeled human and mouse monoclonal IgM antibodies in murine models.

The distribution and kinetics of six human and one murine monoclonal IgM antibodies (MoAb) were studied in BALB/c mice. Labeling was with 111In, 75Se, and 125I. The monomers and pentamers of certain MoAbs were studied. Human distribution studies were also performed. The serum containing [111In]MoAb was obtained from one of the patients 24 hr after administration and injected into mice which were then killed and assayed for 111In distribution. In general, the [75Se] and [111In]MoAbs had distribution and kinetic patterns that were similar while the 125I-labeled MoAbs dehalogenated after 4 hr. Monomers and pentamers had highly similar distributions suggesting that the distribution of IgMs may be based on factors other than molecular size. The murine IgM showed a somewhat different distribution in mice than did human IgMs. Serum from the patient containing [111In]MoAb had a distribution in mice similar to that of the patient with high liver and gastrointestinal uptake. The human imaging indicates that it is possible to target tumor with human IgM MoAbs, but significant problems remain in regard to their clinical use.

Breast cancer imaging with In-111 human IgM monoclonal antibodies: preliminary studies.

Detection of specific tumor sites was studied with scintigraphy and radiolabeled human IgM monoclonal antibodies (MoAbs). Ten patients with metastatic breast cancer received an infusion of one of three indium-111-labeled anti-breast carcinoma MoAbs. The time of infusion ranged from 30 minutes to 2 hours. Three patients received YBB-190 at total doses of 2, 4.25, or 11 mg, four patients received YBM-209 at total doses of 1 mg (n = 1) or 20 mg (n = 3), and three patients each received 22 mg of YBY-088. Imaging was performed immediately after infusion and at 4, 24, 48, 72, 120, and 144 hours. Many presumed sites of metastatic disease were imaged in three of the four patients who received 20 mg of YBM-209 and in two of the three patients who received YBY-088. Tumor was not detected in any of the patients who received YBB-190, in the patient who received a 1-mg dose of YBM-209, or in the patient who received YBY-088 and in whom a biopsy of tumor tissue failed to demonstrate target antigen. The authors conclude that In-111-labeled human IgM MoAbs can target human breast cancer, but antigen expression and antibody dose determine successful immunoscintigraphy.

Radioimmunodetection of cancer with the use of indium-111-labeled monoclonal antibodies.

We have infused 13 111In-labeled murine IgG monoclonal antibodies (MAb) into 73 patients who had been diagnosed as having 7 types of cancers, and 3 111In-labeled human MAb into 8 patients with breast cancer. To each patient, 1.5-5 mCi attached to a maximum of 1 mg MAb had been given in a total MAb dose of 0.5-500 mg. The most encouraging overall results have been obtained with anti-human T-cell MAb T101 (33 of 33 tumor sites imaged in 5 patients), antimelanoma MAb P96.5 (47 of 88 sites imaged in 21 patients), anti-prostate MAb PSA399 (14 of 21 sites imaged in 4 patients), and anti-colon MAb ZCE025 (16 of 26 sites imaged in 12 patients). Poor imaging results were related to lower doses, reactivity with circulating cells, and limited antigen expression in various tumor sites. The problems involved in radioimmunodetection included low extraction of MAb from the serum by the tumor that resulted in poor tumor uptake of the radiopharmaceutical, and high background activity in the liver, heart, spleen, and gastrointestinal tract that made imaging difficult in those areas. Heterogeneous antigen production leaves some tumor deposits without targets, and the immunogenicity of the MAb limits use of these agents repetitively in humans. Nevertheless, these early results are encouraging for their potential diagnostic and therapeutic applications.

Tumor size: effect on monoclonal antibody uptake in tumor models.

Studies were performed to determine the effect of tumor size on the incorporation of radiolabeled monoclonal antitumor antibodies (MoAbs) into human tumors growing in nude mice. The colon tumors ranged in size from 0.03-1.6 g, the melanoma from 0.1 to 6.7 g, and the lymphoma from 0.06 to 10.2 g. Indium-111 was primarily used as the radiolabel, however, both 125I and 111In were used as tracers for the MoAb in one experiment. The per g radiopharmaceutical uptake by tumors was inversely proportional to tumor size when tumor specific MoAb was administered. This finding was independent of the radiolabel and was demonstrable when the mice bore two tumors of differing size. When the MoAb was not specific for the tumor, the data were less well defined and a statistically significant correlation with size did not occur. These data are strong evidence for a decrease in per g uptake of labeled tumor specific antibodies as tumors increase in size.

