Monoclonal antibody BW431/26 labelled with technetium 99m and indium 111: an investigation of the biodistribution and the dosimetry in patients

As a competitive diagnostic tool for the detection of malignant tumours and other pathological conditions, monoclonal antibodies have long been established. Herein we give the biokinetic data of the antibody BW 431/26 and the consequent radiation dose to patients. These parameters were recorded in 39 patients, using the antibody labelled either with technetium 99m or indium 111. Remarkable differences were observed between the two radionuclides. Whereas the indium-labelled one showed biexponential elimination kinetics, the technetium-labelled one is eliminated linearly over time. The distribution pattern of the two is identical, although the radiation dose varies quite a lot, being 20-fold higher with indium 111 when total body exposure is taken into account (for ¹¹¹In the whole-body radiation exposure is 0.1 mGy/MBq; for ^99mTc it is 0.0047 mGy/MBq). With respect to these results and considering the general availability of the technetium-labelled Ab, it is the best choice for diagnostic use.Offprint requests to: P. Benz     

Value of radioimmunoscintigraphy with technetium-99m labelled anti-CEA monoclonal antibody (BW431/26) in the detection of colorectal cancer

This study was undertaken as part of a Coordinated Research Programme initiated by the International Atomic Energy Agency to evaluate the usefulness of radioimmunoscintigraphy (RIS) in the management of patients with colorectal cancer. Technetium-99m labelled BW431/26, a monoclonal antibody against carcino-embryonic antigen (CEA), was used. The study included 73 patients (31 females and 42 males). Sixty-eight patients were suspected of having recurrent colorectal adenocarcinoma while another five were suspected to have primary colorectal cancer. Images were acquired at 10 min and 4 and 24 h following the injection of radioantibody. The efficacy of RIS in tumour detection was evaluated by the findings at surgery, histological investigation and/or other diagnostic modalities and clinical follow-up. Four of five patients with suspected primary colorectal cancer gave true-positive results (three at primary sites, one at the site of a metastatic lesion) while one was false-positive. The overall accuracy of RIS in the diagnosis of recurrent colorectal cancer was 87%. Its sensitivity in the detection of locoregional or abdominal recurrence and liver metastases was 97% and 89% respectively. RIS was more accurate than computed tomography (CT) scan in the detection of pelvic recurrence and liver metastases while CT scan was far superior to RIS in detecting lung metastases. RIS proved most useful in patents who had rising CEA levels on clinical follow-up but in whom other work-up, including CT scan, was negative. The advantages of RIS include the ability to detect tumour recurrence prior to other investigations and to identify tumour recurrence in areas such as the pelvis, where CT and magnetic resonance imaging have their greatest weaknesses in diagnosing recurrent disease. The imaging accuracy is significantly increased when combined CT and antibody imaging is performed.     

Radioimmunoscintigraphy of colorectal carcinoma with a 99Tcm-labelled anti-CEA monoclonal antibody (BW 431/26).

Radioimmunoscintigraphy (RIS) with BW 431/26 monoclonal antibody (MoAb) labelled with 99Tcm (962 MBq) has been performed in 64 patients with colorectal carcinoma, one of them with two independent tumours. The group consisted of 46 primary lesions, 15 pelvic recurrences and four suspected recurrences which were shown to be liver metastases. Imaging of liver was obtained in all patients, but surgical liver examination was performed in only 56 of them. Planar scans were obtained at 4 and 24 h postinjection. Tomographic images were also performed in five patients. The final diagnosis was confirmed in all patients by their clinical course and by findings at surgery and pathology. A comparative study between the RIS results and the final diagnosis gave a global sensitivity in primary tumours and pelvic recurrences of 59.7% with an accuracy of 59.0%. When rectal tumours were excluded, the results were 81.1 and 84.9%, respectively. In liver metastases the sensitivity was 50%, with an accuracy of 85.7% and a specificity of 100%. No correlation has been found between CEA serum levels and lesion detection. In conclusion, RIS is a useful technique for the study and localization of colorectal tumours, being also indicated in patients with normal carcinoembryonic antigen (CEA) serum levels and clinical suspicion of illness.     

