Tamoxifen and breast cancer

Tamoxifen is a hormonal therapy widely used in the treatment of breast cancer. It is commonly prescribed to women with oestrogen-positive cancer following surgery or other treatment, and is often part of a five-year course. (Recent reports have revealed calls to double treatment length to a decade).

The drug itself comes in tablet form and should be swallowed whole with a glass of water. As nausea is a very common side effect, doctors recommend also taking Tamoxifen with food in order to settle the stomach and dispense with the unpleasant ‘metallic’ aftertaste.

Tamoxifen comes in three different strengths (10mg, 20mg or 40mg) and is manufactured under various brand names including Nolvadex, Istubal and Valodex. It should not be taken during pregnancy, as there is a chance it may harm the growing foetus.

In June 2013 it was announced that the NHS should also offer the drug to women at risk of familial breast cancer. This type of cancer is classified after breast, ovarian or any other oestrogen-related cancer has affected a number of family members. Individual cases would study the number of relatives affected, their ages at the time of developing cancer and the comparative age of the person considered to be at risk.

How does Tamoxifen work?

Tamoxifen is an anti-oestrogen drug in that it prevents oestrogen from binding to the proteins in cancer cells, which are known as receptors.

Many breast cancers require a supply of the sex hormone oestrogen in order to grow, as it activates these receptors and stimulates the cancer cells to divide, multiply and spread, causing a tumour to develop.

Tamoxifen acts as an antagonist of the oestrogen receptors, effectively slotting into these proteins, and preventing the hormone from reaching the cancer cells. The direct consequence of this ‘blockage’ is that the cancer either stops growing completely, or its progress is severely hindered.

What are the side effects of taking Tamoxifen?

It is important to remember that each individual will react to any drug in a different way, and that these reactions may change over time. Some people are lucky and experience very few negative reactions to Tamoxifen, while others suffer immensely.

The most common side effects are hot flushes and nausea. It is quite normal for this to occur during the first few months of treatment, then for the side effects to calm down considerably (although not in all cases). If the hot flushes and sweats are particularly severe and long lasting, the doctor might consider switching the patient to a different drug. Taking Tamoxifen with a meal can to a degree help nausea and indigestion.

Younger women who are still having monthly periods may notice a change in menstruation. Their periods might become lighter, less regular and maybe cease altogether. Vaginal discharge might increase, along with general discomfort in that area, and sexual appetite might decrease.

Often patients also complain of weight gain (which might be caused by water retention) and leg cramps while taking Tamoxifen. As a less common side effect of the drug includes thrombosis (blood clots), any red, hot and swollen parts of the body should be reported to the doctor immediately.

Other less common side effects include exhaustion, depression, blurred vision and allergic reactions. Patients naturally suffering from migraines might also experience an increase or change in the pattern of their headaches.

What else should I know?

For some postmenopausal women, a course of Tamoxifen slightly increases the chance of developing endometrial cancer (cancer in the womb). This is because the drug is a selective oestrogen receptor modulator, which, although it acts as an antagonist in breast tissue, it also acts as a partial agonist on the lining of the womb. This is the reason why usage of Tamoxifen is only currently recommended to last five years. Broadly speaking, the pros of taking Tamoxifen to treat an existing breast cancer are generally usually considered to outweigh the cons of potentially increasing the risk of developing endometrial cancer, but this is something each patient should discuss with her doctor on an individual basis.