Lung Lavage Therapy to Lessen the Biological Effects of Inhaled|${}^{144}{\rm Ce}$| in Dogs

To evaluate the therapeutic effects of removal of an internally deposited radionuclide on long-term biological effects, lung lavage was used to treat dogs that had inhaled|${}^{144}{\rm Ce}$| in a relatively insoluble form, in fused aluminosilicate particles. Either 10 lung lavages were performed between Days 2 and 56 after exposure or 20 lung lavages were performed between Days 2 and 84 after exposure. Approximately one-half of the|${}^{144}{\rm Ce}$| was removed by the lavages, resulting in a corresponding reduction in the total absorbed β dose to lung. The mean survival time of the treated dogs was 1270 days compared to 370 days for untreated dogs whose initial pulmonary burdens of|${}^{144}{\rm Ce}$| were similar. Treated dogs died late from cancers of the lung or liver, whereas the untreated dogs died at much earlier times from radiation pneumonitis. Dogs treated with lung lavage but not exposed to|${}^{144}{\rm Ce}$| had a mean survival of 4770 days. We concluded that removal of|${}^{144}{\rm Ce}$| from the lung by lavage resulted in increased survival time and in a change in the biological effects from inhaled|${}^{144}{\rm Ce}$| from early-occurring inflammatory disease to late-occurring effects, principally cancer. In addition, the biological effects occurring in the treated dogs could be better predicted from the total absorbed β dose in the lung and the dose rate after treatment rather than from the original dose rate to the lung. Therefore, we concluded that prompt treatment to remove radioactive materials could be of significant benefit to persons accidentally exposed to high levels of airborne, relatively insoluble, radioactive particles.