"Experiment I. The left-hand panel of Fig. 3 (top) shows the time course of the cumulative incidence of malignant tumors for the groups of RF-field-exposed animals and their sham-exposed controls. The median tumor latency was statistically significantly longer for RF-field-exposed animals than for controls (278 days compared to 145 days, P = 0.009), but the cumulative tumor incidences at day 334 (the latest day on which both curves are comparable) were more or less identical, 82% for exposed animals and 79% for control animals (see Table 1). The right-hand panel of Fig. 3 (top) illustrates the corresponding time course of the cumulative incidence of benign tumors in the experimental and control groups. It is apparent that benign mammary tumors were observed later than malignant tumors, at a time when the development of malignant tumors was more or less completed. The median latencies for benign tumors were practically identical for RF-field-exposed animals and for controls (310 days compared to 316 days, P = 0.878), and the cumulative tumor incidences at day 334 were also almost the same, 91% for the exposed and 90% for the control animals.

Experiment II. The middle panels of Fig. 3 show that there were no differences between RF-field-exposed and sham-exposed animals in the development of either malignant or benign tumors. The statistical analyses (see Table 1) revealed identical median tumor latencies of 95 days for malignant tumors in both groups; tumor latencies for benign tumors were .265 days in controls and 221 days in the RF-field-exposed group, which is statistically insignificant (P = 0.758 and P = 0.557 for differences between the groups for the development of malignant and benign tumors, respectively). Cumulative tumor incidences for malignant tumors were 84% in the controls and 94% in experimental animals. Cumulative tumor incidences for benign tumors were 38% in sham-exposed animals and 60% in RF-field-exposed animals.

Experiment III. The bottom panels of Fig. 3 demonstrate a lack of any difference between RF-field-exposed and sham-exposed animals for the development of malignant as well as benign tumors. Table 1 lists the results of the statistical analysis: There was no difference between RF-fieldexposed and sham-exposed animals in the development of malignant (P = 0.939) and benign (P = 0.568) tumors, with median tumor latencies of 216 days in controls and 195 days in RF-field-exposed animals for malignant tumors and of 293 and 321 days for benign tumors. The cumulative tumor incidences were similar in both groups for malignant tumors (control: 91%; RF-field-exposed: 81%) as well as for benign tumors (controls: 89%; RF-field exposed: 92%).

Comparison between experiments I–III. The likelihood ratio test revealed that tumor development as a whole differed significantly in the three different experiments (P , 0.0001 for malignant tumors and P , 0.0005 for benign tumors). However, there was no significant difference between the development of tumors in the sham- and RFfield-exposed groups (P = 0.47 for malignant tumors and P = 0.38 for benign tumors). Moreover, there were no significant interactions between the three experiments and the two treatments (P = 0.12 for malignant tumors and P = 0.41 for benign tumors). The risk ratios were 1.08 (95% CI: 0.91–1.29) and 0.96 (95% CI: 0.85–1.07) for benign and malignant tumors, respectively."

Sprague-Dawley rats, female - DMBA

HAWC