Diagnosis and treatment of neoplasms with radionuclide-labeled antibodies

Radioimmunotherapy Trials in Germ Testicular Carcinoma: A Phase I Study

Two patients with germ cell testicular cancer were submitted to radioimmunotherapy (RIT) by using the monoclonal antibody 131I-radiolabelled (MoAb) H17E2, raised against placental alkaline phosphatase (PLAP).

Both patients had been previously treated with repeated chemotherapy regimens assisted by autologous bone marrow transplant (ABMT), that, in the end were unsuccessful, thus necessitating further experimental treatment.

RIT was well tolerated and the targeting of multiple neoplastic lesions was satisfactory. Nevertheless, the clinical results of treatment were minimal owing to the extension of the tumour.

The data obtained suggest the possibility of applying this form of treatment in patients with minimal residual disease after previous traditional chemotherapy regimens.

In vivo molecular targeted radiotherapy

Unsealed radionuclides have been in clinical therapeutic use for well over half a century. Following the early inappropriate clinical administrations of radium salts in the early 20th century, the first real clinical benefits became evident with the use of ¹³¹I-sodium iodide for the treatment of hypothyroidism and differentiated thyroid carcinoma and ³²P-sodium phosphate for the treatment of polycythaemia vera. In recent years the use of bone seeking agents ⁸⁹Sr, ¹⁵³Sm and ¹⁸⁶Re for the palliation of bone pain have become widespread and considerable progress has been evident with the use of ¹³¹I-MIBG and ⁹⁰Y-somatostatin receptor binding agents. Although the use of monoclonal antibody based therapeutic products has been slow to evolve, the start of the 21st century has witnessed the first licensed therapeutic antibody conjugates based on ⁹⁰Y and ¹³¹I for the treatment of non-Hodgkin's lymphoma. The future clinical utility of this form of therapy will depend upon the development of radiopharmaceutical conjugates capable of selective binding to molecular targets. The availability of some therapeutic radionuclides such as ¹⁸⁸Re produced from the tungsten generator system which can produce activity as required over many months, may make this type of therapy more widely available in some remote and developing countries.

Future products will involve cytotoxic radionuclides with appropriate potency, but with physical characteristics that will enable the administration of therapeutic doses with the minimal need for patient isolation. Further developments are likely to involve molecular constructs such as aptamers arising from new developments in biotechnology.

Patient trials are still underway and are now examining new methods of administration, dose fractionation and the clinical introduction of alpha emitting radiopharmaceutical conjugates. This review outlines the history, development and future potential of these forms of therapy.

Immunolymphoscintigraphy in breast cancer: evaluation using 131I-labeled monoclonal antibody B72.3

Noninvasive axillary lymph node staging was investigated using [131I]murine monoclonal antibody B72.3 in 16 patients with breast cancer scheduled for axillary dissection. [131I]B72.3 was injected into ipsilateral finger webs or around the breast biopsy. Scintigraphy to 72 h and gamma-counting/immunohistochemistry of nodes were performed. Specific antibody uptake (%ID/g) and the ratio of specific:nonspecific antibody uptake were not significantly different in tumor-positive versus tumor-negative nodes, suggesting that [131I]B72.3 is unsuitable to discriminate axillary node tumor involvement.

Radiolabelled monoclonal antibodies in tumour imaging and therapy: out of fashion?

The initial enthusiasm for the development of diagnostic and therapeutic studies involving the use of monoclonal antibodies was replaced by scepticism as hopes remained unfulfilled. Against this background one needs to ask whether immunoscintigraphy (IS) serves clinical needs effectively and whether radioimmunotherapy (RIT) has a future. The current review considers these questions by reference to relevant studies. Taking colorectal cancer as an example, an appraisal is offered of the ability of IS to detect disease at an early stage and thereby to reduce mortality, and of the influence of the results of IS on patient management. It is concluded that in a limited number of cases of colorectal cancer and other solid tumors, IS will allow surgery to be performed at a stage where cure is still possible because of its ability to detect early recurrence. Turning to RIT, the results of studies in respect of various tumour types are reviewed, with due attention to reported toxicity. As regards colorectal cancer, no consistent therapeutic effects have been achieved, and myelotoxicity is typically the dose-limiting factor. Thus many questions remain to be answered, regarding antigens to be targeted, fractionation schedule, the use of "humanised" antibodies, choice of radionuclide and the use of intact immunoglobulins or fragments. These questions are considered. Overall it is concluded that the most promising application of RIT is as adjuvant therapy in patients with minimal residual disease, and a controlled multicentre trial is recommended. The development of more potent radio-immunoconjugates for therapeutic and ultimately diagnostic purposes will contribute to the improvement and development of IS by increasing its potential to influence prognosis.

