Findings from the ATAC (Arimidex, Tamoxifen Alone or in Combination) Study for the management of early breast cancer were presented at the 18th UICC Cancer Congress in Oslo, Norway. The ATAC Study involved over 9,300 post-menopausal women worldwide.

According to Dr. Sean Duffy of St. James University Hospital in Leeds, UK, a lead ATAC investigator, the ATAC results show that anastrozole, an aromatase inhibitor (AI), is more effective in reducing the risk of cancer recurring in the same breast, the opposite breast, or elsewhere in the body when compared to tamoxifen. He noted that this is the first time an AI has been proved to be superior to tamoxifen in early breast cancer.

Anastrozole was also associated with a number of important tolerability advantages over tamoxifen - a key consideration in early breast cancer where women who are otherwise 'healthy' routinely take hormonal treatment for up to 5 years after initial tumor-removing surgery.

Perhaps the most important of these advantages was that anastrozole reduced the risk of developing abnormalities of the lining of the womb (endometrium) when compared to tamoxifen. Data presented from a sub-study of 279 trial patients demonstrated that anastrozole halved the risk of endometrial abnormalities compared to tamoxifen.

"This is an extremely important finding," said Duffy in his presentation to attendees. "Even though the risk of developing endometrial cancer when taking tamoxifen is small, and the benefits of this therapy far outweigh the risk, it has been a well known concern for doctors and their patients for some time. However, the ATAC study now demonstrates that anastrozole reduces the risk of endometrial cancer as well as the incidence of vaginal bleeding, compared to tamoxifen. This suggests that women treated with anastrozole are less likely to suffer the anxiety of having to undergo invasive procedures in hospital to rule out endometrial cancer as the cause of the bleeding."

Other tolerability advantages in favor of anastrozole reported at the UICC meeting included a significant reduction in the incidence of hot flushes and thromboembolic events such as deep vein thrombosis when compared to tamoxifen.

Although the overall incidence of fractures was lower in the tamoxifen group, the incidence of hip fractures, which are associated with the highest mortality, was lower in the group treated with anastrozole (11 vs. 13 cases, respectively). Tamoxifen is known to have protective effects on bone in postmenopausal women and this may account for the difference in fracture rates between treatments to some extent.

SOURCE:
18th UICC International Cancer Congress, July 3, 2002, Oslo, Norway