Whole-body Autoradiography of Tumor-bearing Hamsters with a New Tumor Imaging Agent, Indium-111-labeled Porphyrin

We have synthesized a new tumor imaging agent, ¹¹¹In-labeled porphyrin (¹¹¹In-ATN-2). In order to image transplantable pancreatic carcinoma in Syrian golden hamsters, we investigated the biodistribution of ¹¹¹In-ATN-2 72 hr after injecting the agent by means of whole-body autoradiography. The efficacy of the agent was compared with that of ⁶⁷Ga citrate. The images with ¹¹¹In-ATN-2 were found to be clearer than those with ⁶⁷Ga citrate. Tumor-to-tissue radiodistribution ratios of the former were higher than those of the latter. Thus, ¹¹¹In-ATN-2 seems to be more useful for tumor diagnosis.     

67Ga-枸橼酸盐用于肺癌显像的诊断分析

目的　探讨６７Ｇａ－枸橼酸盐在肺癌诊断中的应用价值。方法　对１８４ 例住院病人进行了６７Ｇａ的胸部显像。病人均经穿刺活组织检查,手术切除或其他方法获得病理结果,其中肺癌１２７例,良性病变５７ 例。结果　在１２７ 例肺癌中,６７Ｇａ显像阳性１０１ 例,显像阴性２６ 例;５７ 例良性病人中,阳性１２ 例,阴性４５ 例。６７ Ｇａ在肺癌诊断中的显像灵敏度、特异性和准确率分别为７９．５％ 、７８．９％ 和７９．３％ 。阳性预测率８９．４％ ,阴性预测率６３．３％ 。其灵敏度与肿瘤类型及肿块大小有关。结论　６７Ｇａ——枸橼酸盐在用于肺部疾病,尤其在肺癌诊断中具有较好的应用价值。     

Tumor imaging using 201Tl chloride and 67Ga citrate in nucleomedical surveys]

Among nucleomedical examinations for cancer, tumor imaging using 201Tl chloride and 67Ga citrate can be easily performed at almost any hospital. However, the planar images usually obtained are not sufficient to detect small tumorous lesions. For more accurate detection, tomographic images particularly single photon emission CT (SPECT) is necessary. SPECT is also indispensable in cancer diagnosis. Whether 201Tl SPECT or 67Ga SPECT is chosen depends upon tumor localization, histological type, and the final purpose of the study. 201Tl accumulates in almost all tumors, but it is not suitable for detection of abdominal lesions, because there is much physiological accumulation in the small intestine and kidney. In contrast, 67Ga does not always accumulate in adenocarcinomas. 201Tl SPECT and 67Ga SPECT are more useful in the functional imaging of cancer than is morphological tumor diagnosis. Both methods are useful in monitoring treatment effectiveness, detecting recurrent lesions after surgery and radiotherapy, and predicting the grade of malignancy of the tumor. Tumor SPECT using 201Tl chloride and/or 67Ga citrate provides clinically useful information not obtained by morphological tumor diagnosis only.     

Differential diagnosis of AH109A tumor and inflammation by radioscintigraphy with L-[methyl-11C]methionine

For the evaluation of tumor imaging with L-[methyl-11C]methionine (11C-Met), a basic study on the differentiation of tumor from inflammation with 11C-Met and a comparison of the diagnostic value of the image with that obtained using 67Ga citrate, a conventional scintigraphic agent, are important. 11C-Met accumulations into inflammatory lesions, AH109A tumor and normal tissues of rats were examined by means of a tissue distribution study. Aseptic inflammatory lesions on the back of Donryu rats induced by croton oil and 1.5% carrageenan showed significantly lower accumulations of 11C-Met than the AH109A tumor. Histologically, croton oil induced granulomatous inflammation and carrageenan, acute exudative inflammation. Whole-body autoradiography with 14C-Met, a substitute for 11C-Met, was negative in the carrageenan lesion and showed a slightly increased activity at the periphery of the croton oil lesion, in contrast with the high tumor activity. Whole-body autoradiography with 67Ga citrate was performed to compare the imaging ability with that of 14C-Met; it showed high activities in the tumor, bone, and intestine, and a broad increased activity at the periphery of the croton oil lesion, but was negative in the carrageenan lesion. 11C-Met accumulations in the inflammations were very low and clinical application with positron emission tomography, should be useful for the differential diagnosis of tumor from inflammation.     

