Neoplasia in Fast Neutron-Irradiated Beagles

Abstract

One hundred fifty-one beagle dogs were irradiated with either photons or fast neutrons (15 MeV) to one of three dose-limiting normal tissues—spinal cord, lung. or brain. The radiation was given in four fractions per week for 5 weeks (spinal cord), 6 weeks (lung). or 7 weeks (brain) to total doses encompassing those given clinically for cancer management. To date, no non irradiated dogs or photon-irradiated dogs have developed any neoplasms. Seven dogs receiving fast neutrons have developed 9 neoplasms within the irradiated field. Of the neutron-irradiated dogs at risk, the incidence of neoplasia was 15%. The latent period for radiation-induced cancers has varied from 1 to 4½ years at this time in the study.