Switching to Aromasin After Tamoxifen May Reduce Risk of Recurrence
Reviewed study: "Switching to Aromasin After Tamoxifen May Reduce Risk of Recurrence" by R.C. Coombs and others, American Society of Clinical Oncology Annual Meeting, June 2006, Abstract LBA527
Is this for me? If you're postmenopausal and taking tamoxifen and you're considering a switch to an aromatase inhibitor, you might want to read this article.
What question is this study trying to answer? The researchers wanted to know if switching to Aromasin (chemical name: exemestane), an aromatase inhibitor, after 2 to 3 years of tamoxifen would reduce the risk of the cancer coming back (recurrence) in women with early-stage breast cancer.
Breastcancer.org previously has reviewed earlier results from this study, known as the Intergroup Exemestane Study. This is the first analysis of the results when nearly all (95%) of the women were followed for 3 years or more.
Study design: 4742 women with hormone-receptor-positive, early-stage breast cancer participated in the study. The women were all postmenopausal, ages 55 and older. All of the women had taken tamoxifen for 2 to 3 years.
The researchers randomly assigned the women to 2 groups:
- 2362 switched from tamoxifen to Aromasin, which they took for an additional 2 to 3 years.
- 2380 continued to take tamoxifen for about another 2 to 3 years.
More than 90% of the women had finished taking either tamoxifen/Aromasin or tamoxifen alone to complete a total of 5 years of hormonal therapy. Then the researchers looked at disease-free survival (how many women were alive without a recurrence) and overall survival (how many women were alive, with or without a recurrence) in the 2 groups.
Study results: Women who took 2 to 3 years of Aromasin after taking tamoxifen for 2 to 3 years had a 20% reduction in the relative risk of recurrence, compared with women who took tamoxifen for the full 5 years. (Relative risk of recurrence is the number that tells you how much something you do, like taking a combination of medicines, might change your risk, compared with your risk when taking only 1 medicine.)
Almost 84% of the women who took Aromasin had no cancer recurrence, compared with 80% of the women who took only tamoxifen. This difference was statistically significant, meaning it was probably due to the shift over to Aromasin and not just due to chance. Put another way: the women who took tamoxifen for the full 5 years had a 20% risk of recurrence during the 8-year study period. The women who switched from tamoxifen to Aromasin had a 16% risk of recurrence. The difference in risk of survival between the 2 groups is 4%. This 4% difference is a change in the absolute risk of recurrence. Going from the 20% risk down to 16% represents a 20% relative risk decrease.
There was no difference in overall survival between the 2 groups. But when looking at the cancer's estrogen-receptor status, the researchers found that women with cancer that was estrogen-receptor-positive who took Aromasin had a statistically significant increase in overall survival.
What breastcancer.org says about this article…
Switching to Aromasin After Tamoxifen May Reduce Risk of Recurrence
If you're a postmenopausal woman with early-stage, hormone-receptor-positive disease, and you're taking tamoxifen, you have another treatment option to consider. After 2 to 3 years of tamoxifen, you may be able to get greater benefit from switching to Aromasin for the rest of the 5 years (rather than staying on tamoxifen for the full 5 years).The risk-reduction benefit is real—meaning that the statistics behind the results are solid. One should keep in mind, however, that the absolute difference between the groups of 4% is definitely meaningful, but it's not a huge difference. There are many women around the world who only have access to tamoxifen. Aromasin might not be available through their health care system or medical insurance plan. And they can't afford the expense of Aromasin. The company that makes Aromasin, Pfizer, does have a program that helps people with financial hardship cover the cost of the medicine. Access to this program is through your doctor. So, if this is your situation, talk to your doctor about your options.
And, if you're a woman who stays on tamoxifen for the full 5 years (by choice or financial circumstances, or because you can tolerate tamoxifen better)—it's reassuring to know that tamoxifen is still likely to do a very good job of protecting you against recurrence. If you are reading this after you've been on tamoxifen for 5 years, you can also feel reassured that tamoxifen is still a very good medicine.
The impact of a particular medicine on your individual physical and emotional being is truly unique. You and your doctor can design a treatment plan that works just fine. Sometimes, though, 1 medication might agree with you more. So there are women who may be on tamoxifen for less than 2 years, have difficulty with side effects, and switch to an aromatase inhibitor sooner. Or there may be women who switched over to an aromatase inhibitor and had trouble with the side effects, so they switched back to tamoxifen.
Choose the best treatment for YOU. See your doctors regularly for follow-up after treatment. This is the best time to discuss your current treatment plan as well as new options that might benefit you.
