Arimidex Beats Tamoxifen in Keeping Breast Cancer at Bay

FRIDAY, Dec. 14 (HealthDay News) -- The aromatase inhibitor drugArimidex continues to outpace the old standard tamoxifen when it comes topreventing recurrences of hormone-receptor-positive breast cancers inpostmenopausal women.
Even three years after treatment was stopped, women taking Arimidexstill saw a benefit, researchers said.
"It has been very good news," said Dr. Aman Buzdar, U.S. principalinvestigator of the ATAC (Arimidex or Tamoxifen Alone or in Combination)trial, the results of which were expected to be presented Friday at the2007 San Antonio Breast Cancer Symposium.
"A lot more women receiving Arimidex are free of cancer compared totamoxifen, and the 100-month data show that these differences, ifanything, with time actually continued to increase -- meaning there werefewer and fewer recurrences on Arimidex compared with tamoxifen," Buzdarsaid.
"Arimidex is the standard of care for postmenopausal women withreceptor-positive breast cancer," confirmed Dr. Jay Brooks, chairman ofhematology/oncology at Ochsner Health System in Baton Rouge, La. "Onehundred months [over eight years] of follow-up is very profound. It's atrue credit to the investigators to be able to do the study and have thatmuch follow-up, and it shows that we have reached a new level of care forpostmenopausal women. That's what I use and continue to use."
Hormone-receptor-positive cancers respond to circulating estrogen orprogesterone. Experts estimate that from 50 percent to 70 percent ofbreast cancers are hormone receptor positive.
The new findings were also expected to be published in the journalThe Lancet Oncology to coincide with the presentation.
Arimidex (anastrozole) is an aromatase inhibitor, a relatively newclass of compounds that blocks estrogen production in the body. Accordingto Buzdar, who is professor of medicine and deputy chair of the departmentof breast medical oncology at the University of Texas M.D. Anderson CancerCenter, Arimidex is now indicated for postmenopausal women who have ahormone-dependent cancer.
Tamoxifen, which has been the gold standard of care in breast cancertreatment for more than 20 years, hinders the tumor's ability to useestrogen. Because Arimidex does not interfere with ovarian function,tamoxifen should still be used by premenopausal women with activeovaries, Buzdar said.
The first major results from ATAC, reported in 2001, found thatArimidex was more effective than tamoxifen in preventing a breast cancerrecurrence and was better tolerated.
Subsequent data continued to show positive results.
The current data represent five years of active treatment plus threeadditional years of follow-up. In all, more than 9,000 women in 21countries were involved in the study.
All the women had early-stage disease and had undergone surgery with orwithout chemotherapy and/or radiation. Eighty-four percent of participantshad hormone-receptor-positive tumors.
The women were randomized to receive Arimidex alone or tamoxifen alone(a third arm involving a combination therapy had been halted earlier).
At the time of this 100-month follow-up, the mean age of participantswas 72 years.
Arimidex improved disease-free survival by 15 percent compared withtamoxifen in women with hormone-receptor-positive breast cancer. The drugreduced the risk of all recurrences by 24 percent.
The improvement persisted even after treatment was stopped.
"The other question which was in all of our minds was what happensafter you stop the pill," Buzdar said. "The pill was stopped three yearsago, and the effect continues to be there. Even after stopping therapy,there are fewer recurrences in people who took Arimidex in the past."
The most common side effects were joint pain and estrogen deprivationleading to osteoporosis. Once the pill was stopped, however, a woman'srisk of developing osteoporosis returned to normal. No new side effectswere seen.
"Not only are you keeping more patients alive free of disease, but thesafety profile is much more predictable and much more favorable thantamoxifen," Buzdar said.
More information
There's more on aromatase inhibitors at the U.S. National Cancer Institute.