If you are a postmenopausal woman with hormone receptor-positive early breast cancer, you may be concerned about reducing your risk of cancer coming back (recurrence). As you consider your treatment options, it is important to understand the results of a clinical trial called the ATAC trial. "ATAC" stands for "ARIMIDEX, Tamoxifen Alone or in Combination."

Background on the ATAC trial

The ATAC clinical trial was one of the largest breast cancer treatment studies in postmenopausal women with early breast cancer. This clinical trial compared treatment with ARIMIDEX to treatment with the antiestrogen medication tamoxifen, either alone or in combination.

In an earlier analysis of the ATAC trial, results comparing tamoxifen alone to a combination of ARIMIDEX and tamoxifen showed no significant difference. These results suggested that tamoxifen should not be given at the same time as ARIMIDEX. Once these results were available, no additional patients in the study were treated with a combination of ARIMIDEX and tamoxifen. Other important information about the ATAC trial includes:

• Over 6,000 breast cancer patients in the ATAC trial received either ARIMIDEX alone or tamoxifen alone as adjuvant treatment for 5 years
• The ATAC trial followed how these patients did while on their treatment. Most patients were followed for more than 5 years
• Participants in the ATAC trial included 9,366 postmenopausal women from across the globe with early breast cancer who were considered candidates for adjuvant hormonal treatment following initial treatment
• The women who participated in the trial have been followed for a median 100 months (8+–years) — through 5 years of treatment with ARIMIDEX and for 3 years after treatment completion

 

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The 68-month ATAC trial results

In the 68-month ATAC trial results, women who took ARIMIDEX experienced a lower rate of recurrence of their breast cancer or death from any cause, compared with those who took tamoxifen.

Watch a doctor explain the main points of the ATAC trial, and see what these results mean for you.

 

If you cannot view the video, you can read about the 68-month ATAC trial results below.

 

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In the ATAC trial at 68 months of follow-up, ARIMIDEX helped more patients reduce their risk of cancer coming back compared with tamoxifen

In the 68-month ATAC trial results, treatment with ARIMIDEX was shown to be significantly better than treatment with tamoxifen for lowering the risk of breast cancer recurrence in postmenopausal women with hormone receptor-positive early breast cancer. When this analysis was done, half of these patients had been followed for 5½ years or more, and half had been followed for less than 5½ years.

In the 68-month ATAC trial results:

Patients taking ARIMIDEX showed a 17% improvement in disease-free survival compared to patients taking tamoxifen in the hormone receptor-positive subpopulation.

• Disease-free survival refers to patients who were alive and had not experienced a recurrence of their breast cancer at the time of the 68-month ATAC trial results
• 424 of 2,618 patients taking ARIMIDEX had a recurrence or died compared to 497 of 2,598 patients taking tamoxifen
• Overall survival data show 296 deaths from any cause in patients taking ARIMIDEX compared to 301 deaths from any cause in patients taking tamoxifen

 

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In the ATAC trial, patients taking ARIMIDEX had fewer breast cancer events than those taking tamoxifen

• 76 out of 2,618 patients taking ARIMIDEX had cancer come back in the breast or lymph nodes on the same side as their original cancer, compared with 101 out of 2,598 patients taking tamoxifen^*
• 26 out of 2,618 patients taking ARIMIDEX had breast cancer develop in the breast on the side opposite their original cancer, compared with 54 out of 2,598 patients taking tamoxifen^*
• 226 out of 2,618 patients taking ARIMIDEX had cancer spread to other parts of their body beyond their breast, compared to 265 out of 2,598 patients taking tamoxifen^*

*Patients may fall into more than one category.

 

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Patients taking ARIMIDEX were less likely than those taking tamoxifen to stop treatment because of side effects

Certain side effects were looked at in the ATAC trial based on known activity of drugs like tamoxifen and ARIMIDEX.

These side effects were LESS LIKELY with ARIMIDEX:

 

	ARIMIDEX (number of patients = 3092)	Tamoxifen (number of patients = 3094)
Hot flashes	36%	41%
Vaginal bleeding	5%	10%
Vaginal discharge	4%	13%
Blood clots	3%	5%
Stroke	2%	3%
Endometrial (uterine) cancer*	0.2%	0.6%

* Based on number of patients with an intact uterus at baseline.

These side effects were LESS LIKELY with tamoxifen:

 

	ARIMIDEX (number of patients = 3092)	Tamoxifen (number of patients = 3094)
Joint symptoms	36%	29%
All fractures Fractures of spine, hip, or wrist	10% 4%	7% 3%

• Chest pain was reported in more women taking ARIMIDEX than in women taking tamoxifen (71 [2.3%] vs 51 [1.6%])
• Heart attack rates were similar in women taking ARIMIDEX and women taking tamoxifen (37 [1.2%] vs 34 [1.1%])
• More patients taking ARIMIDEX were reported to have elevated serum cholesterol compared with patients taking tamoxifen (9% versus 3.5%)

 

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	Learn more about the side effect profile of ARIMIDEX

The latest ATAC trial results: 100 months of data

The 100-month ATAC trial results presented at the San Antonio Breast Cancer Symposium in December 2007 showed the significant superiority of ARIMIDEX over tamoxifen at reducing the risk of breast cancer recurrence in postmenopausal women with hormone receptor-positive early disease.

ARIMIDEX is the only aromatase inhibitor with over 8 years of clinical data—5 years on treatment and more than 3 years of follow-up that demonstrate efficacy and safety in the initial treatment of early breast cancer in postmenopausal women. For more information, talk to your doctor.

 

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