Cytogenetic damage in marrow cells of mice after injections of yttrium-90-labeled monoclonal antibody

Chromosome aberrations, micronuclei and sister-chromatid exchanges were quantified in marrow cells of athymic nude and B6C3F1 mice at various times up to 14 days after injection of 90Y-labeled monoclonal antibody CO17-1A. Aberrations, predominantly of the chromatid type, were sharply elevated at 24 h post-injection then declined in a curvilinear fashion over the 14 days. Micronucleus numbers among polychromatic erythrocytes peaked 3-4 days after treatment, then declined exponentially but remained at higher than expected levels. Sister-chromatid exchanges were roughly double the control rate with no apparent relation to post-treatment time.

99mTc-anti-CEA radioimmunoscintigraphy of lung adenocarcinoma

Anti-carcinoembryonic antigen radioimmunoscintigraphy (anti-CEA RIS) in colorectal adenocarcinoma has been reported to allow a better estimation of the local tumor extension than other radiologic methods. This study evaluated the clinical feasibility of a 99mTc-labeled anti-CEA monoclonal antibody (BW 431/26, Behring Institute, FRG) in 11 patients for staging of primary adenocarcinoma of the lung. The primary tumor size ranged from 3 to 8 cm with a mean of 4 cm. Mediastinal and hilar nodes were present in four patients, intrapulmonary metastases were present in two patients, and pleural and liver metastases were present in one patient each. The CEA levels were in the range of 2 to 265 ng/ml and elevated (greater than 5 ng/ml) in six patients. Planar scintigraphy was performed at 6 h and 24 h post injection (pi). Analog and digitized images were interpreted by two observers. One patient was imaged twice and experienced serum sickness due to human anti-mouse antibodies (HAMA) after the second study, which showed marked unspecific tracer uptake in liver, spleen, and bone marrow, but no specific uptake by the tumor and was excluded from further analysis. Visual interpretation identified the primary tumor clearly in seven patients. No tumor imaging was observed in two patients. Two patients were classified as having questionable imaging due to a poor separation of tumor uptake from mediastinal blood pool. The primary tumor could be clearly delineated in both patients after comparison with the chest radiograph. Thus, the overall sensitivity for imaging of the primary tumor was 82 percent. The average target/background ratio was 1.31 +/- 0.17:1 at 6 h pi, and 1.30 +/- 0.16:1 at 24 h pi. Hilar and mediastinal nodes were correctly suspected in three patients, but the cardiac blood pool hampered a clear interpretation. Intrapulmonary and pleural metastases were diagnosed in all cases. The single liver metastasis was missed because of the high unspecific tracer uptake. Planar anti-CEA RIS with 99mTc BW 431/26 was superior to computed tomography (CT) in one case with subtotal tumor resection. We summarize that at present, planar anti-CEA RIS with 99mTc BW 431/26 cannot be advised as a routine staging procedure in adenocarcinoma of the lung, but it may be helpful in the detection of residual or recurrent tumor tissue.

111In-labeled nonspecific immunoglobulin scanning in the detection of focal infection

We performed radionuclide scanning after the intravenous injection of human IgG labeled with indium-111 in 128 patients with suspected focal sites of inflammation. Localization of 111In-labeled IgG correlated with clinical findings in 51 infected patients (21 with abdominal or pelvic infections, 11 with intravascular infections, 7 with pulmonary infections, and 12 with skeletal infections). Infecting organisms included gram-positive bacteria, gram-negative bacteria, Pneumocystis carinii, Mycoplasma pneumoniae, and Candida albicans. No focal localization of 111In-labeled IgG was observed in 63 patients without infection. There were five false negative results, and nine results were unusable. Serial scans were carried out in eight patients: continued localization correctly predicted relapse in six, and the absence of localization indicated resolution in two. To determine whether 111In-labeled IgG localization was specific for inflammation, we studied 16 patients with cancer. Focal localization occurred in 13 of these patients (5 with melanomas, 5 with gynecologic cancers, and 1 each with lymphoma, prostate cancer, and malignant fibrous histiocytoma). No localization was seen in patients with renal or colon cancer or metastatic medullary carcinoma of the thyroid. We conclude that 111In-labeled IgG imaging is effective for the detection of focal infection and that serial scans may be useful in assessing therapeutic efficacy. This technique may also be helpful in the evaluation of certain cancers.

