The research involved a combination of two large, international phase 3 clinical trials, which found that a drug known as exemestane is more effective than tamoxifen at preventing breast cancer recurrence in young women with hormone-sensitive breast cancer, a common type of breast cancer. This landmark study is the first to demonstrate that taking exemestane while blocking ovarian function reduces cancer recurrence in young women with hormone-receptive breast cancer. These results provide a new treatment option for premenopausal women formerly available only to postmenopausal women.
The culmination of a decade-long, worldwide collaboration spanning 27 countries and six continents, the breast cancer study is the largest of its kind. The study involved two trials known as TEXT (Tamoxifen and Exemestane Trial) and SOFT (Suppression of Ovarian Function Trial) and showed that treatment with exemestane plus ovarian function suppression (OFS) 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 OFS. At five years from study entry, 92.8 percent of women remained free from breast cancer after treatment with exemestane plus OFS while 88.8 percent were breast cancer-free after receiving tamoxifen plus OFS.
“Previously, aromatase inhibitors like exemestane were only recommended for postmenopausal women,” said Geyer, associate director for clinical research at Massey, who oversaw the National Surgical Breast and Bowel Project’s (NSABP) involvement in SOFT when he served as its director of medical affairs from 2004 to 2011. “These results show that the benefits of treatment involving aromatase inhibitors can be extended to premenopausal women.”
The TEXT and SOFT trials were phase 3 randomized clinical trials that, combined, enrolled more than 5,700 premenopausal women with hormone-sensitive early breast cancer between November 2003 and April 2011. Hormone-sensitive breast cancer, defined as estrogen and/or progesterone receptor-positive breast cancer, represents 79 percent of breast cancers diagnosed in women under age 50 in the United States. Massey was among more than 500 medical institutions that participated in the trials. In the two trials, 4,690 women were randomly assigned to five years of adjuvant, or post-surgical, treatment with exemestane plus OFS or assigned to tamoxifen plus OFS. SOFT included a third treatment – tamoxifen alone – and those results are expected to be analyzed later this year. The women may also have received chemotherapy as part of adjuvant treatment.
“The two trials were designed to be complementary. They were conducted over the same time period, in the same general population and have the two treatments in common,” Geyer said. “This allowed us to meet the study criteria faster so that we could translate the findings into practice sooner.”
In premenopausal women, use of an oral aromatase inhibitor such as exemestane requires suppression of estrogen produced by the ovaries. In TEXT and SOFT, OFS was achieved either by use of monthly injections of a drug known as triptorelin, surgical removal of the ovaries or radiation therapy to the ovaries.
In addition to assessing the treatments’ effectiveness at reducing recurrence, patient-reported quality-of-life assessments as well as physician-reported side effects were collected throughout the five years. Participants reported similar quality-of-life results and frequency of severe side effects regardless of whether they were treated with exemestane or tamoxifen. The side effects in the premenopausal women were similar to those in postmenopausal women for whom tamoxifen and aromatase inhibitors are widely prescribed. Women in both trials will continue to be followed to assess long-term prognosis, tolerability and side effects.
For more information about this research, visit www.ibcsg.org.
By John Wallace
VCU Massey Cancer Center