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Table 1 Effect of estriol on mammary carcinogenesis

From: Prevention of mammary carcinogenesis by short-term estrogen and progestin treatments

Treatment Duration Mammary cancer incidence Rats with mammary cancer (%) Average number of cancers per rat
Control 3 weeks 8/10 80 1.7 ± 0.4
30 mg estriol 1 week 10/12 83 1.6 ± 0.3
200 μg estriol 1 week 11/11 100 1.7 ± 0.3
30 mg estriol + 30 mg progesterone 1 week 7/12 58 1.2 ± 0.3
200 μg estriol + 30 mg progesterone 1 week 9/12 75 1.6 ± 0.3
30 mg estriol 3 weeks 7/11 64 1.0 ± 0.3
200 μg estriol 3 weeks 9/12 75 1.6 ± 0.3
30 mg estriol + 30 mg progesterone 3 weeks 3/12* 25 0.4 ± 0.2*
200 μg estriol + 30 mg progesterone 3 weeks 9/11 82 2.0 ± 0.4
  1. Rats were treated with N-methyl-N-nitrosourea at 7 weeks of age. At 9 weeks of age, the rats were treated with hormones for 1 or 3 weeks. Control rats received empty silastic capsules. *P < 0.05 compared with controls.