Table 3.

Effect of short-term treatments with E alone or with P on mammary carcinogenesis

Treatment	No. of rats with cancer per no. of rats	% of rats with mammary cancer	Average number of cancers per rat	Mammary cancer latency†
Control	13/15	87	2.1  ± 0.4	16.3  ± 4.1
100 μg of E + 30 mg of P (2 weeks)	3/15**	20	0.3  ± 0.1**	24.7  ± 4.8
100 μg of E (2 weeks)	7/16*	44	0.6  ± 0.2*	18.0  ± 3.2
200 μg of E + 30 mg of P (1 week)	2/14**	14	0.2  ± 0.1**	26.0  ± 6.0
200 μg of E (1 week)	3/15**	20	0.2  ± 0.1**	19.4  ± 3.0
100 μg of E + 30 mg of P (1 week)	3/14**	21	0.4  ± 0.3*	28.0  ± 1.5
100 μg of E (1 week)	6/16**	37	0.6  ± 0.2*	23.7  ± 2.6

Effect of short-term treatment with E with or without P treatments on MNU-induced mammary carcinogenesis. Rats were treated with MNU at 7 weeks of age and treated 2 weeks later with E alone or in combination with P for 2 weeks or 1 week. 

^*, P < 0.05; 

^**, P < 0.01; 

^**, P < 0.001 (compared to control). 

^† Average number of weeks to the appearance of the first palpable tumor.