SAN ANTONIO—Neoadjuvant anastrozole(Drug information on anastrozole) (Arimidex, A) produced about the same rate of clinical responses as tamoxifen(Drug information on tamoxifen) (T) or combined anastrozole/tamoxifen (AT) in estrogen-receptor-positive (ER+) breast cancer and was better than either for shrinking tumors enough to permit breast-conserving surgery, researchers reported at the 26th Annual San Antonio Breast Cancer Symposium (abstract 1).
Differences in response to therapy could be predicted after 2 weeks of neoadjuvant therapy by measuring changes in expression of the cell proliferation marker Ki67 (abstract 2).
Ian E. Smith, MD, and Mitch Dowsett, MD, both from the Royal Marsden Hospital, London, reported these conclusions on behalf of investigators from the IMPACT (Immediate Preoperative Arimidex Compared to Tamoxifen) trial of postmenopausal women with ER+ operable breast cancers of 2 cm or greater diameter.
"In the overall population, A and T were similarly effective as neoadjuvant therapy in ER+ operable breast cancer in postmenopausal women. In patients recorded as requiring a mastectomy at baseline, twice as many became eligible for breast-conserving surgery in the A group as in the T group," Dr. Smith said.
This study expanded on work done in the ATAC (Anastrozole, Tamoxifen Alone or in Combination) trial, which showed that anastrozole was more effective than tamoxifen for adjuvant treatment of early hormone-receptor-positive breast cancer, Dr Smith said.
In contrast to a previous randomized neoadjuvant trial (Ann Oncol 12:1527-32, 2001), the IMPACT study enrolled patients who were eligible for breast-conserving surgery as well as those requiring mastectomy. It included 330 postmenopausal women (mean age, 72 years), with core biopsy ER+ invasive, operable breast cancer. Patients were randomized to A (n = 113), T (n = 108), or AT (n = 109) for 3 months’ treatment prior to surgery. Core biopsies were repeated after the second week of treatment. Tissues samples were taken during surgery for biological studies or by core biopsy if surgery was not performed.
The primary study endpoint was objective clinical tumor response (OR)—the product of the two maximum clinical diameters, assessed by calipers and ultrasound. Secondary endpoints included downstaging to permit breast-conserving surgery in patients initially deemed to require mastectomy, identification of surrogate markers for efficacy, and tolerability.