In vivo kinetics of radiolabeled monoclonal anti-CEA antibodies in animal models.

Studies were performed to determine the effect of the radiolabel and circulating carcinoembryonic antigen (CEA) on the pharmacodynamics of monoclonal anti-CEA antibodies (MoAbs). The studies were performed in normal BALB/c mice and in nude mice bearing human colon tumors. Three different tumors were used, each of which produced CEA levels characteristic of that particular tumor's secretory rate. The CEJ-326 MoAb labeled with either 111In or 125I was used in all studies. Circulating CEA induced the removal of 125I and 111In MoAbs from the vascular compartment. Liver concentrations of 111In increased and 125I levels decreased as the CEA secretory rate of the tumor rose. This indicates that circulating CEA complexes form in the vascular compartment which, in an animal model, are removed by the liver and spleen. This results in decreased tumor uptake of the labeled MoAb. The iodinated MoAb complexes are dehalogenated while the 111In is retained by the liver. This dehalogenation may account for the relatively low liver activity observed in radioimmunoimaging with intact radioiodinated anti-CEA MoAbs, provided the CEA complexes are similarly removed from the vascular compartment by the human liver.

Athymic mouse model of a human T-cell tumor.

Because of the large number of different immunoconjugates which can be produced from monoclonal antibody-directed anti-cancer therapy, it would be useful to have in vivo tumor models to compare such preparations. Although historically human leukemias-lymphomas have been difficult to establish in athymic mice we have succeeded in establishing human T-cell tumors from primary MOLT-4 cultures in 290 of 353 animals and have successfully transferred tumors in 42 of 45 animals during ten serial passages. The potential utility of this model for testing immunoconjugates of murine monoclonal antibody T101 have been confirmed by: (a) in all 148 tumors sampled including all passaged tumors the human T-cell antigen, T65, was expressed in a manner identical to that of cultured cells; (b) 111In-T101 was concentrated preferentially in the tumor; and (c) T101 injected by both the i.p. and i.v. routes bound to tumor and induced antigenic modulation to the same extent as that observed previously in vitro and in human studies.

Radioimmunodetection of melanoma utilizing In-111 96.5 monoclonal antibody: a preliminary report.

The murine 96.5 monoclonal antimelanoma antibody (MoAb) was labeled with In-111, and 1-20 mg were administered to 21 patients who had proved or suspected melanoma metastases. One patient was studied twice. In four patients, unlabeled 96.5 MoAb was administered prior to the radiopharmaceutical. All of the patients tolerated the procedure without toxicity regardless of the mass of MoAb administered. The scans were interpreted by two observers, one with full knowledge, the other with no knowledge of the cases. Increasing the MoAb mass or preinfusing unlabeled MoAb prior to the administration of In-111 MoAb resulted in a prolongation of the serum half time, and appeared to improve tumor detection. Lesions were best seen at 72 hours after infusion or later. In all patients who had metastatic disease, at least one tumor site was apparent. Fifty-six per cent of known lesions 1.5 cm or greater in size were detected by the physician who had knowledge of the cases when data from all doses were considered. There were eight lesions detected that were not suspected in the workup of the patient. When these are included, the detection rate rises to 61%. Forty-nine per cent were detected by the other physician. Subtraction techniques were not employed. Lesions were often better seen with single photon emission computed tomography than with planar imaging techniques. The 96.5 In-111 MoAb appears to have utility for the detection of metastatic melanoma. Further clinical evaluation of 96.5 In-111 MoAb is warranted.

Tissue distribution and magnetic resonance spin lattice relaxation effects of gadolinium-DTPA.

