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PubMed1986

Intraoperative probe-directed immunodetection using a monoclonal antibody.

To assess monoclonal antibody (MAb) 17-1A and its F(ab')2 fragment in intraoperative radioimmunodetection and to evaluate further the clinical usefulness of a hand-held gamma-detecting probe (GDP), we injected radiolabeled monoclonal antibody 17-1A three to six days preoperatively or its F(ab')2 fragment two to three days preoperatively into 18 patients with colorectal cancer. Intraoperative GDP counts with tumor-tissue ratios of 1.5:1 or greater were obtained from 15 (75%) of 20 tumor sites, with ratios averaging 2.3:1 for fragments and 3.4:1 for whole antibody. The GDP counts contributed to intraoperative decision making in three patients, either by localization of tumor not identified by inspection or palpation or by mapping margins of resection with histologic confirmation of a local/regional recurrence. These preliminary data demonstrate that probe-directed, intraoperative radioimmunodetection can assist the surgeon in detecting subclinical tumor deposits and thus better evaluate the extent of primary or recurrent colorectal cancers intraoperatively.

Adult↗

PubMed1993

Characterization of second-generation monoclonal antibodies against carcinoembryonic antigen.

BACKGROUND: A second-generation panel of anti-carcinoembryonic antigen (CEA) monoclonal antibodies (MoAb) has been generated, and the specificity has been compared with that of the first panel of MoAb used to differentiate meconium antigen (MA) from CEA. METHODS AND RESULTS: Four of the MoAb had similar specificities to the first-generation panel of NP MoAb. MN-15, like its first-generation equivalent, NP-1, reacts with normal cross-reactive antigen (NCA), MA, and CEA; both MN-15 and NP-1 react strongly with granulocytes. MN-2 has properties similar to Class II NP-2, being reactive with MA and CEA, cross-blocking binding to CEA by NP-1, and having low reactivity with granulocytes; both NP-2 and MN-2 stain granulocytes in frozen tissue sections but show minimal staining of granulocytes in sections fixed in formaldehyde solution and embedded in Paraplast (Fischer Scientific, Pittsburgh, PA). MN-14 demonstrates properties similar to the Class III anti-CEA-specific MoAb, NP-4, being unreactive with NCA and MA. MN-14, as compared with NP-4, demonstrated significantly superior tumor targeting in a human colon tumor xenograft model and consistently stronger staining of frozen sections of colon cancer. A fifth MoAb, MN-3, had properties uniquely different from the NP series of MoAb, reacting strongly with granulocytes but not demonstrating the liquid-phase ion-sensitivity binding of CEA exhibited by MN-15 and NP-1. CONCLUSIONS: MN-14 is being evaluated for radioimmunodetection of and radioimmunotherapy for CEA-containing cancers, whereas MN-3 is being studied for the radioimmunodetection of occult infections and sites of inflammation.

Animals↗

PubMed1994

A peptide-based bifunctional chelating agent for 99mTc- and 186Re-labeling of monoclonal antibodies.

BACKGROUND: The development of new bifunctional chelating agents for the labeling of monoclonal antibodies with radiometals is a desirable goal in the area of radioimmunodetection and radioimmunotherapy of cancer. The authors have developed a new N3S-ligand, N-(S-acetylmercaptoacetyl) (p-NCS)phenylalanylglycylglycine ethyl ester (MAIPGG) for technetium-99m (99mTc) or rhenium-186 (186Re) labeling of monoclonal antibody D612 reactive with human colon cancer. The biodistribution of 99mTc/186Re-MAIPGG-D612 conjugates was studied in nude mice bearing human colon cancer xenografts. METHODS: MAIPGG was synthesized from Boc-p-nitrophenylalanine and was coupled to antibody D612, and the conjugate was labeled with 99mTc using a Glucoscan kit (DuPont, North Billerico, MA) as the reducing system. 186Re-MAIPGG-D612 was prepared by radiolabeling MAIPGG with 186Re, with sodium citrate/SnCl2 used as a reducing system, after which the raiolabeled MAIPGG was coupled to monoclonal antibody D612. The biodistribution of these radioimmunoconjugates in athymic nude mice bearing LS174T human colon cancer xenografts was studied. RESULTS: The cold precursor MAIPGG was prepared easily from Boc-p-nitro phenylalanine with an overall yield of 12-15%, which, when coupled to monoclonal antibody D612, did not affect its binding activity to LS174T cells in vitro. The biodistribution and imaging results demonstrated that these radioimmunoconjugates localized preferentially in tumor. CONCLUSIONS: These preliminary results suggest that MAIPGG may be useful for the radiolabeling of a variety of monoclonal antibodies with 99mTc or 186Re, which then can be used for radioimmunodetection and radioimmunotherapy of cancer.