Reduced technetium 99m labelled NCA-95/CEA-antibody uptake in liver due to gentle antibody reconstitution

The influence of reconstituting a murine monoclonal IgG₁ antibody kit with pertechnetate technetium 99m on antibody distribution in the liver, spleen and sternal bone marrow of patients was examined. The^99mTc-labelled antibody used is directed against nonspecific cross-reacting antigen (NCA-95) and carcinoembryonic antigen (CEA) and has been successfully applied for imaging tissue inflammation and bone marrow scanning. Radioactivity uptake was determined in the liver, spleen, bone marrow and a precordial background region in a consecutive series of 25 patients, examined with an antibody preparation, routinely radiolabelled according to the manufacturer's recommendations and in 14 patients, in whom the antibody was reconstituted with special care, avoiding bubble formation and dropping of buffer into the antibody-containing vial. Gentle compared with routine antibody reconstitution caused a highly significant reduction of the antibody uptake in the liver, as determined by count densities, normalized to injected dose and acquisition time (13.2 ± 5.5 vs 20.1 ± 6.0 cpm per pixel, x±SID,P=0.008). The liver to background ratio was reduced from 3.4 ± 1.4 to 1.9 ±0.5 (P < 0.001). Spleen, sternal bone marrow and precordial background count rates were not significantly affected. These results clearly demonstrate that gentle antibody reconstitution can decrease non-specific antibody uptake in the liver by 34% ± 6.4% (x ± SEM). Thus, scan quality is improved, and the potential deleterious camouflage of underlying structures is avoided.     

Immunoscintigraphy with 99Tcm-labelled monoclonal anti-CEA BW 431/26 antibodies in patients with suspected recurrent and metastatic colorectal carcinoma: two-year follow-up.

The aim of this study was to evaluate immunoscintigraphy with BW 431/26 anti-CEA antibody in the follow-up of 15 patients with colorectal carcinoma. A whole-body scan followed by SPET imaging of the abdomen and pelvis was performed 4-6 and 20-24 h after the intravenous infusion of 0.6-1.0 mg of intact anti-CEA monoclonal BW 431/26 antibody labelled with 814-1110 MBq of 99Tcm. The HAMA response and serum CEA levels were determined. Immunoscintigraphic findings were verified by biopsy, radiologically and/or by 2 year follow-up. On an individual patient basis, immunoscintigraphy demonstrated an overall sensitivity of 83%, specificity of 100%, accuracy of 87%, positive predictive value of 100% and negative predictive value of 60%. Better results were achieved in the pelvic region than in the liver or in the extra-hepatic abdominal region. We evaluated 40 lesions; on an individual lesion basis, immuno-scintigraphy gave a sensitivity of 80% and an accuracy of 80%. SPET images detected significantly more lesions than whole-body planar images (P < 0.05). SPET at 20-24 h detected significantly more 'hot' lesions than at 4-6 h (P < 0.01). No correlation between CEA serum levels and immunoscintigraphy was observed (r = 0.376, P > 0.05). One of nine patients (11%) developed HAMA after immunoscintigraphy. We conclude that immunoscintigraphy with BW 431/26 antibody appears able to differentiate between tumour recurrence and scar tissue, and to evaluate liver metastases of colorectal carcinoma. Serum CEA levels appear not to influence the result of immunoscintigraphy and the HAMA response is minimal. A delayed SPET scan should be part of an immunoscintigraphic imaging protocol when 99Tcm-labelled BW 431/26 monoclonal antibody is used.     

