Biodistribution of indium-111-labeled OC 125 monoclonal antibody intraperitoneally injected into patients operated on for ovarian carcinomas.

The biodistribution of 111In-labeled monoclonal antibody (MAb) OC 125 was studied after i.p. injection in 28 patients who underwent surgery for ovarian carcinoma. Group I (eight patients) received intact 111In-labeled OC 125 MAb, Group II (three patients) intact 111In-labeled irrelevant NS, Group III (five patients) intact 111In-labeled OC 125 MAb associated with 20 mg of the same unlabeled MAb and Group IV (12 patients) F(ab')2 fragments of 111In-labeled OC 125 MAb. The patients were operated on 1 to 3 days after i.p. injection, and the surgeon removed large tumor fragments and/or small tumor nodules and, in some patients, collected the residual perfusion fluid from which malignant cell clusters were isolated. Uptake by large tumor fragments at 24 h was low: 0.0031 +/- 0.0032% injected dose per gram (%ID/g) for Group I and 0.0024 +/- 0.0022%ID/g for Group IV. It was moderately higher than that of Group II (0.0014 +/- 0.0006%ID/g) and Group III (0.0015 +/- 0.0007%ID/g). Uptake by small tumor nodules (0.1302 +/- 0.0802%ID/g at 72 h for Group I) and malignant cell clusters (median: 0.3322, with a maximum value of 4.1614%ID/g at 24 h for Group IV) was markedly higher. Tumor-to-normal tissue ratios with OC 125 MAb [intact or F(ab')2 fragments] ranged between 0.1 and 8.5 for large tumor fragments and 2 and 8,700 for small tumor nodules and malignant cell clusters. It would thus appear that RIT is feasible if an appropriate radionuclide can be selected for antibody labeling.