Animals↗

PubMed1990

Radioimaging of human glioma xenografts with 123I labeled monoclonal antibody G-22 against glioma-associated antigen.

Monoclonal antibody (MCA) G-22 is directed against a human glioma-associated surface antigen. Its availability for the radioimmunodetection of human glioma was analyzed by utilizing the xenografts in athymic mice. Nude mice with subcutaneous grafts of U251-MG or U251-SP glioma received intravenous administration of 123I or 131I labeled F(ab')2 fragment or whole immunoglobulin. Results of radioimaging revealed that 123I-labeled antibody was better than the 131I-labeled. It was also noted that administration of 123I-labeled F(ab')2 fragment of G-22 MCA enabled the imaging of human glioma xenografts weighing 80-650 mg after 48 hours. When biodistribution of 123I MCA was compared between G-22 and control antibodies, the percentages of dose/g in tumors were 5.228-1.799 at 30 hours and 4.112-1.132 at 48 hours with G-22 and they were 4.164-1.248 and 0.314-0.142 with control. The tumor/blood ratio until 72 hours after injection was constantly above 1 with G-22 and less than 1 with control antibody. These results indicate the potential usefulness of G-22 MCA for the radioimmunodetection of human gliomas.

Animals↗

PubMed1988

Imaging pattern of previously in vitro sensitized and interleukin-2 expanded autologous lymphocytes in human cancer.

In vivo patterns of lymphocytes sensitized against autologous tumor (in vitro) were studied in seven patients with metastatic cancer as a potential candidate for an alternative method of radioimmunodetection and adoptive immunocytotherapy. Peripheral blood lymphocytes (PBL) were either activated in Interleukin-2 (IL-2) [lymphokine activated killer (LAK) cells] or sensitized against autologous tumor cells by in vitro co-culture (IVC) and expanded in IL-2 (educated cells); both were then labelled with 111In. Labelled autologous cells (1 x 10(7)-5 x 10(8)) were administered to patients and biodistribution studied by imaging under a gamma camera at various time intervals. In 4/7 cases, imaging with the educated cells showed concentrations of radioactivity at sites that correlated positively with clinically detectable metastatic tumor. By contrast, only one instance of positive uptake was seen with the LAK cells. Other than slight fever in three cases, infusions of labelled PBL were well tolerated. Educated lymphocytes were cytotoxic against autologous tumor cells and the cytotoxic reactivities of the educated cells were maintained in continuous culture in IL-2 for 4-6 weeks. Evidence of accumulation of radiolabelled educated autologous cells at a significantly higher frequency than that of the LAK cells suggests that in vitro expanded educated PBL might be better candidates for radioimmunodetection of human cancer, and continuous cultures of such educated autologous PBL might be sources for repeated administration of these effector cells.

Adult↗

PubMed2005

In vitro and in vivo targeting properties of iodine-123- or iodine-131-labeled monoclonal antibody 14C5 in a non-small cell lung cancer and colon carcinoma model.

