Long-term data show superiority of anastrazole over tamoxifen in early breast cancer

December 14, 2007

NEW YORK (Reuters Health) - Approximately 8 years of follow-up data show that, for postmenopausal women with hormone-sensitive breast cancer, anastrazole (Arimidex) is associated with a lower risk of recurrence than tamoxifen (Novaldex), investigators reported at the annual meeting of the San Antonio Breast Cancer Symposium being held this week.

The multinational Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial involved 6,241 women with localized, invasive breast cancer. Following treatment with surgery, radiotherapy, chemotherapy, or a combination of these primary treatments, the patients were randomized to receive anastrazole, tamoxifen or both drugs for 5 years,.

After a median follow-up of 68 months, disease-free survival was 15% lower with anastrazole, and time to disease recurrence was increased by 25%. Time to distant metastasis was approximately 16% longer and the development of new cancers was reduced by more than 50% with anastrazole.

More than 3 years after completion of treatment, the gap between tamoxifen and anastrazole widened regarding risk of recurrence and risk of distant metastasis, although there was no difference in effect on overall survival.

Principal investigator in the US, Dr. Aman U. Buzdar, of The University of Texas MD Anderson Cancer Center in Houston, told Reuters Health that "there is a persistently positive effect with anastrazole."

"Anastrazole has a lot of the same adverse effects as tamoxifen, such as nausea and vomiting, hair loss, fever and risk of infection, but they are milder. And once treatment has stopped, the risk of fractures with anastrazole drops back down to that of tamoxifen. There is no carry-over effect with fracture risk with anastrazole."

"Over time, the benefits (of anastrazole) become more striking, cutting the risk of recurrence in one out of four women. The risk of uterine cancer is also lower with anastrazole than tamoxifen," Dr. Buzdar added.

"The standard of care is changing for postmenopausal women," Dr. Buzdar said.

Along with the meeting presentation, the ATAC results are being simultaneously published online December 14, 2007 by Lancet Oncology.

Investigator Dr. Anthony Howell of Christie Hospital NHS Trust in Manchester, UK, said in a release issued by The Lancet that "these new data from the ATAC trial suggest that it is not appropriate to wait to start an aromatase inhibitor (in early hormone receptor-positive breast cancer)."

"The higher rates of recurrence (especially in years 1 through 3), and the increased numbers of adverse events and treatment withdrawals associated with tamoxifen, lend support to the approach of offering the most effective and well tolerated therapy at the earliest opportunity."

"Five years of anastrozole should now be considered as the preferred initial adjuvant endocrine treatment for postmenopausal women with hormone-receptor-positive localized breast cancer," Dr. Howell concludes.