Aromatase inhibitor may improve outcome in premenopausal breast cancer

Adjuvant therapy combining ovarian suppression with an aromatase inhibitor-a class of drugs typically only recommended for postmenopausal patients-may be more beneficial for premenopausal patients with breast cancer than tamoxifen. The findings, published in The New England Journal of Medicine, reflect a combined analysis of data from the Tamoxifen and Exemestane Trial (TEXT) and the Suppression of Ovarian Function Trial (SOFT).

The intent-to-treat population for the two Phase III trials, by investigators from the International Breast Cancer Study Group, was 4,690 women median age 43 with hormone receptor-positive early breast cancer. Randomization at Breast International Group and North American Breast Cancer group centers was to exemestane plus ovarian suppression or tamoxifen plus ovarian suppression for 5 years (November 2003 to April 2011). Suppression of ovarian estrogen production was achieved with the gonadotropin-releasing-hormone agonist triptorelin, oophorectomy, or ovarian irradiation.

The disease-free survival rate was 91.1% in the exemestane-ovarian suppression group after median follow up of 68 months, compared with 87.3% in the tamoxifen-ovarian suppression group (hazard ratio for disease recurrence, second invasive cancer, or death, 0.72; 95% confidence interval [CI], 0.60 to 0.85; P<0.001). In the exemestane-ovarian suppression group, the rate of freedom from breast cancer at 5 years was 92.8%, compared with 88.8% in the tamoxifen-ovarian suppression group (hazard ratio for recurrence, 0.66; 95% CI, 0.55 to 0.80; P<0.001). No significant difference was seen in overall survival between the two groups (hazard ratio for death in the exemestane-ovarian suppression group, 1.14; 95% CI, 0.86 to 1.51; P=0.37).

The rate of selected grade 3 or 4 adverse events was similar in the two group: 30.6% for patients receiving exemestane-ovarian suppression versus 29.4% for patients in the tamoxifen-ovarian suppression group. 

“The combined analysis of data from TEXT and SOFT,” the investigators said, “shows that among premenopausal women with hormone-receptor-positive breast cancer, adjuvant therapy with exemestane plus ovarian suppression, as compared with tamoxifen plus ovarian suppression, significantly improved disease-free survival and lengthened the interval of time without breast cancer, and the interval of time without recurrence of breast cancer at a distant site.” Further, the researchers believe that adjuvant therapy with ovarian suppression plus exemestane “provides a new treatment option that reduces the risk of recurrence.”

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