PURPOSE: The monoclonal antibody (mAb) 14C5 is a murine IgG1 directed against a yet undefined molecule involved in cell substrate adhesion found on the surface of malignant breast cancer tissue. mAb 14C5 is able to inhibit cell substrate adhesion and invasion of breast cancer cells in vitro. In normal tissues as well as in the stroma surrounding in situ carcinomas of the breast, no expression of the antigen 14C5 occurs. The aim of this study was to investigate the in vitro and in vivo targeting properties of 123I- and 131I-labeled mAb 14C5 as a novel agent for radioimmunodetection and radioimmunotherapy. EXPERIMENTAL DESIGN: Internalization of mAb 14C5 was investigated with 125I-labeled mAb 14C5 and by confocal laser scanning microscopy. Biodistribution studies of 131I-labeled mAb 14C5 and planar gamma imaging were done in nude mice bearing an A549 (non-small cell lung carcinoma) or a LoVo (colon carcinoma) tumor. RESULTS: Internalization studies with both A549 and LoVo cells showed that 125I-labeled mAb 14C5 is slowly internalized with approximately 30% of the initially bound mAb 14C5 internalized after 2 hours at 37 degrees C. Internalization of mAb 14C5 could be visualized with confocal laser scanning microscopy. In vivo, radioisotope uptake peaked at 24 hours for both tumor models (n = 5) with no significant difference in percentage of injected dose/g tissue (A549 10.4 +/- 0.8 and LoVo 9.3 +/- 0.8). Via planar gamma camera imaging, A549 lung tumors as well as LoVo colon tumors could be clearly visualized. CONCLUSIONS: The in vitro and in vivo targeting properties of 123I- and 131I-labeled mAb 14C5 are promising and could provide a new antibody-based agent for radioimmunodetection and radioimmunotherapy of patients bearing antigen 14C5-expressing tumors.

Animals↗

PubMed1991

Initial clinical study of indium-111-labeled clone 110 anticarcinoembryonic antigen antibody in patients with colorectal cancer.

A murine monoclonal antibody directed against carcinoembryonic antigen (CEA) was labeled with indium-111 (111In) by means of a benzylisothiocyanate derivative of diethylenetriamine penta-acetic acid (DTPA) and used for clinical radioimmunodetection studies. Twenty-one patients having a history of surgically resected colorectal cancer and rising serum CEA levels suggestive of tumor recurrence were studied. Patients were infused over 20 minutes with 5, 10, or 20 mg of the monoclonal antibody labeled with 5 mCi of 111In. The mean radiochemical purity was greater than 96%. No toxicity was seen. The stability of the radiolabel on antibody in patient serum was demonstrated by high-performance liquid chromatography (HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with autoradiography, and immunoprecipitation for up to 96 hours after infusion. Tumor sites were identified in 20 of 21 patients. Sites of antibody accumulation in 20 patients were confirmed as tumor either by resection at laparotomy (16 patients) or fine-needle biopsy (four patients). Nine patients who had the identified lesion resected or irradiated showed return of the serum CEA antigen level to normal or near normal values. In the absence of high levels of circulating CEA (greater than 500 ng/mL), the disappearance of radioactivity from patient serum demonstrated first order elimination kinetics, with a mean half-life of 38 hours. The serum half-life was not affected by the dose of antibody administered or by serum CEA titers below 500 ng/mL. Despite a mean liver uptake of 18% injected dose (ID) 24 hours after administration, hepatic metastases were easily visualized as areas of increased uptake of radioactivity. Radioimmunodetection of recurrent colorectal cancer, not detected by computed tomographic (CT) scans, appears achievable with this agent. This may allow successful clinical intervention in selected patients.

Adult↗

PubMed1986

Clinical applications of monoclonal antibody technology.

Although monoclonal antibody technology has only been with us for slightly more than 10 years, it has already had a great impact on both basic science and clinical medicine. The ability to use these antibodies as highly specific and sensitive reagents that are consistent from batch to batch is invaluable. Because of this ability, monoclonal antibodies are assuming an ever more important role in laboratory assays. In addition, immunohistochemical techniques employing monoclonal antibodies enhance the histologic characterization of pathologic specimens. These clinical benefits are real but are often hidden from the eyes of the physician taking care of his patient. However, other newer uses of monoclonal antibodies are much more spectacular. Clinical imaging with monoclonal antibodies has been shown to be feasible in a variety of systems. Antibodies to colon cancer and melanoma have detected metastatic tumors that were otherwise hidden clinically. Despite these triumphs, the routine use of radioimmunodetection employing radiolabeled monoclonal antibodies has not yet arrived. However, the preliminary data obtained so far are very promising, and radioimmunodetection may well serve to be an important method for diagnosing a variety of cancers in the near future. Immunotherapy is actively being explored in a number of centers but at this stage is strictly experimental. Whether this will be an important addition to our therapeutic armamentarium should be defined over the next several years. The monoclonal antibodies that are currently used for clinical studies are murine, that is, they are mouse antibodies. Although these antibodies have been well tolerated in a number of studies, human monoclonal antibodies would be theoretically more desirable. Preliminary efforts to produce human monoclonal antibodies reactive with tumor-associated antigens have been reported. Future directions of monoclonal antibody technology will employ greater production of human monoclonal antibodies. In addition, the evaluation of antibody conjugates for clinical diagnosis and therapy will continue to be explored.

