. Author manuscript; available in PMC: 2016 Jun 1.

Published in final edited form as: Cancer Prev Res (Phila). 2015 Mar 24;8(6):518–527. doi: 10.1158/1940-6207.CAPR-14-0121

Table 1.

Effect of biguanides on final mammary cancer incidence and multiplicity

Treatment^b	Palpable carcinomas^a		Microcarcinomas		Total
Treatment^b	Incidence %	Multiplicity Number/rat	Incidence %	Multiplicity Number/rat	Incidence %	Multiplicity Number/rat
Control	56.7^c	1.2 ± 0.3^c,d	80.0^c	1.6 ± 0.3^c	83.3^c	2.7 ± 0.4^c,d
Metformin	76.7^c	2.0 ± 0.3^c	86.7^c	1.6 ± 0.2^c	93.3^c	3.6 ± 0.4^c
Buformin	16.7^d	0.2 ± 0.1^e	36.7^d	0.6 ± 0.2^d	43.3^d	0.7 ± 0.2^e
Phenformin	46.7^c,d	0.6 ± 0.1^d,e	63.3^c,d	1.0 ± 0.2^c,d	76.7^c,d	1.6 ± 0.2^d,e
Overall P value	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001

Values are means ± SEM for cancer multiplicity, n = 30 rats/group. Cancer incidence was analyzed by the Fisher exact test and cancer multiplicity by Poisson regression.

Values within a column with different superscripts were statistically different by post hoc multiple comparisons, P < 0.008.

Eleven (9%) of these carcinomas were detected at necropsy. This 9% error rate was not statistically different among groups (P = 0.261).

Biguanide was provided in the diet at concentrations of: 9.3mmol metformin/kg diet, 7.6 mmol buformin/kg diet, or 5.0 mmol phenformin/kg diet.