Tamoxifen FAQ

Anyone who has been on tamoxifen themselves or who sees a loved one taking a daily dose of “TOMY” (nickname for tamoxifen) knows that it is not an easy drug to take…

The side effects can sometimes be so intolerable that even the attractive benefit of preventing a breast cancer recurrence is not enough to justify its continued use. I have many patients who have stopped using it and are too afraid to admit this to their oncologists… So, they just pretend that they are still taking it and hope for the best.

What I hope to do in this article is make you aware of all the facts around tomy. Make a fully informed decision that includes the opinions of your health team. It does not matter what you decide – ultimately the choice is yours to make – just be fully informed!

What is tamoxifen?

Tamoxifen is a pill taken once a day. It is used mostly in the prevention or treatment of breast cancer in the following situations:

• To reduce the risk of breast cancer in someone who has a very high risk of getting it; for example someone with a strong family history.

• After surgical treatment in women and men with breast cancer who have early stage hormone receptor positive cancers. This is to prevent recurrence. It can be used in both premenopausal and postmenopausal women.

• In women and men diagnosed with advanced receptor positive breast cancers. It does not work for hormone-receptor-negative cancers.

How does it work?

It belongs to a class of drug called SERMs (selective estrogen receptor modulators). This means that TOMY is able to attach itself to estrogen receptors anywhere in the body; and depending on the organ it is in, it can have different effects. So, in the breast it will make the tissue less sensitive to estrogen and in doing so stop and prevent the growth of breast cancer cells. In other tissue like bone and the uterus, it acts like estrogen, stimulating bone formation and preventing osteoporosis. It also stimulates the growth of endometrial tissue in the uterus.

How long is the treatment?

Previously, standard treatment was for five years. New research now shows that 10 years gives a better survival advantage, a lower risk of cancer recurrence, including a lower risk of the cancer developing in the opposite breast.

What benefits can I expect from tamoxifen?

• If you are premenopausal, 30-50% reduced risk of the cancer returning.

• If you are postmenopausal, 40-50% reduced risk of the cancer returning.

• 50% reduced risk of the cancer developing in the opposite breast,

What are the side effects?

The side effects are many. They can have a major impact on quality of life and this is what prompts many women to stop using it. Firstly, remember that not all women are affected in the same way. Secondly they can be dose dependent. Starting on the lower dose and building up may be helpful. Speak to your doctor to find out if this is appropriate for you!

Also, sometimes timing is everything – it may be influenced by the time of day you are swallowing your pill.

Commonly experienced side effects are:

• Hot flushes

• Bone and joint pain; stiffness of the joints

• Vaginal dryness, irritation or discharge, loss of libido

• Weight gain

• Nausea, fatigue, constipation

• Mood swings, depression

In 2008, a British study found that women who experienced hot flushes and night sweats while taking hormone therapy for breast cancer were less likely to have the cancer come back. Knowing this may just make it more worthwhile to persevere.

Other more serious side effects are an increased risk of stroke, ovarian cysts and uterine polyps or cancer. This is why your oncologist will ask you to see your gynaecologist before you start TOMY and yearly while you are on it.

REMEMBER: if you are not tolerating the side effects speak to your oncologist. There may well be an alternative drug or strategy in your situation.

Another helpful resource is a support group, both in person or online. Just knowing that you are not alone in your experiences makes a huge difference. Chatting to other people in similar situations can bring immense emotional comfort.

What if I am on other medication, can it affect tamoxifen?

Yes! TOMY is converted to its active form in our livers. To do this properly, it needs a functioning enzyme system called CYP2D6. Some medications, especially anti-depressants, will impair this enzyme- activation system and make Tamoxifen less effective. This may impact on whether or not the cancer returns. Below is a list:

Anti-depressants that don’t affect tamoxifen are: Efexor and Lexapro.

IF YOU ARE UNSURE ABOUT YOUR CURRENT MEDICATION CHECK IT WITH YOUR DOCTOR OR PHARMACIST!

Can I get pregnant while on tamoxifen?

If you are not menopausal yet and on TOMY, it is wise to use a non-hormonal form of contraception. Pregnancy is still a possibility! Condoms, a diaphragm along with spermicide or a copper IUD would be acceptable options during Tamoxifen treatment and for a period of two months thereafter. Tamoxifen may cause damage to a developing fetus!