Human sarcoma-associated murine monoclonal antibody labeled with indium-111, gallium-67, and iodine-125

Monoclonal antibody (MAb) 23H7 is a hybridoma-derived IgG that is generated following fusion of mouse myeloma cell line P3U1 and spleen cells from BALB/c mice hyperimmunized with a human fibrosarcoma. It detects a mesenchymal antigen of 23KD expressed on human sarcoma tissues and other neoplasms, including myeloid leukemias, but it rarely binds to normal tissues. The MAb 23H7 was labeled with 67Ga and 111In using the bifunctional ligand method. The 67Ga was chelated to the MAb via desferrioxamine B, while 111In was chelated via the cyclic anhydride of diethylenetriamine pentaacetic acid. Higher specific activity was obtained with 67Ga than with 111In (4.5 and 2 muCi/microgram, respectively); both gave stable complexes. When 23H7 was labeled with 125I, considerable breakdown was observed. This, together with the physical shortcomings of this isotope, emphasizes the advantages of labeling with 111In and 67Ga. The rapid blood clearance of the labeled sarcoma-associated MAb may be beneficial for early tumor uptake and for imaging shortly after injection.     

Neuroendocrine tumor targeting: study of novel gallium-labeled somatostatin radiopeptides in a rat pancreatic tumor model

Somatostatin analogs labeled with radionuclides are of considerable interest in the diagnosis and therapy of SSTR-expressing tumors, such as gastroenteropancreatic, small cell lung, breast and frequently nervous system tumors. In view of the favorable physical characteristics of the Ga isotopes (67)Ga and (68)Ga, enabling conventional tumor scintigraphy, PET and possibly internal radiotherapy, we focused on the development of a Ga-labeled somatostatin analog suitable for targeting SSTR-expressing tumors. For this purpose, 3 somatostatin analogs, OC, TOC and TATE were conjugated to the metal chelator DOTA and labeled with the radiometals (111)In, (90)Y and (67)Ga. They were then evaluated for their performance in the AR4-2J pancreatic tumor model by testing SSTR2-binding affinity, internalization/externalization in isolated cells and biodistribution in tumor-bearing nude mice. Surprisingly, we found that, compared to (111)In or (90)Y, labeling with (67)Ga considerably improved the biologic performance of the tested somatostatin analogs with respect to SSTR2 affinity and tissue distribution. (67)Ga-labeled DOTA-somatostatin analogs were rapidly excreted from nontarget tissues, leading to excellent tumor-to-nontarget tissue uptake ratios. Of interest for radiotherapeutic application, [(67)Ga]DOTATOC was strongly internalized by AR4-2J cells. Furthermore, our results suggest a link between the radioligand charge and its kidney retention. The excellent tumor selectivity of Ga-DOTA somatostatin analogs together with the different applications of Ga in nuclear oncology suggests that Ga-DOTA somatostatin analogs will become an important tool in the management of SSTR-positive tumors.     

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.     

Labeling of sarcoma associated monoclonal antibody with 111In, 67Ga and 125I

Labeling of human sarcoma-associated murine monoclonal antibody (MAb) 23H7 with 67Ga and 111In by the bifunctional ligand method is reported. 67Ga was chelated to the MAb via desferrioxamine B and 111In via the cyclic anhydride of DTPA. Higher specific activity was obtained with 67Ga (4-5 microCi/micrograms) as compared with 111In (2 microCi/micrograms). The binding capacity of the MAb was confirmed by repeated indirect immuno-fluorescence assays performed before and after labeling. A fast blood clearance was observed: 33% recovered dose (R.D.) blood level 3 h post-injection as compared with 56% after injection of control polyclonal IgG. Preliminary results on chemically induced sarcoma bearing mice showed a relatively high tumor uptake of the labeled antibody.     