Gadolinium-DTPA complex (Gd-DTPA) is a potential clinical magnetic resonance (MR) contrast agent that enhances images primarily by decreasing spin-lattice relaxation time (T1) in tissues in which it localizes. This study was designed to determine the immediate tissue distribution of intravenously administered Gd-DTPA in selected organs of interest as a function of administered dose and tissue Gd-DTPA concentration. An intravenous bolus of Gd-DTPA with a tracer quantity of Gd-153 was administered to three groups of rabbits at the following doses: 0.01 mM/kg (n = 6); 0.05 mM/kg (n = 6); 0.10 mM/kg (n = 6). A control group received sham injections. Five minutes after Gd-DTPA was administered, all animals were killed; samples of serum, lung, heart, kidney, liver, and spleen were analyzed in a 0.25 T MR spectrometer to measure T1, and then in a gamma well counter to determine tissue concentration of Gd-DTPA. Tissue distribution (per cent dose/tissue weight in g) at five minutes after injection was proportionally constant over the range of doses given. Tissue concentration varied linearly with injected dose (r greater than 0.98 for all tissues). Relaxation rate (1/T1) varied linearly with injected dose and with tissue Gd-DTPA concentration (r greater than 0.97 for all tissues). The order of tissue relaxation rate response to a given dose was: kidney greater than serum greater than lung greater than heart greater than liver greater than spleen. We conclude that because of its extracellular distribution and linear relaxation rate versus concentration relationship, Gd-DTPA enhancement in MR images may be a good marker of relative organ perfusion.

Stability, characterization, and kinetics of 111In-labeled monoclonal antitumor antibodies in normal animals and nude mouse-human tumor models.

Monoclonal antibodies (MoAbs) against carcinoembryonic antigen were successfully radiolabeled with 111In, and the radiopharmaceutical was characterized in vitro and in normal and tumor-bearing mice. The 111In-MoAb proved to be stable in vitro and in vivo under normal conditions, although instability could be induced in vitro with large quantities of iron-free transferrin. Animal distribution studies with 111In-MoAb demonstrated tumor localization superior to 67Ga and pharmacokinetics that were highly similar to those of endogenously labeled 75Se-MoAb. The 111In-MoAb followed first-order kinetics and fit a two-compartmental model when studied in nude mice bearing human colon tumors known to express carcinoembryonic antigen. Significant quantities of radiolabel appeared in tissues other than tumor, with liver and skin having the highest concentrations. Sufficient tumor/background ratios were formed for scanning purposes. The data indicate that 111In-MoAb may prove to be effective as a radiopharmaceutical for tumor imaging.

The effect of certain variables on the tumor and tissue distribution of tracers: VI. False-carrier effect, Part III, Fe.

Previous work has shown that Fe3+, when administered in the proper dose and time sequence, increases the tumor uptake of gallium-67 (67Ga) while decreasing its uptake by normal tissues. The purpose of this series of experiments was to examine further the postulate that the false carrier effect is mediated at the cellular as well as the vascular level, determine the lowest concentration of ionic Fe3+ that will induce near maximum tumor/background ratios (T/Bkg), determine the best technique for its administration, and decide whether Benadryl and dexamethasone could be used to offset side effects of the Fe3+ without altering tumor and tissue kinetics. Fe3+ altered tissue levels of 67Ga prior to changes in the blood. The threshold for initiation of the false-carrier effect varied to some extent from one organ to another. Tumor uptake of 67Ga was either enhanced or unaltered at 4 hours after injection; 0.3 mg Fe3+/kg administered 0.5 hour before and 2 hours after the 67Ga enhanced 4-hour T/Bkg by a factor of about ten. Twenty-four-hour ratios were improved (to a lesser extent than 4-hour), but decreased concentrations of 67Ga occurred in the tumor. Dexamethasone and Benadryl did not alter the outcome of the experiment. This technique should be useful for imaging with gallium-68 and the PET camera.

The effect of certain variables on the tumor and tissue distribution of tracers V: false carrier effect, II, Fe.

