Comparison 2. Aromatase inhibitors (AI) versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Overall breast cancer incidence	2	8424	Risk Ratio (M‐H, Fixed, 95% CI)	0.47 [0.35, 0.63]
1.1 Anastrozole vs placebo	1	3864	Risk Ratio (M‐H, Fixed, 95% CI)	0.48 [0.33, 0.69]
1.2 Exemestane vs placebo	1	4560	Risk Ratio (M‐H, Fixed, 95% CI)	0.45 [0.27, 0.77]
2 Severe toxicity	2	8352	Risk Ratio (M‐H, Fixed, 95% CI)	1.18 [1.09, 1.28]
2.1 Anastrozole vs placebo	1	3864	Risk Ratio (M‐H, Fixed, 95% CI)	1.14 [1.02, 1.28]
2.2 Exemestane vs placebo	1	4488	Risk Ratio (M‐H, Fixed, 95% CI)	1.22 [1.10, 1.36]
3 Invasive breast cancer incidence	2	8424	Risk Ratio (M‐H, Fixed, 95% CI)	0.45 [0.32, 0.64]
3.1 Anastrozole vs placebo	1	3864	Risk Ratio (M‐H, Fixed, 95% CI)	0.51 [0.33, 0.77]
3.2 Exemestane vs placebo	1	4560	Risk Ratio (M‐H, Fixed, 95% CI)	0.34 [0.17, 0.68]
4 Overall toxicity	2	8352	Risk Ratio (M‐H, Fixed, 95% CI)	1.02 [1.00, 1.04]
4.1 Anastrozole vs placebo	1	3864	Risk Ratio (M‐H, Fixed, 95% CI)	1.00 [0.98, 1.03]
4.2 Exemestane vs placebo	1	4488	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [1.01, 1.06]