Tumor bearing impairs hemopoietic recovery and survival after irradiation.

These investigations were undertaken to determine whether the hemopoietic abnormalities induced by bearing a solid sarcoma-180 (S-180) impaired recovery of hemopoiesis and shortened survival of mice after sublethal total body irradiation. Mice, intramuscularly injected with 4 x 10(6) S-180 cells before or after 600 or 700 rad total body (TB) irradiation were followed for over 1 month postirradiation compared to irradiated control mice or to tumor bearing mice receiving no irradiation. Whereas more than half of the control mice survived doses of 600 to 700 rad TB, none of the tumor bearing mice survived the same dose for over 3 weeks. Irradiated tumor bearing mice all died with smaller tumors before unirradiated tumor bearing mice began to die. Because bearing tumor profoundly suppressed medullary hemopoietic stem cells (CFUS), it was not surprising to observe impaired recovery of hemopoiesis after irradiation. Except for myeloid hyperplasia induced by tumor bearing, hemopoietic repopulation in locally irradiated femoral bone marrow (1000 rad LI) by endogenous cells was greatly diminished for at least 3 weeks. The results of these studies led us to conclude that bearing a small solid tumor of S-180 dramatically shortened survival after hematosuppressive treatment with sublethal doses of total body irradiation. Since the tumor suppressed medullary stem cells (CFUS) and inhibited endogenous repopulation of locally irradiated bone marrow, we postulate that the tumor impaired recovery of hemopoiesis after irradiation leading to bone marrow failure and premature death.