The effect of Fe3+ citrate on carrier-free 67Ga and 59Fe kinetics was studied in a Buffalo rat-Morris 7777 hepatoma model. Two mg Fe3+ citrate/Kg were administered intravenously in a variety of time sequences, prior to and following the tracers, and the rats were killed at 4 or 24 hours. 67Ga concentrations could be increased in tumor and decreased in most normal tissues. Administering Fe3+ both one half hour before and 2 hours after the tracers produced 67Ga values equivalent to 72-hour carrier-free values after 4 hours, while simultaneously decreasing gut secretion and increasing urinary excretion. The 59Fe and 67Ga kinetics suggested that events at both vascular and cellular levels were responsible for these changes. This study demonstrated the potential utility of Fe3+ citrate for improving both conventional 67Ga and positron (68Ga) imaging of tumors.

The effect of certain variables on the tumor and tissue distribution of tracers. IV. False carriers: ferric citrate.

The intravenous administration of Fe+3 -citrate (1.6 mg/kg body weight) was demonstrated to alter the concentration of carrier-free 67Ga and 54Mn in malignant and healthy tissues of the rat, Morris 7777 hepatoma model. When the Fe+3 was injected 2 hours before, simultaneously with, or 2 hours after 67Ga (and the rats sacrificed 4 hours after injection), the 67Ga in most normal tissues decreased, and the viable tumor concentrations increased by 135, 24, and 47%, respectively. Twenty-four hours after a simultaneous administration of Fe+3 and 67Ga, egress of 67Ga from the tumor was much less than from the healthy tissues. These changes resulted in significant improvements in viable tumor to background ratios, especially at 4 hours. These changes induced in the distribution of the two tracers by Fe+3 indicate that some kinetic characteristics are shared. This is discussed in the light of their response to carrier Ga and Mn. The use of Fe+3 shows promise as a means of improving tumor/background ratios for 68Ga and 52mMn, two short-lived positron emitters that can be used with positron scanners. Gallium-67 imaging may also be improved by these techniques. The Fe+3 increases excretion of 67Ga from the animal, and this could result in a lower radiation dose to a patient.

Cytotoxic activity, tumor accumulation, and tissue distribution of ruthenium-103-labeled bleomycin.

Bleomycin (BLM) was labeled with gamma-emitting 103Ru. Yields of 103Ru-labeled BLM as high as 50.6% were attained. 103Ru-labeled BLM was stable in vitro and the 103ru label was not displaced by large excesses of Cu (II) and Co (II) or Fe (III). Chromatography of the urine following 103Ru-labeled BLM injection indicated no in vivo decomposition. Pharmacokinetic studies in healthy inbred SD and tumor-bearing inbred BUF rats demonstrated tumor accumulations, tissue distributions, and clearance nearly identical with those reported for 3H-labeled BLM. Cytotoxicity studies on a WI-L2 human B-cell line showed that BLM labeled with nonradioactive Ru retained 100% of the activity demonstrated by native BLM. Thus BLM may be labeled with isotopes of Ru to form stable complexes by a simple, rapid reaction without loss of its chemotherapeutic properties or variations in its in vivo distribution. BLM labeled with the proper Ru isotope should prove useful as a gamma-emitting tracer for BLM or a beta-emitting compound capable of providing combination chemotherapy and radiotherapy of tumors.

Quantitation of skeletal-muscle necrosis in a model compartment syndrome.

UNLABELLED: Skeletal-muscle necrosis was evaluated in previously pressurized canine compartments using technetium-99m stannous pyrophosphate and classic histological criteria. Intracompartmental necrosis was quantitated in the anterolateral muscle compartment of each dog by uptake of 99mTc stannous pyrophosphate using the contralateral anterolateral compartment as an internal control. Representative specimens of muscle were sampled in experimental and control legs of each dog and were analyzed by qualitative histological techniques. Muscle necrosis was assessed in compartments forty-eight hours after pressurization to levels of ten to 120 millimeters of mercury for eight hours in thirty-seven dogs. In another dog, neither anterolateral compartment was pressurized so that both compartments acted as control muscle. The results in these experiments identify a threshold pressure level (thirty millimeters of mercury) and duration (eight hours) at which significant muscle necrosis occurs at normal blood pressure. Our findings imply that a quantitative relationship exists between incorporation of 99mTc stannous pyrophosphate and the level of intracompartmental pressure. This uptake technique, however, is not suitable for diagnosing compartment syndrome in patients with a threatened compartment syndrome. We suggest that intracompartmental pressure measurements by the wick-catheter technique, in conjunction with clinical findings, offer the best means for diagnosing compartment syndrome. CLINICAL RELEVANCE: Significant muscle necrosis associated with an impending compartment syndrome occurs at a threshold intracompartmental pressure of thirty millimeters of mercury after eight hours. Since time variables are often unknown in suspected compartment syndromes, fasciotomy is recommended when intracompartmental pressure exceeds thirty millimeters of mercury in a patient with normal blood pressure. The use of this threshold pressure level as an indication for fasciotomy requires a device for measuring intracompartmental pressure such as the wick catheter.

