Aromatase inhibitors reduce risk of breast cancer recurrence in premenopausal women

May 2022 Clinical Practice Nalinee Pandey
3d illustration Breast Cancer Cell

A recent clinical study in premenopausal women has found that treatment with aromatase inhibitor reduces the risk of breast cancer recurrence. The findings of this study were published in the journal Lancet Oncology.

Adjuvant tamoxifen reduces the 15-year breast cancer mortality by a third in women with early-stage oestrogen receptor (ER)-positive breast cancer. Aromatase inhibitors show better efficacy than tamoxifen in postmenopausal women. However, this is not the case for premenopausal women without ovarian suppression. Therefore, the study compared the effectiveness of aromatase inhibitor versus tamoxifen in premenopausal women treated with ovarian suppression.


The researchers performed a meta-analysis of data obtained from four clinical trials (ABCSG XII, SOFT, TEXT, and HOBOE trials) comparing aromatase inhibitor use with tamoxifen for 3 to 5 years in women with ER-positive. These trials included data from 7030 ER-positive breast cancer cases with a median follow up of 8.0 years. The study’s primary outcomes were breast cancer recurrence, breast cancer mortality, death without recurrence, and all-cause mortality.

Main findings

Breast cancer recurrence was reduced in women receiving aromatase inhibitors than those on tamoxifen (RR 0.9, 95% CI 0.69–0.90, p=0.0005). During the first four years (0-4), the 5-year recurrence risk was reduced from 10.1% to 6.9% due to aromatase inhibitor treatment. Also, distant recurrence was decreased with an aromatase inhibitor (RR 0.83, 95% CI 0.71–0.97; p=0.018). Notably, no further gain or loss of benefit was seen in years 5-9 or beyond ten years. Additionally, no difference in overall survival was seen in both the treatment groups. Among observed side effects, more women had bone fractures with aromatase inhibitors (5.1%) than tamoxifen (3.8%).


The data demonstrate the efficacy of aromatase inhibitors in reducing breast cancer recurrence in premenopausal women. Longer follows up are needed to assess its effect on mortality as well.


Early Breast Cancer Trial ists’ Collaborative Group (EBCTCG). Aromatase inhibitors versus tamoxifen in premenopausal women with oestrogen receptor-positive early-stage breast cancer treated with ovarian suppression: a patient-level meta-analysis of 7030 women from four randomised trials. Lancet Oncol. 2022 Mar;23(3):382-392. doi: 10.1016/S1470-2045(21)00758-0. Epub 2022 Feb 3. Erratum in: Lancet Oncol. 2022 Apr;23(4):e161. PMID: 35123662; PMCID: PMC8885431.