ENDOBRONCHIAL ADMINISTRATION OF I-131 B72.3 MONOCLONAL-ANTIBODY IN PATIENTS WITH LUNG-CANCER

We tested the feasibility of endobronchial administration of radiolabelled monoclonal antibodies (MoAbs) and the biodistribution of the radiotracer. Ten patients with histological confirmed adenocarcinoma or squamous cell carcinoma were studied. Nine received 470-mu-Ci (103-mu-g) of Iodine-131-B72.3, a monoclonal antibody reacting against TAG 72 antigen, while one patient received 502-mu-Ci (291-mu-g) of I-131-4C4, an indifferent antibody used for comparison in a negative control study. The radiolabelled antibody was administered through a flexible fiberoptic bronchoscope and placed on the tumuor mass under visual monitoring. Scans with a large field-of-view gamma-camera showed retention of I-131-B72.3 at the tumour site up to 6-9 days in six of eight patients. No other organs were visualized with the exception of faint activity in the gastrointestinal tract, bladder and thyroid. On the contrary, the indifferent antibody I-131-4C4 was not retained at the tumour site 6 days after MoAb administration, and more prominent activity was found in the gastrointestinal tract. In one patient the study was not technically adequate because of failure of the delivery system. The vascular compartment contained less than 3% of the administered dose. We conclude that endobronchial administration is a feasible technique and allows stable and specific targetting of bronchial tumuors. Furthermore, the low activity found in the plasma and other organs suggests that this approach may be used to deliver therapeutic doses of MoAbs to lung cancers.