AROMASIN is an aromatase inhibitor indicated for:...adjuvant treatment of postmenopausal women with estrogen-receptor positive early breast cancer who have received two to three years of tamoxifen and are switched to AROMASIN for completion of a total of five consecutive years of adjuvant hormonal therapy...

4724 postmenopausal patients with unilateral invasive, oestrogen-receptor-positive or oestrogen-receptor-unknown breast cancer who were disease-free on 2–3 years of tamoxifen, were randomly assigned to switch to exemestane (n=2352) or to continue tamoxifen (n=2372) for the remainder of a 5-year endocrine treatment period....After a median follow-up of 55·7 months (range 0–89·7), 809 events contributing to the analysis of disease-free survival had been reported (354 exemestane, 455 tamoxifen); unadjusted hazard ratio 0·76 (95% CI 0·66–0·88, p=0·0001) in favour of exemestane, absolute benefit 3·3% (95% CI 1·6–4·9) by end of treatment (ie, 2·5 years after randomisation).

...DISEASE CHARACTERISTICS: At diagnosis: Histologically confirmed unilateral adenocarcinoma of the breast that was considered operable Must have had adequate therapy for primary disease including chemotherapy/ovarian ablation if appropriate and local postoperative radiotherapy if the patient received conservative (breast preserving) surgery Must have remained disease-free after therapy for primary disease Must have been receiving tamoxifen for minimum of 2 years and maximum of 3 years 1 month with no more than 1 month break at any one time No inflammatory breast cancer, histologically positive supraclavicular nodes, or ulceration/infiltration or skin metastases No evidence of local relapse or distant metastasis (on chest x-ray, scintigraphic bone scanning and liver ultrasonography/CT scanning) at any time Hormone receptor status: Estrogen receptor positive or unknown...

Event-free survival probability at 36 months was 91.4% (95% CI, 87.7%-95.1%)….This study supports the efficacy and safety of exemestane in postmenopausal Chinese women with ER+ breast cancer previously treated with adjuvant tamoxifen for 2-3 years.

We did a meta-analysis of individual patient data from randomised trials comparing aromatase inhibitors (anastrozole, exemestane, or letrozole) versus tamoxifen for 3 or 5 years in premenopausal women with ER-positive breast cancer receiving ovarian suppression (goserelin or triptorelin) or ablation....The rate of breast cancer recurrence was lower for women allocated to an aromatase inhibitor than for women assigned to tamoxifen (RR 0·79, 95% CI 0·69-0·90, p=0·0005). The main benefit was seen in years 0-4 (RR 0·68, 99% CI 0·55-0·85; p<0·0001)...