Aromatase inhibitors and tamoxifen are two types of hormonal therapy medicine given to post-menopausal women to lower the risk of hormone-receptor-positive, early-stage breast cancer coming back (recurrence). Hormonal therapy medicine given after surgery and other treatments (chemotherapy, radiation therapy) is called adjuvant hormonal therapy.
The study reviewed here found that taking the aromatase inhibitor Aromasin (chemical name: exemestane) as adjuvant hormonal therapy lowers the risk of breast cancer coming back somewhat better than tamoxifen. These results were presented at the 2008 San Antonio Breast Cancer Symposium.
Post-menopausal women treated for early-stage, hormone-receptor-positive breast cancer commonly take hormonal therapy medicine for 5 years after surgery and other treatments. In some cases, women start taking tamoxifen and then switch to an aromatase inhibitor after a couple years. Some research suggests that taking hormonal therapy medicine for longer than 5 years might make sense for some women.
In this study, researchers found that women who took Aromasin as their first adjuvant hormonal therapy medicine were 17% less likely to have the cancer come back than women who took tamoxifen as their first adjuvant hormonal therapy medicine. Other research has shown that taking either of the other aromatase inhibitors: Armidex (chemical name: anastrozole) or Femara (chemical name: letrozole) as the first adjuvant hormonal therapy medicine also does a somewhat better job than tamoxifen at reducing the risk of breast cancer coming back. The benefits compared to tamoxifen is about the same for each of the three aromatase inhibitors.
Aromatase inhibitors help stop breast cancer from coming back by preventing the formation of estrogen. Tamoxifen works by blocking the effects of estrogen on breast cancer cells.
The study reviewed also is trying to figure out if starting on one type of adjuvant hormonal therapy medicine and then switching to another type after several years offers benefits. Other research has suggested that switching hormonal therapy types may make sense for some women.
Research continues to show that an aromatase inhibitor is the best hormonal therapy medicine to start with after initial breast cancer treatment for post-menopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer. But tamoxifen is still a good choice, depending on your unique situation. For a number of reasons, including side effects and cost, tamoxifen may be a better choice for some women.
When you're deciding on a treatment plan, keep two things in mind:
If you're a post-menopausal woman being treated for hormone-receptor-positive, early-stage breast cancer, talk to your doctor about the differences in benefits and side effects of aromatase inhibitors and tamoxifen. If you're currently taking tamoxifen, discuss whether switching to an aromatase inhibitor makes sense for you. Together, you can decide on a treatment plan that is best for YOU.
SAN ANTONIO, Dec. 15 (MedPage Today) -- For postmenopausal women with hormone-sensitive early stage breast cancer, exemestane (Aromasin) may be a modestly better initial adjuvant therapy than tamoxifen.
Exemestane monotherapy improved disease-free survival 17% compared with tamoxifen (P=0.02), Stephen E. Jones, M.D., of U.S. Oncology Research in Houston, and colleagues reported at the San Antonio Breast Cancer Symposium.
Although the intent-to-treat analysis of the open-label trial -- muddied by a high degree of treatment crossovers -- showed only a trend for improvement on this endpoint, the findings from the initial analysis provide the "missing link" for exemestane, Dr. Jones said.
Exemestane is the last of the aromatase inhibitors to be tested as initial adjuvant endocrine therapy against tamoxifen, but the results are consistent with the generally better results for the newer class of drugs, he said.
"At least as initial therapy, it is very consistent that these are superior to treatment with tamoxifen," he said.
The phase III TEAM (Tamoxifen Exemestane Adjuvant Multinational) trial was originally designed as an open-label study comparing once daily tamoxifen (20 mg) to exemestane (25 mg) for five years among postmenopausal women with early stage invasive tumors expressing receptors for estrogen, progesterone, or both.
But things got complicated after the Intergroup Exemestane Study revealed that patients who switched from tamoxifen to exemestane had better disease-free and overall survival.
So, the protocol was amended and all women in the tamoxifen arm were switched to exemestane after 2.5 to three years for a total of five years of treatment.
Additional patients were enrolled as well, to a total of 9,775, making this the largest such aromatase inhibitor study ever, Dr. Jones said.
To isolate just the effect of exemestane as initial therapy, all patients were censored for events after 2.75 years. At that point, exemestane did not significantly improve the primary endpoint of disease-free survival compared with tamoxifen (hazard ratio 0.89, P=0.12).
The trial was further complicated by the open-label design, which resulted in 29.5% of tamoxifen-treated patients switching to an aromatase inhibitor before the protocol called for it, and 18.9% of exemestane-treated patients changing therapies as well.
Once the researchers purged the results of never-treated and post-switch patients, a significant improvement in disease-free survival emerged (HR 0.83, P=0.02).
"Women who actually took [exemestane] had better results. That shouldn't be a surprise," Dr. Jones said.
But even in the intent-to-treat analysis, the aromatase inhibitor did have an advantage for relapse-free survival (HR 0.72, P=0.05) and time to distant metastases (HR 0.81, P<0.03), which Dr. Jones noted ultimately reflects overall survival in many trials.
Compliance, a growing issue in all the aromatase inhibitor trials, likely affected the outcome of the trial, Dr. Jones noted.
Another problem for the trial was the low event rate -- around 740 among the almost 10,000 women -- although good news for patients, he said. "These drugs are very effective in reducing recurrence."
He said the full five-year data comparing exemestane monotherapy to the tamoxifen-exemestane switch group should be available next year.
The study was supported by Pfizer.
Dr. Jones disclosed that he is on the speakers' bureau and is a consultant for Pfizer. His coauthors reported conflicts of interest for Pfizer, AstraZeneca, and Novartis. Two authors reported being employees of Pfizer.
Primary source: San Antonio Breast Cancer Symposium Source reference: Jones SE, et al "Results of the first planned analysis of the TEAM (tamoxifen exemestane adjuvant multinational) prospective randomized phase III trial in hormone sensitive postmenopausal early breast cancer" SABCS 2008; Abstract 15.
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