Recurrence Risk Reduced With AI vs Tamoxifen in Premenopausal ER+ Breast Cancer

Premenopausal women undergoing ovarian suppression for estrogen receptor-positive (ER+) early stage breast cancer had an approximately 20% reduction in risk of breast cancer recurrence when treated with an aromatase inhibitor (AI) rather than tamoxifen, according to the results of a meta-analysis presented at the 2021 San Antonio Breast Cancer Symposium (SABCS).

Results of the study were presented by Rosie Bradley, of University of Oxford, United Kingdom. Bradley and colleagues performed a meta-analysis that included individual patient data from 4 randomized clinical trials including 7030 premenopausal women with ER+ breast cancer.

All women had undergone ovarian suppression or ablation and were randomly assigned to either an AI or tamoxifen for 3 years (ABCSG XII trial) or 5 years (SOFT, TEXT, and HOBOE trials). The primary outcomes were time to invasive breast cancer recurrence and breast cancer mortality.

Looking at these trials, the annual rate of recurrence averaged 21% lower for women assigned to an AI compared with tamoxifen (rate ratio [RR], 0.79; 99% CI, 0.69-0.90; P =.0005). At 10 years, there was a 2.8% absolute gain in any recurrence (17.5% for tamoxifen vs 14.7% for AI).

The researchers next looked at recurrence by follow-up period. The main benefit from an AI was seen in years 0 to 4 (RR, 0.68; 95% CI, 0.58-0.80), during the years when treatment was different. Subgroup analyses showed that the reduction in recurrence during this period did not vary by age; body mass index; or by tumor size, grade, histological subtype; or presence and absence of chemotherapy.

There was no further benefit or loss of benefit in years 5 to 9 (RR, 0.98; 99% CI, 0.73-1.32). The researchers noted there are limited follow-up data beyond 10 years.

Although distant recurrence was reduced with an AI (RR, 0.83; 95% CI, 0.71-0.97; P =.02), there was no difference in breast cancer mortality. According to Ms Bradley, longer follow-up is needed to assess this effect.

Finally, Ms Bradley noted that there was no increase in non-breast cancer deaths and more fractures occurred in women receiving an AI.

Reference

Bradley R, Braybrooke J, Gray R, et al. Aromatase inhibitors versus tamoxifen in pre-menopausal women with estrogen receptor positive early stage breast cancer treated with ovarian suppression: a patient level meta-analysis of 7,030 women in four randomized trials. Presented at SABCS 2021; December 7-10, 2021; San Antonio, TX. Abstract GS2-04.

This article originally appeared on Cancer Therapy Advisor