Radioimmunoscintigraphy of colorectal cancer using the anti-CEA monoclonal antibody BW 431/26. Final results

The anti-carcinoembryonic antigen (CEA) antibody, BW 431/26 (Scintimun CEA, Behringwerke, Marburg, Germany ) labeled with technetium pertechnectate (99mTc), is an intact immunoglobulin G1, monoclonal antibody that has been used to image colorectal cancer. Planar and SPECT images of chest, abdomen and pelvis were performed at 10 minutes, 4-6 and 18-24 hours after the intravenous antibody injection. 44 patients were studied and the pathological antibody concentration localization by radioimmunoimaging (RI) were correlated with surgical, clinical and other imaging modality findings to validate the RI. The RI was positive in 29 patients and negative in the other 15 patients. The CEA and CA 19.9 were elevated in the serum of some patients with primary tumors or recurrence. The HAMA were determined in all the patients before and after the RI.     

Reduced technetium 99m labelled NCA-95/CEA-antibody uptake in liver due to gentle antibody reconstitution. Technical note

The influence of reconstituting a murine monoclonal IgG1 antibody kit with pertechnetate technetium 99m on antibody distribution in the liver, spleen and sternal bone marrow of patients was examined. The 99mTc-labelled antibody used is directed against non-specific cross-reacting antigen (NCA-95) and carcinoembryonic antigen (CEA) and has been successfully applied for imaging tissue inflammation and bone marrow scanning. Radioactivity uptake was determined in the liver, spleen, bone marrow and a precordial background region in a consecutive series of 25 patients, examined with an antibody preparation, routinely radiolabelled according to the manufacturer's recommendations and in 14 patients, in whom the antibody was reconstituted with special care, avoiding bubble formation and dropping of buffer into the antibody-containing vial. Gentle compared with routine antibody reconstitution caused a highly significant reduction of the antibody uptake in the liver, as determined by count densities, normalized to injected dose and acquisition time (13.2 +/- 5.5 vs 20.1 +/- 6.0 cpm per pixel, means +/- SD, P = 0.008). The liver to background ratio was reduced from 3.4 +/- 1.4 to 1.9 +/- 0.5 (P less than 0.001). Spleen, sternal bone marrow and precordial background count rates were not significantly affected. These results clearly demonstrate that gentle antibody reconstitution can decrease non-specific antibody uptake in the liver by 34% +/- 6.4% (means +/- SEM). Thus, scan quality is improved, and the potential deleterious camouflage of underlying structures is avoided.     

Anti-carcinoembryonic antigen immunoscintigraphy (technetium-99m-monoclonal antibody BW 431/26) and serum CEA levels in patients with suspected primary and recurrent colorectal carcinoma

This study comprises a total of 141 patients with suspected primary and recurrent colorectal carcinomas, in whom immunoscintigraphy with 99mTc-Mab BW 431/26 was performed. Whole-body scans were done 5.5 hr and SPECT imaging of the abdominal region was done at 6 and 24 hr postinjection of 1100 MBq 99mTc-labeled Mab (1 mg). In the course of primary tumor identification (n = 65), sensitivity of anti-CEA immunoscintigraphy was 95%, specificity 91%. In the diagnosis of early recurrences (n = 76), immunoscintigraphy was the method of choice to clarify the problem (sensitivity 94%; specificity 86%). Overall sensitivity of immunoscintigraphy in patients with suspected colorectal carcinomas and early recurrences was 95%, specificity 88%. Human anti-mouse antibodies were found in 29% (80% predominantly anti-isotypic, 20% predominantly anti-idiotypic). In contrast to anti-CEA immunoscintigraphy, the results of serum CEA levels were rather disappointing. Only 18 out of the 43 surgically verified primary colorectal carcinomas and 17 out of 32 patients with recurrences showed elevated serum CEA levels. In our clinical experience with this 99mTc-labeled anti-CEA antibody, immunoscintigraphy can play an important role in the identification of early colorectal recurrences and in postoperative colorectal cancer patients it should be performed in cases with unclear transmission computed tomography.     