The gallium-67 scan in clinical assessment of cancer

By 1 April 1973, 770 patients with malignancy were studied using Gallium-67 (⁶⁷Ga) citrate radioisotopic scanning at the Clinical Center, National Institutes of Health. Of these, 21 had brain tumors, 19 (90%) of which concentrated ⁶⁷Ga. Forty-four patients with melanoma had 54% of proven sites visualized on ⁶⁷Ga scan (masses larger than 2 cm were detected in 75% of the sites). Ewing's sarcoma was studied in 15 patients with ⁶⁷Ga scanning and all 15 primary tumors were visualized. Thirty-two of 43 scans performed on 30 patients with acute leukemia were abnormal. Sites of leukemic involvement in bone marrow and as myeloblastomas in soft tissue contained high levels of ⁶⁷Ga. Patients with untreated Hodgkin's disease were abnormal in 90% of cases on ⁶⁷Ga scan with 70% of proven sites of involvement being detectable. Sixty percent of non-Hodgkin's lymphoma sites were detected on ⁶⁷Ga scans. Approximately 85% of anatomic sites involved with lung cancer were detected on scan. ⁶⁷Ga citrate whole body scanning has proven to be useful in diagnosing and staging a wide variety of human tumors. The ⁶⁷Ga study is most reliable when positive findings are recorded, but should be approached with caution when the findings are negative.     

Common pathway for tumor cell uptake of gallium-67 and iron-59 via a transferrin receptor

We studied the tumor uptake of [67Ga]citrate, [59Fe]citrate, and 125I-labeled transferrin (TF) by the in vitro growth form of EMT-6, a sarcoma-like mammary tumor of BALB/c mice. In analyzing the binding experiments, we developed a new mathematical model based on a formulation originally used to express the interaction of hormones with specific tissue receptors. The uptake of both carrier-free 67Ga and 59Fe by tumor cells was mediated by kinetically identical TF receptors. We also studied teric acid extracts of the stroma of EMT-6 tumors grown both in vivo and in vitro. Chromatography of these extracts on Sephacryl S-200 SF demonstrated that the cellular stroma contained specific TF-binding macromolecules. On the basis of these findings, we proposed the "transferrin receptor hypothesis" for the mechanism of 67Ga uptake by tumors. According to this view, a tumor-associated TF receptor is the functional unit responsible for the affinity of gallium for certain neoplasms. This receptor was also active in the uptake of iron by tumors.     

Image diagnosis: nuclear medicine

Delineation of malignant tumor by scintigraphy is divided into two categories; visualizing tumor as positive foci or negative foci. Our clinical experiences with 67Ga, 201Tl, 131I-MIBG and 131Imonoclonal antibodies including 111In-ZMEO18 were described and literatures relevant to positive delineation of malignant tumor were reviewed.     

Malignant lymphoma of the ileum

A 53-year-old man with malignant lymphoma of the ileum is reported. He was admitted to our hospital because of lower abdominal discomfort. 67Ga citrate radionuclide imaging revealed an abnormal round uptake in his lower abdomen. CT scans showed an abnormal soft tissue density mass and a remarkably dilated small intestine in the pelvis. X-ray studies of the small intestine revealed a giant diverticulum-like lesion. Angiograms showed a hypovascular tumor with irregularity of the small vessels. A resected specimen revealed non-Hodgkin's malignant lymphoma, diffuse large-cell type. 67Ga citrate radionuclide imaging was useful in screening for neoplastic lesions in the small intestine because of its easiness and safety.     

Preparation and properties of antitumor monoclonal antibodies labeled with metallic radionuclides indium-111, gallium-67, and technetium-99m

In this study, metallic radionuclides such as 111In, 67Ga, or 99mTc produced clear visualization in scintigraphic imaging of tumors; they have short half-lives and can easily be used in the radiolabeling of monoclonal antibodies by using bifunctional chelating agents. Under selected conditions, these radiolabeled antibodies were stable both in vitro and in vivo with no loss of the antigen-binding activity. Despite high background imaging of the liver and kidney, transplanted tumors in nude mice were clearly visualized with 111In-, 67Ga-, and 99mTc-labeled antibodies at 6, 24, or 48 hours after the injection. Although tissue distribution in the liver, kidney, and bone was different among radionuclides used for the labeling, all tumor to blood ratios were higher than those of radioiodinated monoclonal antibodies. These results provide a good basis for studies of the clinical usefulness of 111In-, 67Ga-, and 99mTc-labeled monoclonal antibodies for radioimmunoimaging.     

