Does body size contribute to sensitivity of bone tumor induction by radionuclide exposure?

Investigation of a possible increase in sensitivity to occurrence of radionuclide-induced skeletal malignancy with increasing body size was analyzed among 358 beagles injected as young adults with either 226Ra or monomeric 239Pu and maintained for their lifespans. Corresponding analyses were performed for about 240 other beagles injected as young adults with 90Sr, 228Ra, or 228Th. Body masses at the time of injection ranged between about 5.6 and 16 kg. Logistic regression analysis using body mass and cumulative skeletal radiation dose as the independent variables indicated that there could not be established a dependency of tumor occurrence upon body mass, although skeletal dose was found to be significantly correlated with occurrence of bone cancer. Regression analysis indicated that for any dosage group there could not be established a correlation between body mass and skeletal dose. Each dosage group having similar injected kBq kg(-1) for each nuclide was divided into 2 subgroups of equal size, one containing the less massive dogs and the other containing the more massive dogs. These subgroups within a roughly uniform value of skeletal dose-rate were compared by Fisher's Exact Test, and the less massive subgroups were combined within each nuclide for an additional, separate analysis against the combined more massive subgroups using the same method. In only one instance (the dosage group given 3607 kBq 90Sr kg(-1)) was there indicated a substantially greater tumor occurrence among dogs in the more massive subgroup (p = 0.061). However, for the group given 0.382 kBq 239Pu kg(-1) there was indicated a significant difference between subgroups, but the effect was exactly opposite to that found for the highest level 90Sr dogs in that the less massive subgroup had a higher relative tumor occurrence than the most massive (p = 0.042). For all groups with a p-value < 0.10, a possible correlation was investigated between survival and body mass at injection (since bone tumor occurrence might be a function of longevity), but a significant relationship could not be determined. No significant differences could be established between the combined more massive and the combined less massive subgroups for any radionuclide. We conclude that, for the conditions in our experiment, relative size within a species does not contribute importantly to the sensitivity (lifetime occurrence) for induction of skeletal malignancy.