The fractional distribution of the cardiac output in man using microspheres labelled with technetium 99m

To investigate the distribution of organ blood flow in patients we have developed a method of quantitating the whole-body fractional distribution of 99Tcm-labelled microspheres. The microspheres were injected into the left ventricle in nine patients with normal cardiac indices (greater than 3 1/min/m2; Group A) and 11 patients with low cardiac indices (less than 2.51 l/min/m2; Group B). The fractional organ content of the total injected dose was estimated following correction for geometry and transmission using a gamma camera. Cerebral blood flow was 579 +/- 163 ml/min (mean +/- SD) in Group A and 593 +/- 158 ml/min in Group B (p not significant (NS)). Myocardial flow in Group A was 266 +/- 82 ml/min and in Group B was 237 +/- 57 ml/min (p, NS). Total renal blood flow was 749 +/- 161 ml/min in Group A and 614 +/- 181 ml/min in Group B (p less than 0.01). There was a negative correlation between cardiac index and the percentage of the cardiac output distributed to brain (r = -0.70, p less than 0.01), heart (r = -0.67, p less than 0.01) and kidneys (r = -0.47), p less than 0.05). Low output cardiac failure is, therefore, associated with relative preservation of cerebral and myocardial blood flow and, to a lesser extent, of renal flow. A similar technique using dual labelling would allow an accurate estimation in individual patients, of the change in organ blood flow associated with transient alterations in cardiac output states.     

Measurement of synovial inflammation in rheumatoid arthritis with technetium 99m labelled human polyclonal immunoglobulin G

The ability of technetium 99m labelled nonspecific, polyclonal human immunoglobulin G (^99mTc-IgG) scintigraphy to depict and quantify synovial inflammation was studied in patients with rheumatoid arthritis (RA). Eight patients with clinically active synovitis were injected with 350 MBq ^99mTc-IgG, and imaging took place 4 h later. This resulted in excellent images of inflamed synovium. Significant correlations were observed between individual joint uptake on the scan and scores for joint pain (n=316, p<0.001), joint swelling (n = 300, p < 0.001) or the average of pain and swelling (n = 300, p < 0.001). These results suggest that ^99mTc-IgG scintigraphy may provide an objective, non-invasive test to detect and measure synovitis. Offprint requests to: P.A.H.M. van der Lubbe     

Measurement of synovial inflammation in rheumatoid arthritis with technetium 99m labelled human polyclonal immunoglobulin G

The ability of technetium 99m labelled nonspecific, polyclonal human immunoglobulin G (99mTc-IgG) scintigraphy to depict and quantify synovial inflammation was studied in patients with rheumatoid arthritis (RA). Eight patients with clinically active synovitis were injected with 350 MBq 99mTc-IgG, and imaging took place 4 h later. This resulted in excellent images of inflamed synovium. Significant correlations were observed between individual joint uptake on the scan and scores for joint pain (n = 316, p less than 0.001), joint swelling (n = 300, p less than 0.001) or the average of pain and swelling (n = 300, p less than 0.001). These results suggest that 99mTc-IgG scintigraphy may provide an objective, non-invasive test to detect and measure synovitis.     

Early immunoscintigraphic localisation of a mediastinal tumour with indium 111-DTPA CEA-specific F(ab')2 monoclonal antibody fragments (BW 431/31) using second tracer isocontour technique

A female patient with steadily increasing carcinoembryonic antigen (CEA) serum levels of unknown origin was referred for immunoscintigraphy with indium 111-labelled CEA-specific monoclonal antibody. The procedure revealed a tumour, undetectable by conventional diagnostic methods. Anatomical landmarking using the second tracer isocontour technique allowed the distinction between an intra- or extrapulmonary lesion. Two months later, tumour infiltration along the aortic arch was confirmed by a targeted angio-CT scan. Upon surgery, the diagnosis was definitely established histologically (undifferentiated, solid large cell carcinoma, most probably arising from the bronchus), and staining by CEA-specific immunohistochemistry confirmed the presence of the CEA antigen.     

