The results of a recently completed clinical study presented at the 2014 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago and now published online in the New England Journal of Medicine demonstrate that Aromasin® (exemestane), is more effective than tamoxifen, in preventing breast cancer recurrence in young women who also receive post-surgical treatment to suppress ovarian function.
Treatment with an aromatase inhibitor, such as Aromasin, has previously been demonstrated to benefit postmenopausal breast cancer patients compared to treatment with tamoxifen. Aromatase inhibitors prevent the formation of estradiol, a female hormone, by interfering with an aromatase enzyme. Both trials in the current report were conducted to determine whether this benefit could be extended to premenopausal women by combining Aromasin with ovarian function suppression. Hormone-sensitive breast cancer, defined as estrogen and/or progesterone receptor-positive breast cancer, represents 80 percent of breast cancers diagnosed in women under age 50 in the United States.
The trials reporting these results were phase III, randomized clinical trials that enrolled 2,672 and 3,066 premenopausal women with hormone receptor-positive early breast cancer, respectively, between November 2003 and April 2011. In the two trials, 4,690 women were randomly assigned to 5 years of post-surgical ovarian function suppression and either Aromasin or tamoxifen and directly compared. Ovarian function suppression was achieved by use of monthly injections of the GnRH agonist Trelstar® (triptorelin), surgical removal of both ovaries, or radiation therapy to the ovaries.
Treatment with Aromasin plus ovarian function suppression reduced the risk of any invasive cancer by 28 percent, and reduced the risk of invasive breast cancer recurrence by 34 percent, compared to treatment with tamoxifen plus ovarian function suppression. At five years from study entry, 92.8 percent of women remained free from breast cancer after treatment with Aromasin plus ovarian function suppression compared to 88.8 percent of those treated with tamoxifen plus ovarian function suppression.
The trials demonstrate that an aromatase inhibitor, previously recommended only for postmenopausal women, is also effective for premenopausal women when combined with ovarian function suppression. These results provide a new treatment option for young women with hormone-sensitive breast cancer. In the two treatments studied, the patient-reported quality of life results were similar overall, as was the frequency of severe side effects
Reference: Pagani O, et al. Adjuvant exemestane with ovarian suppression in premenopausal breast cancer. NEJM early online. June 1, 2014. ASCO late breaking abstract #1.