ANTI-CEA IMMUNOSCINTIGRAPHY MIGHT BE MORE USEFUL THAN COMPUTED-TOMOGRAPHY IN THE PREOPERATIVE THORACIC EVALUATION OF LUNG-CANCER - A COMPARISON BETWEEN PLANAR IMMUNOSCINTIGRAPHY, SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY (SPECT), AND COMPUTED-TOMOGRAPHY

While a clinical, plain radiographic, and bronchoscopic assessment yie lds most of the essential information in lung cancer, computed tomogra phy (CT) of the thorax provides diagnostic information previously unob tainable, potentially capable of reducing the number of explorative th oracotomies. In a few recent studies, immunoscintigraphy with anticarc inoembryonic antigen (anti-CEA) monoclonal antibodies (MA) has shown r emarkable staging potential. To compare the diagnostic accuracy of the two techniques, we photoscanned with indium-111 (In-111)-labeled-F(ab ')2 fragments of the murine anti-CEA MA FO23C5 45 patients, who were p athologically assessed for possible loco-regional extension of lung ca ncer. Both planar and single photo emission computed tomography (SPECT ) images were obtained. Additionally, CT of the thorax (contiguous CT slices, 10 mm thick, from the lung apices to the upper abdomen), and o ther routine tests of preoperative evaluation were obtained. On the ba sis of 37 (N1, T3, and T4), 38 (N2), and 12 (N3) pathologically docume nted sites, an accuracy of 65, 76, 92, 78, and 89 percent (immunoscint igraphic planar images), 68, 78, 92, 78, and 86 percent (SPECT images) , and 62, 68, 42, 78, and 84 percent (CT images) was calculated (figur es are relevant to N1, N2, N3, T3, and T4 disease, respectively). Thus , both techniques shared a significant margin of error in almost all t he categories of evaluation; however, immunoscintigraphy showed equiva lent, and, in the lymph node assessment, superior results to CT. A mar ginal improvement of diagnostic accuracy was recorded combining the th ree techniques in one case (SPECT plus planar immunoscintigraphic imag es), while there was no benefit in any possible integration of CT and immunoscintigraphic images. In patients with peripheral nonsquamous ce ll cancers, the accuracy of anti-CEA immunoscintigraphy was of 90 perc ent or higher. Variations in the modality of performing immunoscintigr aphy, such as changes in the dose of antibody fragments to be injected , in the percentage of radiolabeling, or in the time of imaging; affec ted the quality of immunoscintigraphic series, and the consequent inte rpretation of findings. At the present time, there am very few reliabl e tests capable of selecting patients to proceed directly to thoracoto my or to receive some intermediate surgical test, such as a prior medi astinoscopy. TraditionallY, CT has been this type of ''filter-test.'' If current findings will be confirmed in future studies, anti-CEA immu noscintigraphy might replace CT in the evaluation of particular subgro ups of patients, such as patients with peripheral nonsquamous cell bro nchogenic carcinoma.