Tamoxifen and exemestane trial
I have seen information about a new breast cancer drug called exemestane. I'm currently taking tamoxifen - should I be taking this drug instead?
The two drugs you are asking about are both hormone treatments for breast cancer. The type of hormone therapy you need depends on a number of factors. This page tells you about
Hormones are substances that occur naturally in the body. They control the growth and activity of normal cells. Female hormones such as oestrogen can affect the growth of some breast cancer cells. This is known as having an 'oestrogen receptor positive' breast cancer. Drugs or treatments that block oestrogen and progesterone, or lower the levels in the body, can be used to treat some types of breast cancer.
Tamoxifen is a very successful treatment for breast cancer. It is the standard hormone treatment for premenopausal women. You usually take it for 5 years after surgery to remove breast cancer. Tamoxifen works by blocking these oestrogen receptors, so that the hormone can no longer get to the cancer cells and stimulate them to grow. There is more information about tamoxifen on CancerHelp UK. And more about ER receptors and how they work. Tamoxifen also reduces the chance of cancer coming back in postmenopausal women.
Exemestane is a different type of hormone treatment. It's brand name is Aromasin. It is a type of drug called an aromatase inhibitor. Women who have had their menopause no longer produce oestrogen from their ovaries. But they do still produce a small amount in the fatty tissues of the body. Aromatase inhibitors block this oestrogen from being made. They are only used to treat postmenopausal women.
Researchers looked at whether switching from tamoxifen to a drug called exemestane in postmenopausal women could lower the risk of the cancer coming back even more than just taking tamoxifen. One research study (the IES trial) involved nearly 5,000 women worldwide. All the women taking part had already had their menopause. On joining the trial, they had been taking tamoxifen for 2 to 3 years as part of their treatment for early breast cancer. They then either continued taking tamoxifen or switched to exemestane for a further 2 or 3 years, so that they had all taken hormone therapy for a total of 5 years. Neither the patients nor their doctors knew whether they were taking tamoxifen or exemestane.
Results showed that switching to exemestane after 2 to 3 years of tamoxifen reduced the risk of breast cancer coming back by about a third. It also reduced the risk of cancer spreading and cancer occurring in the other breast. Women who switched to exemestane had a lower risk of dying.
The researchers also looked at the unwanted side effects of both drugs. Overall, many of the side effects of exemestane and tamoxifen are similar. But there are some differences. In these early results, the risk of womb cancer (endometrial cancer) was lower for the women taking exemestane than for tamoxifen. The exemestane group were also less likely to have problems with blood clotting disorders. More patients on exemestane reported diarrhoea and joint pains, while more women on tamoxifen reported gynaecological problems and muscle cramps. There was an increased risk of osteoporosis and fractures with exemestane, compared to tamoxifen.
In February 2009, The National Institute for Health and Clinical Excellence (NICE) recommended letrozole or anastrozole (another type of aromatase inhibitor) as a first line hormone treatment for women after surgery if
- They have ER positive breast cancer, and
- They have been through the menopause, and
- Their doctors think there is more than a low risk of the cancer coming back
If you cannot take an aromatase inhibitor for any reason, then you should be offered tamoxifen. If you are going to have chemotherapy for early breast cancer, you will usually start hormone therapy once your chemo has finished.
If you have already been taking tamoxifen for 2 to 3 years, NICE recommend that you should be offered exemestane or anastrozole.
If you have already been taking tamoxifen for 5 years, and you had cancer in your lymph nodes when you had your operation, NICE recommend that you are offered letrozole for another 2 to 3 years.
Please be assured that tamoxifen is still a very effective treatment for breast cancer. Your doctor can discuss with you which treatment is most suitable for you. And they should take into account factors such as the side effects and benefits of each different hormone therapy, how long you've already had treatment with tamoxifen, and what they think the risk of your cancer coming back might be. Only your cancer specialist can advise you on the treatment options that are best for you.
CancerHelp UK has a large breast cancer section, including information about hormone therapy for early breast cancer.
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