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."

How do the ATAC trial results affect you?

In the ATAC trial, women who took ARIMIDEX for a full 5 years 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 ATAC trial results below.

 

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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 with the 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 over 5 years

 

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In the ATAC trial, ARIMIDEX helped more patients reduce their risk of cancer coming back compared with tamoxifen

In the latest 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 ATAC trial:

Patients taking ARIMIDEX showed a 17% improvement in disease-free survival compared to patients taking tamoxifen

• Disease-free survival refers to patients who were alive and had not experienced a recurrence of their breast cancer at the time of the latest ATAC trial results analysis
• 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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Patients taking ARIMIDEX had fewer breast cancer events

• 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