Repeated Intraperitoneal -Radioimmunotherapy of Ovarian Cancer in Mice

The aim of this study was to investigate the therapeutic efficacy of -radioimmunotherapy of ovarian cancer in mice using different fractionated treatment regimens. The study was performed using the monoclonal antibody MX35 F labeled with the -particle emitter .Methods. Nude mice were intraperitoneally inoculated with ~ cells of the cell line NIH:OVCAR-3. Four weeks later 6 groups of animals were given F as a single or as a repeated treatment of up to 6 times ( in each group). The fractionated treatments were given every seventh day. Control animals were treated with unlabeled F (). Eight weeks posttreatment the animals were sacrificed and the presence of macro- and microscopic tumors and ascites was determined.Results. The tumor-free fractions (TFFs) of the animals, defined as the fraction of animals with no macro- and microtumors and no ascites, were 0.17, 0.11, 0.39, 0.44, 0.44, and 0.67 when treated with F once or 2, 3, 4, 5, or 6 times, respectively. Repeated treatment 3 times or more resulted in a significantly higher () TFF than compared to treatment once or twice. The presence of ascites decreased from 15 out of 18 animals in the group given only one treatment to zero for the 2 groups given 5 or 6 fractions. Treatment with unlabeled F resulted in a TFF of zero.Conclusion. Weekly repeated intraperitoneal injections of tolerable amounts of activity of F of up to 6 times produced increased therapeutic efficacy without observed toxicity, indicating a potential increase of the therapeutic index.