Use of simultaneous double-tracer SPECT with 99m-Tc-technetril and 67-Ga-citrate for follow-up of patients with non-small cell lung cancer

In 20 primary patients with focal abnormalities on conventional CT we evaluated diagnostic properties of simultaneous double-tracer SPECT. Scintigraphy was performed as a single examination with simultaneous registration of 67Ga and 99mTc-MIBI. Image acquisition was started 48-74 hours after IV injection of 130-175 MBq 67Ga-citrate and immediately after IV injection of 500-740 MBq of 99mTc-MIBI. All images for each agent were classified as positive and negative for primary tumor, N1 and N2 lymph-nodes (LN). According to histology 18 of 20 evaluated patients had non-small cell lung cancer (NSCLC), the other two patients had tuberculosis and nonspecific inflammation. SPECT with 99mTc-MIBI correctly visualized tumor in 18, 67Ga allowed correct visualization in 16 cases. Both tracers were truly negative in a patient with tuberculosis and false positive in a patient with nonspecific inflammation. Double-tracer SPECT was slightly more specific than CT in primary lesions. In 18 patients histological verification of LN status was obtained: NO was revealed in 9 cases, N1 in 4 and N2 in 5 cases. Both tracers correctly discriminated LN-positive and LN-negative cases with 94% specificity. On the contrary, CT was false-positive in 3 and false-negative in another 5 patients. Differentiation between N1 and N2 LN involvement is crucial for therapy planning. 99mTc MIBI and 67Ga revealed N1 in 2 cases and N2 in 4 cases, the diagnosis was later verified by postoperative morphology. In 2 patients SPECT overestimated extent of LN involvement and LN status was changed after surgery from N2 to N1. In 18 patients results of 99mTc-MIBI and 67Ga augmented each other. Accuracy of LN staging by SPECT with 99mTc-MIBI and 67Ga was 83%. CT accurately determined LN stage only in 7 patients, it was overestimated in 7 and underestimated in 4 cases. SPECT with 99mTc-MIBI and 67Ga demonstrated high overall accuracy in diagnostics of regional LN invasion for patients with NSCLC. Diagnostic value of conventional CT was significantly lower. Correct level of LN involvement was determined by SPECT in 83% of cases.     

Transferrin promotion of 67Ga and 59Fe uptake by cultured mouse myeloma cells

Radiotracer 67Ga-citrate is used as a tumor-seeking agent in clinical imaging investigations although fundamental reasons for its high uptake in certain malignant lesions remain unexplained. The mechanism by which 67Ga becomes concentrated in tumor cells has been investigated by comparing 67Ga and 59Fe uptake by cultured mouse myeloma cells with particular reference to uptake stimulation by transferrin. Concentrations of human transferrin down to 2 microgram/ml greatly stimulated cellular uptake of both tracers, whereas bovine transferrin proved relatively inactive. The rates of stimulated uptake of both tracers were similar as was their high degree of retention by cells, but their quantitative dependencies on transferrin concentration showed characteristic differences. Pretreatment of human transferrin with saturating amounts of nonradioactive Fe3+ canceled its ability to promote 59Fe uptake, but it had little effect on its promotion of 67Ga uptake. Further increase in the amount of added Fe3+ did cause a progressive depression of 67Ga uptake, but this effect probably relates to the iron distribution in the whole-cell culture system including the fetal calf serum component of cell growth medium. The results suggest that 67Ga and 59Fe reveal different aspects of the interaction of transferrin with cells.     

Gallium-67 citrate scanning in Hodgkin's disease and non-Hodgkin's lymphoma.

Gallium-67 citrate scintigraphy was performed in 33 patients with Hodgkin's disease and 25 patients with non-Hodgkin's lymphoma. Three hundred twenty-eight sites of potential involvement were investigated. Confirmation of involvement was made by physical examination, roentgenographic evaluation and histopathologic examination of tissue obtained at diagnostic laparotomy. The results of scintigraphy correlated with all other clinicopathologic data in only 35% of patients, the true-positive rate being significantly higher above the diaphragm (61%) than below (40%). The overall true-positive and true-negative rates were 53 and 90%, respectively. A significant correlation existed between tumor histology and scanning accuracy; the true-positive rate in Hodgkin's disease was 74% compared to only 13% in patients with lymphocytic lymphoma. A similar variation of 67Ga concentration with tumor histology was also noted in 70 tissue specimens obtained from 28 patients at the time of diagnostic laparotomy or biopsy. The routine use of 67Ga-citrate to detect splenic involvement with tumor appeared to be precluded by the low true-positive and high false-negative rates of 57 and 27%, respectively. Gallium-67-citrate scintigraphy may be useful as an adjunct to established clinical staging procedures in untreated patients and in the detection of recurrent disease in treated patients. Our data indicate it is not sifficiently reliable to replace established methods presently used for clinical staging.     

