Arimidex

The primary treatment for breast cancer is typically the surgical removal of the tumour. Unfortunately, this does not always mean that you will then be tumour free as breast cancer has a nasty habit of reoccurring. To deal with this problem a new front-line therapy has been developed - Arimidex - a non-steroidal treatment particularly useful for post-menopausal women.

What does Arimidex do?
Arimidex is an adjuvant therapy. Adjuvant therapies are added to primary treatment in order to try and decrease the risk of breast cancer from returning. They include chemotherapy drugs, radiation, targeted therapy, hormone therapy or a combination of the above. Adjuvant therapies help to destroy any cancer cells that were not removed during surgery and, by doing so, reduce the chances of there being a reoccurrence of the disease.

Arimidex is the trade name for anastrozole - a hormone therapy that is particularly helpful to postmenopausal women diagnosed with hormone receptor positive early breast cancer.

Hormone receptor positive breast cancer tumour cells have hormone receptors - molecules in the tumour cells that recognize and bind with specific hormones. The hormone receptor positive tumour cells depend on the hormones to grow. About 75% of breast cancers are estrogen-receptor-positive ("ER-positive" or "ER+"). and about 65% of ER-positive breast cancers are also progesterone-receptor-positive ("PR-positive" or "PR+").

Although Arimidex’s primary use is an adjuvant therapy for post-menopausal women with hormone receptor positive early breast cancer, it can also be used for the treatment of advanced breast cancer in post- menopausal women.

Arimidex has been found to slow the growth of advanced cancer within the breast and cancer that has spread to other parts of the body.

How does Arimidex work?
Arimidex is a hormonal treatment. It helps in the fight against breast cancer by significantly lowering the levels of certain estrogens in the body. It does this by a process known as aromatase inhibition. Reducing estrogen levels in those patients suffering from estrogen receptor positive early breast cancer is vitally important because the tumour cells use the estrogen to grow. As breast tissue is stimulated by estrogens, decreasing their production is a way of suppressing recurrence of the breast tumour tissue.

What is aromatase inhibition?
Prior to the menopause, a woman’s main source of estrogen production is via her ovaries. Once a woman has gone through the menopause, her ovaries cease to produce estrogen and her adrenal gland becomes her body’s main producer of the hormone. The adrenal gland produces estrogens by converting androgens into estrogens. This process of conversion is known as aromatization and relies upon the action of the enzyme aromatase. Arimidex inhibits (stops) aromatase activity by binding to the aromatase. This prevents the aromatase from converting androgens into estrogens. Arimidex is therefore known as an aromatase inhibitor.

Why is Arimidex not used for the treatment of cancer in pre-menopausal women?
Aromatase inhibitors such as Arimidex are generally not used to treat breast cancer in pre-menopausal women. Stopping the conversion of androgens into estrogens in pre-menopausal women does not have a significant effect on the amount of estrogen circulating around their bodies because the majority of their estrogen is produced by their ovaries.

Indeed, an aromatase inhibitor may be completely ineffectual in lowering estrogen levels in a pre-menopausal woman. The decrease in the amount of estrogen circulating in her body caused by the aromatase inhibitor can lead to the activation of the hypothalamus and pituitary axis. This results in an increase in gonadotropin secretion, which in turn stimulates the ovaries to increase androgen production and androgens are the precursors to estrogens.

The ATAC (Arimidex, ‘Tamoxifen Alone’ or in Combination) Study
The ATAC clinical trial was one of the largest studies into the treatments used in post-menopausal women with early breast cancer. The study compared treatment with Arimidex to treatment with tamoxifen either alone or as a combination of the two. Over 9000 post-menopausal women with localized breast cancer (that is, the cancer hadn’t spread or metastasized) were enrolled into the study.

As an anti-estrogen medication, tamoxifen had become a standard adjuvant therapy for post-menopausal women treated for early breast cancer. But taking tamoxifen did increase their chances of developing endometrial cancer and blood clot disorders.

Early results showed that tamoxifen should not be given at the same time as Arimidex. Once this information was available no more women in the trial were treated with a combined therapy. However, over 6000 patients received Arimidex alone or tamoxifen alone as an adjuvant treatment for a period of 5 years. The study followed how the women fared throughout the 5 year treatment period and, in most cases, well beyond that.

The results of the ATAC trial have shown that Arimidex is a significantly better treatment than tamoxifen for lowering the risk of breast cancer reoccurrence in post-menopausal women with hormone receptor positive early breast cancer. Compared to tamoxifen, patients taking Arimidex increased disease free survival by 10 percent; increased time to relapse by about 20 percent; reduced the occurrence of cancer spreading to other organs (distant metastases) by 14 percent, and reduced the occurrence of cancer in the other breast by more than 40 percent.

Just as important was the finding that women taking Arimidex were less likely to stop taking the treatment because of side effects than those on tamoxifen.

Can Arimidex be used by men?
This may seem an unusual question to ask given that Arimidex’s approved use is for breast cancer treatment in post-menopausal women – but the process of aromatization also occurs in men because men also have estrogens in their bodies just as females have testosterone in theirs. As with women, it’s important that the levels of estrogen in the male body are kept in balance.

Excessive levels of estrogens, in particular estradiol, in men can cause benign prostatic hyperplasia (BPH), gynecomastia (the development of male breasts), and symptoms of hypogoadism (lack of function in the testes).

Therefore, men wishing to reduce their estrogen levels and increase their free testosterone levels may benefit from taking Arimidex. This will reduce the amount of testosterone and adrenal hormones that are converted into estrogens.

Dosage
Men who wish to reduce their estrogen levels and increase their free testosterone levels should take an average of 0.25mg to 0.50mg Arimidex per week. Arimidex is a most potent aromatase inhibitor and even these doses could have significant effects, therefore always monitor your blood levels and seek a health professionals advice.

Side effects
Many people are concerned about the side effects that can occur with medicines designed for the treatment of cancer. But patients should be reassured because Arimidex can offer powerful proven protection against reoccurrence of their breast but at the same time is less likely to cause certain side effects than tamoxifen.

The most common side effects included hot flashes, thinning of the hair, joint symptoms, weakness, mood changes, pain, sore throat, nausea and vomiting, loss of appetite, depression, high blood pressure, osteoporosis, swelling of arms/legs, vaginal dryness, vaginal bleeding (usually within the first few weeks) and headache. Although this list seems to be rather alarming, you may not experience any side effects at all. If you do, do not stop taking the medication but talk to your doctor.

Caution
As with all medicines you must tell your doctor about any other medicines that you are taking. Arimidex should not be taken if any of the following apply:-
• You are pre-menopausal.
• You are pregnant or breast feeding your baby.
• You have a kidney or liver disease or disorder (you should consult your doctor further about this).
• You are taking tamoxifen or estrogen containing medicine such as hormone replacement therapy.