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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