Yu D, Shen Y, Kuster N, Fu Y, et al. (2006)
Five hundred female Sprague-Dawley rats were treated with a single dose of 35 mg/kg DMBA, which is known to induce mammary tumours in rats. The animals were then divided into 5 groups in a blinded and randomized fashion. There was a cage control group and 4 exposure groups, including 3 exposed to RFR and 1 sham-exposed. The RFR exposure was at 900 MHz frequency. The RFR groups were exposed for 4 h/day, 5 days a week, for 26 weeks, and then humanely euthanized. The whole-body average SAR was 4.0, 1.33, and 0.44 W/kg for the exposed groups.
Twenty rats became ill and were euthanized earlier than the 26 weeks of the planned study. They were from all the different groups. There were no statistically significant differences between sham- and RFR-exposed groups in body weight, overall tumour incidence, latency to tumour onset, tumour multiplicity, or tumour size. There were significant differences between the cage controls and the experimental groups. In the cage control the body weight and mammary tumour incidence was higher than in the other groups, and the latency to tumour onset was significantly shorter. The authors point out that the cage control rats had no limitation on feeding, while the exposed groups were no fed during their exposure periods. It has been previously reported by other authors that dietary restriction can reduce the incidence of mammary tumourigenesis.