Antibodies, Monoclonal↗

PubMed1984

Carcinoembryonic antigen production, secretion, and kinetics in BALB/c mice and a nude mouse-human tumor model.

Carcinoembryonic antigen (CEA) is currently being used as a target antigen in the radioimmunodetection of cancer. Circulating CEA may adversely affect the outcome of such studies by formation of intravascular immune complexes. The following studies were undertaken to expand our knowledge of the production, secretion, and pharmacokinetics of CEA, since these factors should have a direct bearing on the serum levels of CEA encountered in radioimmunodetection. The production of CEA was assessed in nude mice given implants of the T-380 CEA secreting human colon tumor. Serum CEA rose linearly as the tumors enlarged; however, the concentration of CEA per g of extracted tumor remained constant throughout the weight range studied. The secretory rate of the T-380 tumor was determined by surgically removing all blood flow to the liver and gastrointestinal tract of the nude mouse model. This procedure removes the known sites of CEA degradation. Serum CEA levels rose progressively following surgery, the values being directly related to the tumor size. The secretory rate was also proportional to tumor size but was a constant 13.8 +/- 3.6 (S.D.) ng/g tumor/hr when expressed on a per g tumor basis. To determine if the serum levels of CEA observed in patients could be due to unique differences in the clearance rates of each patient's CEA, serum from three patients with CEA levels of 2150, 709, and 58 ng/ml was administered i.v. to groups of mice at the original and diluted concentrations. The kinetics of all samples followed a single exponential clearance pattern with a half-time of about 2.5 hr. This was dramatically different from the kinetics of tumor-extracted CEA which exhibited a multiexponential pattern, the first component having a half-time of 3 min. These data suggest that CEA secreted by a tumor is in some way different from that adhering to the tumor. If the secreted CEA truly has a monoexponential clearance with a fixed rate as the experiments suggest, the absolute values of serum CEA are either entirely a function of the tumor secretory rate, or else the product having the short half-time is not measured in serum samples obtained from patients.

Animals↗

PubMed1984

Diagnosis of and therapy for solid tumors with radiolabeled antibodies and immune fragments.

Antibodies which are directed against human tumor-associated antigens can potentially be used as carriers of radioactivity for in vivo diagnosis (radioimmunodetection) or treatment (radioimmunotherapy) of solid tumors, including colon, hepatoma, cholangiocarcinoma, and melanoma. Murine monoclonal antibodies (MOAB), produced by the hybridoma technique of Kohler and Milstein, are replacing conventional heterosera as sources of antibodies, because MOAB can be produced in large quantities as reproducible reagents with homogeneous binding properties. We have studied human melanoma using MOAB IgG and Fab fragments that recognize the human melanoma-associated antigens p97 and "high-molecular-weight antigen." Both antigens are found in the membrane of melanomas at much larger concentrations than in normal adult tissues. We have performed radioimmunodetection studies with whole immunoglobulin and have detected 88% of lesions greater than 1.5 cm. We have used Fab fragments for radioimmunotherapy and have found that large doses of radiolabeled antibodies (up to 342 mCi) can be repetitively given to patients without excessive end-organ toxicity. Two of three patients treated with high-dose radiolabeled antimelanoma Fab showed an effect from the treatment. Although both technical and biologic problems remain, the use of radiolabeled antibodies that are directed against tumor-associated antigens holds future promise as a new therapeutic approach to solid tumors that are resistant to conventional therapy.

Animals↗

PubMed1991

Detection of squamous cell carcinoma xenografts in nude mice by radiolabeled monoclonal antibody E48.

