Hormonal therapies for DCIS

Hormones occur naturally in the body and help control how cells grow and what they do. Hormones, particularly oestrogen, can encourage breast cancer cells to grow.

Hormonal therapies reduce the level of oestrogen in the body, or prevent it from attaching to the cancer cells. They are only given to women who have oestrogen-receptor positive cancers.

Hormonal therapies are commonly prescribed for women with invasive breast cancer because they reduce the risk of breast cancer coming back. Doctors know that there are benefits of using hormonal therapy for DCIS, but they don’t know exactly how useful this treatment is. Hormonal therapies are mainly given to treat DICS in research trials. The type of hormonal therapy you have depends on whether you’ve been through the menopause or not.

Tamoxifen

Trials have shown that a hormonal therapy called tamoxifen may reduce the risk of ER-positive DCIS coming back. It can also reduce the risk of invasive cancer in both breasts. However, the amount of benefit isn’t clear so tamoxifen isn’t used routinely in all women.

Your specialist will explain the possible advantages of tamoxifen in your situation. It can be used whether you have been through the menopause or not.

Tamoxifen is taken daily as a tablet, usually for five years. The side effects are similar to the effects of the menopause and may include:

  • hot flushes and sweats
  • vaginal dryness or an increased vaginal discharge
  • weight gain
  • tiredness
  • leg cramps.

For women who’ve been through the menopause, tamoxifen can slightly increase the risk of womb (endometrial) cancer, blood clots in the leg and strokes. Although this sounds frightening, these effects are very rare. If they occur, they’re usually picked up very early when they can be successfully treated.

Aromatase inhibitors

Aromatase inhibitors (AIs) are the main hormonal therapy used in women with invasive breast cancer after the menopause. Like tamoxifen, these drugs only work in ER-positive DCIS. They stop oestrogen being made in the fatty tissue.

Research has shown that they can be used to treat DCIS, but they aren’t a standard treatment. There are trials to find out which women should have them. Your doctor or breast care nurse can tell you more about any trials that you may be suitable for.

Your doctor may prescribe an aromatase inhibitor such as:

These drugs are taken daily as a tablet. Side effects can include tiredness, joint and muscle pain, vaginal dryness or hot flushes.