Methods: 14387 mice were exposed to whole-body neutron dosages ranging from 0.94 to 301.44 cGy. 5625 mice were controls. Mice lived the remainder of their natural lifespan. Rates of tumors were determined from the pathology of mice. A weighted regression analysis compared the prevalence of tumors to neutron dosages. Pearson correlations and p-values for the analysis were determined.

Results: There was a significant positive relationship between neutron dosage and non-lethal GI, non-lethal non-lymphoreticular connective tissue, non-lethal adrenal gland, non-lethal kidney, non-lethal urinary bladder, lethal Haderian gland, and lethal adrenal gland tumors. There was a significant negative relationship between neutron dosage and lethal lymphoreticular and lethal lung tumors. Mice exposed to higher neutron dosages died sooner. The relationship was a loss of 1.4 days of life per cGy of neutron exposure.

Discussion: Multiple tumors were associated with increasing dosages. It is important to note that the cause of death was not determined for all mice; therefore, even if a tumor is classified as non-lethal, it could in actuality have been the cause of death. The negative relationship between neutron dosage and certain tumors could be explained by the fact that mice exposed to higher neutron dosages had a shorter life-span, and thus did not live long enough to develop these tumors. Further analysis could help to determine to what extent neutrons associated with IMRT can affect the incidence of secondary malignancies.