Tumor concentration and distribution of carcinoembryonic antigen measured by in vitro quantitative autoradiography.

UNLABELLED

One of the most critical factors in successful immunoscintigraphy and radioimmunotherapy is the local concentration and distribution of the target antigen. The purpose of this study was to evaluate the concentration and distribution of carcinoembryonic antigen (CEA) in various carcinomas.

METHODS

In vitro quantitative autoradiography was performed in carcinomas of the stomach (32 cases), colon (20 cases), breast (29 cases) and lung (26 cases). Frozen tumor sections were incubated with varying concentrations of 125I-labeled monoclonal antibody (Mab) CEA-79.1 (IgG2a), which is specific for CEA. Digitized autoradiographic images from these sections were compared to adjacent H & E and immunoperoxidase-stained sections. Computer analysis of specific antibody binding quantitated the maximal value (Bmax), which is equal to the concentrations of CEA.

RESULTS

Stomach cancer expressed CEA in 31 cases (97%). All colon cancer specimens exhibited CEA and breast cancer expressed CEA in 24 cases (83%). In adenocarcinoma of the lung, CEA was measured in all specimens. The concentration of CEA did not vary significantly among the pathologic types or among the various degrees of differentiation in each carcinoma. CEA was expressed homogeneously in adenocarcinomas of the colon and lung. However, CEA exhibited a heterogeneous distribution in a significant number of breast cancer (42%) and bronchogenic squamous-cell carcinoma (78%) specimens.

CONCLUSIONS

CEA was expressed in most cases of stomach, colon, breast and lung carcinomas. These carcinomas, however, exhibited wide variation in the concentration and distribution of CEA expression. The concentration and distribution of CEA in a particular tumor type should be considered before undertaking tumor targeting methods.