Neoplasms in young dogs after perinatal irradiation.

For a study of the life-time effects of irradiation during development, 1,680 beagles were given single, whole-body exposures to 60Co gamma-radiation at one of three prenatal (preimplantation, embryonic, and fetal) or at one of three postnatal (neonatal, juvenile, and young adult) ages. Mean doses were 0, 0.16, or 0.83 Gy. For comparison with data on childhood cancer after prenatal irradiation, examination was made of tumors occurring in young dogs in this life-span experiment. Up to 4 years of age, 18 dogs had neoplasms diagnosed, 2 of these being in controls. Four dogs that were irradiated in the perinatal (late fetal or neonatal) period died of cancers prior to 2 years of age. This risk was of significant increase compared to the risks for other experimental groups and for the canine population in general. Overall, 71% (5 of 7) of all cancers and 56% (10 of 18) of all benign and malignant neoplasms seen in the first 4 years of life occurred in 29% (480 of 1,680) of the dogs irradiated in the perinatal period. These data suggest an increased risk for neoplasia after perinatal irradiation in dogs.