Table 3.

Effect of the dose of estradiol on mammary carcinogenesis

Treatment	Mammary cancer incidence	Percent of rats with mammary cancer	Average number cancers per rat
Control	7/7	100	3.6  ±  1.2
2 mg of E plus 30 mg of P	2/9	22*	0.2  ±  0.1‡
200 μg of E plus 30 mg of P	3/11	27*	0.4  ±  0.2‡
20 μg of E plus 30 mg of P	7/11	67†	0.8  ±  0.2‡

Rats were treated with MNU at 7 weeks of age. At 9 weeks of age, the rats were treated with various dosages of E plus 30 mg of P for 3 weeks. 

^*P < 0.0025 compared to control. 

^†P < 0.07 compared to control. 

^‡P < 0.05 compared to control.