Results of IES presented at ECCO

Pfizer Inc today announced new, longer-term data from the Intergroup Exemestane Study (IES) showing that women who switched to AROMASIN® (exemestane tablets) after taking tamoxifen for two to three years experienced a significant reduction (18%) in the risk of disease-free survival (DFS) events. In addition, IES showed that AROMASIN prolonged overall survival (OS) in the ER+/unknown population with a 14% reduction in the risk of dying. These results demonstrate that the benefits of treatment are maintained in long term follow-up. These results were presented at the joint ECCO 15/ESMO 34 meeting in Berlin, Germany.

“These new, long-term follow-up data of the IES demonstrate a significant survival benefit for patients who switched to AROMASIN compared to those who stayed on tamoxifen,” said Charles Coombes, head of the oncology department at Imperial College, London, UK and principal investigator of the IES. “These findings are important to patients and physicians alike as they reaffirm their confidence in switching to AROMASIN after two to three years of tamoxifen.”

IES is a landmark trial with the longest follow-up of endocrine treatment in the adjuvant switch setting. It is a randomized, double-blind, multinational trial of postmenopausal women with early breast cancer.  IES evaluates the clinical benefits of switching 2,352 patients to AROMASIN after two to three years of tamoxifen versus continuing 2,372 patients on tamoxifen for a full five years of therapy. The primary endpoint of the study was DFS in the intent-to-treat (ITT)population. Within the IES, 97% of the study population was oestrogen-receptor positive/unknown.

In postmenopausal women with early breast cancer at a median follow-up of 91 months, switching to AROMASIN after two to three years of tamoxifen, for a total of five years of treatment, was shown to result in a:

• 16% reduction in the risk of DFS events, defined as local or distant recurrence of breast cancer, contralateral breast cancer, or death from any cause, compared to staying on tamoxifen for five years population.
• For the secondary endpoint of overall survival in the ITT population, there was an 11% relative risk reduction of death. There was a statistically significant 14% reduction in the risk of death noted in the ER+/unknown population.

These DFS and OS data are consistent with the previous IES update at 55.7 months. Additionally, AROMASIN’s safety profile at 91 months was similar to that shown previously. An analysis of events of interest including cardiovascular and musculoskeletal showed no new serious adverse events in comparison to the previous analysis.

“AROMASIN has proven to be an effective treatment for postmenopausal women with oestrogen-receptor positive early breast cancer after 2-3 years of tamoxifen treatment,” said Mace Rothenberg, MD, senior vice president, clinical development and medical affairs, Pfizer Oncology. “The extraordinarily long-term follow up of patients enrolled in this study adds to the body of data supporting AROMASIN’s benefits and further underscores Pfizer’s commitment to oncology.”