Translation of dosimetric results of preclinical radionuclide therapy to clinical situations: influence of photon irradiation

The radionuclide evaluation for therapy starts with preclinical studies in, for example, mice and rats, and various radionuclides have shown promising results. However, many radionuclides emit photons that will irradiate normal tissues. The risk of normal tissue toxicity in patients (e.g., bone marrow suppression) may be underestimated when relying on preclinical results. To illustrate the influence of photons in preclinical and clinical trials, the ratio between the tumor-to-normal tissue absorbed-dose rate ratio (TND) was calculated for humans, rats, and mice for 111In, 125I, 67Ga, 90Y, 131I, and 177Lu. The normal tissues were simulated by 70-kg, 300-g, and 20-g ellipsoids for humans, rats, and mice, respectively. It was assumed that the radionuclides were uniformly distributed, and that the activity concentration was 25 times higher in the tumor than in the normal tissue. There were only small differences between the TND values for the different species for 90Y and 177Lu. 131I showed similar TND values for rats and mice, whereas they were lower for humans. For 111In, 125I, and 67Ga, however, there were large differences between the different species. The influence of photons may thus be much lower in preclinical studies than in clinical situations. Therefore, translations of absorbed doses from animals to humans must be performed with caution.     

The diagnosis of perifocal inflammation in cancer of the colon]

The study discusses the experience gained with application of a complex of methods for early diagnosis of perifocal inflammation in 50 patients with cancer of the colon. Endoscopic, roentgenologic and radionuclide (using 67Ga citrate) methods were mainly employed. Perifocal inflammation was established in 38 (76%) patients. The diagnosis was further confirmed by morphologic examination of resected material. Application of the methods assured early diagnosis of asymptomatic perifocal inflammation associated with tumor.     

High-dose gallium-67 therapy in patients with relapsed acute leukaemia: a feasibility study.

Gallium-67 (67Ga) accumulates in malignant tissues via the transferrin receptor without need for a monoclonal antibody and emits cytotoxic low-energy electrons. In this study we investigated the feasibility, pharmacokinetics, toxicity and preliminary efficiency of high-dose 67Ga injected intravenously (i.v.) in patients with acute leukaemia not responding to conventional therapy. Twelve doses of 36-105 mCi of Gallium67 citrate were administered as a push injection to eight patients with resistant leukaemia in a pilot study. All five patients with acute myeloid leukaemia (AML) and three patients with acute lymphoblastic leukaemia (ALL) had resistant disease or resistant relapse. No (sub)acute toxicity was observed. Independent of the administered dose, whole-blood radioactivity levels 10 min after administration measured only 1.25 +/- 1.39 microCi ml-1, indicating a large volume of distribution. Urine excretion in the first 24 h ranged from 18% to 51.5% (median 29.5%) of the administered dose. Cellular uptake of 67Ga was less than in previous in vitro studies. Whole-body radiation dose was estimated to be 0.25 +/- 0.03 cGy mCi-1. Red marrow dose was estimated to be between 0.18 +/- 0.02 and 0.97 +/- 0.12 cGy mCi-1. One definite response was observed in an ALL patient with disappearance of skin lesions, normalisation of the enlarged spleen and profound leucopenia. Three other patients showed transient reductions in white blood cell counts without disappearance of blasts from the peripheral blood. We conclude that high-dose i.v. 67Ga can be safely administered but that the uptake of 67Ga in blast cells must increase to make 67Ga therapeutically useful in patients with relapsed leukaemia.     

Role of 18F-FDG PET in tumor grading and evaluating effectiveness of therapy in malignant lymphomas

The report compares the results of (multi-layer spiral computed tomography) (MSCT), 67 Ga citrate lymph scintigraphy and 18FDG PET in patients with Hodgkin's disease. The predictive significance of the latter method exceeded that of MSCT and ultrasound in diagnosing lymph node neoplasia below the diaphragm. As far as peripheral and mediastinal lymph nodes are concerned, the MSCT efficiency of the three procedures was comparable. Advantage was offered by PET in early evaluation of therapeutic effectiveness. Moreover, its practical significance for assessing tumor sensitivity to therapy as well as differentiation between viable tumor tissue and fibrosis was demonstrated.