[Immunoscintigraphy using 111In-DTPA-labeled monoclonal antibodies: comparison with ECT and planar scintigraphy]

Area of Science:

• Nuclear Medicine
• Oncology
• Radiopharmacology

Background:

• Immunoscintigraphy (IS) is crucial for detecting tumors, recurrences, and metastases.
• Traditional Iodine-131 (131I)-labeled monoclonal antibody (MAb) fragments have limitations in sensitivity and image quality.
• Tomographic imaging techniques like Emission Computed Tomography (ECT) offer better localization but require high tracer sensitivity.

Purpose of the Study:

• To evaluate if Indium-111 (111In)-DTPA-labeled MAb fragments enhance tomographic immunoscintigraphy sensitivity compared to 131I-labeled fragments.
• To compare the sensitivity of planar imaging versus tomographic imaging using 111In-labeled MAb fragments intra-individually.

Main Methods:

• Eleven patients with various primary tumors, local recurrences, or metastases underwent immunoscintigraphy.
• 111In-DTPA-labeled F(ab')2 fragments of MAbs (anti-CEA, OC 125, anti-hTG) were used for both planar and tomographic imaging.
• Results were compared intra-individually and with conventional diagnostic procedures (CT, ultrasound, 131I scintigraphy, histology).

Main Results:

• Immunoscintigraphy detected tumors in 10/11 cases with planar imaging and 9/11 cases with ECT using 111In-labeled fragments.
• Intra-individual comparison showed similar sensitivity between ECT and planar imaging with 111In-labeled fragments.
• 111In's physical properties are better suited for common gamma cameras, enabling sufficient count rates for ECT in reasonable times.

Conclusions:

• 111In-labeled MAb fragments improve ECT sensitivity for tumor detection, potentially matching planar imaging sensitivity.
• The use of 111In facilitates combining IS with ECT's advantages for superior tumor localization and artifact reduction.
• This approach enhances diagnostic accuracy in oncology by improving imaging resolution and reducing superimposed background signals.