Radioimmunoscintigraphy of ovarian cancer with 131-iodine labeled OC-125 antibody fragments

Radioimmunoscintigraphy (RIS) with 131I labeled OC-125 F(ab')2 monoclonal antibody fragments was prospectively studied in 43 women for primary diagnosis and follow up of ovarian cancer. Total body planar photoscans with a scintillation camera were performed one to seven days after antibody application and results were compared with operation and or CT examination. By the region of interest technique the tumor to non tumor tissue ratio (T/N) was calculated in vivo. Sensitivity in primary diagnosis was 100% (10/10), specificity 33% (1/3). For local recurrency, sensitivity was 86% (19/22), for metastatic loci 80% (17/21). Specificity was 75% and 50%. T/N ratio was in the rage from 1.3 to 2.8. Sensitivity for ovarian cancer is high in primary diagnosis and follow up. By the region of interest technique it is possible to detect small recurrencies and to presume peritoneal carcinosis. Antibody accumulations in diseases different from ovarian cancer however diminish specificity.

Radioimmunodetection of cancer with monoclonal antibodies: current status, problems, and future directions

Early studies of immunoscintography with affinity-purified 131I-labeled polyclonal antibodies reactive against oncofetal antigens such as carcinoembryonic antigen (CEA) were moderately successful in detecting metastatic colorectal carcinoma. However, because of low tumor to background ratios of isotope, background subtraction techniques using 99Tc-labeled albumin were required to visualize small lesions. Antisera were often of low titer and lacked specificity. These problems could be overcome for the most part following the development of highly specific monoclonal antibodies (MoAb) against a variety of tumor-associated antigens. A number of clinical trials using 131I- or 111In-labeled MoAb to image tumors have demonstrated successful localization without the use of subtraction techniques. Variables limiting the usefulness of murine MoAb for diagnosis have included increased localization in liver and spleen, tumor vascularity and heterogeneity of antigen expression, and development of human antimurine globulins. Methods to overcome some of these problems are discussed. Radiolabeled MoAb appear useful as an adjunct to conventional diagnostic techniques both as a means to predict which antibodies might be useful for treatment and, in select patients, as a basis for treatment decisions.

In vitro production of human antibodies specifically reactive with human gastric cancer cells of established lines and autologous tissues

Human lymphocytes derived from regional lymph nodes adjacent to the primary gastric cancer were transformed with Epstein-Barr virus (EBV) to establish lymphoblastoid cell lines secreting human antibodies reactive with cell surface antigens expressed on the gastric cancer cells. The EBV transformation technique was applied to lymph node lymphocytes obtained from 4 gastric cancer patients. As a result of mass screening with the radioactive cell binding assay for the production of anti-gastric cancer related antibodies, one culture (TGc-106) among 1,400 microcultures was identified to secrete human antibody specifically reactive with an established human gastric cancer cell line as target (MKN-45). Furthermore, it was demonstrated with the autologous assay system by the histoimmunofluorescence method that cell surface antigens of autologous gastric cancer cells could be clearly defined with human antibody from one culture (TEb-079) out of 470 microcultures established from a gastric cancer patient (GCP-26); there was no reactivity against the surrounding normal cells constructing the gastric wall. The immunoglobulin class of the human antibodies produced both in TGc-106 and TEb-079 was determined from immunodiffusion tests to be IgM.

The use and abuse of imaging in gynecologic cancer

The radiologic detection in staging of gynecologic malignancies comprises a variety of noninvasive and invasive procedures. In the last few years, the emergence of the cross-sectional imaging techniques such as ultrasonography (US), computerized tomography (CT), and more recently, magnetic resonance imaging (MRI) have enabled the radiologist to determine more accurately the entire degree and extent of pathologic processes both within the pelvis and spread of disease outside the pelvis. The radiologist has also become more involved in invasive procedures such as percutaneous biopsies, aspirations of fluid collections, and transcatheter intraarterial infusion and occlusions. Although the newer imaging modalities will be emphasized, an attempt will be made to point out both their strengths and weaknesses relative to the older modalities. The discussion will concentrate on ovarian and cervical cancers while the other cancers of the female genital tract will be superficially discussed. The thrust of the presentation will emphasize the workup of gynecologic patients, that the workup may be quick, thorough, and as practical as possible.

Radioimmunoscintigraphy of ocular melanoma with 99mTc labelled cutaneous melanoma antibody fragments

The possibility of using radiolabelled monoclonal antibody fragments to image uveal melanomas has been assessed in a pilot study. 99mTc labelled F(ab')2 fragments of MoAb 225.28S raised against cutaneous melanomas were used. Initially 10 patients were imaged. In five patients the clinical findings were typical of uveal melanoma. Immunoscintigraphy was positive in all five cases. In a further five patients there was doubt about the diagnosis. One was though to have a choroidal haemangioma but failed to respond to treatment and immunoscintigraphy was positive, suggesting a diagnosis of melanoma. Two patients were assigned a diagnosis of choroidal haemangioma, one of melanocytoma or possible retinal pigment epithelium carcinoma, and one of metastasis. Immunoscintigraphy was negative in all these four cases. In combination with established diagnostic tests immunoscintigraphy may have a part to play in differentiating uveal melanoma from other similar tumours.