Optimal handling of dimercaptosuccinic acid for quantitative renal scanning.

Methods of optimizing quantitative renal imaging with Tc-99m dimercaptosuccinic acid (DSMA) were investigated. Rats were injected with DMSA (one kit per rat) and sacrificed at 0.5, 2.0, and 24 hr after injection. Fifty percent of the injected dose localized in the kidneys at 0.5, 2, and 24 hr after injection while background activity peaked at 0.5 hr and then declined to give substantially higher kidney-to-background ratios at 24 hr. Delayed scanning should increase the accuracy of clinical studies in patients with low kidney-to-background ratios at 1-2 hr. After injection of DMSA, 1 ml of air was introduced into the reaction vials and incubated 20 min. Kidney uptake decreased from 50 to 40% and liver uptake increased from 7.5 to 17%. If multiple doses must be drawn from a single vial, air should not be introduced, and the doses should be drawn together and administered immediately to minimize radiopharmaceutical deterioration.

The effect of parathyroid hormone on technetium-99m pyrophosphate distribution in rats.

Sprague-Dawley rats were treated with varying quantities of parathyroid hormone for 1--3 days, then sacrificed at periods ranging from 1--6 h after administration of 99mTc-pyrophosphate. Very little increase in bone accumulation of tracer occurred with this treatment. A small, but obvious decrease occurred in the blood levels of 99mTc-pyrophosphate and a smaller and less consistent decrease was affected in the muscle levels of the radiopharmaceutical. The overall result was an improvement in the bone/blood and bone/muscle ratios. It is suggested that the basis of the "supernormal" bone scan of hyperparathyroidism is achieved by this mechanism and that the increased bone uptake of other ions in response to parathyroid hormone is not shared by 99mTc-pyrophosphate.

The effect of certain variables on the tumor and tissue distribution of tracers. II. Carrier effect: rapidity of onset and concentrations necessary for initiation and maximum response.

The smallest quantity of carrier Ga and Mn necessary to initiate and maximize a carrier effect was studied in the Morris 7777 rat hepatoma model. The quantity needed for a maximum response did not appear to adversely effect the rats. Not all tissues were equally affected at the same plasma concentrations. If carrier Ga was administered 2 hours following 67Ga injection and the rats sacrificed 30 minutes later, a dramatic change occurred in background activity, which was more pronounced in healthy than malignant tissues. Early viable and nonviable tumor/background ratios were improved by this technique. The data suggest that the use of carrier Ga and Mn might improve early lesion/background ratios in patients. This could be of use if tumor imaging were undertaken with 68Ga or 52mMn with positron detector systems.

The effect of certain variables on the tumor and tissue distribution of tracers. Part 1; Carrier.

Buffalo rats bearing thigh-implanted strain-7777 Morris hepatomas were used as a model for studying the effect of carrier material on the body distribution, tumor uptake, excretion, and tumor-to-background ratios of 67Ga and 54Mn. An effort was also made to observe the changes in 67Ga and 54Mn concentrations induced by carrier in viable tumor and skeletal muscle, relative to their interstitial fluid space. This value is referred to as the Tissue Distribution Index. Carrier manipulation resulted in striking changes in the distribution of the two ions from the carrier-free state. The data also indicated a difference in the pharmacodynamics of 67Ga and 54Mn in malignant and healthy tissues which could be of importance to nuclear medicine and oncology.