Seven trials (30,023 patients) were included in the review. The median follow-up ranged from 28 to 100 months.
Pooled analysis of all three cohorts showed that longer duration of aromatase inhibitor use significantly increased the risk of cardiovascular disease (OR 1.26, 95% CI 1.10 to 1.43; seven trials; NNH=132) and bone fractures (OR 1.47, 95% CI 1.34 to 1.61, six trials; NNH=46).
The risk of venous thrombosis (OR 0.55, 95% CI 0.46 to 0.64; six trials; NNH=79) and endometrial carcinoma (OR 0.34, 95% CI 0.22 to 0.53; six trials; NNH=258) were significantly reduced with longer duration of aromatase inhibitor use. Subgroup analysis showed no significant difference between longer duration aromatase inhibitors versus switching from tamoxifen to aromatase inhibitors for these two outcomes.
There was a non-statistically significant increased risk of death without breast cancer recurrence in the analysis of treatment with five years of aromatase inhibitors versus five years of tamoxifen alone or switching from tamoxifen to an aromatase inhibitor. No differences were observed between the treatment strategies in terms of cerebrovascular disease and other second cancers.
There was no statistically significant heterogeneity. Sensitivity analysis did not alter the main findings.
Further results were reported in the review.