SAN ANTONIONeoadjuvant anastrozole (Arimidex, A) produced about the same
rate of clinical responses as 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
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
"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
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.