Abstract

The relationship between I 131 trapping and the growth and development or regression of tumor grafts was studied. Isografts and homografts of a transmissible fibrosarcoma elicited iodide-trapping in the host. This was first observed in the area adjacent to the tumor, but at a later time the entire host was affected. Homoiografts, which initially had a high percentage of takes and a 5- to 7-day period of growth prior to regression, did not elicit iodide trapping in the host. This normally would have occurred in the preregression phase in susceptible animals. The data presented suggests that local and systemic iodide trapping parallels progressive tumor growth and that it is absent in tumor implants destined to regress. * This work was supported by a grant from the Henry, Laura, and Irene B. Dernham Fund of the American Cancer Society, California Division, and by Cancer Research funds of the University of California.