ABSTRACT
BACKGROUND: In most preclinical models, assessment of intraperitoneal tumor location and size require killing the animal. The dynamics of postoperative intraperitoneal tumor implantation and growth remain unclear. A noninvasive method allowing reliable in vivo, real-time assessment of tumor growth is desirable. METHODS: An intraperitoneal tumor homograft using cultured CC531 colorectal cells was created by laparotomy in 24 Wistar Albino Glaxo rats. Eight additional rats were used as controls. Then, 10 MBq technetium 99m-labeled anticarcinoembryonic antigen (anti-CEA) monoclonal antibodies were administrated intravenously and radioactivity uptake was measured by using extracorporeal gamma counting at various time points. Subsequently, the animals were killed for tumor weighting. In 2 more groups of 8 animals, real-time, repeated measures were performed. RESULTS: Correlation between gamma counting and tumor weight was highly significant (P <.001). The regression equation obtained by using the least squares method was: tumor weight (g) = 2.422 + 0.267 x counts. It was possible to obtain real-time tumor growth curves when repeated measurements of radioactivity were performed. At day 25, the predicted tumor weight was 8.49 +/- 0.76 g, the measured weight was 8.16 +/- 0.99 g. CONCLUSIONS: Immunoscintigraphic measurements with technetium 99m anti-CEA antibodies are highly correlated with tumor weight in this model. As opposed to other tumor graft models based on autopsy findings, real-time monitoring is possible. This will allow dynamic studies of intraperitoneal tumor implantation and growth and will reduce the number of animals used in further studies.
