Breast cancer clinical trial results
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 breast cancer 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 breast cancer clinical trial
The ATAC study was one of the largest clinical trials of adjuvant breast cancer treatment 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 early analysis of the ATAC trial at 33 months, results comparing tamoxifen alone to a combination of ARIMIDEX and tamoxifen showed no significant difference.
Data from the ATAC clinical trial were analyzed at a median of 68 months, when the majority of women had completed the 5 years of treatment, at a median of 100 months, when women had been off treatment for 3 years or more, and at a median of 120 months, when women had been off treatment for 5 years or more. The data from these analyses showed that women who took ARIMIDEX experienced a lower rate of a combination of treatment results (length of time until breast cancer came back, a new breast cancer developed, and death from any cause) compared with those who took tamoxifen.
Other important information about the ATAC clinical trial of breast cancer treatment includes:
- Participants in the ATAC trial included 9366 postmenopausal women from across the globe with early breast cancer who were considered candidates for adjuvant hormonal treatment following initial treatment
- Over 6000 breast cancer patients in the ATAC trial received either ARIMIDEX alone or tamoxifen alone as adjuvant treatment
- The women who participated in the trial have been followed for a median of 120 months (10+ years)—through five years of treatment with ARIMIDEX and for five years after completion of treatment
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The 68-month ATAC breast cancer clinical trial results
Data from the ATAC trial were studied after women had been on treatment for a median of 68 months. The data showed that women who took ARIMIDEX experienced a lower rate of a combination of treatment results (length of time until breast cancer came back, a new breast cancer developed, and death from any cause) compared with those who took tamoxifen.
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In the ATAC clinical 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. At the time of the analysis, 8% of patients were still receiving or still on treatment.
The 68-month ATAC trial results showed that patients taking ARIMIDEX had a 17% improvement in disease-free survival compared with 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 2618 patients taking ARIMIDEX had a recurrence or died compared with 497 of 2598 patients taking tamoxifen
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Patients taking ARIMIDEX had fewer breast cancer events than those taking tamoxifen
- 402 out of 3092 patients taking ARIMIDEX had recurrence of breast cancer, compared with 498 out of 3094 patients taking tamoxifen*
- 35 out of 3092 patients taking ARIMIDEX had breast cancer develop in the breast on the side opposite their original cancer, compared with 59 out of 3094 patients taking tamoxifen*
- 324 out of 3092 patients taking ARIMIDEX had cancer spread to other parts of their body beyond their breast, compared with 375 out of 3094 patients taking tamoxifen*
*Patients may fall into more than one category.
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In the ATAC breast cancer clinical trial, 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% |
These side effects were LESS LIKELY with tamoxifen.
| |
ARIMIDEX
(number of patients = 3092)
|
Tamoxifen
(number of patients = 3094)
|
| Joint symptoms |
36% |
29% |
All fractures
|
10%
|
7%
|
|
Fractures of spine, hip, or wrist
|
4%
|
3%
|
- Chest pain was reported more in 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 (278 [9%] vs 108 [3.5%])
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The 100-month ATAC breast cancer clinical trial results
An analysis of a median of 100 months of clinical data from the ATAC trial shows ARIMIDEX to be effective and superior to tamoxifen at reducing the risk of breast cancer recurrence in postmenopausal women with hormone receptor-positive early breast cancer.
The 100-month ATAC data show ARIMIDEX works to help reduce recurrence both throughout the five-year hormonal treatment regimen and for more than three years afterward.
ARIMIDEX is an aromatase inhibitor with over eight years of clinical data—five years on treatment and more than three years of follow-up—in the initial adjuvant treatment of early breast cancer in postmenopausal women. For more information, talk to your doctor.
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The 120-month ATAC breast cancer clinical trial results
The 120-month ATAC breast cancer clinical trial results are consistent with those in the previous analyses.
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Learn more about the side effect profile of ARIMIDEX