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ATAC Update: Arimidex Works Better than Tamoxifen for Some Post-Menopausal Women

San Antonio Breast Cancer Symposium, December 2004, Abstract #1

A. Howell, on behalf of the ATAC Trialists' Group A

Background and importance of the study: Many post-menopausal women with early-stage, hormone-receptor-positive breast cancer want to know whats the best hormonal therapy is for them. A study called ATAC is trying to answer this question by comparing three different treatments in more than 9,300 women. The treatments are tamoxifen alone, Arimidex (chemical name: anastrozole) alone, or tamoxifen and Arimidex in combination.

Early results were reported in 2001 and updated in 2003. The report reviewed here is the second update.

All the results so far are consistent. Arimidex is more beneficial than tamoxifen for post-menopausal women with early-stage, hormone-receptor-positive disease.

Results: By the time of the 2004 report, almost all the women in the study had been followed for more than five years. The median follow-up was 68 months, or 5.6 years.

The results continued to show that:

Arimidex alone was better than tamoxifen alone, and
Arimidex alone was better than tamoxifen and Arimidex together.
The improvements were seen in women with any combination of hormone-positive receptors: estrogen-receptor positive, progesterone-receptor-positive, or both.

Specifically, Arimidex was better than tamoxifen for:

reducing the risk or delaying the cancer coming back in the breast or lymph nodes (by 26% compared with tamoxifen);
decreasing the risk of cancer spreading to other parts of the body (by 14% compared with tamoxifen); and
lowering the risk of a new breast cancer developing in the other breast (by 42% compared with tamoxifen).
Arimidex reduced the risk of dying of breast cancer by 17%.

Overall survival (how long women live) was the same for women taking Arimidex and those taking tamoxifen. This was not a surprise, because differences in survival take a long time to show up in women who have early-stage disease. These women are expected to live a long time whether they take tamoxifen or Arimidex.

The medications had different side effects. Women taking Arimidex had fewer hot flashes, less vaginal discharge or bleeding, fewer cases of endometrial cancer, fewer blood clots, and fewer strokes. But women taking Arimidex had more joint aches and pains and more bone fractures.

Conclusions: The ATAC Trial is following more than 9,300 post-menopausal women with hormone-receptor-positive, early-stage breast cancer. After more than five years, the latest ATAC results confirm that Arimidex offered greater benefits and caused fewer side effects than tamoxifen. The women in the study will continue to be followed for a total of 10 years, and further updates will show if the benefits remain strong throughout the whole period. The researchers will also look at possible long-term side effects from Arimidex.

Take-home message: Arimidex offers stronger benefits and fewer side effects compared to tamoxifen as initial hormonal therapy for post-menopausal women with hormone-receptor-positive, early-stage breast cancer. Women taking Arimidex had a better chance than those taking tamoxifen of living free of:

recurrence in the breast area,
spread elsewhere in the body, and
cancer in the other breast.
Both moderate and serious side effects were less common in women taking Arimidex. The risk of fractures and joint aches was worse with Arimidex, however.

If you're trying to figure out the best hormonal therapy for you after completing initial treatment (surgery, radiation, or chemotherapy), talk to your doctor about these important results from the ATAC Study.

Keep in mind that this study was NOT designed to look at what happens when you start on tamoxifen and switch to Arimidex. If you're already taking tamoxifen and you're wondering if you should switch to Arimidex, you'll want to read about a study from earlier this year and another reviewed in this Research News. Another study has looked at women who switch from tamoxifen to Aromasin after two to three years. And if you've completed five years of tamoxifen, you may consider taking Femara (chemical name: letrozole).

While Arimidex performed better than tamoxifen in this study, it's important to point out that tamoxifen is still a very good and powerful drug.

Not everyone has access to Arimidex yet. It may not be approved and available in your country. Also, as a relatively new brand on the market, Arimidex is a great deal more expensive than tamoxifen, which is now available as a generic drug because its patent has expired. If you have serious financial concerns, or do not have insurance that will pay for Arimidex, you may need to continue tamoxifen therapy.

