In a new study, a team of researchers from the UK found that postmenopausal women with ductal carcinoma in situ (DCIS) had similar rates of cancer recurrence whether they took tamoxifen (brand name Nolvadex) or anastrozole (Arimidex) after surgery. Side effects were significantly different between the two drugs, however.
"Anastrozole offers another choice for treating patients with estrogen receptor-positive DCIS," said lead study author Jack Cuzick, PhD, director of the Wolfson Institute of Preventive Medicine at Queen Mary University of London, in a press release. "Choice may depend more on tolerability and existing conditions related to side effects than efficacy."
DCIS is a type of breast cancer that starts in the milk ducts. DCIS is noninvasive, meaning it hasn't yet spread to other parts of the breast.
For this study, Dr. Cuzick and team looked at 2,980 postmenopausal women in remission from DCIS. These patients were randomly assigned to treatment with tamoxifen or anastrozole for five years. Both groups also received a placebo of the drug they were not assigned to.
After an average of seven years, 144 of these women developed cancer again. Four died as a result.
The women on anastrozole were 11 percent less likely to experience DCIS recurrence or progress to invasive cancer than those on tamoxifen. This difference was not large enough to be considered significant, however.
The anastrozole group developed fewer endometrial, ovarian and skin cancers than the tamoxifen group — but more strokes, fractures and musculoskeletal issues. On the other hand, the tamoxifen group experienced more major blood clots and gynecological issues.
This study was presented Dec. 11 at the 2015 San Antonio Breast Cancer Symposium. It was published simultaneously in the journal The Lancet.
Cancer Research UK, the National Health and Medical Research Council of Australia, the Breast Cancer Research Fund and AstraZeneca funded this research.
Dr. Cuzick disclosed ties to AstraZeneca, a pharmaceutical company that makes products used in the treatment of breast cancer.