Hormonal Therapy

Breast cancer cells may be sensitive to the female hormones oestrogen and progesterone. Many cells have specific receptors that are activated by these hormones and stimulate the cell to divide. We can test for the presence of these receptors in the laboratory. If your cancer cells are receptor positive we can use drugs that block the effect of these circulating hormones thus slowing or stopping the growth of the cancer.

Tamoxifen was the first drug to be developed in this category. It has a similar shape to the oestrogen molecule and is able to bind to the cell receptors without stimulating the cell to divide. This blocks the receptors and means that there are less open receptors for the hormone to bind to.

Tamoxifen is usually taken as a single 20mg tablet once daily. Usual length of treatment is 5 years.

New information December 2012:

Article: Long term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor positive breast cancer:ATLAS, a randomised study. The Lancet, Volume 381, Issue 9869, Pages 805 - 816, 9 March 2013doi:10.1016/S0140-6736(12)61963-1

A new study shows that women who took Tamoxifen for 10 years lowered their risk of recurrence by 25% and of dying from breast cancer by 29% compared to those who took Tamoxifen for 5 years.

6846 patients who had already taken tamoxifen for 5 years were randomised to either take tamoxifen or placebo pills for another 5 years.

Longer therapy doubled risk of endometrial cancer but this was seldom fatal.

presented at San Antonio December 2012

Side effects:

  • Tamoxifen blocks the effect of oestrogen and it is therefore not surprising that many of the side effects are menopausal symptoms.
  • Hot flushes
  • Mood swings
  • Vaginal dryness
  • Uterine cancer increased risk
  • DVT increased risk

Tamoxifen: MedlinePlus Drug information

In premenopausal women oestrogen production can be reduced temporarily by using a drug called Goserelin (Zoladex). This is given as a four weekly injection and inhibits oestrogen production. On stopping the drug your periods will usually return. The more definitive but irreversible option is to remove the ovaries (oophorectomy). This can be done as a laparoscopic procedure.

Aromatase inhibitors. Are a newer group of drugs that work by blocking the conversion of steroids to oestrogen that occurs in the fatty tissue of the body. This is the major source of oestrogen in post- menopausal women.

  • Anastrazole Arimidex
  • Letrozole Femara
  • Exemestane Arimisin

Since the arrival of the aromatase inhibitors studies now suggest that the best results are obtained by 2 years Tamoxifen then a switch to an Aromatase inhibitor for 2-3 years. Trials are still underway to clarify the optimum duration,combination and dose of these medications. Information seems to change every few months as new results are published. Your oncologist will keep you up to date with changes that may affect you. You may also be asked to participate in one of these trials.
Side effects

  • Menopausal symptoms
  • Bone and joint pain
  • Osteoporosis
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