Anastrozole Reduces Recurrence in Early Breast Cancer

The trial Arimidex, Tamoxifen alone or in combination (ATAC) was a double-blind Phase III clinical study was designed to compare the ability of the AI ​​anastrozole, tamoxifen, and two drugs in combination with cancer recurrence breast cancer in postmenopausal women with hormone receptor positive tumors.

The study included 9366 postmenopausal women with localized breast cancer (eg, cancer had not spread or metastasis). The women were randomly assigned to adjuvant 5 years with anastrozole alone, tamoxifen, or a combination of both. (The combination group was then abandoned because the results for patients in this group were essentially the same as those in the group treated with tamoxifen.) Most participants (84 percent) had a disease of hormone receptors positive.

The results after a median follow up of 68 months (5.7 years), published in 2005 (see summary of newspaper) showed that, compared with tamoxifen, anastrozole prolongs disease-free survival by 13 percent, increased the time a decrease of 21 percent, reduced the incidence of cancer spread to other organs (distant metastases) by 14 percent and reduced the incidence of breast cancer in the other by more than 40 percent. The differences are even greater when the analysis was restricted to women with hormone receptor-positive tumors.

In addition, anastrozole was associated with less severe side effects (endometrial cancer, blood clots, hot flashes and vaginal bleeding) than tamoxifen, although the fractures and joint pain are more common in patients in the anastrozole. However, overall survival was similar in both groups.

In 2006, researchers reported data from the ATAC trial showed that anastrozole was better tolerated than tamoxifen and has resulted in less severe complications (see the journal abstract). In addition, anastrozole had a favorable overall benefit-risk profile compared with tamoxifen, anastrozole and women who had a lower relapse rate than those treated with tamoxifen.

Mainly on the basis of results published in 2005, treatment with an AI has been the standard adjuvant treatment of breast cancer in hormone receptor positive, even if tamoxifen is still considered a reasonable alternative. Other studies involving a total of more than 30,000 women, confirmed that treatment with an AI alone or after tamoxifen was beneficial in patients with breast cancer hormone-sensitive.

This study reports the results from the ATAC participants were followed for a median of 10 years.

This analysis was an advantage for anastrozole compared with tamoxifen show. In women with hormone receptor positive tumors, which are randomly assigned to treatment with anastrozole had a rate of 4.3 per cent or more absolute recurrence of breast cancer after 10 years, and a rate of 2.6 per cent lower distant metastasis never, or randomly assigned to treatment with tamoxifen.

The differences between anastrozole and tamoxifen in time to recurrence, breast cancer and disease-free survival was greater in the first two years of treatment, but were maintained throughout the follow-up period, including period after treatment was completed. However, the authors found that the "effect of transferring so-called" - where the benefits go beyond the treatment period - began to decline after about 8 years.

During treatment, women in the anastrozole group had fewer treatment-related serious adverse events than women in the tamoxifen group. After treatment was completed, however, the rates of serious adverse events resolved between the two groups. Patients treated with anastrozole reported more fractures during treatment than those on tamoxifen, but after completion of treatment of fractures was again similar in both groups.

In patients taking tamoxifen had high rates of endometrial cancer and melanoma than those who anastrozole. There was a slight trend toward increased cancer and lung cancer patients treated with anastrozole compared with those of tamoxifen. Overall, however, other types of cancer, breast cancer occurred with similar frequency in both groups.

The death toll of the patient, with or without breast cancer recurrence was similar in both groups after 10 years of follow-up. Thus, treatment with anastrozole does not improve overall survival compared to tamoxifen.