New data from the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-33 study, presented today at the San Antonio Breast Cancer Symposium, showed that postmenopausal women with hormone receptor-positive breast cancer who received Aromasin after five years of tamoxifen were 56% less likely to have a relapse of breast cancer than those who received placebo (P=0.004).
"Aromasin provided patients with improved relapse-free survival despite early study closure, unblinding and crossover in the placebo arm," said Dr. Terry Mamounas, NSABP breast committee chairman and lead investigator for the B-33 study. Median follow-up of 30 months also showed that disease-free survival was improved by 32% (P=0.07). Toxicity experienced with Aromasin in the B-33 trial was acceptable for the adjuvant setting.
These results continue to add to the body of evidence supporting the use of Aromasin after tamoxifen. According to Professor Charles Coombes, lead investigator for the landmark Intergroup Exemestane Study (IES) and director of cancer medicine, Imperial College, London, "Results from the IES show a clear benefit for women who receive Aromasin after two to three years of tamoxifen. The B-33 study results presented today show that Aromasin is also effective in the extended adjuvant setting after five years of tamoxifen."
The B-33 trial was a randomized, placebo-controlled, double-blind trial open to hormone receptor-positive breast cancer patients who were breast cancer free, having completed about five years of tamoxifen therapy - the standard treatment at the time of the start of the trial. Patients were randomly assigned to receive either exemestane or placebo for two years, which was later extended to five years in order to assess the clinical benefits of using Aromasin in the extended adjuvant setting.
Accrual of the B-33 study stopped in October 2003, after disclosure of results from the NCIC MA.17 trial. By this time, about half the intended number of patients had been enrolled (1598) and the study was unblinded. All patients receiving placebo were offered Aromasin and 44% of such patients chose to cross over to Aromasin. The majority of patients on the Aromasin arm (72%) continued with the trial.
In addition to disease free survival and relapse free survival, the B-33 trial also evaluated overall survival. At 30 months median follow-up, no overall survival benefit was shown (13 deaths on placebo vs. 16 on Aromasin, HR=1.2, P=0.63).
Toxicity experienced with Aromasin in the B-33 trial was acceptable for the adjuvant setting. Up until the time of unblinding, the most common grade 3-4 toxicities in Aromasin vs. placebo were arthralgia (1.0% vs. 0.5%), fatigue (0.9% vs. 0.5%) and bone pain (0.5% vs. 0.7%). At six months after the unblinding of the study, there was no statistically significant difference in fractures with Aromasin in comparison to placebo - 28 patients with fractures in the Aromasin arm vs. 20 in the placebo arm (P=0.33), and no differences were experienced in a range of quality of life categories; vasomotor, psychosocial, physical or sexual symptoms.
About Breast Cancer
Breast cancer is the second most common cancer among women. Every year, more than one million women worldwide are diagnosed with the disease. Estrogen is one of the most significant contributors to the development of breast cancer: and two-thirds of all breast cancer cases are estrogen-dependent. Hormonal therapy, such as Aromasin, is an important treatment option for early breast cancer.
Aromasin is currently indicated for the adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer who have received two to three years of tamoxifen and are switched to Aromasin for the completion of a total of five consecutive years of adjuvant hormonal therapy. This indication is based on the results of the IES study. Study results from a median follow-up of 34.5 months showed that switching to AROMASIN after two to three years of tamoxifen, for a total of five years treatment resulted in a 31% lower risk of breast cancer recurrence than staying on tamoxifen in the intent-to-treat [ITT] population. The results also demonstrated a 35% risk reduction in breast cancer recurrence for patients with hormone receptor-positive breast cancer. Overall survival data were not statistically significant at 34.5 months.
Updated 56 month follow-up data, presented at the 2006 American Society of Clinical Oncology (ASCO) meeting, demonstrate a 17% overall survival benefit in the ITT population and a 25% lower risk of breast cancer recurrence for patients with ER+/unknown breast cancer.
Aromasin is also indicated for the treatment of advanced breast cancer in women with natural or induced postmenopausal states, whose disease has progressed following tamoxifen therapy.
Aromasin was approved in the United States in 2005 for treatment of postmenopausal women with estrogen-receptor positive early breast cancer following two to three years of tamoxifen, for a combined total of five consecutive years of therapy. It also is approved for use in Canada, Europe, Japan and South America. Currently, Aromasin is available in more than 80 countries and is approved in the early breast cancer setting in more than 40 countries.
Aromasin should not be used in women who are premenopausal, are nursing or pregnant, have a known hypersensitivity to the drug, or are taking estrogen-containing agents. Dose modification is recommended for patients who are receiving certain medications, including strong CYP 3A4 inducers such as rifampicin and phenytoin.
In patients with early breast cancer, elevations in bilirubin, alkaline phosphatase, and creatinine were more common in those receiving Aromasin than either tamoxifen or placebo. Incidence of adverse events (AEs;%) occurring in = 10% of patients in any treatment group (Aromasin vs tamoxifen) in IES were hot flushes (21.2 vs. 19.9), fatigue (16.1 vs. 14.7) arthralgia (14.6 vs. 8.6), headache (13.1 vs. 10.8, insomnia (12.4 vs. 8.9), and increased sweating (11.8 vs. 10.4). Most common adverse events reported for advanced breast cancer were mild to moderate and included hot flashes (13%), nausea (9%), fatigue (8%), increased sweating (4%) and increased appetite (3%).