Two Drugs Equal For Early Breast Cancer
By Kathleen Doheny
FRIDAY, Dec. 11, 2015 (HealthDay News) — Postmenopausal women who have an early, noninvasive form of breast cancer had similar recurrence rates of disease whether they took the drug tamoxifen or the aromatase inhibitor anastrozole after surgery, new research shows.
However, the side effects of the two medications differed greatly, said study author Jack Cuzick, director of the Wolfson Institute of Preventive Medicine at Queen Mary University of London, England.
His team looked at nearly 3,000 women, all past menopause, who had hormone-receptor positive ductal carcinoma in situ (DCIS) breast cancer and underwent surgery to excise it. With DCIS, the cells that line the milk ducts have changed but not spread into the surrounding breast tissue.
Half the women were randomly assigned to take 1 milligram (mg) a day of anastrozole (Arimidex), while the other half took 20 mg a day of tamoxifen (Nolvadex). Each group also took a placebo pill to look like the pill they were not assigned to take, so they wouldn’t be biased about side effects.
The aim of the study was to look at breast cancer recurrence, and to see whether it was more likely with one drug than the other.
The researchers said that aromatase inhibitors such as anastrozole have been shown in other studies to be better than tamoxifen in postmenopausal women who have invasive cancers. The less-researched area, Cuzick explained, is DCIS.
After a follow-up of about seven years, those who took anastrozole had an 11 percent lower breast cancer recurrence rate than those who took tamoxifen, but that difference was not substantial from a statistical point of view, Cuzick said.
“Our results show anastrozole to be slightly better, but it was not significant,” he said. However, the side effect profiles were slightly better with anastrozole, he added.
“Tamoxifen has [potential] blood clot problems, and those don’t occur with anastrozole,” Cuzick said. And while those on anastrozole reported more aches and pains, those on tamoxifen were more likely to have hot flashes.
Tamoxifen blocks estrogen receptors in the breast cells to hamper cancer growth. Anastrozole stops estrogen production in fat tissue, which makes small amounts of hormone.