Early immunoscintigraphic localisation of a mediastinal tumour with indium 111-DTPA CEA-specific F(ab')2 monoclonal antibody fragments (BW 431/31) using second tracer isocontour technique

A female patient with steadily increasing carcinoembryonic antigen (CEA) serum levels of unknown origin was referred for immunoscintigraphy with indium 111-labelled CEA-specific monoclonal antibody. The procedure revealed a tumour, undetectable by conventional diagnostic methods. Anatomical landmarking using the second tracer isocontour technique allowed the distinction between an intra- or extrapulmonary lesion. Two months later, tumour infiltration along the aortic arch was confirmed by a targeted angio-CT scan. Upon surgery, the diagnosis was definitely established histologically (undifferentiated, solid large cell carcinoma, most probably arising from the bronchus), and staining by CEA-specific immunohistochemistry confirmed the presence of the CEA antigen.     

In vivo imaging of rat lymphocytes with an indium 111-labelled anti-T cell monoclonal antibody: a comparison with indium 111-labelled lymphocytes

An indium 111-labelled mouse anti-rat T cell monoclonal antibody, MRC OX-19, was injected intravenously into rats to establish the usefulness of radiolabelled anti-lymphocyte antibodies in imaging lymphoid tissues. Antibody binding in vivo, measured by immunofluorescence analysis of cell suspensions made from lymphoid tissues, was detectable on lymphocytes in blood, spleen and lymph nodes. The extent of binding was time and antibody-dose dependent. Doses of antibody above 80 g/kg body weight resulted in modulation, i.e. loss of CD 5 (T 1) molecules from the cell surface, although the cells remained in the circulation. Modulation was demonstrable within 2 h and for at least 24 h after a single injection of antibody. Intravenous injection of¹¹¹In-MRC OX-19 resulted in levels of in vivo binding comparable with those seen with unlabelled antibody. Scintillation imaging showed early splenic localisation persisting over 48h, a more gradual localisation in the lymph nodes seen clearly at 24 h and a steady background. Comparison of the in vivo distribution of labelled antibody and¹¹¹In-tropolone-labelled lymphocytes showed that both could be used for external imaging of lymphocytes by scintillation camera.     

In vivo imaging of rat lymphocytes with an indium 111-labelled anti-T cell monoclonal antibody: a comparison with indium 111-labelled lymphocytes

An indium 111-labelled mouse anti-rat T cell monoclonal antibody, MRC OX-19, was injected intravenously into rats to establish the usefulness of radiolabelled anti-lymphocyte antibodies in imaging lymphoid tissues. Antibody binding in vivo, measured by immunofluorescence analysis of cell suspensions made from lymphoid tissues, was detectable on lymphocytes in blood, spleen and lymph nodes. The extent of binding was time and antibody-dose dependent. Doses of antibody above 80 micrograms/kg body weight resulted in modulation, i.e. loss of CD 5 (T1) molecules from the cell surface, although the cells remained in the circulation. Modulation was demonstrable within 2 h and for at least 24 h after a single injection of antibody. Intravenous injection of 111In-MRC OX-19 resulted in levels of in vivo binding comparable with those seen with unlabelled antibody. Scintillation imaging showed early splenic localisation persisting over 48 h, a more gradual localisation in the lymph nodes seen clearly at 24 h and a steady background. Comparison of the in vivo distribution of labelled antibody and 111In-tropolone-labelled lymphocytes showed that both could be used for external imaging of lymphocytes by scintillation camera.     

99m Tc-HMPAO labelled leukocyte scintigraphy in patients with rheumatoid arthritis: a comparison with disease activity.

The aim of this study was to test the applicability of 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO) labelled leukocyte joint scintigraphy in the assessment of disease activity in 21 patients with rheumatoid arthritis, and to compare leukocyte scintigraphy with the Disease Activity Score (DAS), a validated activity index developed by the European League Against Rheumatism (EULAR). Twenty-one patients with rheumatoid arthritis were investigated by using 99mTc-HMPAO labelled leukocyte joint scintigraphy. The clinical and laboratory data were recorded, and the DAS was calculated and compared with the scintigraphic results in each case. A relatively high DAS score (4.71+/-1.07) was found in the majority of patients. The degree of accumulation of 99mTc-HMPAO leukocytes showed no correlation with a patient's age, gender, duration of disease, use of disease modifying anti-rheumatic drugs (DMARDs), visual analogue scale (VAS), Richie index, DAS, or any laboratory parameters. In contrast, a significant correlation was found between the global regional accumulation of the labelled leukocytes of the hands and feet, and the swollen-joint count. It is concluded that radiolabelled leukocyte scintigraphy could become one of the promising methods in the assessment of disease activity in patients with rheumatoid arthritis.     