We recently produced the monoclonal antibody E48 as a specific reagent for squamous cell carcinomas. In our ongoing investigations to use E48 for clinical tumor detection and therapy, fundamental aspects of the antigen have to be elucidated and practical applications of the antibody have to be tested in a preclinical model. Immunoelectron-microscopic studies localized the E48 antigen along the cell surface and in between desmosomes, suggesting that the antigen serves as an adhesion molecule. To evaluate the usefulness of E48 for radioimmunodetection of neck node metastases, nodes from 20 neck dissection specimens were tested. A strong reactivity was observed. Furthermore, F(ab')2 fragments of E48 were compared with the complete IgG E48 for selective tumor detection in an animal model. It was demonstrated that E48 F(ab')2 fragments localize faster and reach higher tumor-nontumor ratios than the whole molecule.

Animals↗

PubMed1992

99mTc-IMMU-4 monoclonal antibody scan in colorectal cancer. A prospective study.

A blinded prospective study of 34 patients with colorectal adenocarcinoma using the Fab' fragment of the anticarcinoembryonic antigen monoclonal antibody type IMMU-4 labeled with technetium 99m was conducted to compare, on a lesion-by-lesion basis, the findings of radioimmunoscintigraphy, preoperative computed tomography, and exploratory celiotomy. Of 115 lesions detected at surgery, 113 were adenocarcinoma. Radioimmunoscintigraphy detected 59 lesions and computed tomography detected 62; both studies combined detected 72. Twenty-nine (54%) lesions missed by radioimmunoscintigraphy and 24 (45%) missed by computed tomography were 1 cm or smaller. When both studies were combined, the sensitivities were 90%, 24%, and 42%, and the specificities were 52%, 86%, and 61% for hepatic, extrahepatic intra-abdominal, and pelvic lesions, respectively. In 10 patients, additional information obtained with the radioimmunoscintigram could have altered the treatment of these patients. In this study, radioimmunodetection scan was complementary to computed tomographic scan in the examination of patients with colorectal carcinoma.

Adenocarcinoma↗

PubMed1998

Role of radioimmunolocalization in the staging of gastric carcinoma.

Intraoperative radioimmunolocalization is a potentially useful technique for staging gastric neoplasms without resorting to extensive surgical intervention. Before preoperative immunohistochemical typing for the presence or absence of tumor-associated glycoprotein (TAG) 72, we performed intraoperative radioimmunodetection on three patients presenting with gastric carcinoma using a whole monoclonal antibody (B72.3) marked with Indium-111 injected 1 week before operation. The results were calculated on the number of lymph node stations and yielded a high sensitivity due to a specificity of 72% and the absence of false negatives. Intraoperative radioimmunolocalization is a promising method for noninvasive staging of both early and advanced gastric carcinoma.

Antibodies, Monoclonal↗

PubMed1998

Radioimmunoguided surgery in colorectal cancer: a 6-year experience with four different technical solutions.

Intraoperative radioimmunodetection is a new staging technique for epithelial neoplasms. After intravenous injection, a radioimmunoconjugate compound (monoclonal antibody and isotope) attaches itself to the antigens expressed on the surface of neoplastic cells, causing them to emit gamma rays. Radioactivity is detected at the presurgical stage by immunoscintigraphy and intraoperatively with a gamma-detecting probe (GDP). In our experience, intraoperative tumor-to-normal-tissue (T/NT) GDP ratio counts > or =3:1 were considered positive radioimmunoguided surgery (RIGS) findings. We studied 52 colorectal cancer patients, 48 with primary lesions and 7 with relapses. Positive RIGS findings were obtained in 33 patients whose lymph node assessments were characterised by eight false positive identifications. In 10 patients, RIGS data yielded a more accurate staging of the disease. Unreliable RIGS findings were recorded in 15 patients: four injected with monoclonal antibody (MAb) B72.3 labeled with Iodine-125; five with MAb anti-carcinoembryonic antigen (CEA) labeled with 99mTechnetium (Tc); two with MAb B72.3 labeled with Indium-111; and three with MAb B72.3 labeled with Iodine-131 plus interferon-beta. In analysis, our experience did not permit definitive evaluation of the method's diagnostic and staging accuracy.