If tamoxifen is your only realistic option, please know that it is likely to give you substantial life-saving benefits. As time goes by, and as more health insurance policies start to cover Arimidex as initial treatment, or as a treatment to switch to, it may become an option for you. If you are without the funds or health coverage to get any medicines, ask your doctor about applying for free medication through the company that makes it.

This article is from breastcancer.org

http://www.breastcancer.org/research_hormonal_012003_pf.html

New ASCO Technology Assessment Recommends Aromatase Inhibitors as Adjuvant Therapy

EMBARGOED FOR RELEASE:
November 15, 2004 at 6 p.m. (ET)

CONTACT:
Jenny Huemann (703) 519-1427

--Benefits over Tamoxifen for Postmenopausal Women With Hormone Receptor-Positive Breast Cancer--

Alexandria, VA – Adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer should include an aromatase inhibitor in order to lower the risk of tumor recurrence, according to an updated technology assessment from the American Society of Clinical Oncology (ASCO).

This new technology assessment updates ASCO's previous recommendation on adjuvant hormonal therapy for this specific group of women. These new recommendations, based on results from multiple large randomized trials, indicate that aromatase inhibitors are appropriate either following a course of tamoxifen or used as initial treatment. Options include treatment with tamoxifen for 2 to 5 years, followed by treatment with aromatase inhibitors, or treatment for 5 years with an aromatase inhibitor alone.

“These findings show a modest but consistent improvement in disease-free survival among women who received an aromatase inhibitor compared to those who did not,” said Eric P. Winer, MD, Director of the Breast Oncology Center at the Dana Farber Cancer Institute in Boston, Massachusetts, and lead author of the Technology Assessment. “In women with hormone receptor-positive early breast cancer, hormones can influence the growth of the cancer. In postmenopausal women, aromatase inhibitors can block estrogen production and reduce estrogen levels by more than 90 percent.”

The ASCO panel recommends the following general guidelines for use of aromatase inhibitors:

* Postmenopausal women with hormone receptor-positive breast cancer may substitute an aromatase inhibitor for tamoxifen as initial adjuvant therapy.Alternatively, women can still begin treatment with tamoxifen and plan to switch to an aromatase inhibitor after 2 to 5 years.It not clear at this time which strategy is superior.

* Postmenopausal women who are currently taking tamoxifen may considering switching to an aromatase inhibitor after 2 to 5 years of tamoxifen therapy.

* Women who switch to an aromatase inhibitor may continue this therapy for 2 to 3 more years, but no longer than 5 years. Women are advised that the result of treatment with an aromatase inhibitor for longer than 5 years has not been studied and should only be done in the context of a clinical trial.

* There are no data to recommend taking tamoxifen after an aromatase inhibitor.

In addition, women who develop invasive hormone receptor-positive breast cancer while taking tamoxifen for breast cancer risk reduction, and women who cannot take tamoxifen because of high risk of severe side effects, or who have tried tamoxifen and had to stop because of severe side effects, might be advised to consider using an aromatase inhibitor.

The three types of aromatase inhibitors highlighted in ASCO Technology Assessment are anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin). Doctors do not yet know if these drugs can be used interchangeably. In addition, the long-term side effects of aromatase inhibitors are not known. Early data suggest that when compared with tamoxifen, aromatase inhibitors may reduce the chance of blood clots and uterine cancer and may increase the risk of osteoporosis and fractures.

“While researchers await more mature results and findings from additional trials using the aromatase inhibitors in the adjuvant setting, many patients and physicians have elected to use the third-generation aromatase inhibitors either as initial therapy in the adjuvant setting or following a course of tamoxifen,” Winer said.

ASCO also released a new evidence-based technology assessment, Aromatase Inhibitors for Early Breast Cancer, the patient version of the clinical practice recommendations. The patient guide will be available online at www.PLWC.org on November 15.

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American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer: Status report 2004, Eric P. Winer, MD, et al., Dana Farber Cancer Institute, Boston, Massachusetts.

The technology assessment has been published ahead of print November 15, 2004, in the Journal of Clinical Oncology (JCO), the semi-monthly peer-reviewed journal of the American Society of Clinical Oncology (ASCO), the world's leading professional society representing physicians who treat people with cancer. The new technology assessment is available on ASCO's patient website at www.PLWC.org.