[Pilot study with the monoclonal antibody IOR-C5 as a potential agent of radioimmunoscintigraphy in colorectal cancer]

IOR C-5 is a G1 immunoglobulin type intact murine monoclonal antibody (MAb) that was developed in the Center of Molecular Immunology in Havana City, Cuba. In immunohistochemical studies, this demonstrated a significant affinity for the epithelial tissues so that it was used in a pilot clinical study to perform a radioimmunoscintigraphy of the colorectal primary tumors and their locoregional recurrences. It was labeled with 99mTc using the Schwarz method, with a > 95% performance. Planar images of the chest, abdomen and pelvis were performed at 10 minutes, 4-6 hours and 18-24 hours post-injection in the anterior and posterior projections and the SPECT was performed 4-6 hours and 18-24 hours post-injection of 1.85 GBq 99mTC. This study has aimed to verify in vivo the capacity of ior-C5 MAb to accumulate in the malignant colorectal lesions. ior-C5 accumulated in 5 out of the 7 patients who were studied and who were suffering from colorectal cancer or in whom there was suspicion of recurrence. There was a negative case of primary tumors, which was an adenocarcinoma in situ in a tubular-papillary adenoma. The second case with a negative radioimmunoscintigraphy was a true negative case.

CONCLUSIONS

It can be concluded that even though the number of patients is quite low, ior-C5 fulfilled the expectations of recognizing the epitope expressed in colorectal tumors in an in vivo human environment.

99mTc-labeled antihuman epidermal growth factor receptor antibody in patients with tumors of epithelial origin: Part III. Clinical trials safety and diagnostic efficacy

Monoclonal antibody (moAb) ior egf/r3 is an IgG2a that recognizes the epidermal growth factor receptor (EGF-R). The aim of this study was to evaluate the diagnostic efficacy of the 99mTc-labeled moAb ior egf/r3 for the detection of epithelial-derived tumors, their metastases and recurrences.

METHODS

One hundred forty-eight adult patients (51 women, 97 men; mean age 53 +/- 13 y) who were suspected of having cancer of epithelial origin were administered 3 mg/50 mCi (1.85 GBq) 99mTc-labeled moAb ior egf/r3 by intravenous bolus injection. Planar anterior and posterior images of the lesion sites and suspected metastases were acquired at 2, 4, 6 and 24 h after injection, and SPECT images were scanned at 5 h postinjection, using a 360 degrees circular orbit with 64 images. The backprojection method was used for image reconstruction with a Hamming-Hann filter.

RESULTS

Labeling efficiency was always greater than 98.5% +/- 2.1 %. No adverse reactions or side effects were observed. Results of the biopsy specimens showed that 85.1% (126/148) of the patients had tumors of epithelial origin, 14.2% (21/148) were negative and 0.7% (1/148) had non-Hodgkin's lymphoma. The sensitivity rate by organ was as follows: brain (8/8, 100%), digestive tract (10/11, 90.9%), head and neck (17/23, 73.9%), lung (52/62, 83.9%) and breast (16/18, 88.9%). Overall sensitivity, specificity, accuracy, and positive and negative predictive values of the immunoscintigraphic imaging were 84.2% (106/126), 100.0% (22/22), 86.5% (128/148), 100% (106/106) and 52.4% (22/42), respectively. New metastases not identified previously by other diagnostic methods were detected in the 50% of the patients.

CONCLUSION

Immunoscintigraphy with 99mTc-labeled moAb ior egf/r3 could be a useful procedure for the diagnosis and follow-up of the patients with tumors of epithelial origin.

[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.

[Validation of the imagamma interface for connecting gamma cameras to personal computers]

An electronic interface, imagamma, has been designed in order to link analog gamma cameras to IBM personal computers (PCs). The performance of the interface was assessed for a camera-computer system composed by a GE Maxicamera II-400T gamma camera and an IBM PC, which has a DX 80486 processor, 8 Mb RAM and a suitable acquisition and processing software. Quality control tests for gamma camera-computer systems, established by the International Atomic Energy Agency in the IAEA-TECDOC-602 for <<Quality Control of Nuclear Medicine Instruments 1991>>, were performed. The main performance characteristics of the gamma camera: intrinsic flood field uniformity, intrinsic spatial resolution and spatial linearity were tested as well as the system time performance for dynamic and gated studies. The results obtained for the camera-computer system performance parameters show a good stability. Those results concerning the dynamic characteristics of the interface are between the limits of acceptability, established for each test by the IAEA standards. We conclude that the imagamma interface has suitable performance characteristics to link analog gamma cameras to PC based computer systems in order to be used with clinical application purposes.

Value of ellipsoid volume masking in myocardial tomography

The circumferential profile technique, used to obtain a bull's eye image from short axis slices in myocardial perfusion tomography, requires isolation of the reconstructed volume from other neighbouring structures that may take up the radiopharmaceutical used. If this is not possible, some regional artefacts can be introduced in the polar map that do not represent the actual myocardial perfusion at the corresponding level. In this case report we describe a method for volume masking that permits the myocardium inside in ellipsoidal volume to be enclosed. This technique is compared with the spherical method used in a Sophy 20P system in a case with impaired perfusion of an inferolateral segment and an extracardiac "hot" structure located in the same area. The results obtained show the usefulness of our method in such cases.