Adolescent↗

PubMed1995

Characterization and biodistribution of a mouse/human chimeric antibody directed against pancreatic cancer mucin.

BACKGROUND: Nd2 is a murine monoclonal antibody (MoAb) directed against purified mucins of the human pancreatic cancer cell line SW1990. The authors previously reported promising results with Nd2 for immunotargeting pancreatic cancer. However, murine MoAbs induce human anti-mouse antibodies (HAMAs), a serious problem for clinical use. Mouse/human chimeric antibodies may be less immunogenic and therefore reduce the incidence of HAMAs. In this study, the binding affinity, tumor specificity, biodistribution, and immunoimaging of chimeric Nd2 were evaluated. METHODS: The affinity of chimeric Nd2 was evaluated by competition radioimmunoassay and Scatchard analysis using 125I-chimeric Nd2, 125I-murine Nd2, and SW1990 mucin. Immunoreactivity against pancreatic cancer tissues was examined histochemically by the avidin-biotin peroxidase complex method. The biodistribution of the MoAbs was examined in athymic nude mice bearing SW1990 xenografts that were administered intravenous 125I-labeled chimeric or murine Nd2. 111In-chimeric Nd2 was injected into the same xenograft models, and scintigrams were obtained on day 3. RESULTS: Affinity analysis and immunohistochemical studies showed that chimeric Nd2 had the same affinity to SW1990 mucin and the same specificity for pancreas cancer tissues as murine Nd2. Intravenous administration of 125I-chimeric Nd2 resulted in a maximum tumor accumulation of 43% of the initial dose/gram of tumor, which was almost identical to the accumulation of 125I-murine Nd2. Distinct immunoscintigrams of tumors in nude mice were obtained with 111In-chimeric Nd2. CONCLUSION: Chimeric Nd2 may have clinical potential in the radioimmunodetection and immunotherapy of pancreatic cancer.

Animals↗

PubMed1995

Monoclonal antibodies used in the detection and treatment of epithelial ovarian cancer.

Conventional therapy for epithelial ovarian cancer, including aggressive cytoreductive surgery followed by combination chemotherapy regimens, has failed to reduce the number of deaths caused by this disease, which remains the most lethal of gynecologic malignancies. Monoclonal antibodies, which offer the promise of high selectivity for detection and therapy, may be targeted to tumor-associated antigens, growth factors, receptors, or oncogenes. They may be used alone as immunotherapeutic agents or conjugated to chemotherapeutic drugs, toxins, or radionuclides. Radioimmunoconjugates may also be used for preoperative or intraoperative tumor localization. The authors focused on the clinical utility, technical limitations, and potential of monoclonal antibodies in the detection and treatment of epithelial ovarian cancer with emphasis on radioimmunodetection and radioimmunotherapy.

Antibodies, Monoclonal↗

PubMed1997

Binding of a human monoclonal antithyroglobulin antibody to cultured human thyroid cancer cells.

To develop a new method of radioimmunodetection for thyroid cancer, we tested the binding ability of a human antithyroglobulin monoclonal antibody, VB5, to primary culture of human thyroid cancer cells. VB5 was able to immunostain cytoplasmic thyroglobulin (Tg) in the acetone-fixed cancer cells when used in a labeled streptavidin-biotin method but not in a conventional indirect immunoperoxidase technique. The antibody was readily labeled with I-125 in the standard chloramin-T method, and showed specific binding to the antigen on cultured malignant thyrocytes displaceable with non-labeled VB5 or with excess Tg antigen. Although these initial results in vitro are encouraging, the observed low specific binding (about 1% at room temperature) to intact cells with a single monoclonal antibody seems insufficient to conduct any in vivo immunolocalization experiments in animals. To obtain more binding, we would need a cocktail of several monoclonal antibodies to different epitopes, and also fragmentation of antibody molecules to penetrate into cytoplasm.

Antibodies, Monoclonal↗

PubMed1996

99mTc-CD19 monoclonal antibody is not useful for imaging of B cell non-Hodgkin's lymphoma.

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

Adult↗