Current status of cancer imaging with radiolabeled antibodies

This editorial reviews the development, current status, and future prospects of cancer imaging with radioactive antibodies, termed radioimmunodetection (RAID). There has been a slow and steady development of this field for more than 35 years, with more recent activity and progress resulting from the identification of human tumor-associated antibodies and suitable human tumor xenograft models, the demonstration that circulating antigens do not prevent radioantibody localization in tumor, the development of computer-assisted and biological methods for reducing non-target background radioactivity, and the advent of hybridoma-produced monoclonal antibodies. At the present time, tumor sites in the range of 1.5 to 2.0 cm can be imaged, with the best resolution of 0.4-0.5 cm being reported with new chelates of 99mTc. A number of factors, including character of the radioantibody and its bioavailability, the tumor antigen site and bioavailability, the character of the radiolabel, and the target tumor's size, location and vascularization, contribute to the sensitivity, specificity, accuracy, and resolution of the method. Already at this early stage of development, RAID has been shown to have, in certain tumor types and with particular antibody and imaging systems, an accuracy of tumor site detection of over 90%, with the disclosure of occult lesions. Carefully designed prospective trials are needed to fully assess the role of this new modality in the management of cancer patients, particularly in early detection of primary and recurrent tumors.

Tumor detection using radiolabeled monoclonal antibodies

Radioisotope conjugated to monoclonal antibody products has been used for imaging tumors targeted by the antibody. As imaging progresses, new sets of procedural and technical questions arise. In this chapter, we discuss several current problems in imaging tumor with radiolabeled monoclonal antibody. These include (1) methods for selection of specific antibody and, once the particular antibody is selected, which fragment form is to be used; (2) imaging procedures: what are the optimum imaging parameters, such as optimum time for imaging after administration of tracer and considerations regarding background subtraction; and (3) noninvasive quantitative techniques: quantitation of localization of antibody indirectly from quantitative information in the images.

A rat model system for radioimmunodetection of kappa myeloma antigen on malignant B cells

A novel experimental model was established in normal rats for studying the localisation and tissue distribution of a murine monoclonal antibody directed against kappa light chain B cell malignancies. The antibody, K-1-21 was raised against human kappa Bence Jones Proteins and reacts with a cell membrane antigen KMA which is restricted to some kappa myeloma and lymphoma cells. In the rat model, kappa or lambda Bence Jones protein-conjugated sepharose was implanted subcutaneously on either flank 24 h before the injection of 131I-labelled K-1-21 or its F(ab')2 fragment. Gamma camera imaging and tissue distribution studies showed specific localisation of the K-1-21 antibody in the kappa sepharose. Injection of F(ab')2 antibody fragments resulted in faster background clearance, earlier delineation of the specific image and significantly higher target to blood ratios than those obtained with the intact antibody. These results suggest that the model may provide an alternative system to tumour xenograft bearing nude mice for studying localisation of antibodies with therapeutic potential.

Advances in pediatric tumor imaging

The continuing improvement in the outlook for pediatric malignant disease depends on modern imaging techniques. The roles of magnetic resonance imaging, computed tomography, ultrasound, nuclear radiology, and angiography are discussed in relationship to the accurate staging of the primary tumor and the effect of therapy.

Uptake of a monoclonal antibody against CEA (Tumak 431/31) in a human colon tumor (Co-112) xenografted in the nude mouse. Dependence on tumor size and injected dose

A monoclonal antibody (Tumak) against carcinoembryonic antigen (CEA) was injected into nude mice bearing a human colon carcinoma (Co-112). The tumor uptake was found to be dependent on the size of the tumors: relative uptake (percentage of the injected dose/gram tumor (% i.d./g) decreased for tumors with weights up to approximately 1 g, although the absolute uptake (% i.d./tumor) still increased over the same weight range. In the constant region (greater than or equal to 1 g) mean relative tumor uptake was approximately 4% i.d./g. The same tumor size dependence was found for the relative Tumak uptake in the other mouse organs studied (e.g., blood, liver, spleen and muscle). Consequently tumor/organ ratios were found to be independent of tumor size. Tumor uptake was also studied for various doses of Tumak (0.07-120 micrograms) in tumors of approximately 1 g. Evidence was found for a threshold dose of 0.1 microgram under which no serious tumor uptake appeared. From 1 to 120 micrograms no further dependence of Tumak distribution on applied dose was found: the relative uptake of all organs remained the same but the absolute uptake increased with dose.