A model of tumor cell dormancy: effects of anesthesia and surgery.

Three cloned populations of tumor cells obtained from a murine fibrosarcoma were able to remain viable for a long period of time in syngeneic mice which failed to exhibit clinically evident tumors following tumor cell inoculation. Viable tumor cells under such conditions can be considered to be in a dormant state. On the basis of past studies, two of the lines were shown to have low malignant potential, while the third line was shown to have a higher degree of malignant potential. The rates of spontaneous reactivation of tumor growth in animals carrying the low malignant cells were 3 and 4%, while a rate of 30% was observed in animals with the more malignant cells. Treatment of animals carrying the low malignant cells in a dormant state with anesthesia alone, (thiopental) or with anethesia and surgery, increased the rate of reactivation to 20-22%.