Radioimmunoscintigraphy in patients with breast adenocarcinoma using technetium-99m labelled monoclonal antibody 170H.82: Report of a phase II study

Fifty-three women with clinical evidence of adenocarcinoma of the breast were studied with technetium-99m labelled monoclonal antibody (MAb) 170H.82 at protein doses of 1, 2 and 4 mg. An overall per lesion efficacy of 83.5% sensitivity and 97.7% positive predictive value was obtained. Efficacy appears higher in lesions restricted to the breast and local regional disease than systemic metastases. For the 2 mg dose the breast/local regional disease efficacy was 90% sensitivity and 90.2% positive predictive value. The biodistribution of this MAb was best represented by a two-compartment model with a distribution-phase half-life of 4.0±1.4 h, followed by an elimination-phase half-life of 39.6±6.6 h. In all six patients studied, the crticial organ was the kidney, with a mean radiation absorbed dose of 37±6.9 mGy/GBq. The accuracy of this imaging technique allows the development of diagnostic strategies for the routine use of the compound in patients with breast cancer.     

Bone marrow scintigraphy with 99m Tc labelled monoclonal anti-NCA 90 Fab' fragment: a feasibility study and comparison of bone marrow uptake with 99m Tc labelled monoclonal anti-NCA 95 antigranulocyte antibody

The aim of this retrospective study was to evaluate the usefulness of 99mTc labelled monoclonal anti-NCA 90 antigranulocyte antibody Fab' fragment (MN3 Fab') as a bone marrow imaging agent. One hundred and ten planar scans (88 patients) of the lumbar and sacroiliac regions as well as whole-body scans were performed after 1, 5 and 24 h. All the scans were evaluated visually and bone marrow uptake was determined semiquantitatively as count density ratio from sacroiliac-minus-background to background area. Results were compared to 50 age-matched patients with normal bone marrow scans obtained with the intact 99mTc labelled monoclonal anti-NCA 95 antigranulocyte antibody (BW 250/183) in a previous study. Seventy-three patients showed a physiological activity distribution in the central bone marrow. Ten patients showed a bone marrow extension, while in two patients central bone marrow depression was observed. Evaluation of the ribs, lower thoracic and upper lumbar spine was hampered by soft-tissue activity. Bone marrow uptake was 1.36+/-0.56 after 1 h, decreased thereafter and was significantly lower than that of BW 250/183 (P < 0.001). In conclusion, MN3 Fab' cannot be recommended for bone marrow scintigraphy, because relevant parts of the haemopoietically active bone marrow are not accessible to visual evaluation. A significant role of the semiquantitative evaluation of MN3 Fab' bone marrow uptake in patients with potential marrow depression seems unlikely.     

Experience with the iodine-123 and technetium-99m labelled anti-granulocyte antibody MAb47: a comparison of labelling methods

Four different methods of radiolabelling the anti-granulocyte monoclonal antibody MAW were compared and their influence on diagnostic value studied. The best clinical images were obtained following labelling with iodine-123 by the Iodogen method and direct labelling with technetium-99m after tris-(carboxyethyl)-phosphine treatment of MAW to achieve disulphide bridge reduction.^99mTc labelling using a specific ligand (MAb47-mtp), or a second method involving direct reduction with mercaptoethanol, led to an increased background activity in clinical studies, thus impeding the diagnosis of chronic disease. Fresh infections were clearly localized by all four preparations. The elimination of the activity from the blood was slower in the case of the iodinated MAb47, while the collected urine samples showed an excrection of about 10% of the injected activity per day independent of the labelling method. The results in terms of sensitivity and specificity were rather similar for all labelling methods and ranged from 90% to 99%.